Journal of Behavioral and Brain Science, 2011, 1, 242-261
doi:10.4236/jbbs.2011.14031 Published Online November 2011 (
Copyright © 2011 SciRes. JBBS
Advances in Interdisciplinary Researches to Construct a
Theory of Consciousness
Pierre R. Blanquet
Club d’Histoire des Neurosciences, University P. & M. Curie, Paris, France
Received August 22, 2011; revised October 13, 201 1; accepted October 28, 2011
The interdisciplinary researches for a scientific explanation of consciousness constitute one of the most ex-
citing challenges of contemporary science. However, although considerable progress has been made in the
neurophysiology of states of consciousness such as sleep/waking cycles, investigation of subjective and ob-
jective nature of consciousness contents raises still serious difficulties. Based on a wide range of analysis and
experimental studies, approaches to modeling consciousness actually focus on both philosophical, non-neural
and neural approaches. Philosophical and non-neural approaches include the naturalistic dualism model of
Chalmers, the multiple draft cognitive model of Dennett, the phenomenological theory of Varela and
Maturana, and the physics-based hypothesis of Hameroff and Penrose. The neurobiological approaches in-
clude the neurodynamical model of Freeman, the visual system-based theories of Lamme, Zeki, Milner and
Goodale, the phenomenal/access hypothesis of Block, the emotive somatosensory theory of Damasio, the
synchronized cortical model of Llinas and of Crick and Koch, and the global neurophysiological brain model
of Changeux and Edelman. There have been also many efforts in recent years to study the artificial intelli-
gence systems such as neurorobots and some supercomputer programs, based on laws of computational ma-
chines and on laws of processing capabilities of biological systems. This approach has proven to be a fertile
physical enterprise to check some hypothesis about the functioning of brain architecture. Until now, however,
no machine has been capable of reproducing an artificial consciousness.
Keywords: Models of Consciousness, Third and First-Person Data/Qualia, Neuronal Workspace,
Thalamo-Cortical Neurons, Artificial Intelligence
1. Introduction
By separating the immaterial mind and the material body,
Descartes (1596-1650) traced a dividing line between
two incommensurable worlds: the sp iritual and the mate-
rial world [1]. From this ontological dualism is born an
epistemological dualism according to which the material
must be known by science and the mind by introspection.
During the 18 th century, the definition of the mind started
to emerge with that of consciousness, recognized as in-
strument of knowledge of the world which surrounds us
as also of our interiority. Hume (1711-1776), for example,
defined the mind: “as an interior theatre on which all that
is ‘mental’ ravels in a chaotic way in front of an interior
eye whose eyelids would not blink” [2]. On the contrary,
the materialist philosophers of the 18th century will give
up the cartesian immaterial su bstance, but they will keep
the metaphor of the body-machine and will extend this
metaphor to all human functions, including thought. Far
from showing the immateriality of the heart, indeed, the
cartesian cogito would prove rather for La Mettrie (1709-
1751), Diderot (1713-1784) and Holbach (1723-1789)
that the matter can think. In this line of idea, transform-
ist/proto-evolutionist and darwinian theories of 18th and
19th centuries, by introducing the id ea of a biological ori-
gin of the man, introduced the vast field of investigation
of the “living matter” and the problem of “when” and
“how” of the mind [3].
However, it was necessary to await the arise of the psy-
chology in the mid-nineteenth century, so that conscious-
ness becomes the central object of a new discipline claim-
ing science and asserting its independence with regard to
philosophy. This introspective approach of mind domi-
nated the investigations of researchers such as Herman
von Helmholtz (1821-1894), Wilhelm Wundt (1832-1920)
and William James (1842-1910) [4-6]. In the end of the
19th century, in his founder text for a phenomenology,
Husserl (1859-1938) exposed his thesis on the nature of
consciousness [7]. Following Brentano’s work, he adopted
the concept of intentionality and gave it a central role
concerning the transcendental ego. He taught that con-
sciousness is never empty: it always aims an object and,
more generally, the world. The ego always carries in it the
r e l at ionsh ip wi th the wor ld as in tens iona l aimi ng. Th e earl y
20th century saw the eclipse of consciousness from scien-
tific psychology [8,9]. Without denying the reality of sub-
jective experiences, the strategy of behaviorists was to
draw aside consciousness of the direct field of investiga-
tion and to regard the brain as a “puzzle-box”. They then
put “between brackets” the irresolute problems which en-
cumbered the psychology to study stimuli and answers,
i.e. behaviors which reduce the analysis to rigid relations
between inputs (stimuli) and outputs (movements). In the
1960s, the grip of behaviorism weakened with the rise of
the cognitive psychology [10,11]. However, despite this
re newed emphasis on expla ining cogn itive capacitie s such
as memory, perception and language comprehension, con-
sciousness remained a largely neglected topic until the ma-
jor scientific and philosophical researches in the 1980s.
Researches on the correlations between the identifiable
mental activities and the objectivable cerebral activities
succeeded the traditional questioning on the relation be-
tween the mind and the brain. They were approached by
neurophilosophers, neurobiologists and researchers in ar-
tif icial intellige nce as familiar with the epide miologic an d
ontological questions as with the methodologic and empi-
ric ones. My pu rpose here is to rev iew the ma in at tempts to
provide an adequate explanatory basis for consciousness.
2. Consciousness, a Challenge for Philosophy
and Science
2.1. Difficulties in Philosophically Tackling the
Problem of Consciousness
Traditionally, one supposed in philosophy of mind that
there was a fundamental distinction between the dualist
philosophers, for which there are two kinds of phenom-
ena in the world, the mind and the body, and the monist
philosophers, for which the world is made of only one
substance. Although dualism can be of substance, as Des-
cartes thought it, the majority of dualist philosophers cur-
rently adopt a dualism of property which admits that the
matter can have both mental and physical properties. Like-
wise , if the monism can be an idealism (in the sense of
the philosopher Berkeley), the totality of monist philo-
sophers in the present time are materialists. Dualism of
property asserts the existence of conscious properties that
are neither identical with nor reductible to physical pro-
perties, but which may nevertheless be instantiated by the
very same things that instantiate p hysical properties. The
most radical dualism is the “psychological parallelism”,
which seeks to account for the psychophysiological cor-
relations while postulating that the mental state and the
cerebral state correspond mutually without acting one on
the other [12]. A less radical version, “the epiphenome-
nalism”, recognizes the existence of causal influences of
br a in on the mental states, but not the reverse [13]. In con-
trast to dualism, the monism claims that everything that
exists must be made of matter. A modern version of ma-
terialism is the physicalism. One type of physicalist ma-
terialism is the radical current of thought called “elimi-
nativism”, which rejects the very notion of consciousness
as muddled or wrong headed. It affirms that the mental
states are only temporary beliefs intended to be replaced
by neurobiologic models of research [14]. Another form
of physicalist materialism is the thesis of the stron g iden-
tity. It affirms the existence of an internal principle of
control (the mental principle) which is anything else only
the brain: the mental is reducible with the biological
properties, which themselves are reducible with physics.
However, the thesis most commonly adopted is that of
functionalism. The functionalism has been proposed to
answer an intriguing question: how to explain, if the the-
ory of identity is admitted, that two ind ividuals can have
different cerebral states and nevertheless to have at one
precise time exactly the same mental state? The response
of functionalists is as follows: what there is identical in
the two different cerebral occurrences from the same men-
tal state, it is the function. Whatever the physical consti-
tution of the cerebral state, several mental states are iden-
tical if their relations are causal. For the functionalists,
the mental states are thus defined by their functional role
inside the mental economy of the subject [15].
To accept traditional dualism it is agree to make a strict
distinction between the mental and the physical proper-
ties. In other words, it is to give up the unified neurosci-
entific theory which one can hope for to obtain one day.
But to accept the solutions recommended by the physi-
calist materialism is worse still, because those end up
denying the obvious fact that consciousness has internal
subjective and qualitative states. For this reason, certain
philosophers tried to solve the problem, either by adopt-
ing a mixed theory, both materialistic and dualistic, or by
denying the existence of subjective states of conscious-
ness. David Chalmers, for example, adopted the first so-
lution. Chalmers is known for his formulation of the dis-
tinction between the “easy” problem of consciousness
and the single “hard” problem [16,17]. The essential differ-
ence between the easy problem and the hard (phenomenal)
problem is that the former is at least theoretically an-
swerable via the standard strategy of functionalism. In
Copyright © 2011 SciRes. JBBS
support of this, in a thought experiment, Chalmers pro-
posed that if zombies are conceivably complete physical
duplicates of human beings, lacking only qualitative ex-
perience, then they must be logically possible and subjec-
tive personal experiences are not fully explained by physi-
cal properties alone. Instead, he argued that consciousness
is a fundamental property ontologically autonomous of
any known physical properties. Chalmers describ ed ther e-
fore the mind as having “phenomenal” and “psychologi-
cal” aspects. He proposed that mind can be explained by
a form of “naturalistic dualism”. That is, Chalmers ac-
cepted the analysis of functionalists while introducing the
concept of consciousness irreducible into his system.
According to him, since the functional organization pro-
vides the elements of mental states in their nonconscious
forms, it is necessary that consciousness is added again
to this organization.
Other philosophers, on the contrary, claimed that clos-
ing the explanatory gap and fully accounting for subject-
tive personal experiences is not merely hard but rather
impossible. This positi on was most closely associated with
tha t , for example, of Colin McGinn, Thomas Nagel [18,19]
and Daniel Dennett [20]. In particular, Dennett argued
that the concept of qualia is so confused that it cannot be
put to any use or understood in any non-contradictory way.
Having related the consciousness to properties, he then
declared that these properties are actually judgements of
properties. That is, he considered judgements of proper-
ties of consciousness to be identical to the properties
themselves. Having identified “properties” with judgeme nts
of properties, he could then show that since the judge-
ments are insubstantial, the properties are insubstantial
and thence the qualia are insubstantial. Dennett conclude d
therefore that qualia can be rejected as non-existent [20].
For Dennett, consciousness is a mystifying word because
it supposes the existen ce of a unified center of piloting of
thoughts and behaviors. For him, psychism is a hetero-
geneous unit which combines a series of mental proc-
esses that one knows little about such as perception, pro-
duction of the language, training, etc…: we allot, with the
others and ourself, some “intentions”, a “consciousness”,
because our behaviors are finalized [21,22]. In other writ-
ings, Dennett defended an original th esis on the free will
[23]. For that, he rested on evolutionary biology, on cog-
nitive sciences, on the theory of cellular au tomata and on
memetics [24,25]. Taking the opposite course to the ar-
gument of those which say that evolutionary psychology,
together with memetics, implies necessarily a world de-
prived of any possibility of choice, Dennett estimated on
the contrary that there is something of special in the hu-
man subject. According to him, the theory of evolution
supports the selective advent of avoiding agents. These
agents have the capacity to extract information of the
environment to work out strategies in order to avoid the
risks and to choose the judicious behaviors. Now, the per-
formance of this capacity is much more important for the
man than for the animal because each human individual
memorizes an important quantity of social and cultural
informations. It is therefor e ab surd to conceive a linear de-
terminism similar to that of the “demon” of Laplace. For
Dennett, the free will must rather be designed like the cha-
ot ic determinism of a vast neuromimetic network, in which
informations received in entries are combined according
to their respective weights to give completely unfore-
seeable and nonreproducible, but non random, outputs.
2.2. Difficulties in Scientifically Tackling the
Problem of Consciousness
One of difficulties in scientifically tackling the problem
raised by consciousness comes from the obvious fact that
it is the originating principle from which are generated
the categories of the interpersonal world and the subjec-
tivity of each personal world. Consciousness is not a sub-
stance but an act in itself non objectivable; it escapes an y
from representation. What consciousness has disconcert-
ing, notes Edelman, it is that it does not seem to raise of
the behavior. It is, quite simply, always there [26]. An-
other difficulty comes owing to the fact that conscious-
ness is a Janus Bifron, in the sense that it has both on-
tology with the first-person perspective and ontology with
the third-person perspective, irreducible one with the other
[27]. It has a first-person perspective because the mental
states are purely subjective interior experiences of each
moment of the life of men and animals. Principal sorts of
firs t-person data include visual, perc eptual, bodily and emo-
tional experiences, mental imagery and occurent thoughts.
