Journal of Behavioral and Brain Science, 2011, 1, 23-36
doi:10.4236/jbbs.2011.12005 Published Online May 2011 (http://www.SciRP.org/journal/jbbs)
Copyright © 2011 SciRes. JBBS
There are Two Different Language Systems in the Brain
Department of Communication Sciences and Disorders Florida International University, Miami, USA
Received February 12, 20 1 1; revised March 26 , 20 1 1; accepted March 28, 2011
In this paper it is emphasized that human language has two rather different dimensions corresponding to two
different language systems: lexical/semantic and grammatical. These two language systems are supported by
different brain structures (temporal and frontal), and based in different learning strategies (declarative and
procedural). In cases of brain pathology, each one can be independently impaired (Wernicke aphasia and
Broca aphasia). While the lexical/semantic language system may have appeared during human evolution
long before the contemporary man, the grammatical language system probably represents a relatively recent
acquisition. Language grammar may be the departing ability for the development of the metacognitive ex-
ecutive functions and is probably based in the ability to internally represent actions.
Keywords: Language Evolution, Grammar, Aphasia, Executive Functions
It is usually assumed that throughout human history (and
also during child language development) there is a con-
tinuous and progressive complexization of language [1,2].
Thus, it is supposed that the child acquires the first words
around the age of 12 months ; at this age the ability to
repeat what he/she hears as a result of the maturation of
the arcuate fasciculus also develops ; and later when
the vocabulary reaches a large enough number of words,
he/she begins to combine them, initially two words, fur-
ther three and more words, some of them with a purely
connecting (grammatical) function . Consequently, it
is generally assumed that there is a steady progression in
language evolution an d language development.
In this paper it is emphasized that human language in-
deed has two rather different dimensions: lexical/ seman-
tic and grammatical, correlated with two different evolu-
tionary patterns. The lexical/semantic system (i.e., rep-
resenting external elements with sounds) has its roots in
the animal communication systems, and most likely has
existed since the early hominids, and even before .
The emergence of grammar (set of structural rules
governing the composition of sentences –syntax- and
words –morphology-) in human evolution is not just a
quantitative but rather qualitative change (e.g., ),
probably associated with the emergence of the so-called
metacognitive executive functions (problem solving,
planning, concept formation, strategy development and
implementation, controlling attention, working memory,
and the like) . The emergence of grammar represents
indeed the most crucial leap in human language evolu-
These two language systems (lexical/semantic and
grammatical) are correlated with the activity of two dis-
tinct brain areas of the left hemisphere (temporal and
frontal) (e.g., [8,9]); they are mediated by different
learning processes (explicit an d implicit memory) [10-14]
and they appear during ontogeny and phylogeny at two
different moments [1,2]. Clinical observations clearly
demonstrate that there are two major aphasia syndromes
(Wernicke-type and Broca-type aphasia) (for a review,
see: ) due to damage in rather different brain areas
(temporal and frontal) and associated with the impair-
ment of each one of these language dimensions (lexical/
semantic and grammatical) (Figure 1).
This distinction between a lexical/semantic and a
grammatical system is obviously well known in linguis-
tics. For instance, Jakobson  referred to two different
language axes (paradigmatic – lexical/semantic; and syn-
tagmatic – grammatical); and Chomsky  clearly il-
lustrated that the lexical/semantic system is independ-
ent from the grammatical system. Nonetheless, in cogni-
tive neurosciences such a distinction is frequently ob-
scured by the assumption that there are several (seven
and even more) forms of language disturbances (aphasias)
e.g., [18-23]) associated with focal brain damage. There (
Figure 1. Traditionally it has been accepted that there are two major areas involved in language: frontal
Broca’s area and temporal Wernicke’s area.
is the implicit assumption that language includes a diver-
sity of functions (phoneme discrimination, lexical mem-
ory, grammar, repetition, language initiatio n ability, etc.),
each one associated with the activity of a specific brain
area. The different aphasia subtypes (Broca aphasia,
conduction aphasia, Wernicke aphasia, aphasia of the
supplementary motor area, transcortical sensory aphasia,
etc.) are interpreted as conceptually equivalent, and in
each one a specific language function or ability is sup-
posed to be disturbed. Hence, it is concluded that there
are seven (and even more) language functions.
2.1. Initial Communication Systems
The origin of human language remains controversial and
different explanatory proposals have been presented (e.g.,
[1,24,25]. Ardila  suggested that human language
evolved through three diff erent stages:
1) Initial communication systems using sounds and
other types of information – such as gestures, etc., simi-
lar to the communication systems observed in other ani-
mals, including nonhuman primates .
2) Primitive language systems using combined sounds
(words) but without a grammar (language as a lexical/
semantic system). This type of language probably existed
in other hominids  and could be linked to the holo-
phrasic period in language development, observed in
children around 1 to 1.5 years of age [2,3].