But consciousness has also ontology with the third-person
perspective that concerns the behavior and the brain pr-
ocesses of conscious systems [22]. These behavioral and
neurophysiological data relevant to the third-person per-
spective provide the traditional material of interest for cog-
nitive psychology. Principal sorts of third-person data in-
clude perceptual discrimination of external stimuli, inte-
gration of information to do with the across sen sory mo-
dalities, automatic and voluntary actions, levels of access
to internally repr esented information, verbal reportability
of internal states and differences between sleep and wake-
fulness. The problem to scientifically approach the con-
sciousness phenomenon is much more complex still be-
cause the first-person experience is common for qualia
(singular ‘quale’), intentionality and self-consciousness.
In troduced by Lewis [28], the term of qualia is either used
in contemporary usage to refer to the introspectively ac-
cessible phenomenal aspects of our mental live [29], or
used in a more restricted way so that qualia are intrinsic
opyright © 2011 SciRes. JBBS
properties of experiences that are ineffable, nonphysical,
and given incorrigibly [30], or still used by some phi-
losophers such as Whitehead, which admits that qualia
are fundamental components of physical reality and de-
scribed the ultimate concrete entities in the cosmos as
being actual “occasions of experience” [31]. Experiences
with qualia are involved, for example, in seeing green,
hearing loud trumpets or tasting liquorice, bodily sensa-
tions such as feeling a twinge of pain, feeling an itch,
feeling hungry, etc… They are also involved in felt reac-
tions, passions or emotions such as feeling delight, lust,
fear or love, and felt moods such as feeling elated, de-
pressed, calm, etc… [32,33]. Intentionality and qualia ne-
cessarily coexist in the generation of conscious states,
but the aspect “qualia” may be distinguished from the as-
pect “intentionality” insofar as the perception of an object,
the evocation of a memory or an abstract thought can be
accompanied by different affective experiences (joy or
annoys, wellbeing or faintness, etc…) [34].
3. Experimental Approaches to a Science of
3.1. Neurophysiological Studies of Neural
Networks and Neuro-Mental Correlations
There are two common, but quite distinct, usages of the
term of consciousness, one revolving around arousal or
states of consciousness and another around the contents
of consciousness or conscious states. States of conscious-
ness are states of vigilance (i.e., the continuum of states
which encompasses wakefulness, sleep, coma, anesthesia,
etc) with which attention is associated. They are cyclic
and can last several hours. In contrast, conscious states
(percept, thought, memory or subjective experiences such
as qualia) are not cyclic nor reproductible and can last
only a few minutes, seconds or sometimes milliseconds.
Conscious states are situated in a spatiotemporal context.
They may refer to the past or the future but are always
experienced in the present. They introduce the conscious
representations and, more or less explicitly, global models
of self, alter-ego and world. States of consciousness and
contents of consciousness offer therefore very unequal
difficulties to the neuroscientific investigation [35-37].
3.1.1. Neurophysiological Studies of States of
Considerable progress has been made during the last de-
cade in the neurophysiology of states of consciousness. In
particular, impressive progress has been made in the neu-
rophysi olo gical i nve sti gat io n o f stat es of vi gi l a nce. N ota bly ,
the molecular mechanisms of distinct sleep/wake cycles
have been thoroughly studied [38]. The neuroanatomical
systems, the cellular and molecular mechanisms, and the
principal types of neurotransmitters involved in these me-
chanisms for the most part have been identified. In par-
ticular, an important line of research has investigate the
arousal in altered states of consciousness, for instance, in
and after epileptic seizures, after taking psychedelic drugs,
during global anesthesia or after severe traumatic brain
injury. These studies demonstrate that a plethora of nuclei
with distinct chemical signatures in the thalamus, mid-
brain and pons, must function for a subject to be in a suf-
ficient state of brain arousal to experience anything at all.
In particular, sleep/wake cycles essentially depend on ana-
tomical system which comprises structures of brainstem,
thalamic and hypothalamic nuclei, and the nucleus of
Meynert. Awak ening into the vigilan t state correlates with
a progressive increase in regional cerebral blood flow,
fi rst in the b rai nste m and th ala mus, then in th e cortex wit h
a particularly important increase in prefrontal-cingulate
activation and functional connectivity [38,39]. Anesthetic,
sleep, vegetative state and coma are all associated with
modulations of the activity of this thalamocortical network.
Although most dreams occur in paradoxical sleep, the
neurobiological mechanisms of walkefulness and para-
doxical sleep are identical at the thalamocortical level; the
only difference between the two states is at the brainstem
level. What differentiates these states is the relationship
with the environment: walkefulness brings into play motor
and sensory interactions with the external world, while
the paradoxical sleep is relatively independent of the ex-
ternal world. Thus, deaming may be considered to be an
incomplete form of consciousness, uncontrolled by the
environment, mainly reflecting internal factors [38].
3.1.2. Neurophysiologic al Studies of Contents of
Contrary to the study of consciousness states, the study
of consciousness contents raises very many problems.
Much difficulties are due to the brevity and not very re-
producible nature of subjective experiences. In addition,
the mechanisms of conscious thoughts often result from
processes at the same time conscious and unconscious
which coexist and ev en interact (the language, for exam-
ple, brings into play the unconscious use of linguistic rou-
tines). To explain the contents of consciousness of the third-
person perspective, we need actually to specify the neural
and/or behavioral mechanisms that perform the functions
[27]. The availability of behavioral data is reasonably
straightforward, because researchers have accumulated a
rich body of behavioral data relevant to consciousness.
But the body of neural data that has been obtained to date
is correspondingly more limited because of technological
limitations [33,40]. To study neural mechanisms, resear-
chers use currently a variety of neuroscientific measure-
Copyright © 2011 SciRes. JBBS
ment techniques including brain imaging via functional
magnetic resonance imaging (fMRI) and positron emis-
sion tomography (PET) technology, single-cell recording
through insertion of electrodes, and surface recording
through electroencephalography (EEG) and magnetoen-
cephalography (MEG) [27,41,42]. However, though these
approaches seem quite promising, many experimental find-
ings proved to be not univocal results and must be com-
pare and integrate with findings obtained from other ap-
p roaches . For ex a mpl e, when one se e s a fac e th ere be mu ch
activities (for example, on the retina and in the early vi-
sual cortex) that seem explanatorily redundant for the
formation of the conscious percept of the face [37]. To
specify precisely the neuronal basis of such a conscious
perception, psychologists have perfected a num ber of tech-
niques (masking, binocular rivalry, continuous flash sup-
pression, motion-induced blindness, ch ange blindness, inat -
te ntional blindness) [43]. In this design, one keep s as many
things as possible constant, including the stimuli, while
varying the conscious percept, so that changes in neural
activation reflect changes in the conscious percept rather
than changes in the stimuli. For instance, a stimulus can
be perceptually suppressed for seconds of time: the image
is projected into one of the observer’s eyes but is invisi-
ble, not seen. In this manner, the neural mechanisms that
respond to the subjective percep t rather than th e physical
stimulus can be isolated, permitting the footprints of visual
consciousness to be tracked in the brain. In some per-
ceptual illusion experiments, on the contrary, the physical
stimulus remains fixed while the percept fluctuates. A
good example is the Necker cube whose 12 lines can be
perceived in one of tw o di fferent ways in dept h.
Contrarily to techniques used for studying the third-
person experiences, methodologies for investigating first-
person experiences (in particular qualia) are relatively
thin on the ground, and formalisms for expressing them
are even thinner. The most obvious obstacle to the gath-
ering of first-person data concerns the privacy of such
data. Indeed, first-person data are directly available only
to the subject having these experiences. To others, these
first-person data are only indirectly available, mediated
by observation of the subject’s behavior or brain proc-
esses. In practice, the most common way of gathering
data about the conscious experiences of other subjects is
to rely on their verbal reports. However, verbal reports
have some limits. Some aspects of conscious experience
(e.g. the experience of emotion) are very difficult to de-
scribe. Moreover, verbal reports cannot be used at all in
subjects without language, such as infants and animals.
In these cases, one needs to rely on other behavior indi-
cators. For example, if an individual presses one of two
buttons depending on which of two ways the creature
perceives a Necker cube at a time, this button pressing is
a source of first-person data. A second obstacle is posed
by the absence of general formalisms with which first-
person data can be expressed. Reseachers typically rely
either on simple qualitative characterizations of data or
on simple parameterization of ones. These formalisms suf-
fice for some purposes, but they are unlikely to suffice
for the formulation of systematic theories [27,33].
3.1.3. Appro a c hes to Res earch Animal C o nsc i ousness
There is now abundant and increasing behavioral and
neurophysiological evidence consistent with, and even
suggestive of, conscious states in some animals. This is
due to the fact that human studies involving the correla-
tion of accurate reports with neural correlates can pro-
vide a valuable benchmark for assessing evidence from
studies of animal behavior and neurophysiology of some
animals [44]. Relevant forms of report included analysis
of responses to binocular rivalry in the case of primates,
vocalization in the case of birds such as african grey parrots,
and coloration and body patterning in the case of cepha-
lopods such as Octopus vulgaris. Rhesus macaque mon-
keys, for example, were trained to press a lever to report
perceived stimuli in a binocular rivalry paradigm. The
results from these studies were consistent with evidence
from humans subjected to binocular rivalry and magne-
toencephalography. They suggested that consciousness of
an object in monkeys involves widespread coherent syn-
chronous cortical activity. Likewise, similarities have been
found among the functional circuitry underlying the or-
ganization and sequencing of motor behaviors related to
vocalization in birds and mammals capable of vocal learn-
ing. Much of the neural basis for song learning in some
birds was found to reside in an anterior forebrain path-
way involving the basal ganglia, in particular a striatal
neuronal area ressemblin g that presen t in the mammalian
striatum. These homologies were strongly suggestive of
neural dynamics that support consciousness in birds. The
case of cephalopod mollusks is much less clear. Indeed,
cephalopod such as Octopus possesses a large population
of sensory receptors (they communicate with a nervous
system containing between 170 and 500 million cells)
and numerous nucleus-like lobes in its brain. Its optic
lobe, containing as many as 65 million neurons, plays a
critical role in higher motor control and establishment of
memory. Moreover, a number of other lobes appear to be
functionally equivalent to vertebrate forebrain structures,
though their organization bears little resemblance to the
laminar sheets of mammalian cortex. Recently, laboratory
tests and observations in a natural environment showed
that Octopus is heavily dependent on learning, and even
might form simple concepts. This strongly suggested that
cephalopod mollusks have a certain form of primary con-
sci o usness [45].
opyright © 2011 SciRes. JBBS
3.2. Approaches to Build Artificial
Intelligence Systems
Artificial Intelligence has not been sparing of metaphors
concerning the functioning of the human mind [46]. In
1950, Alan Turing tackled the problem of computation-
alism by proposing its famous test to establish whether
one can consider a machine as intell igen t as a hu man [47] .
So far, however, no computer has given responses totally
indistinguishable from the human responses. It appears
that this computational cognitivism is limited insofar as
it is founded on the formal character of calculation (in
this case, to think is equivalent to pro cess data, i.e. to cal-
culate, to handle symbols). This neuroscientific ap proach
is not very different from that where computer simula-
tions and mathematical models are used to study systems
such as stomachs, planetary movements, tornadoes, and
so on. In contrast, connectionism equates thinking with
the operation of a network of neurons and argues that
every cognitive operation is the result of countless inter-
connected units interacting among themselves, with no
central control. The connexionnist networks are in general
adaptive and allow the study of mechanisms of training
[48,49]. Such an approach is based on the view that the
nervous system itself computes [50]. In this topic, new
research has particularly developed that consists in mak-
ing work equations put in darwinian competition thanks
to evolutionary algorithms inspired by the modeling of
certain natural systems (for example, the competition be-
tween the social insects in the construction of the nest)
[51-53]. These systems, which are generic population-
based metaheuristic optimization algorithms, are able to
solve problems using some mechanisms inspired by the
biological evolution such as the reproduction, mutation,
recombination and selection. The principle on which they
are founded consists in initializing a population of indi-
viduals in a way dependent on the problem to be solved
(environment), then to make move this population of ge-
neration in generation using operators of selection, re-
combination and change. Actually, a number of cyber-
neticians try to approach this difficult problem with sys-
tems multi-agents (SMA), or “Massively Multi-Agents”
[54-60]. An agent-based model is a class of computa-
tional models for simulating the actions and interactions
of autonomous agents (both individuals or collective en-
tities such as organizations or groups) with the view to
assessing their effects on the system as a whole. This model
simulates the simultaneous operation s and interactions of
multiple agents located in an environment made up of
objects which are not agents and nonlikely of evolution,
in an attempt to re-create and predict the appearance of
complex phenomena. The agents can thus substitute for
the programmer and even produce unexpected results. In
this vein of approaches, a novel area of great interest is
the construction of robotic organisms. One essential pro-
perty of neurorobots is that, like living organisms, they
must organize the unlabeled signals they receive from the
environment into categories. This organization of signals,
which in general depends on a combination of sensory
modalities (e.g. vision, sound, taste, or touch), is a percep-
tual categorization, as in living organisms, makes object
recognition possible based on experience but without a
priori knowledge or instruction. Like the brain, neuroro-
bots op erate according to selectio nal principles: they fo rm
categorical memory, associate categories with innate
values, and adapt to the environment [61].
An important problem arises however with these new
perspectives of research: any constructive and exhaustive
approach of artificial consciousness must define a system
which has access, as the human primary consciousness,
within the meaning of its own knowledge. To inv estigate
this question, as Owen Holland said it, the system must
be able simultaneously to produce an intentional repre-
sentation and the perception in its own organization of
this intentionally generated form; it must be self-aware
[62]. A question then becomes: when will a machine be-
come self-aware? Although an answer to this question is
hazardous, one can determine at least a plausible neces-
sary precondition without which a machine could not de-
velop self-awareness. Th is precondition derives from the
assertion that, to develop self-awareness, a neural netwo rk
must be at least as complex as the human brain. Recently,
an enormous project (Human Brain Project) was given
for objective, believing this could be achievable in as
little as 10 years time, to succeed in simulating the func-
tioning of the neocortex of mammals by means of the
fastest supercomputer architectu re in th e world, th e IBM ’ s
Blue Gene platform [63]. For the moment, one modelled
a single cortical column consisting of approximately 60,000
neurons and 5 km of interconnecting synapses, chosen
from about 15,000 experiments carried out in laboratory.
This Blue Brain project requires to reproduce in the fu-
ture the equivalent of the million functional units that
holds the neocortex. It should be however noted that this
project refers only to a necessary but not sufficient con-
dition for the development of an artificial consciousn ess.
Even if the machine becomes as skilled as humans in
many disciplines, one cannot assume that it has become
selfaware. The existence of a powerful computer equipped
with millions of gigabytes is not in itself sufficient to
guarantee that the machine will be a self-awareness intel-
ligence. Moreover, it remains to define the criteria which
will make possible to recognize that an artificial entity
has a conscious state. Indeed, the problem is not to know
if a machine suffers, but if it behaves “as if” it suffered
Copyright © 2011 SciRes. JBBS
4. Explanatory Theories of Consciousness
Explanatory theories of consciousness should be distin-
guished from the experimental approaches to phenomena
of consciousnesss. While the ide ntif ication of correlation s
b etween aspects of brain activ ity and aspects of conscio us -
ness may constrain the specification of neurobiologically
plausible models, such correlations do not by themselves
provide explanatory links between neural activity and con-
sciousness. Models of consciousness are valuable preci-
sely to the extent that they propose such explanatory links.
To days, one can arbitrarily classify the various approache s
to modeling consciousness into two categories: the theo-
ries making correspond certain functional modes of the
brain to the conscious activity, and the theories binding
the structure of neural networks to conscious activity .
4.1. Theories Making Correspond Certain
Modes of the Brain to the Conscious Activity
In this category, one finds mainly the phenomenological
approaches of Francisco Varela and Humberto Maturana,
the physics-based hypothesis of Stuart Hameroff and Ro-
ger Penrose, and the neurodynamical model of Walter J.
Model of Varela and Maturana. Varella, and his men-
tor Humberto Maturana, developed a model based on the
notion of autopoiesis [66-70]. Based on cellular life,
autopoiesis attempts to define, beyond the div ersity of all
living organisms, a common denominator that allows for
the discrimination of the living from the non-living. In-
side the boundary of a cell, many reactions and many
chemical transformations occur but, despite all these pro-
cesses, the cell always remains itself and maintains its own
identity. The con sequence is that the interaction between
a living autopoietic unit and a component of its environ-
ment is only dictated by the way in which this compo-
nent is ‘seen’ by the living unit. To characterize this very
particular nature of interaction, Maturana and Varela used
the term of “cognition”. In their theory, the environment
has its own structural dynamics but it does not de termine
the changes in organism. Although it can induce a reac-
tion in the organism, the accepted changes are determined
by the internal structure of the organism itself. The con-
sequence is that the environment bring s to life the organ-
ism and the organism creates the environment with its
own perceptory sensorium. It should be emphasize that
this thinking is clo se to certain european philosophies, in
particular to that of Merleau-Ponty [71]. To express this
proce ss of mu tua l cal ling in to ex ist ence, this co -eme rgence ,
this equivalence between life and cognition, Varela and
Maturana used the word of “enaction”. For Varela, the
mind as a phenomenology in action, viewed from either
the first- or the third-person perspective, can only be de-
scribed as a behavior literally situated in a specific cycle
of operation [72]. For him, the mind is not in the head, it
is in a non-place of the co-determination of inner and
outer [73]. There is no separation between the cognitive
act and the organic structure of life, they are one ; the
traditional cartesian division between matter and mind
disappears at the level of human cognition at which the
notion of consciousness appears. To signify that human
consciousness has its counterpart in the organic structure,
that there is no consciousness outside the reality of bod-
ily experience, Varela used the term of “embodiment”
[74]. We are therefore global dynamic processes, in dy-
namical equilibrium, emerging and acting from interac-
tions of constituents and interactions of interactions. In
this thesis, the brain level is o nly considered to contribute
to properties of conscious experiences. At the phenome-
nal level, the constitution of conscious moments implies
a high temporal integration of multiple contents emerging
in a transitory way. According to Varela, because of its
biophysical organization (its organizational closure), the
brain belongs to multistable dynamical systems, in which
eigenbehaviors are constrained by a landscape of multiple
non-stable attractors. There are however some methodo-
logical problem s in this theory. The fi rst is the ol d problem
that the mere act of attention to one’s experience trans-
forms that experience. This is not too much of a problem
at the start of investigation, because one has a long way
to go until this degree of subtlety even comes into play,
but it may eventually lead to deep paradoxes of obser-
vership. The second problem is that of developing a lan-
guage or a formalism in which phenomenological data
can be expressed. Indeed, the notorious ineffability of con-
scious experience plays a role here, because the language
one has for describing experiences is largely derivative
on the language one has for describing the external world.
The third difficulty lies in the failure, or at least the limi-
tations, of incorrigibility: judgments could be wrong.
Model of Hameroff and Penrose. For Stuart Hamer-
off and Roger Penrose, neurons belong to world of tradi-
tio nal physics, are calculable and cannot explain as a such
consciousness. They propo sed th erefor e a new physics of
objective reduction which appeals to a form of quantum
gravity to provide an useful description of fundamental
processes at the quantum/classical borderline [75-78].
Within this scheme, consciousness occurs if an appropri-
ately organized system is able to develop and maintain
quantum coherent superposition until a specific “objective”
criterion (a threshold related to quantum gravity) is rea-
ched; the coherent system then self-reduces (objective
reduction). This type of objective self-collapse introdu ces
non-computability, an essential feature of consciousness
which distinguishes our mind from classical computers.
opyright © 2011 SciRes. JBBS
Objective reduction is taken as an instantaneous event
(the climax of a self-organizing process in fundamental
sp ace-time) [31]. In this model, quantum-superposed states
develop in microtubules subunit proteins (tubulins) within
the brain neurons. They recruit more superposed tubulins
until a mass-time-energy threshold (related to quantum
gravity) is reached. At this point, self-collapse, or objec-
tive reduction, abruptly occurs. One equares the pre-re-
duction, coherent superposition phase with pre-conscious
processes, and each instantaneous (and non-computable)
objective reduction, or self-collap se, with a discrete con-
scious event. Sequences of objective reduction give rise
to a “stream” of consciousness. Microtubule-associated-
proteins can “tune” the quantum oscillations of the co-
herent superposed states. The objective reduction is thus
self-organized, or “orchestrated”. Each orchestrated ob-
jective reduction event selects (non-computably) micro-
tubule subunit states which regulate synaptic/neural func-
tions using classical signaling. The quantum gravity thre-
shold for self-collapse is relevant to consciousness be-
cause macroscopic superposed quantum states each have
their own superposed space-time geometries. However,
when these geometries are sufficiently separated, their
superposition becomes significantly unstable and reduce
to a single universe state. Quantum gravity determines
thus non-computably th e limits of the instability. In sum,
each orchestrated objective reduction event is a self-se-
lectio n of spac e- ti me geometry coupled to t he br ain th rough
microtubules and other molecules. This orchestrated ob-
jective reduction provides us with a completely new and
uniquely promising perspective on the hard problem of
consciousness [77,78]. The model of Hameroff and Pen-
rose has received serious criticism, notably from certains
philosophers such as Rick Grush and Patricia Churchland
[79]. These authors pointed out that microtubules are
found in all plant and animal cells, and not only in brain
neurons. They also stated that some chemicals that are
known to destroy microtubules do not seem to have any
effects on consciousness and that, conversely, anaesthet-
ics act without affecting the microtubules. Another ob-
jection addresses one of the strengths of Penrose and
Hameroff’s model, which is, according to its authors, that
it can account for the unity of consciousness. Indeed, if
th is impression of human consciousne ss unity should prov e
to be an illusion, then explanation s based on non-locality
and quantum coherence would become irrelevant.
Model of Freeman. The work of Walter J. Freeman
was based mainly on electrophysiological recording of
the olfactory system of awake and behaving rabbits [80-84].
Freeman found that the central code for olfaction is spa-
tial. Although this had been predicted by others on the
basis of studies in the hedgehog, certain aspects of his
results were surprising. For example, Freeman showed
that the information is uniformly distributed over the
entire olfactory bulb for every odorant. By inference every
neuron participates in every discrimination, even if and
perhaps especially if it does not fire, because a spatial
pattern requires both black and white. He discovered that
the bulbar information does not relate to the stimulus
directly but instead to the meaning of the stimulus. This
means that the brain does not process information in the
commonly used sense of the word. When one scans a
photograph or an abstract, one takes in its import, not its
number of pixels or bits. The brain processes meaning as
in this example. He also found that the carrier wave is
aperiodic: it does not show oscillations at single frequen-
cies, but instead has wave forms that are erratic and un-
predictable, irrespective of odorant condition. In the the-
ory of Freeman, the chaotic activity distributed among
the neuronal populations is th e carrier of a spatial pattern
of amplitude modulation that can be described by the
local heights of the recorded waveform. When an input
reaches the mixed population, an increase in the nonlin-
ear feedback gain will produce a giv en amplitude-modu-
lat ion pattern. The emergence of this pattern is considered
to be the first step in perception: meaning is embodied in
these amplitude-modulation patterns of neural activity,
whose structure is dependent on synaptic changes due to
previous experience. Through the divergence and con-
vergence of neural activity onto the entorhinal cortex, the
pulse p atterns coming from the bulb are smoothed, ther eb y
enhancing the macroscopic amplitude-modulation pat-
tern, while attenuating the sensory-driven microscopic
activity. Thus, what the cortex “sees” is a construction
made by the bulb, not a mapping of the stimulus. Hence,
perception is an essential active process, closer to hy-
pothesis testing than to passive recovery of incoming
information. The stimulus then confirms or disconfirms
the hypothesis, through state transition s that generate the
amplitude-modulation patterns. Fin ally, through multiple
feedback loops, global amplitude-modulation patterns of
chaotic activity emerge throughout th e entire hemisphere
directing its subsequent activity. These loops comprise
feedforward flow from the sensory systems to the en-
torhinal cortex and the motor systems, and feedback flow
from the motor systems to the entorhinal cortex and from
the entorhinal cortex to the sensory systems. Such global
brain states emerge, persist for a small fraction of a sec-
ond, then disappear and are replaced by other states. It is
this level of emergent and global cooperative activity
that is crucial for consciousness. Freeman tackled also
the enigmatic problem of the nature of the free will. He
proposed that the man, entirely engaged in a project and
in permanent relation with the other men and the world,
takes his decisions in real time by implying all his body.