3) By the end of the second year, children begin to
combine words into simple sentences. Initially, sentences
have a telegraphic style (telegraphic speech) (around 24 -
30 months of age), including two-word utterances in
which connecting elements are omitted (e.g., “dog big”)
; later, words with a grammatical function are found.
Probably this type of language is historically recent and
can be observed only in the Homo sapiens likely linked
to some specific genetic mutations [6,28,29]. No ques-
tion, the emergence of a grammatical language repre-
sents a crucial leap in human evolution.
It simply means that likely language initially emerges
as a system of words with a particular content (meaning)
(lexical/semantic system), and only later as a system of
opyright © 2011 SciRes. JBBS
relations (grammatical system). Bickerton  deve-
loped the idea that a protolanguage must have preceded
the full-fledged syntax of today’s discourse. Echoes of
this protolanguage can be seen, he argued, (a) in pidgin
languages, (b) in the first words of infants, (c) in the
symbols used by trained chimpanzees, and (d) in the
syntax free utterances of children who do not learn to
speak at the normal age. Bickerton  considers that
such a proto-language existed already in the earliest
Homo (about 2.3 to 2.4 million years), and was deve-
loped due to the pressure of the behavioral adaptations
faced by Homo habilis (2.3 to 1.4 million years ago).
It is easy to assume that at the beginning of the human
language, communication systems were similar to the
communication systems found in nonhuman primates. It
is known that chimpanzees and other nonhuman primates
in their natural environment can use some communica-
tion strategies . Chimpanzees employ a variety of
gestures and facial expressions to communicate and keep
in touch with each other. They possess a simple reper-
toire of noises and postures (body language) that can be
used in different contexts with specific communication
purposes. Observations have been collected in different
environments, including natural environments and cap-
tive groups in human controlled environments .
Chimpanzees make use of simple gestures, make facial
expressions and produce a limited amount of vocalize-
tions. Unlike humans, chimps only produce about 12
different vocalizations. In captive conditions and under
human training, chimpanzees can learn some artificial
languages and close to about 200 “words” [31,32].
Different attempts have been made to teach nonhuman
primates to use more complex communication systems.
Initially, Hayes and Hayes  trained the chimp Vicki.
She became able to produce only four different words in
six years! (“mom,” “pa,” “cup,” and “up”). Other chimps
and gorillas have also participated in communication
training programs: Nim and Koko used signs; Sara used
plastic chips; Lana, Sherman, and Austion manipulated
combinations of buttons to communicate [34-36].
Regardless of the relatively large amount of meaning-
ful elements that chimpanzees can learn, they fail in de-
veloping sequencing of elements (syntax). Kanzi learned
to use around 200 symbols on a portable electronic
symbol board but learning grammar was not evident. It
has been pointed out that while chimpanzees can learn to
order their symbols to get what they want, it is not clear
that they have mastered syntax [37,38]. The reason is
that when they initiate communication, they often aban-
don the order they have learned and word order becomes
The question becomes: how this type of simple com-
munication system found in nonhuman primates in natu-
ral conditions (i.e., to use some few vocalizations, ges-
tures and facial expressions) further developed into con-
temporary human language? Certain mechanisms poten-
tially could be used to create meaningful sequences of
sounds (i.e., words); for example, new words can be cre-
ated departing from onomatopoeias, emotional expre-
ssions, interjections, gestures, etc. Indeed, a diversity of
mechanisms has been proposed to account for how hu-
man words emerged . This is an ability that is not
found in nonhuman primates. Using these strategies cer-
tainly requires a brain notoriously more advanced than
the chimpanzee’s brain. Interestingly, it has been found
that the arcuate fasciculus is much smaller or absent in
nonhuman primates (chimpanzees and macaques) com-
pared with humans , potentially limiting the lan-
guage repetition ability and the possibility to transmit
language from parents to children.
2.2. The Lexical/Semantic System
Paleoneurology (study and analysis of fossil endocasts)
can significantly contribute to the understanding of the
origins of the language. How did the brain areas partici-
pating in human lexical/semantic knowledge (i. e., left
temporal lobe) evolve?
It is known that in monkeys, the temporal lobes are
involved in recognizing the sounds and calls of the own
species [41-44], and evidently the temporal lobe was a
crucial area in developing a complex lexical/semantic
system. Human sounds and calls are obviously at the
origin of language words. Gannon et al.  observed
that the anatomic pattern and left hemisphere size pre-
dominance of the planum temporale, a language area of
the human brain, are also present in chimpanzees. They
found that the left planum temporale was significantly
larger in 94% of chimpanzee brains examined. Hence,
the crucial lexical/semantic difference between humans
and chimpanzees cannot be related to the planum tem-
porale. By the same token, it has been observed that
anatomical temporal-lobe asymmetries favoring the left
hemisphere are found in several Old and New World
monkey species . Hopkins and Nir  examined
whether chimpanzees show asymmetries in the planum
temporale for grey matter volume and surface area in a
sample of 103 chimpanzees from magnetic resonance
images. The results indicated that, overall, the chimpan-
zees showed population-level leftward asymmetries for
both surface area and grey matter volumes. Furthermore,
chimpanzees that prefer to gesture with their right-hand
had significantly greater leftward grey matter asymm-
tries compared to ambiguously- and left-handed apes.
Development of a human lexical/semantic communiction
system in consequence cannot be related to the temporal
Copyright © 2011 SciRes. JBBS
26 A. ARDILA
lobe asymmetry, because this asymmetry is observed
long before the beginning of the human language. This
asymmetry seems to be related with a left temporal lobe
specialization for intra-specific communication system.
Spocter et al.  affirm that leftward asymmetry of
Wernicke’s area originated prior to the appearance of
modern human language and before our divergence from
the last common ancestor.
Nonetheless, differences between humans and non-
human primates can be related with the temporal lobe
volume. Rilling et al.  analyzed the volume of the
temporal lobe in different primates. Whole brain,
T1-weighted MRI scans were collected from 44 living
anthropoid primates spanning 11 species. The surface
areas of both the entire temporal lobe and the superior
temporal gyrus were measured, as was temporal cortical
gyrification. Allometric regressions of temporal lobe
structures on brain volu me consistently showed apes and
monkeys to scale along different trajectories, with the
monkeys typically lying at a higher elevation than the
apes. Within the temporal lobe, overall volume, surface
area, and white matter volume were significantly larger
in humans than predicted by the ape regression lines. The
largest departure from allometry in humans was for the
temporal lobe white matter volume which, in addition to
being significantly larger than predicted for brain size,
was also significantly larger than predicted for temporal
lobe volume. Among the nonhuman primate sample,
Cebus have small temporal lobes for their brain size, and
Macaca and Papio have large superior temporal gyri for
their brain size. The observed departures from allometry
might reflect neurobiological adaptations supporting spe-
cies-specific communication in both humans and Old
World monkeys. The authors concluded that entire hu-
man temporal lobe and some of its component structures
are significantly larger than predicted for a primate brain
of human size. The most dramatic allometric departure is
in the volume of the human temporal lobe white matter,
which, in addition to being large relative to brain size, is
also large relative to temporal lobe size. These allometric
departures in humans could reflect a reorganization of
the temporal lobes driven by expansion of language cor-
tex and its associated connectio ns. It is interesting to note
that in primates the superior temporal gyrus contains
neurons tuned to species-specific calls, the magnitude of
different species’ relate to the repertoire of vocal com-
municative signals as reflections of the complexity of
their respective social environments.
It has been calculated that this enlargement of the
temporal lobe may have occurred some 200 - 300 thou-
sand years ago . It can thus be conjectured that
hominids existing before the contemporary Homo
sapiens sapiens could have developed certain complex
lexical/semantic communication systems. For instance, it
could be speculated that Neanderthal man (Homo sapiens
neanderthalensis) could have had a relatively complex
language at least as a lexical/semantic system.
2.3. The Emergence of Grammar
What was the crucial leap for the development of lan-
guage grammar? (i.e., syntagmatic dimension of the lan-
guage). Obviously grammar was initially simple, and
“sentences” contained only two words. How to link two
words to create a new higher-level unit (syntagm)? Fur-
ther, how to mark the relationship between the two
words? The mechanism has to be the simplest one, and it
is not unlikely that it may be similar to the mechanism
observed in children during language development.
Suppose that we have two lexical units: animal – fruit.
Different relations between these two words can exist;
but the relationship requires an action (verb); it means
that there is an interaction between both elements, such
as: animal eats fruit; animal has fruit, animal receives
fruit; animal likes fruit, etc.
In consequence, before creating a syntagmatic rela-
tionship between the words, different word categories
have to be separated (e.g., objects and actions).
For creating a phrase, indeed only two types of ele-
ments are really required: nouns (nominal phrase) and
verbs (verbal phrase). If putting together two words cor-
responding to two different classes (e.g., animal sleep),
there is already a syntagm and grammar has appeared. In
childhood language it is observed that words corre-
sponding to two different classes are combined such as,
“big dog,” “food good,” “dad gone.” They contain a
grammar, because the words belong to two different
classes. In the first two examples (“big dog,” “food
good,”), there is an existenc e verb (to be) that is implicit
and omitted (as currently observed in some contempo-
rary languages, such as Russian). “Mom dad” is not a
phrase, but “mom big” is a primitive sentence.