The perceived will as conscious is informed only with a
Copyright © 2011 SciRes. JBBS
light delay. Not deciding a behavior in progress, it only
takes action to modulate the various aspects of the vol-
untary decision an d to legitimate it taking into con sidera-
tion whole of significances which constitute the subject.
There are however some problems in this interesting
Freeman’s account [85]. The mechanisms of origine and
the control of gamma oscillations are not yet entirely
clear. As predicted by Freeman, during gamma oscilla-
tions an average lead/lag relation exists between local
excitatory and inhibitory cells. Now, recent analyses of
the cellular dynamics concluded that recurrent inhibition
from fast spiking inhibitory cells is largely responsible
for maintaining the rhythmic drive, but the role played
by excitatory processes in modulating or driving the os-
cillations remains undetermined. Since cortical networks
form a dilute and massively interconnected network, a
satisfactory explanation for gamma activity should ex-
plain the on set and offset of ga mma activity in relation to
events at more distant sites and at larger scale in the
brain. Without clarification of these mechanisms it re-
mains difficult to define the link of gamma activity to
storage, retrieval and transmission of information, and
between thermodynamic and cognitive or informational
4.2. Theories Binding the Structure of Neural
Pathways to Conscious Activity
In this second category of models, a first strategy consists
in being focused on the visual system. This approach has
been mainly studied by Viktor Lamme, Semir Zeki, David
Milner and Melvyn Goodale. A second stategy, based on
a more global neurophysiological approach, has been
mainly developed by Ned Block, by Francis Crick and
Christof Koch, and by Rodolfo Llinas, Antonio Damasio,
Jean-Pierre Changeux and Gerald Edelman. In spite of
some “overwhelming commonalities” among these theo-
ries, as Chalmers said it [17], nearly all of them have
given a major role to interactions between the thalamus
and the cortex.
4.2.1. First Str ate g y F ocusing on the Visual System
Model of Lamme. The Local Recurrence theory of Vik-
tor Lamme distinguished between three hierarchical types
of neural processes related to consciousness [86-88]. The
first stage involves a “feedforward sweep” during which
the information is fed forward from striate visual regions
(i.e., V1) toward extrastriate areas as well as parietal and
temporal cortices, without being accompanied by any
conscious experience of the visual input. The second
stage involves the “localized recurrent processing” dur-
ing which the information is fed back to the early visual
cortex. It is this recurrent interaction between early and
higher visual areas which leads to v isual experien ce. Th e
third and final stages consist of “widespread recurrent
processing” which involves global interactions (as in the
global workspace of Changeux) and extends toward the
executive (i.e., the frontoparietal network) and language
areas. This final step also involves the attentional, execu-
tive, and linguistic processes that are necessary for con-
scious access and reportability of the stimulus. An inter-
esting aspect of this theory is that it offers an explanation
for the difference between conscious and unconscious
perception in mechanistic rather in architectural terms.
Another interesting aspect of this theory, although pro-
vocative, is that consciousness should not be defined by
behavioral indexes such as the introspective reports of
the subject. Instead, on e should rely on neural ind exes of
consciousness, one of which is neural recurrence. Indeed,
Lamme is concerned with the question of defining phe-
nomenological consciousness when a report is impossible.
However, one main difficulty with this theory is that it
fails to take into account the recurrent connections that
exist between regions that are not associated with con-
sciousness (for instance between the area V1 and the tha-
lamus). Although it remains possible that consciousness
involves local recurrence between some cerebral com-
ponents, this processus cannot then be considered as a
sufficient condition for consciousness since it requires
the involvement of additional mechanisms for explaining
why it only applies to a restricted set of brain regions.
Model of Zeki. In the microconsciousness theory of
Semir Zeki, it is assumed that instead of a single con-
sciousness, there are multiple consciousness that are dis-
tributed in time and space [89,90]. This theory reflects
the large functional specialization of the visual cortex.
For example, while the perception of colors is associated
with neural activity in area V4, motion perception re-
flects neural activity in MT/V 5. Zeki took these findings
as evidence that consciousness is not a unitary and sin-
gular phenomenon, but rather that it involves multiple
consciousness that are distributed across processing sites,
which are independent from each other. Another evi-
dence in favor of this hypothesis is that the conscious
perception of different attributes is not synchronous and
can respect a temporal hierarchy. For example, psycho-
physical measures have shown that color is perceived a
few tens of milliseconds before motion, reflecting the
fact that neural activity during perception reaches V4
before reaching MT/V5. One main difficulty with this
theory is that any processing region in the brain should,
at first glance, constitute a neural correlates of conscious-
ness in the multiple-consciousness theory. As such, it
remains unclear why conscious perception is not associ-
ated with activity in most brain regions, including the
cerebellum and subcortical regions, especially those con-
opyright © 2011 SciRes. JBBS
veying visual signals (e.g., the lateral geniculate nucleus).
Another difficulty for this hypothesis is that visual re-
gions can lead to the binding of several attributes in the
absence of consciousness. This has been shown, for in-
stance, in a patient with a bilateral parietal damage, sug-
gesting that the binding mechanisms that are supposed to
lead to microconsciousness can in fact operate in the
absence of con sci ousness.
Model of Milner and Goodale. The duplex vision
theory proposed by David Milner and Melvyn Goodale
postulates that visual perception involves two intercon-
nected, but distinctive pathways in the visual cortex, na-
mely, the dorsal and the ventral stream [91,92]. After
being conveyed along retinal and subcortical (i.e., geni-
culate) structures, visual information reaches V1 and
then involves two streams. The ventral stream projects
toward the inferior part of the temporal cortex and serves
to construct a conscious perceptual representation of ob-
jects, whereas the dorsal stream projects toward the pos-
terior parietal cortex and mediates the control of actions
directed at those objects. The two streams also differ at
the computational and functional levels. On the on e side,
the ventral stream conveys information about the endur-
ing (i.e., long-lasting) characteristics that will be used to
identify the objects correctly, and subsequently to link
them to a meaning and classify them in relation to other
elements of the visual scene. On the other side, the dorsal
stream can be regarded as a fast and online visuomotor
system dealing with the moment-to-moment information
available to the system, which will be used to perform
actions in real time. Recent evidence with visual masking
has revealed unconscious neural activity in ventral re-
gions, including the fusiform face area. This type of evi-
dence is problematic for the duplex vision hypothesis
since it predicts that conscious perceptions should be
proportional to neural activity in the ventral system. Such
a possibility of unconscious ventral processing can be
nevertheless accommodated by assuming a threshold me-
chanism, as proposed in the model of Zeki [90]. How-
ever, including this threshold leads the theory to lose it
former appeal, since consciousness is “only partially cor-
related” with activity in the ventral system.
4.2.2. Second Strategy Based on a Gl obal
Neurophysiological Approach
Model of Block. One of the most influential issue in
recent years has been the potential distinction between
phenomenal and access consciousness proposed by Ned
Block [93-95]. According to Block: “phenomenal con-
sciousness is experience; the phenomenally conscious
aspect of a state is what it is like to be in that state. The
mark of access-consciousness, by contrast, is availability
for use in reasoning and rationally guiding speech and
action”. In short, phenomenal consciousness results from
sensory experiences such as hearing, smelling, tasting,
and having pains. Block grouped together as phenomenal
consciousness the experiences such as sensations, feel-
ings, perceptions, thoughts, wants and emotions, whereas
he excluded anything having to do with cognition, inten-
tionality, or with properties definable in a computer pro-
gram. In contrast, access consciousness is available for
use in reasoning and for direct conscious control of ac-
tion and speech. Access consciousness must be “repre-
sentational” because only representational content can fi-
gure in reasoning. Examples of access consciousness are
thoughts, beliefs, and desires. A point of controversy for
this attempt to divide consciousness into phenomenal and
access consciousness is that some people view the mind
as resulting from fundamentally computational processes.
This view of mind implies that all of consciousness is
definable in a computer program. In fact, Block felt that
phenomenal consciousness and access consciousness nor-
mally interact, but it is possible to have access conscious-
ness without phenomenal consciousness. In particular,
Block believed that zombies are possible and a robot
could exist that is “computation ally id en tical to a person”
while having no phenomenal consciousness. Similarly,
Block felt that one can have an animal with phenomenal
consciousness but no access consciousness. If the dis-
tinction of Block between phenomenal and access con-
sciousness is correct, then it has important implications
for attempts by neuroscientifists to identify the neural
correlates of consciousness and for attempts by computer
scientis ts to produce artificial con sciousness in man-mad e
devices such as robots. In particular, Block suggested that
non-computational mechanisms for producing the sub-
jective experiences of phenomenal consciousness must
be found in order to account for the richness of human
consciousnesss, or for there to be a way to rationally en-
dow man-made machines with a similarly rich scope of
personal experiences of “what it is lik e to be in co nscious
states”. However, many advocates of the idea that there
is a fundamentally computational basis of mind felt that
the phenomenal aspects of consciousness do not lie out-
side of the bounds of what can be accomplished by com-
putation. Indeed, some of the conflict over the importance
of the distinction between phenomenal consciousness
and access consciousness centers on just what is meant
by terms such as “computation”, “program” and “algo-
rithm”, because one cannot know if it is within the power
of “computation”, “program” or “algorithm” to produce
human-like consciousness.
Model of Llinas. Rodolfo Llinas proposed a model in
which the notion of emergent collective activity plays a
central role [96-98]. He suggested that the brain is essen-
tially a closed system capable of self-generated activity
Copyright © 2011 SciRes. JBBS
based on the intrinsic electrical properties of its compo-
nent neurons and their connectivity. For Llinas, con-
sciousness arises from the ongoing dialogue between the
cortex and the thalamus. The hypothesis that the brain is
a closed system followed from the observation that the
thalamus input from the cortex is larger than that from
the peripheral sensory system, suggesting that thalamo-
cortical iterative recurrent activity is the basis for con-
sciousness. A crucial feature of this proposal was the pre-
cise temporal relations established by neurons in the cor-
tico-thalamic loop. This temporal mapping was viewed
as a functional geometry, and involved oscillatory activity
at different scales, ranging from individual neurons to the
cortical mantle. Oscillations that traverse the cortex in a
highly spatially structured manner were therefore con-
sidered as candidates for the production of a temporal
conjunction of rhythmic activity over large ensemble of
neurons. Such gamma oscillations were believed to be
sustained by a thalamo-cortical resonant circuit involving
pyramidal neurons in layer IV of the neocortex, relay-
thalamic neurons, and reticular-nucleus neurons. In this
context, functional states such as wakefulness or sleep
and other sleep stages are prominent examples of the
breadth of variation that self-generated brain activ ity will
yield. Since no gross morphological changes occur in the
brain between wakefulness and dreamless sleep, the dif-
ference must be functional. Llimas proposed therefore
that conscious processes of changes observed in the cy-
cle sleep/dream/awakening rest on pairs of coupled os-
cillators, each pair connecting thalamus and the cortical
region. He suggested also that temporal binding is gener-
ated by the conjunction of a specific circuit involving
specific sensory and motor nuclei projecting to layer IV
and the feedback via the reticular nucleus, and a non-
specific circuit involving non- specific in trala minar nuclei
projecting to the most superficial layer of the cortex and
collaterals to the reticular and non-specific thalamic nu-
clei. Thus, the specific system was supposed to supply
the content that relates to the external world, and the non-
specific system was supposed to give rise to the temporal
conjunction or the context. Together, they were consid-
ered as generating a single cognitive experience.
Model of Crick and Koch. In their framework, Fran-
cis Crick and Christof Koch tried to find the neural cor-
relates of consciousness and suggested the existence of
dynamic coalitions of neurons, in the form of neural as-
semblies whose sustained activity embodies the contents
of consciousness [99-101]. By cortex they meant the re-
gions closely associated with it, such as the thalamus and
the claustrum. Crick and Koch began their theory with
the notion of an “unconscious homunculus”, which is a
system consisting of frontal regions of the brain “looking
at the back, mostly sensory region”. They proposed that
we are not consciou s of our thoug hts, bu t only of sen sory
representations of them in imagination. The brain presents
multiple rapid, transient, stereotyped and unconscious
processing modules that act as “zombie” modes. This is
in contrast to the conscious mode, that deals more slowly
with broader, less stereotyped thoughts and respons es. In
this model, the cortex acts by forming temporary coali-
tions of neurons which support each other activity. The
coalitions compete among each other, and the winning
coalition represents what we are conscious of. These coa-
litions can vary in how widespread they are over the
brain, and in how vivid and sustained they are. Moreover,
more than one coalition can win at a given time. Espe-
cially, there might be different coalitions in the back and
in the front of the cortex, where the coalitions in th e fro nt
represent feelings such as happiness. An important point
in this model is that consciousness may arise from cer-
tain oscillations in the cerebral cortex, which become
synchronized as neurons fire 40 times per second. Crick
and Koch believed the phenomenon might explain how
different attributes of a single perceived object (its color
and shape, for example), which are processed in different
parts of the brain, are merged into a coherent whole. In
this hypothesis, two pieces of information become bound
together precisely when they are represented by synchro-
nized neural firing. However, the extent and importance
of this synchronized firing in the cortex is controversial.
In particular, it remains a mystery: why should synchro-
nized oscillations give rise to a v isual experience, no ma tt er
how much integration is taking place? It should be added
tha t, in this model, the neurons that are a part of the neural
correlate of consciousness will influence many other neu-
rons outside this correlate. These are called the penumbra,
which exists of synaptic changes and firing rates. It also
includes past associations, expected consequences of mo-
vements, and so on. It is by definition not conscious, but
it might become so. Also, the penumbra might be the site
of unconscious priming.
Model of Damasio. Antonio Damasio explored mainly
the complexity of the human brain taking into con sidera-
tion emotion, feeling, language and memory. According
to him, the more important concepts are emotion, feeling,
and feeling a feeling for the core consciousness [102,103].
The substrate for the representation of an emotional state
is a collection of neural dispositions in the brain which
are activated as a reaction on a certain stimulus. Once
this occurs, it entails modification of both the body state
and the brain state. This process starts as soon as the or-
ganism perceives, in the form of simple or complex sen-
sory messages, proprioceptive or behavioral indicators
meaning the danger or, on the contrary, the welfare. For
Damasio, the emergence of feeling is based on the cen-
tral role played by the proto-self that provides a map of
opyright © 2011 SciRes. JBBS
the state of the body [102]. The neuronal patterns which
constitute the substrate of feeling arise in two classes of
changes: changes related to body state, and changes re-
lated to cognitive state. Thus, a feeling emerges when the
collection of neural patterns contributing to the emotion
leads to mental images. The feelings correspond to the
perception of a certain state of the body to which the
perception of the corresponding state of mind is added,
i.e. thoughts that the brain generates taking into account
what it perceives of the state of the body. The notion of
feeling is based on the organism detecting that the repre-
sentation of its own body state has been changed by the
occurence of a certain object [102]. Consciousness is
thus built on the ba sis of emotions transformed into feel-
ings and feeling a feeling ; it mobilizes and gathers con-
stantly, in a workspace, a certain number of informations
necessary to strategies of survival and decision making.
In this theory, consciousness is defined explicitly as a
state of mind in which there is knowledge of one’s own
existence and of the existence of surroundings. Accord-
ing to Damasio, the emotions generate three types of
levels of consciousness during the darwinian evolution:
pr otoself, core self, and oneself-autobiographical [102,104 ].
The protoself is the oneself most primitive and most wi-
despread within the alive species. It is constituted by
special kinds of mental images of the body produced in
body-mapping structures, below the level of the cerebral
cortex. It results from the coherent but temporary inter-
connections of variou s cerebral charts of reentries of sig-
nals that represent the state of the organism at a given time.
The protoself is an integrated collection of separate neu-
ral p atte rns t hat ma p mo me nt b y moment, t h e most s t a ble
aspects of the organism’s physical structure. The first
product of the protoself is primordial feelings. Whenever
one is awake there has to be some form of feeling. On a
higher level, the second form of the self, the core self, is
about action. Damasio said that the core self unfold s in a
sequence of images that described an object engaging the
protoself and modifying that protoself, including its pri-
mordial feelings. These images are now conscious be-
cause they have encountered the self. On a still higher
level there is the autobiographical self, constituted in
large part by memories of facts and events about the self
and about its social setting. It develops during social in-
teractions to form what Damasio called “the wide con-
sciousness”. That is, the protoself and the core self con-
stitute a “material me” whereas the autobiographical self
co nstitut es a “s ocial me”. Our sense of p erson an d iden tity
is therefore in the autobiographical self.
All emotions engage structures related to the repre-
sentation and/or regulation of organism state as, for ex-
ample, the insular cortex, the secondary somatosensory
cortex, the cingulated cortex, and nuclei in brainstem
tegmentum and hypothalamus [105]. These regions share
a major feature in that they are all direct and indirect
recipients of signals from the internal milieu, viscera and
musculoskeletal frame. Damasio considered that no man
can make decisions that are independent of the state of
his body and his emotions. The influences that he un-
dergoes are so numerous, that the assumption of a linear
determinism which would determine him is not defend-
able. Till now, most theories had addressed emotion as a
consequence of a decision rather than as the reaction
arising directly from the decision itself. On the contrary,
Damasio proposed that individuals make judgements not
only by assessing the severity of outcomes and their
probability of occurrence, but also primarily in terms of
their emotional quality [106]. The key idea of Damasio
was that decision making is a process that is influenced
by signals that arise in bioregulatory processes, including
those that express themselves in emotions and feelings.
Decision making is not mediated by the orbito-frontal
cortex alone, but arises from large-scale systems that
include cortical and subcortical components. Like Den-
nett and Freeman, therefore, Damasio asserted that the
individuals are under the influence of a chaotic causality
of processes imprédictibles, indescribable, nonreproduci-
ble, but not random. Two main criticisms have been made
about this theory [107]. First, Damasio tried to give an
account of the mind as a set of unconscious mapping
activities of the brain, and this did not presuppose, or at
least it did not obviously presu ppose, that these activities
are conscious. But it is hard to understand any of these
divisions of the self, protoself, core self and autobio-
graphical self without supposing that they are already
conscious. Second, Damasio stumbled over dreaming.
Although phenomenal consciousness can be very vivid in
dreams even when the rational processes of self-cons-
ci ousness are much diminished, Damasio described dreams
as mind processes unassisted by consciousness. He claime d
that wakefulness is a necessary condition for conscious-
ness. He described dreaming as paradoxical since, ac-
cording to him, the mental processes in dreaming are not
guided by a regular, properly functioning self of the kind
we deploy when we reflect and deliberate. However,
contrary to this point of view, it should be noted that
dreaming is paradoxical only if one adopts a model of
phenomenal consciousness based on self-consciousness
(on knowledge, rationality, reflection and wakefulness).
Model of Changeux. The model of Changeux, devel-
oped with Stanislas Dehaene and collaborator s [108,109],
is founded on the idea that cerebral plasticity is mainly
assured by a vast unit of interconnected neurons based on
the model of “global workspace”, historically related to
Baar’s cognitive model propo sed in the 1980s [110]. Re-
call that the global workspace model of Baar is a process
Copyright © 2011 SciRes. JBBS
which implies a pooling of information in a complex
system of neural circuits, in order to solve problems that
none of circuits could solve alone. This theory makes
possible to explain how the consciousness is able to mo-
bilize many unconscious processes, autonomous and lo-
calised in various cerebral regions (sensory, perceptuals,
or imply in attention, evaluation, etc…), in order to treat
them in a flexible and adjusted way [111]. Based on this
workspace theory, Changeux proposed that neurons dis-
tributed with long-distance connections are capable of
interconnecting multiple specialized processors. He also
proposed that, when presented with a stimulus at thresh-
old, workspace neurons can broadcast signals at the brain
scale in an all-or-none manner, either highly activated or
totally inactivated [108,112-114]. Workspace neurons thus
allow many different processors to exchange information
in a global and flexible manner. These neurons are as-
sumed to be the targets of two different types of neuro-
modulatory inputs. First, they display a constantly fluc-
tuating spontaneous activity, whose intensity is modu-
lated by activating systems from cholinergic, noradren-
ergic and serotoninergic nuclei in the brain stem, basal
forebrain and hypothalamus. These systems modify the
state of consciousness through different levels of arousal.
Second, their activity is modulated by inputs arising from
the limbic system, via connections to the anterior cingu-
lated, orbitofrontal cortex , and the direct influen ce of do-
paminergic inputs [115].
In this global workspace model, highly variable net-
works of neural cells are selected and their activity is
reinforced by environmental stimuli. These reinforced
networks can be said to ‘represent’ the stimuli, thoug h no
particular network of neural cells exclusively represents
any one set of stimuli. The environment does not imprin t
precise images in memory. Rather, working through sense s,
the environment selects certain networks and reinforces
the connections between them. These processes connect
memory to the acquisition of knowledge and the testing
of its validity. Every evocation of memory is a recon-
struction on the basis of physical relativel stable traces
stored in the brain in latent form [116]. Changeux and
Dehaene distinguished three kinds of neuronal represen-
ta t i ons: per cepts; ima ges, conce pts, and int entions ; and pre-
representations. Percepts consist of correlated activity of
neurons that is determined by the outer world and disin-
tegrate as soon as external stimulation is terminated. Im-
ages, concepts, and intentions are activated objects of
memory, which result from activating a stable memory
trace (similar to the “remembered present” of Edelman).
Prerepresentations are multiple, spontaneously arising
unstable; they are transient activity patterns that can be
selected or eliminated [117]. In this line of idea, though ts
can be defined in terms of “calculations on the mental
objects” [118]. To be cap able to be mobilized in the con-
scious workspace, a mental object must meet three crit er ia :
1) The object must be represented as a firing pattern of
neurons; 2) The active workspace neurons must possess
a sufficient number of reciprocal anatomical connections,
particular in prefrontal, parietal and cingulated cortices;
3) At any moment, workspace neurons can only sustain a
single global representation, the rest of workspace neu-
rons being inhibited. This implies that only one active cor-
tical representation will receive the appropriate top-down
amplification and be mobilized into consciousness, the
other representations being temporarily unconscious [119].
When a new situation happens, selection would occur
from an abundance of spontaneously occurring prerepre-
sentations, namely those that are adequate to new circum-
stances and fit existing percepts and concepts. The free
will is b ased o n this adap tatio n pro cess called ‘resonan ce ’,
because planning and decision making result from this
selective adaptation process [117]. As in evolution, this
could be a random recombination of representations. The
meaning of representations involved would be given by
their proper functions. Plans gen erated in this way would
be intelligible because they could be appropriate for the
situation. Naturally, linguistically coded representations
could therein also be of central importance. It results from
this global neurophysiological model that, as Changeux
said it, the identity between mental states and physio-
logical or physicochemical states of the brain is essential
in all legitimacy and that it is enough with the man to be
a neuronal man [118,120]. One important aspect that fol-
lows from this theory is that once a set of processors
have stated to communicate through workspace connec-
tions, this multidomain processing stream also becomes
more and more automatized through practice, resultin g in
direct interconnections, without requiring the use of work-
space neurons and without involving consciousness. An-
other important aspect of this theory is that information
computed in neural processors that do not possess direct
long-range connections with workspace neurons, will al-
ways remain unconscious. This global workspace model
has however been considered by some authors as a re-
strictive theory of access consciousness sacrificing some
phenomenological aspects of consciousness. In other terms,
it has been criticized for confounding the subjective ex-
perience of consciousness with the subsequent executive
processes that are used to access its content.