Brown  found that the majority of the utterances at
the beginning of the child’s grammar could be described
by a small set of functional relationships between words:
1) “agent + action” baby kiss
2) “action + object” pull car
3) “agent + object” daddy ball
4) “action + location” sit chair
5) “object + location” cup table
6) “possessor + possession” mommy sock
7) “object + attribute” car red
8) “demonstrative + object” there car
The crucial point in emerging grammar is not the ex-
tension of the vocabulary. What is really crucial is to
have words corresponding to two different classes that
Copyright © 2011 SciRes. JBBS
can be combined to form a higher-level unit (syntagm).
One of the words has to be a noun; the other is a verb.
Hence, the problem becomes: how verbs appeared. To
create nouns does not seem so complicated (e.g., nouns
can be created departing from onomatopoeias, etc. ).
Verbs, on the other hand, can be created departing from
the nouns, but with the meaning of an action (e.g., baby
kiss). Action usually means moving, doing, executing,
not simply perceiving and associating with some visual
(or auditory or tactile) information. “Kiss” can be associ-
ated with some sensory information, and obviously the
temporal, parietal, and occipital brain areas have to par-
ticipate (“kiss” as a noun). “Kiss” can also be associated
with an action, and obviously the frontal areas have to be
involved in this second type of association (“kiss” as a
verb). It is well known that impairments in finding nouns
are associated with temporal lobe pathology, whereas
impairments in finding verbs are associated with left
frontal damage and Broca’s aphasia [52,53].
Grammatical words, such as prepositions, have an
original spatial meanin g. Prepositions link words (n ouns,
pronouns and phrases) in a sentence. A preposition
usually indicates the temporal, spatial or logical
relationship of its object to the rest of the sentence (e.g.,
the pencil is on the table; I go to class; etc.). That is, a
preposition lo cates the noun in sp ace (or in time). Simply
speaking, the use of preposition as a basic grammatical
element supposes a representation of actions (moving,
2.4. Understanding Broca’s Area
In the last decade there has been a significant interest in
re-analyzing the function of Broca’s area (e.g., [54-56]).
So-called Broca’s area includes the pars opercularis
(Brodmann’s area-BA44) and probably the pars train-
gularis (BA45) of the inferior frontal gyrus  (see
Figure 2). BA45 probably is more “cognitive” than
BA44, which seems to be more motor, more phonetic.
From the traditional point of view, Broca’s area corre-
sponds to BA44, but several contemporary authors also
include BA45. In the traditional aphasia literature it was
assumed that damage in the Broca’s area was responsible
for the clinical manifestations observed in Broca’s apha-
sia. Only with the introduction of the CT scan did it be-
come evident that the damage restricted to the Broca’s
area was not enough to produce the “classical” Broca’s
aphasia; extension to the insula, lower motor cortex, and
subjacent subcortical and periventricular white matter is
also required . “Broca’s area aphasia” (“minor
Broca’s aphasia”) is characterized by mildly non-fluent
speech, relatively short sentences and mild agrammatism;
phonetic deviations and a few phonological paraphasias
can be observed ; some foreign accent can also be
noticed . Interestingly, electrical stimulation of
Broca’s area enhances implicit learning of an artificial
Simultaneously including both BA44 and BA45 in-
Broca’s area is problematic. BA44 is a premotor dys-
granular area, whereas BA45 has a granular layer IV and
belongs to the heteromodal prefrontal lobe (granular
cortex) . So, from a cytoarchitectonic point of view,
BA44 and BA45 are quite different. BA44 is a premo-
tor area whereas BA45 corresponds to the prefrontal
cortex. From the aphasia perspective, some authors have
referred to different clinical manifestations associated
with damage in BA44 (Broca-type aphasia) and BA45
(transcortical motor/dynamic aphasia) (e.g., ).
Broca’s area is, more than likely, involved in different
language and language related functions . Some au-
thors have pointed out that indeed Broca’s area is a col-
lective term that can be fractionated in different sub-
areas . Hagoort [55,65] refers to the “Broca’s com-
plex”, including BA44 (premotor), and also BA45 and
BA47 (prefrontal cortex). He argues that Broca’s com-
plex is not a language-specific area, and it becomes ac-
tive during some nonlanguage activities, such as mental
imagery of grasping movements . Functional defined
sub-regions could be distinguished in the Broca’s com-
plex: BA47 and BA45 are involved in semantic process-
ing, BA44, BA45 and BA46 participate in syntactic
processing, and BA44 is involved in phonological proc-
essing [67,68]. Hagoort  proposes that “the common
denominator of the Broca’s complex is its role in selec-
tion and unification operations by which individual
pieces of lexical information are bound together into
representational structures spanning multiword utter-
ances” (p. 166). Its core function is, consequently, bind-
ing the elements of the language. Thompson-Schill 
analyzed the different deficits observed in cases of dam-
age in the Broca’s area: articulation, syntax, selection,
and verbal working memory, suggesting that there may
be more than a single function of Broca’s area.