Model of Edelman. To explain the primary conscious-
ness, Edelman argued that living organisms must organize
into perceptual categorization the unlabeled signals they
receive from the environment. He started therefore his
model by proposing a hypothesis which describes the
fundamental process of categorization. This highly arti-
culated hypothesis is mainly based on the theory of neu-
opyright © 2011 SciRes. JBBS
ronal group selection implying a basic process termed
‘reentry’, a massively recursive activity between neuronal
groups. It is also based on the fundamental concept called
“degeneracy”, whereby elements that are structurally dif-
ferent can perform the same function. The first idea of
Edelman was to use the assumption of tying, imagined
by Francis Crick for visual perception [22], to expl ai n how
the categories go from the form, color, texture and move-
ment of external stimulations to the constitution of ob-
jectivity. His theory is based on the concept of neuronal
chart. A chart is a sheet of neurons whose points are sys-
tematically connected, on the one hand, at points on sheets
of receiving cells (skin, retina of the eye, etc…) to satisfy
entries of signals and, on the other hand, at points located
on other charts to satisfy reentries of signals functioning
in the two directions. His second idea was to admit that
the brain, genetically equipped at the birth with a su-
perabundance of neurons, develops thanks to the death of
a number of these neurons due to a process of darwinian
selection. Lastly, his third idea was that parallel reentries
of signals occur between the charts to ensure an adaptive
answer. It is the ongoing recursive dynamic interchange
of signals occurring in parallel between maps that con-
tinually interrelates these maps to each other in space and
time. Categorization, therefore, is ensured by the dyna-
mic network of a considerable number of entries and
reentries selected by a multitude of charts [26,121,122].
Although distributed on many surfaces of the brain, the
inputs, at the same time connected between them and
connected to charts of reentries, can thus react the ones
on the others in a mechanism of functional segregation
for finally giving a unified representation of the object.
In other words, categorization is a global “encartage”
which does not need a program a priori, a “homoncule”,
to produce it. For Edelman, this mechanism is a plausible
working hypothesis because his research group has shown
that brain-based devices are capable of perceptual cate-
gorization and conditioned behavior [123]. Over the last
14 years, a series of robotic organisms (called Darwin se-
ries) have indeed been used to study perception, operant
conditioning, episodic and spatial memory, and motor
control through the simulation of brain regions such as the
visual cortex, the dopaminergic reward system, the hip-
pocampus, and the cerebellum [124]. However, to reach
the major stage of conscious perceptive experience, Edel-
man thought that at least six further conditions shou ld be
met [26,122,125,126]. Firstly, the brain must have mem-
ory. Memory, according to Edelman, is an active process
of recategorization on the basis of a former categorizatio n .
The perceptible category, for example, is acquired by an
experience by means of charts of reentries. But if there is
a perceptive entry by seeing, for example, a table again,
one recategorizes this entry by improving preceding ca-
tegorization, and so on; one reinvents the category con-
tinuously. In other terms, memory generates “informa-
tion” by construction: it is creative but nonreplicative.
Secondly, the brain must have a system of training. The
training implies changes of behavior which rest on cate-
gorization controls by positive or negative values; an ani-
mal can choose, for example, what is clear or dark, hot or
co ld, etc, to satisfy i ts needs for surv ival. Thirdly, altho ug h
self-awareness appears only with the higher conscious-
ness, the brain must have a system of diffuse feelings
which enables it to discrimin ate between oneself and not
oneself. Fourthly, the brain must be able to categorize the
succession of events in time and to form concepts pre-
linguistics. Edelman thought that the categorization of
successive events and the formation of these concepts
have a common neurobiological substrate. Fifthly, there
must be continuous interaction s between cond itions 1, 2,
3 and 4 so that a particular memorial system for the val-
ue s is formed. Sixtly, the brain needs also to have reentrant
connections between this particular memorial system and
the anatomical systems. That is, according to Edelman,
to formulate a model of primary consciousness it is nec-
essary to have the notions of perceptual categorization,
concept formation, and value-category memory in hand.
As Changeux, Edelman considered that it is the tha-
lamo-cortical system, called “dynamic core”, which con-
tributes directly to the conscious experience [125,126]. It
is a dense fibre network inter-connected in the two direc-
tions, in which connections occur unceasingly and come
in competition so that the most effective fibres carry it
(according to a process of darwinian competition). This
reentrant dynamic core is thus a process, not a substance.
It is in perpetual rebuilding (with periods of time of a
few hundred milliseconds), in wide space but formed
nevertheless of unified and highly integrated elements.
As spatial process, it ensures the coherence of conscious-
nesses states ; it is the principal dynamic driving core of
the constitution of self. The key structures for the emer-
gence of consciousness are the specific thalamic nuclei,
modulated by the reticular nucleus in their reentrant con-
nectivity to cortex, the intralaminar nuclei of the thala-
mus, and the grand system of corticocortical fibers. What
emerges from these interactions is th e ability to cons truct
a scene. This activity is influ enced by animal’s history of
rewards and punishments accumulated during its past. It
is essential for constructing, within a time window of
fractions of seconds up to several seconds, the particular
memory of animals, that is the “remembered present”
[126]. Higherorder consciousness is consciousness to be
conscious, self-awareness. It is accompanied by a sense
of self and the ability to construct past and future scenes
in the waking state. It is the activity of the dynamic core
which converts th e signals received from the outside and
Copyright © 2011 SciRes. JBBS
inside of the body into oneself, what Edelman called “phe-
nomenal transformation” [125]. This higher conscious-
ness requires, at the minimum, a semantic capability and,
in its most developed form, a linguistic capability which
makes possible to symbolize the relations of the past,
present and future and to do representations. On the other
hand, Edelman asserted that the linkage proceeds from
the underlying neural activity to the conscious process
and not the reverse, but that consciousness is not directly
caused by the neural processes, it accompanies them.
Rather, they are the neural processes and the entire body
which are causal. Consciousness is “reincorporated” in
the body, insofar as it is one of the modulations by which
the body expresses its decisions; it amplifies the effects
of the body to produce th e free will [125]. Since the body
“is decided” by many nonlinear and chaotic determinisms
(described by Alain Berthoz [127]), consciousness is thus
also “decided” by these complex body determinations.
However, consciousness adds to the body an additional
level of complexity, because it is able to make differences
within a vast repertory of informations. What makes in-
deed informative a state of human consciousness is the
fact that the man is able to make a difference between
billion states different of things. The intentional under-
standing of consciousness to reduce uncertainty is always
singular and gives the character subjective and private to
mental-lived of each individual at every moment. Like
Dennett, Freeman and Damasio, Edelman thus admitted
that the free will is a nonlinear chaotic causality, gener-
ally circular, which results from the complex interactions
between the body and the brain in the local environmental
contexts. The model of Edelman offers an interesting ten-
tative of unifying the hard and easy problems. Indeed,
since the reentrant dynamic core theory considers con-
sciousness as an emergent property of any system shar-
ing specific core mechanisms of differentiated integra-
tion, the most reliable index of consciousness should
reflect the quantification of this core mechanism. How-
ever, a conceptual difficulty of this h ypothesis lies in the
paradox of trying to prove that neural indexes are more
respectable because they supposedly probe phenomenal
and not access consciousness. Indeed, neural indexes of
any sort have to be validated by confronting them at one
point with some kind of report, hence with access and
not phenomenal consciousness. Even if it turns out that
one of these neural indexes turns out to be perfectly cor-
related with consciousness, and thus becomes a perfectly
reliable measure of consciousness, then one might still
ask whether we have made any progress.
5. Conclusions
A great variety of specific theories have been proposed,
whether cognitive, phenomenal, physics, neural or based
on Artificial Intelligence, to explain consciousness as a
natural feature of the physical world. The most prominent
examples of philosophical and non-neural approaches
included the naturalistic dualism model of David Chal-
mers, the multiple draft cognitive model of Daniel Dennett,
the phenomenological theory of Franscisco Varela and
Humberto Maturana and the physics-based approaches of
Stuart Hameroff and Roger Penrose. The major neuro-
physiological theories included the emerging spatiotem-
poral patterns of Walter Freeman, the visual system-based
approaches of Viktor Lamme, Semir Zeki, David Milner
and Melvyn Goodale, the phenomenal/access conscious-
ness model of Ned Block, the synchronous cortico-thalamic
rhythms of Rodolfo Llinas, the synchronized firing corti-
cal oscillations of Francis Crick and Christof Koch, the
emotive somatosensory processes of Antonio Damasio,
the neuronal global workspace of Jean-Pierre Changeux
and Stanislas De haen e, an d the reentrant cortical loops of
Gerald Edelman and Giulio Tononi. It is foreseeable that
the range of these models will extend in the future. For
example, it is supposed now that consciousness associ-
ated with the dream would be a rebuilding at the time of
the waking, related to relaxations of specific neuromodu-
lators on very short intervals of time [128]. Such a hy-
pothesis might generate new models. On the other hand,
new perspectives of Artificial Intelligence hav e a ttempt to
check the hypothesis of the functioning of brain archi-
tecture and simulate consciousness using both the meth-
ods and laws of informational machines and the process-
ing capabilities of biological systems. For example, series
of brain-based robots have been tested over the last dec-
ade to study perception, operant conditioning, episodic
and spatial memory, and motor control. Moreover, a su-
percomputer program, called Human Brain Project, was
given for objective to attempt to reproduce an artificial
consciousness in the future.
One can be skeptic, like Paul Ricoeur, as for the pos-
sibility of obtaining a true theory which makes a complete
synthesis between a speech “neuro” and a “psychologica l”
speech. The body is this object which is both me and mien,
but there is no passage from one speech to another [120].
Any attempt to confuse the figures of the body-object and
body-lived of consciousness, was it founded on the prin-
ciples and methods of neuroscientific approaches more
innovating, is obviously impossible for ontologi cal reasons.
However, like Edelman says it, to deplore that one
cannot build a scientific model of consciousness without
being able to theoretically explain the quality of a quale
(what one feels, for example, by seeing the red of a flower)
is a non-problem; it is a problem of the same order as to
want to answer the famous philosophical question: “why
there is something and why not rather nothing?” [46].
opyright © 2011 SciRes. JBBS
The subjective aspect of consciousness is a pure obvi-
ousness of the real world. It is a pure sensitive which is
given of only one blow of the medium of itself [129],
which it is impossible to analyze it without causing its
disappearance immediately. It does not remain about it
less than the neurobiological understanding of relation-
ships between the brain and the objective aspects of
consciousness is the great challenge which will animate
researches of future decades. Certainly, the phenomeno-
logical model of Varela is compatible with some experi-
mental neurobiological approaches. Likewise, the phys-
ics-based model of Hameroff and Penrose could be open
to some researches of mental-brain correlations via the
study of signaling mechanisms of synaptic functions.
Moreover, Artificial Intelligence has proven to be a fertile
physical enterprise to check some hypothesis about the
functioning of brain architecture, although no machine
has been capable of reproducing an artificial conscious-
ness. However, only the advances in neurosciences seems
actually capable of taking into account the constraints of
a wide range of complex properties to provide an ade-
quate explanatory basis for consciousness. Of these pro-
perties, several stand out as particular challenges to theo-
retical effort, in particular the property of intentionality,
the problem of explaining both the first-person and third-
person aspects of consciousness, and the question of plausi-
ble necessary preconditions to develop self-awareness. As
attests it analysis and the myriad of neurophysiological
data already available, the states (arousal) of conscioun-
ess, the behavior, the brain processes of conscious sys-
tems, and a number of subjective contents of conscious-
ness (some qualia) are objectivable and can be experi-
mentally studied. In spite of innumerable difficulties which
one will still meet to study and understand a phenome-
non which is the originating base of categorical repr esenta-
tions of the intersubjective and subjective world, it is
therefore possible that one will manage one day to build
a naturalistic satisfying explanation of consciousness that
links together molecular, neuronal, behavioral, psycholo-
gical and subjective data in an unified, coherent scientific
6. References
[1] R. Descartes, “The Philosophical Works of Descartes,”
Cambridge University Press, Cambridge, 1975.
[2] P. H. Nidditch, “Enquiries Concerning the Human Un-
derstanding,” 3rd Edition, Clarendon Press, Oxford,
[3] J.-N. Missa, “Que Peut-On Espérer d’Une Théorie
Neuroscientifique de la Conscience? Plaidoyer Pour une
Approche Evolutionniste,” In: P. Poirier and L. Faucher,
Eds., Des neurosciences à la philosophie. Neurophi-
losophie et philosophie des neurosciences, Syllepse, Paris,
2008, pp. 356-357.
[4] S. Nicolas, “Psychologie de W. Wundt,” L’Harmattan,
Paris, 2003.
[5] R. Rudio, “William James, Philosophie, Psychologie
Religion,” L’Harmattan, Paris, 2008.
[6] G. Schiemann, “Hermann von Helmholtz’s Mechanism:
The Loss of Certainty. A Study on the Transition from
Classical to Modern Philosophy of Nature,” Springer,
Dordrecht, 2009.
[7] E. Husserl, “Idées Directrices Pour une Phénoméno-
logie,” Gallimard, Paris, 1950.
[8] J. Watson, “Behaviorism,” W. W. Norton, New York, 1924.
[9] B. F. Skinner, “Science and Human Behaviour,” Mac
Millan, New York, 1953.
[10] U. Neisser, “Cognitive Psychology,” Prentice Hall, Eng-
lewood Cliffs, 1965.
[11] H. Gardner, “Frames of Mind: The Theory of Multiple
Intelligences,” Basic Books, New York, 1983.
[12] M. Heidelberger, “Archived Draft of the Mind-Body Pro-
blem in the Origin of Logical Empirism: Herbert Feigle
and Psychophysical Parallelism,” Pittsburg University
Press, Pittsburg, 2003.
[13] D. Robinson, “Epiphenomenalism, Laws and Properties,”
Philosophical Studies, Vol. 69, No. 1, 1982, pp. 1-34.
[14] P. S. Churchland, “Que Peut Nous Enseigner la Neuro-
biologie au Sujet de la Conscience?” Poirier Faucher,
2008, pp. 329-354.
[15] J. M. Roy, “Naturalism Emergentist and Causal Explana-
tion,” Intellectica , Vol. 39, 2004, pp. 199-227.
[16] D. J. Chalmers, “Facing Up to the Problem of Conscious-
ness,” Journal of Consciousness Studies, Vol. 2, 1995, pp.
[17] D. J. Chalmers, “The Conscious Mind: In Search of a
Fundamental Theory,” Oxford University Press, Oxford,
[18] C. Mc Ginn, “Consciousness and Its Objects,” Oxford Uni-
versity Press, Oxford, 2004.
[19] T. Nagel, “What Is It Like to Be a Bat?” Philosophical
Review, Vol. 83, No. 4, 1974, pp. 435-450.
[20] D.C. Dennett, “Quining Qualia,” In: A. Marcel and E.
Bisiach, Eds., Consciousness in Contemporary Science,
Oxford University Press, Oxford, 1988, pp 42-77.
[21] D. C. Dennett and M. Kinsbourne, “Time and the Ob-
server: The Where and When of Consciousness in the
Brain,” Behavioral and Brain Sciences, Vol. 15, No. 2,
1992, pp. 183-247. doi:10.1017/S0140525X00068229
[22] J. R. Searle, “Le Mystère de la Conscience,” Odile Jacob,
Paris, 1999.
[23] D. C. Dennett, “Freedom Evolves,” Viking Press, New
York, 2003.
[24] D. C. Dennett, “Darwin’ s Dangerous Idea: Evolution and
the Meanings of Life,” Simon & Schuster, New York,
Copyright © 2011 SciRes. JBBS
[25] R. Dawkin, “The Selfish Gene,” 2nd Edition, Oxford
University Press, Oxford, 1989.
[26] G. M. Edelman, “Bright Air, Brilliant Fire: On the Matter
of Mind,” The Penguin Press, London, 1992.
[27] D. J. Chalmers, “The Cognitive Neurosciences III,” MIT
Press, Cambridge, 2004.
[28] C. I. Lewis, “Mind and the World Order,” Charles Scrib-
ners Sons, New York, 1929.
[29] B. Keeley, “T he Early History of the Qua le and Its Rela-
tion to the Senses,” In: J. Symons and P. Calvo, Eds.,
Routledge Companion to the Philosophy of Psychology,
Routledge Press, New York, 2009.
[30] J. Levine, “Qualia: Intrinsic, Relational or What?” In: T.
Metzinger, Ed., Conscious Experience, Schöningh, Pad-
erborn, 1995, pp. 277-292.
[31] A. N. Whitehead, “Process and Reality: An Essay in Cos-
mology,” Macmillan, New York, 1929.
[32] J. Haugeland, “Artificial Intelligence: The Very Idea,”
The MIT Press, Cambridge, 1985.
[33] C. Koch,“The Quest forConsciousness:Neurobiological Ap-
proach,” Roberts, Englewood, 2004.
[34] T. Horgan and J. Tienson, “The Intentionality of Pheno-
menology and Phenomenology of Intentionality,” In: D.
Chalmers, Ed., Philosophy Ofmind: Classical and Con-
temporary Readings, Oxford University Press, 2002, pp.
[35] J. Delacour, “Conscience and Brain. The New Border of
the Neurosciences,” DeBoeck University, Brussels, 2001.
[36] J. Delacour, “Biology of the Conscience,” Philosophical Re-
view of France and Abroad, Vol. 129, 2004, pp. 315-332.
[37] J. Hohwy, “The Neural Correlates of Consciousness:
New Experimental Approaches Needed?” Consciousness
and Cognition, Vol. 18, No. 2, 2009, pp. 428-438.
[38] J. Delacour, “Neurobiology of Consciousness: An Over-
view,” Behavioural Brain Research, Vol. 85, No. 2, 1997,
pp. 127-141. doi:10.1016/S0166-4328(96)00161-1
[39] T. J. Balkin, A. L. Braun, N. J. Wesensten, K. Jeffries, M.
Varga, P. Baldwin, G. Belenky and P. Herscovitch, “The
Process of Awakening: A PET Study of Regional Brain
Activity Patterns Mediating the Re-Establishment of Al-
ertness and Consciousness,” Brain, Vol. 125, No. 10, 2002,
pp. 2308-2319 . doi:10.1093/brain/awf228
[40] D. J. Chalmers, “What Is a Neural Correlate of con-
sciousness?” In: T. Metzinger, Ed., Neural Correlates of
Consciousness: Empirical and Conceptual Questions,
MIT Press, Cambridge, 2000.
[41] G. M. Edelman, “Naturalizing Consciousness: A Theo-
retical Framework,” Proceedings of the National Acad-
emy of Sciences USA, Vol. 100, No. 9, 2003, pp. 5520-
5524. doi:10.1073/pnas.0931349100
[42] G. Tononi and C. Koch, “The Neural Correlates Ofcon-
sciousness: An Update,” Annals of the New York Acad-
emy of Sciences, Vol. 1124, No. 1, 2008, pp. 261-298.
[43] C.-Y. Kim an d R. Blake, “Psychophysica l Magic: Rendering
the Visible ‘Invisible’,” Trends in Cognitive Sciences,
Vol. 9, No. 8, 2004, 381-388.
[44] D. G. Edelman and A. K. Seth, “Animal Consciousness:
A Synthetic Approach,” Trends in Neurosciences, Vol.
32, No. 9, 2009, pp. 476-484.
[45] J. A. Mather, “Cephalopod Consciousness: Behavioural
Evidence,” Consciousness and Cognition, Vol. 17, No. 1,
2008, pp. 37-48. doi:10.1016/j.concog.2006.11.006
[46] B. Lechevalier, F. Eustace and F. Viader, “Conscience
and Its Disorders,” De Boeck University, Brussels, 1998,
pp. 151-166.
[47] G. Buttazzo, “Can a Machine Ever Become Self-Aware?
Artificial Humans,” Goethe Institute, Los Angeles, 2000,
pp. 45-49.
[48] G. G. Towell and J. W. Shavlik, “Knowledge-Base Arti-
fi ci al Neural Networks,” Artificial Intell igence, Vol. 70, N o .
1-2 , 1994, pp. 119-165.
[49] R. Andrews, J. Diederich and A. B. Tickle, “Survey an
Critique of Techniques for Extracting Rules from Trained
Artificial Neural Networks,” Knowledge-Based System,
Vol. 8, No. 6, 1995, pp. 373-389.
[50] P. Stern and J. Travis, “Of Bytes and Brains,” Scien ce, Vol.
314, No. 5796, 2006, pp. 75-77.
[51] D. E. Goldberg, “Genetic Algorithms in Search, Optimi-
zation and Machine Learning,” Addison-Wesley, Reading,
[52] Z. Michalewicz, “Genetic Algorithm, Data Structures, Evo-
lution Programs,” 3rd Edition, Springer-Verlag, New
York, 1996.
[53] A. E. Eiben and M. Schoenauer, “Evolutionary Comput-
ing,” Information Processing Letters, Vol. 82, No. 1,
2002, pp. 1-6. doi:10.1016/S0020-0190(02)00204-1
[54] E. Bonabeau, “Agent-Based Modeling: Methods and
Techniques for Simulating Human Systems,” Proceed-
ings of the National Academy of Sciences USA, Vol. 99,
No. 3, 2002, pp. 7280-7287.
[55] A. Cardon, “A Multi-Agent Model for Co-Operative
Communications in Crisis Management Systems: The Act of
Communication,” Information Modeling and Knowledge
Bases, IOS Press, Amsterdam, 1998, pp. 66-82.
[56] A. Cardon, T. Galinho and J.-P. Vacher, “Genetic Algo-
rithm Using Multi-Objective in a Multi-Agent System,”
Robotic and Autonomous Systems, Vol. 33, 2000, pp.
[57] A. Cardon, “Design and Behaviour of a Massive Organi-
zation of Agents,” Design of Intelligent Multi-Agent Sys-
tems, Human-Centredness, Architectures, Learning and
Adaptation, Springer, Berlin/Heidelberg, Vol. 162, 2004,
pp. 133-190.
opyright © 2011 SciRes. JBBS
[58] A. Cardon, “Artificial Consciousness, Artificial Emotions,
and Autonomous Robots,” Springer, Berlin/Heidelberg,
[59] R. Sanz, I. Lopez and J. Bermejo-Alonso, “A Rational
and Vision for Machine Consciousness in Complex Con-
trollers” Artificial Consciousness, Imprint Acade mic, Exe-
ter , 2007.
[60] Y. Shoham and K. Leyton-Brown, “Multiagent Systems:
Algorithmic, Game-Theoretic, and Logical Foundations,”
Cambridge University Press, Cambridge, 2009.
[61] J. L. Krichmar and G.M. Edelman,“Machine Psychology:
Autonomous Behavior, Perceptual Categorization, and
Conditioning in a Brain-Based Device” Cerebral Cortex,
Vol. 12, No. 8, 2002, pp. 818-830.
[62] O. Holland, R. Knight and R. Newcombe, “The Role of
the Self Process in Embodied Machine Consciousness,”
Artificial Consciousness, Imprint Academic, Exeter, 2007.
[63] H. Markram, “The Blue Brain Project,” Nature Reviews
Neuroscience, Vol. 7, 2006, pp. 153-160.
[64] D. Hofstadter and D. Dennett, “Sights of the Spirit,” In-
terEditions, Paris, 1987.
[65] G. Hesslow and D. A. Jirenhed, “Must Machines Be
Zombie? Internal Simulation as a Mechanism for Machine
Consciousness,” AAA Symposium, Washington DC, 8-11
November 2007, pp. 1-6.
[66] H. Maturana and F. Varela, “Autopoiesis and Cognition:
The Realization of the Living,” D. Reidel Publishing Co.,
Dordrecht, 1980. doi:10.1007/978-94-009-8947-4
[67] F. J. Varela, “Neurophenomenology: A Methodological
Remedy for the Hard Problem,” Journal of Conscious-
ness Studies, Vol. 3, 1996, pp. 330-349.
[68] F. J. Varela, “The Naturalization of Phenomenology as
the Transcendence of Nature: Searching for Mutual
Generative Constraints,” Alter: Revue de Phénoménologie,
Vol. 5, 1997, pp. 355-385.