The author proposes a framework for describing the
deficits observed in different patients. The proposed
framework suggests that Broca’s area may be involved in
selecting information among competing sources. Fadiga,
Craighero, and Roy  speculates that the original role
played by Broca’s area relates to generating/extracting
action meanings; that is, organising/interpreting the se-
quence of individual meaningless movements. Ardila and
Bernal  conjectured that the central role of Broca’s
area was related to sequencing motor/expressive ele-
ments. Novick, Trueswell, and Thompson  consider
that the role of Broca’s area is related with a general
cognitive control mechanism for th e syntactic processing
Copyright © 2011 SciRes. JBBS
Copyright © 2011 SciRes. JBBS
Figure 2. Map illustrating the Brodmann’s areas (BA).
Grodzinsky [72-73] has presented an extensive analy-
sis of the role of Broca’s area. He proposed that most
syntax is not located in Broca’s area and its vicinity (op-
erculum, insula, and subjacent white matter). This brain
area does have a role in syntactic processing, but a highly
specific one: it is the neural home to receptive mecha-
nisms involved in the computation of the relation be-
tween transformationally moved phrasal constituents and
their extraction sites (syntactic movement). He further
assumes that Broca’s area is also involved in the con-
struction of higher parts of the syntactic tree in speech
production. Interestingly, blood flow in Broca’s area
increases when participants process complex syntax .
Santi and Grodzinsky  also recognize its role in
working memory related with a specific syntactic role in
processing filler-gaps dependency relations. Syntax is
indeed neurologically segregated, and its components are
housed in several distinct cerebral locations, far beyond
the tradition al ones (Broca’s and Wernicke’s regions). A
new brain map for syntax would also include portions of
the right cerebral hemisphere .
Haverkort  emphasizes that a clear distinction
should be established between linguistic knowledge and
linguistic use. Patients with Broca’s aphasia have a limi-
tation in the use of grammar, but their grammatical
knowledge is available. Broca’s aphasia patients present
a simplified syntax and phrases are short. They select
simpler syntactic structures that are less complex because
they impose less burden on working memory. In cones-
quence, one major factor in Broca’s aphasia relates to an
impairme nt in ver bal wo rking memory .
In summary, regardless that expressive language dis-
turbances have been associated for over a century with
damage in the left inferior frontal gyrus (later known as
“Broca’s area”), currently there is incomplete agreement
about its limits and its specific functions in language.
Different proposals have been presented to explain lan-
guage disturbances in so-called Broca’s aphasia, as sum-
marized in Table 1.
2.5. Brain Organization of Nouns and Verbs
It has been observed that verbs and nouns clearly de-
pend on the activity of different brain areas, and naming
objects and actions are disrupted in cases of different
types of brain pathology. While speaking or thinking in
nouns increased activity is observed in the left temporal
lobe, whereas speaking or thinking verbs activates the
Broca frontal area . By the same token, impairments
in finding nouns are associated with temporal lobe pa-
thology, whereas impairments in finding verbs is associ-
ated with left frontal damage and Broca aphasia [52,53].
It has been reported that the damage restricted to the
Broca’s area can result in a selective defect in finding
verbs and name actions whereas objects, colors, body
parts, and qualities can be named in a normal way . It
has also been observed that naming actions activates the
left frontal operculum roughly corresponding to Broca’s
Brain organization of the lexical/semantic system
seems to be related to the type of association between
words and perceptions (percepts, meanings). When the
words are associated with own body information (e.g.,
the word “finger”), brain representation of the lexicon
seems associated with a parietal extension; when the
word has visual associations (e.g., the word “book”), an
occipital extension is found . That is, the temporal
lobe plays the role of discriminating the speech sounds
and sequences of sounds (lexicon) but the meaning (se-
mantic) requires an association with one or several sen-
In anomia it has been traditionally recognized that
naming body parts, external objects and colors depend
(and are altered) upon the activity of different brain areas
. It has also been found that fin er distinctions can be
Copyright © 2011 SciRes. JBBS
Table 1. Different proposals about the role of Broca’s area.
Binding the elements of the language 
Selecting information among competing sources 
Generating/extracting action meanings 
Sequencing motor/expressive elements 
Cognitive control mechanism f or the syntactic processing of sen ten ces 
Construction of higher parts of the syntactic tree in s pe ec h production [72,73]
Verb al wo rk in g memory 
made with regard to naming defects, which can be lim-
ited to a rather specific semantic category (e.g., people’s
names, living things, tools, geographical names, etc.)
(e.g., [82-85] and even as specific as “medical terms”
. A brain “mapping” of the memory organization of
different semantic categories could be supposed.
That means that the neural correlates of naming con-
crete entities such as tools (with nouns) and naming ac-
tions (with verbs) are partially distinct: the former are
linked to the left inferotemporal region, whereas the lat-
ter are linked to the left frontal opercular and left poste-
rior middle temporal regions . Simply speaking,
nouns and verbs are rela t ed with different brain system s.
2.6. Two Memory Systems in Language
Two major memory systems are frequently distinguished
in contemporary memory literature: declarative memory
(divided into semantic and episodic or experiential) and
procedural memory . It has been suggested that the
lexical/semantic and grammar aspects of the language
are subserved by different neuroanatomic brain circuit-
ries and depend upon these two different memory sys-
tems [10-14]. Whereas lexical/semantic aspects of the
language depend on a declarative semantic memory
(knowledge about the meaning of the words), grammar
depends on a procedural m em ory.
Lexical/semantic aspect of the language is explicitly
learned, and represents a type of knowledge we are
aware of (declarative memory). It depends on retro-ro-
landic cortical structures and the hippocampus. Grammar
(language sequences, contiguity) is acquired incidentally.
Procedural memory for grammar supposes implicit lan-
guage knowledge. Procedural grammatical learning is
related to the execution of seq uences of elements (skilled
articulatory acts and grammar) used for speaking but also
for syntax. Procedural memory is related with fron-
tal/subcortical circuitries .
Broca’s area damage results in a defect in grammar
and also in an inability to find verbs. In consequence,
brain representation of actions and brain representation
of grammar is coincidental. Using verbs and using
grammar depends upon the very same type of brain ac-
tivity and both are simultaneously disrupted in cases of
Broca aphasia. It can be conjectured that verbs and
grammar appeared simultaneously in human language; or
rather, they are the two sides of the same coin. Further-
more, grammar is associated with oral praxis skills (i.e.,
agrammatism and apraxia of speech appear simultane-
ously in Broca aphasia), and hence, all three have to have
appeared simultaneously in the evolution of human lan-
guage: using verbs, using grammar, and rapidly se-
quencing movements with the articulatory organs. It can
be speculated that grammar, speech praxis movements,
and using verbs appeared roughly simultaneously in hu-
man history. Ther efore, they are strong ly interrelated and
depend upon a common neural activity.
2.7. There are Only Two Fundamental Aphasia
Since the 19th century it has been well established that
there are two major and fundamental aphasic syndromes,
named in different ways, but roughly corresponding to
Wernicke-type aphasia and Broca-type aphasia (e.g.,
[19-22,89-9 9]; see [100 ] for review). Th is is a mo st basic
departure point in aphasia: Aphasia is not a single and
unified clinical syndrome, but two rather different (even
opposed) clinical syndromes. These two major aphasic
syndromes have been related with the two basic linguis-
tic operations: selecting (language as paradigm; that is,
language as a lexical/semantic system) and sequencing
(language as syntagm; that is, language as a grammatical
system) [101-103]. Jakobson  proposed that aphasia
tends to involve one of two types of linguistic deficiency.
A patient may lose the ability to use language in two
rather different ways: the language impairment can be
situated on the paradigmatic axis (similarity disord er due
to an impairment in the lexical/semantic knowledge) or
the syntagmatic axis (contiguity disorder due to an im-
pairment in the grammatical system).
Luria  emphasized that the selection disorder can
30 A. ARDILA
be observed at different levels of the language, corre-
sponding to different aphasia subtypes: phoneme selec-
tion (acoustic agnosic aphasia), word selection (acoustic
amnesic aphasia), and meaning selection (amnesic apha-
sia). By the same token, the contiguity disorder can be
observed at different levels: sequencing words (kinetic
motor aphasia – Broca aphasia) or sequencing sentences
(dynamic aphasia – transcorticalmotor aphasia). Note-
worthy, different subtypes of Wernicke aphasia are fre-
quently distinguished (e.g., ) and Luria’s acoustic
agnosic, acoustic amnesic, and amnesic aphasia can be
considered as subtypes of the language impairment syn-
drome referred as a whole as Wernicke aphasia.
2.7.1. Wernicke Aphasia: Grammar without Content
The Wernicke-type of aphasia represents the clinical
syndrome characterized by impairments in the lexi-
cal/semantic system. In Wernicke aphasia, the lexical
repertoire tends to decrease and language understanding
difficulties are evid ent. Wernicke aphasia p atients do not
fully discriminate the acoustic information contained in
speech. Lexical (word) forms and semantic (meaning)
associations become deficient. Patients have problems in
recalling the words (memory of the words) and also in
associating the words with specific meanings. It means,
at least three different deficits underlie Wernicke-type
aphasia: (1) phoneme discrimination defects, (2) verbal
memory defects, and finally (3) lexical/semantic associa-
tion deficit s [1 5,106].