[69] F. J. Varela, “A Science of Consciousness as If Experi-
ence Mattered,” In: S. Hamerof f, A. W. Kasznia k and A. C.
Scott, Eds., Towards a Science of Consciousness II; The
Second Tucson Discussions and Debates, MIT Press,
Cambridge, 1998.
[70] D. Rudrauf, A. Lutz, D. Cosmelli, J.-P. Lachaux and M.
LeVan Quyen, “From Autopoiesis to Neurophenomenol-
ogy: Francisco Varela’s Exploration of the Biophysics of
Being,” Biological Research, Vol. 36, 2003 pp. 1-28.
[71] M. Merleau-Ponty, “The Structure of Behavior,” Beacon
Press, Boston, 1963.
[72] F. J. Varela, “Organism: Ameshworkof Selfless Selves,”
Organism and the Origin of Self, Kluwer, Dordrecht,
1991, pp. 79-107.
[73] F. J. Varela, “Steps to a Science of Interbeing: Unfolding
Implicit the Dharma in Modern Cognitive Science,” In: S.
Bachelor, G. Claxton and G. Watson, Eds., The Psychology
of Awakening: Buddhism, Science and Our Day to Day
Lives, Rider/Randol House, New York, 1999, pp. 71-89.
[74] P. L. Luisi, “Autopoiesis: A Review and a Reappraisal,”
Naturwissenschaften, Vol. 90, 2003, pp. 49-59.
[75] R. Penrose, “The Emperor’s New Mind,” Oxford Univer-
sity Press, Oxford, 1989.
[76] R. Penrose, “Shadows of the Mind: A Search for the Miss-
ing Science of Consciousness,” Oxford University Press,
Oxford, 1994.
[77] S. Hameroff and R. Penrose, “Orchestrated Reduction of
Quantum Coherence in Brain Microtubules: A Model for
Consciousness,” Neural Network World, Vol. 5, 1995, pp.
[78] S. Hameroff and R. Penrose, “Orchestrated Reduction of
Quantum Coherence in Brain Microtubules: A Model for
Consciousness,” In: S. R. Hameroff and A. C. Scott, Eds.,
Toward a Science of Consciousness, The First Tucson
Discussions and Debates, MIT Press, Cambridge, 1996.
[79] R. Grush and P. Churchland, “Gaps in Penrose’s Toil-
ing,” Journal of Consciousness Studies, Vol. 2, 1995, pp.
[80] W. J. Freeman, “Mass Action in the Nervous System,”
Elsevier Science & Technology Books, New York, 1975.
[81] W. J. Freeman, “How Brains Make Up to Their Minds,”
Weidenfeld, L ondon, 1999.
[82] W. J. Freeman, “Neurody namics; Exploration of Mesosco-
pic Brain Dynamics,” Springer-Verlag, London, 2000.
[83] W. J. Freeman, “Mass Action in the Nervous System,”
[84] W. J. Freeman “Origin, Structure and Role of Back-
ground EEG Activity, Part 3, Neural Frame Simulation,”
Clinical Neurophysiology, Vol. 116, No. 5, 2006, pp.
1118-1129. doi:10.1016/j.clinph.2004.12.023
[85] J. J. Wright, “Cortical Phase Transitions: Properties Dem-
onstrated in Continuum Simulations at Mesoscopic and
Macroscopic Scales,” Journal of New Mathematics and Na
tural Computation. Vol. 5, No. 1, 2009, pp. 159-193.
[86] V. A. F. Lamme and P. R. Roelfsema, “The Distinct
Modes of Vision Offered by feedforward and Recurrent
Processing,” Trends in Neurosciences, Vol. 23, No. 11,
2000, pp. 571-579.
[87] V. A. F. Lamme, “Why Visual Attention and Awareness
Are Different,” Trends in Cognitive Sciences, Vol. 7, No.
1, 2003, pp. 12-18. doi:10.1016/S1364-6613(02)00013-X
[88] V. A. F. Lamme, “Towards a True Neural Stance on Con-
sciousness,” Trends in Cognitive Sciences, Vol . 1 0 , No. 11,
2006, pp. 494-50 1. doi:10.1016/j.tics.2006.09.001
[89] S. Zeki, “A Vision of the Brain,” Blackwell Scientific
Publications, Oxford, 1993.
[90] S. Zeki, “Inner Vision: An Exploration of Art and the
Brain,” Oxford University Press, Oxford, 1999.
[91] A. D. Milner and M. A. Goodale, “The Vi sual Brain in Ac-
tion,” Oxford University Press, Oxford, 1998.
[92] M. A. Goodale and A. D. Milner, “Sight Unseen: An
Exploration of Conscious and Unconscious Vision,” Ox-
Copyright © 2011 SciRes. JBBS
ford University Press, Oxford, 2004, p. 135.
[93] N. Block, “How Can We Find the Neural Correlate of
Consciousness?” Trends in Neuros ciences , Vol. 19 , 1996, pp.
[94] N. Block, “On a Confusion Abo ut a Function of Conscious-
ness,” In: N. Block, O. Flanagan and G. Güzeldere, Eds.,
The Nature of Consciousness: Philosophical Debates, The
MIT Press, Cambridge, 1997, pp. 375-416.
[95] N. Block, “Consciousness, Accessibility, and the Mesh
between Psychology and Neuroscience,” Behavioral and
Brain Sciences, Vol. 30, No. 5-6, 2007, pp. 481-548.
[96] R. Llinas and D. Pare, “Of Dreaming and Wakefulness,”
Neuroscience, Vol. 44, No. 3, 1991, pp. 521-535.
[97] R. Llinas, U. Ribary, D. Contreras and C. Pedroarena,
“The Neuronal Basis for Consciousness,” Philosophical
Transactions of the Royal Society B: Biological Sciences,
Vol. 353, No. 1377, 1998, pp. 1841-1849.
[98] R. Llinas and U. Ribary, “Consciousness and the Brain.
The Thalamocortical Dialogue in Health and Disease,”
Annals of the New York Academy of Sciences, Vol. 929,
2001, pp. 166-175.
[99] F. C. Crick and C. Koch, “Towards a Neurobiological The-
ory of Consciousness,” Seminars in Neuroscience, Vol. 2,
1990, pp. 263 275.
[100] F. C. Crick and C. Koch, “Consciousness and Neurosci-
ence,” Cerebral Cortex, Vol. 8, No. 2, 1998, 97-107.
[101] F. C. Crick and C. Koch, “A Framework for Conscious-
ness,” Nature Reviews Neuroscience, Vol. 6, 2003, pp.
[102] A. R. Damasio, “The Feeling of What Happens: Body
and Emotion in the Making of Consciousness,” Harcour
Brace & Co, New York, 1999.
[103] A. R. Damasio, “Looking for Spinoza: Joy, Sorrow, and
the Feeling Brain,” Harcourt Inc, Orland, 2003.
[104] A. R. Damasio, “Descartes’s Error,” Avon Books, New
York, 1994.
[105] A. Damasio, T. Ji. Grabowsk, A. Bechara, H. Damasio, L.
L. B. Ponto, J. Parvizi and R. D. Hichwa, “Subcortical
and Cortical Brain Activity during the Feeling of
Self-Generated Emotions,” Nature Reviews Neuroscience,
Vol. 3, 2000, pp. 1049-1056.
[106] A. Bechara, H. Damasio and A. R. Damasio, “Emotion,
Decision Making and the Orbitofrontal Cortex,” Cerebral
Cortex, Vol. 10, No. 3, 2000, pp. 295-307.
[107] J. R. Searle, “The Mystery of Consciousness Continues,”
The New York Review of Books, 2000,
[108] S. Dehaene, M. Kerszberg and J.-P. Changeux, “A Neu-
ronal Model of a Global Workspace in Effortful Cogni-
tive Tasks,” Proceedings of the National Academy of
Sciences USA, Vol. 95, No. 24, 1998, pp. 14529-14534.
[109] S. Dehaene, J.-P. Changeux, L. Naccache, J. Sackur and
C. Sergeant, “Conscious, Preconscious, and Subliminal
Processing: Has Testable Taxonomy,” Trends in Cogni-
tive Sciences, Vol. 10, 2006, pp. 204-211.
[110] B. J. Baars, T. Z. Ramsoy and S. Laureys, “Brain Con-
scious Experience and the Observing Self,” Trends in
Cognitive Sciences, Vol. 26, No. 12, 2003, pp. 671-675.
[111] B. J. Baar, “A Cognitive Theory of Consciousness,”
Cambridge University Press, Cambridge, 1988.
[112] S. Dehaene and J.-P. Changeux , “Reward-Dependent Learn-
ing in Neuronal Networks for Planning and Decision
Making,” Progress in Brain Research, Vol. 126, 2000, pp.
[113] S. Dehae ne and L . Naccac he, “Towards a Cognitive Neu-
roscience of Consciousness: Basic Evidence and a Work-
space Framework,” Cognition, Vol. 79, No. 1-2, 2001, pp.
1-37. doi:10.1016/S0010-0277(00)00123-2
[114] S. Dehaene, C. Sergent and J.-P.Changeux, “A Neuronal
Network Model Linking Subjective Reports and Objec-
tive Physiological Data during Conscious Perception,”
Proceedings of the National Academy of Sciences USA,
Vol. 100, No. 14, 2003, pp. 8520-8525.
[115] J.-P. Changeux and S. Dehaene, “The Workspace Model:
Conscious Processing and Learning,” In: R. Menzel, Ed.,
Learning Theory and Behavio r, Vol 1 of Learning and Me-
mory: A Comprehensive Reference, Elsevier, Oxford,
2008, pp. 729-758.
[116] J.-P. Changeux, “The Physiology of Truth,” Harvard
University Press, Cambridge, 2004.
[117] H. Walter, “Neurophilosophy of Free Will. Frontal Cor-
tex and Intelligibility,” The Oxford Handbook of Free
Will, 2002, pp. 565-570.
[118] J.-P. Changeux, “The Neuronal Man: The Biology of
Mind,” Princeton University Press, Princeton, 1985.
[119] S. Dehaene and J.-P. Changeux, “Neural Mechanisms for
Access to Consciousness,” The Cognitive Neurosciences
III, MIT Press, Cambridge, 2004.
[120] J.-P. Changeux and P. Ricoeur, “What Makes Us Think,”
Princeton University Press, Princeton, 2002.
[121] G. Tononi, O. Sporns and G. M. Edelman, “Reentry and
The Problem of Integrating Multiple Cortical Areas:
Simulation of Dynamic Integration in the Visual Sys-
tem,” Cerebral Co r te x, Vol. 2, No. 4, 1992, pp. 310-335.
[122] G. M. Edelman and G. Tononi, “A Universe of Conscious-
ness: How Matter Becomes Imagination,” In: G. M. Edel-
man and G. Tononi, Eds ., Bas ic Books , New York, 2000.
[123] G. N. Reeke, L. H. Finkel, O. Sporns and G. M. Edelman,
“Synthetic Neural Modeling: A Multilevel Approach to
the Analysis of Brain Complexity,” Bulletin of the French
opyright © 2011 SciRes. JBBS
Copyright © 2011 SciRes. JBBS
Company of Philosophy, Conference of February 28,
1990, pp. 607-707.
[124] J. L. Krichmar and G. M. Edelman, “Brain-Based De-
vices for the Study of Nervous Systems and the Devel-
opment of Intelligent Machines,” Artificial Life, Vol. 11,
No. 1-2, 2005, pp. 63-77.
doi:10.1162/1064546053 278 946
[125] G. M. Edelman, “Vaster than the Sky. The Gift of Conscious -
ness,” Yale University Press, New Haven/London, 2004.
[126] G. M. Edelman, “Building a Picture of the Brain,” Dae-
dalus, Vol. 127, 1998, pp. 37-69.
[127] A. Berthoz, “La Direction du Mouvement,” Odile Jacob,
Paris, 1997.
[128] J. P. Tassin, “Le Rêve Naît du Sommeil,” Pour la Science,
Vol. 28, 1995, pp. 22-23.
[129] M. Merleau-Ponty,“Phenomenology of Perception,” Hu-
manities Press, New York, 1962.