In the Wernicke-type of aphasia obviously the lan-
guage defect is situated at the level of the meaningful
words (nouns). Phoneme and word selection are deficient,
but language syntax (contiguity: sequencing elements) is
well preserved and even overused (paragrammatism in
Wernicke aphasia). Nouns seem to depend on an organ-
ized pattern of brain activity. Contemporary clinical and
neuroimaging studies have corroborated that different
semantic categories are differentially impaired in cases
of brain pathol ogy (e.g., ).
2.7.2. Broca Aphasia: Content without Grammar
The Broca-type of aphasia represents the clinical syn-
drome characterized by impairments in the sequencing
process (grammar). It is usually recognized that Broca
aphasia has two different distinguishing characteristics:
(a) a motor component (lack of fluency, disintegration of
the speech kinetic melodies, verbal-articulatory defects,
etc. that is usually referred to as apraxia of speech); and
(b) agrammatism (e.g., [19,20,22,107]). If both defects
are simultaneously observed (i.e., they are very highly
correlated), it simply means they both are just two dif-
ferent manifestations of a single underlying defect. It is
not easy to understand what could be the single factor
responsible for these two clinical manifestations; but it
may be kind of an “inability to sequence expressive ele-
ments” [15,70]. A single common factor underlying both
defects should be assumed. Broca’s area, most likely, is
not specialized in producing language, but in certain neu-
ral activities that can suppo rt not only skilled movements
required for speech, but also morphosyntax. It is inter-
esting to note that deaf-mute subjects (who, in cones-
quence have never produced verbal articulatory move-
ments) present a virtually total impossibility to learn,
understand, and use language grammar . Probably,
the lack of normal verbal articulatory development and
practice may contribute to this lack of normal grammati-
2.8. Grammar at the Origin of the Executive
So-called executive functions represent one of the most
intensively studied neuroscience questions during the last
decade (e.g., [109-113]). Disagreement persists, however,
around the potential unitary factor in executive functions
[114,115]. Ardila  emphasized that ‘‘action represent-
tation” (i.e., internally representing movements or ac-
tions) may constitute at least one basic executive func-
tion factor. It could be speculated that ‘‘action represent-
tation” and also ‘‘time perception” (potentially derived
from action representation) may depend upon one single
core ability (“sequencing?”).
Two departing observations are important to support
the involvement of prefrontal cortex in motor representa-
1) Anatomical observation. Prefrontal cortex repre-
sents an extension and further evolution of the frontal
motor areas [116,117]. It may be conjectured that the
prefrontal lobe should participate in complex and elabo-
rated motor (“executive”) activities.
2) Clinical observation. A diversity of motor control
disturbances are observed in prefrontal pathology, such
as perseveration, utilization behavior, paratonia, primi-
tive reflexes, etc. (e.g., [118,119]).
Throughout recent history several authors have argued
that thought, reasoning, and other forms of complex cog-
nition (“metacognition”) depend on an internalization of
actions. Vygotsky [120-122] for instance, proposed that
thought (and in general, complex cognitive processes) is
associated with some “inner speech”. Vygotsky repre-
sents the most classical author suggesting this interpreta-
tion for complex cognition. More recently, Lieberman
[123,124] suggested that language in particular and cog-
nition in general arise from complex sequences of motor
The central point in Vygotsky’s  idea is that
Copyright © 2011 SciRes. JBBS
higher forms of cognition (“cognitive executive func-
tions”) depend on certain mediation (langu age, writin g or
any other); the instruments used for mediating these
complex cognitive processes are culturally developed.
According to Vygotsky , the invention (or disco-
very) of these instruments, will result in a new type of
evolution (cultural evolution), not requiring any further
biological changes. Thinking is interpreted as a covert
motor activity (“inner speech”). Vocalization becomes
unnecessary because the child ‘‘thinks” the words in-
stead of pronouncing them. Inner speech is for oneself,
while external, social speech is for others. In brief, Vy-
gotsky  argued that complex psychological proc-
esses (metacognitive executive functions) derives from
language internalization. Thinking relies in the develop-
ment of an instrument (language or any other), that
represents a cultural product.
Lieberman [123,124] refers specifically to the origins
of language. He postulates that neural circuits linking
activity in anatomically segregated populations of neu-
rons in subcortical structures and the neocortex through-
out the human brain regulate complex behaviors such as
walking, talking, and comprehending the meaning of
sentences. The neural substrate that regulates motor con-
trol (basal ganglia, cerebellum, and frontal cortex) in the
common ancestor of apes and humans most likely was
modified to enhance cognitive and linguistic ability. The
cerebellum and prefrontal cortex are also involved in
learning motor acts (e.g., [123-126]. Lieberman [123,124]
proposes that the frontal regions of the cortex are impli-
cated in virtually all cognitiv e acts and the acquisition of
cognitive criteria; posterior cortical regions are clearly
active elements of the brain’s dictionary. Real-word
knowledge appears to reflect stored conceptual knowl-
edge in regions of the brain traditionally associated with
visual perception and motor control. Some aspects of
human linguistic ability, such as the basic conceptual
structure of words and simple syntax, are phylogeneti-
cally primitive and most likely were present in the earli-
est hominids. Lieberman [123,124] further suggests that
speech production, complex syntax, and a large vocabu-
lary developed in the course of hominid evolution, and
Homo erectus most likely talked, had large vocabularies,
and commanded fairly complex syntax.
These two authors (Vygotsky and Lieberman), alth-
ough using rather different approaches, have both postu-
lated that the development of language and complex cog-
nition are related with some motor programs, sequencing,
internalizing actions, and the like. Many other authors
have presented a similar point of view (e.g., [127-132]).
Some contemporary research seems to support this
interpretation; for instance, Clerget, Winderickx, Fadiga,
and Olivier  using transcranial magnetic stimulation
to interfere transiently with the function of left BA44 in
healthy individuals found that a virtual lesion of left
BA44 impairs individual performance only for biological
actions, and more specifically for object-oriented syntac-
tic actions. The authors concluded that these finding pro-
vides evidence that Broca’s area plays a crucial role in
encoding complex human movements, a process which
may be crucial for understanding and/or programming
The recent discovery of mirror neurons [134-136]
could significantly contribute to the understanding of the
brain organization for verbs. A mirror neuron is a neuron
which fires both when an animal performs an action and
also when the animal observes the same action per-
formed by another animal. Mirror neurons were initially
observed in monkeys , but in humans, brain activity
consistent with mirror neurons has been found in the
premotor cortex and the inferior parietal cortex [136,137].
These neurons (mirror neurons) appear to represent a
system that matches observed events to similar, inter-
nally generated actions.
Transcranial magnetic stimulation and positron emis-
sion tomography (PET) experiments suggest that a mir-
ror system for gesture recognition indeed exists in hu-
mans and includes Broca’s area . The discovery of
mirror neurons in Broca’s area might have important
consequences for understanding brain language organi-
zation and language evolution [138,139]. An obvious
implication of mirror neurons is that they can participate
in the internal representation of actions, and the internal
representation of actions may represent the origin of
grammar. Neuroimaging data have shown that interact-
tions involving Broca’s area and other cortical areas are
weakest when listening to spoken language accompanied
by meaningful speech-associated gestures (hence, reduc-
ing semantic ambiguity), and strongest when spoken
language is accompanied by self grooming hand move-
ments or by no hand movements at all suggesting that
Broca’s area may be involved in action recognition .
PET studies have associated the neural correlates of in-
ner speech with activity of Broca’s area . De Zubi-
caray et al.  emphasize the importance of Broca’s
area to covert verbalization. Clerget et al.  using
transcranial magnetic stimulation to interfere transiently
with the function of left BA44 in healthy individuals
found that a virtual lesion of left BA44 impairs individ-
ual performance only for biological actions, and more
specifically for object-oriented syntactic actions. The
authors concluded that these finding provides evidence
that Broca’s area plays a crucial role in encoding com-
plex human movements, a process which may be crucial
for understa n di ng and/ o r programmi ng actio ns.
In brief, there is some converging evidence that some-
Copyright © 2011 SciRes. JBBS
32 A. ARDILA
thing like “action representation” may constitute the de-
parting point for both, grammar and executive functions.
Regardless that the distinction between language as a
lexical/semantic system and language as a grammatical
system is evident in linguistics, this distinction has not
been incorporated in contemporary cognitive neurosci-
ences yet, probably due to the frequent assumption that
there are several aphasia subtypes and hence, several
language functions supported by diverse brain language
subsystems. This assumption overlooks the most impor-
tant and basic departing point in aphasia: in cases of
brain pathology language can be disturbed in two rather
different ways: as a lexical/semantic system (Wer-
nicke-type aphasia) and as a grammatical system
Both language systems not only depend upon different
brain areas (temporal and frontal) but also are based on
different types of learning (declarative and procedural)
supported by different neuroanatomical circuitries.
Grammar may be correlated with the ability to represent
actions. This is an ability that depends on the so-called
Broca’s area and related brain circuits, but also depends,
is correlated, and likely appeared simultaneously in hu-
man history with the ability to rapidly sequen ce articula-
tory movements (speech praxis).
Language as a lexical/semantic system may have ap-
peared long before language as a syntactic system,
whereas language as a grammatical system may have
appeared relatively recently [16,28,29,143-145] and
seems to be exclusive to Homo sapiens. Probably, lan-
guage grammar represents the departing ability for the
development of the executive functions and is based in
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