Recent theories on natural and synthetic consciousness overlook the geometric structure necessary for awareness of 3-dimensional space, as strikingly illustrated by left-neglect disorder. Furthermore, awareness of 3-dimensional space entails some surprisingly tenacious optical illusions, as demonstrated by an experiment in the text. Awareness of linear time is also crucial and complex. As a consequence, synthetic consciousness cannot be realized by simply intercomnecting a large number of electronic circuits constructed from ordinary chips and transistors. Since consciousness is a subjective experience, there is no sufficient condition for consciousness that can be experimentally confirmed. The most we can hope for is agreement on the necessary conditions for consciousness. Toward that end, this paper reviews some relevant clinical phenomena.
Advances in functional magnetic resonance imaging (fMRI) have made it possible to observe the reaction of the human brain to a given stimulus during both waking consciousness and deep unconsciousness, e.g., due to the administration of propofol [1-11]. During waking consciousness, but not otherwise, a stimulus generates integrated global activity all across specialized regions of the brain. This has led to the conjecture that such an information-processing methodology may be a sufficient condition for consciousness and thus admits to the possibility of synthetic or non-biologic consciousness. However, this theory is contradicted by rare neurological disorders that provide empirical evidence as to which conditions are, and are not, necessary for consciousness. The oversight is no doubt due, at least in part, to the fact that only a small number of clinical neurologists have ever seen the disorders in question. Also, there is a bias that only large controlled studies provide reliable information. While this is true for clinical trials of therapeutic and diagnostic methods, the first law of information theory tells us that rare events are precisely the ones that provide the most information [12,13].
Since consciousness is a subjective experience, there is no sufficient condition for consciousness that can be experimentally tested. To the contrary, the mimicking of conscious behavior by an artificial brain would only tempt us to assume it is experiencing consciousness based upon, say, an analog for the Glasgow Coma Score [14, 15] when there is no scientific basis for this assumption. The most we can hope to achieve is agreement on the characteristics of the human brain that are necessary for consciousness. We could then assume that an artificial brain satisfying all of these criteria would be capable of consciousness under the general rule that like causes produce like effects. Toward that end, the present paper reviews the implications of some real clinical phenomena as a guide to recognizing the necessary conditions for consciousness.
The rare condition known as left-neglect disorder is caused by a lesion on the right hemisphere of the brain [16-18]. Patients with this condition cannot perceive anything to the left of a reference point, including but not limited to, the left side of their own bodies. Indeed, they cannot even conceive of leftness (see
words, the anatomy of the cerebral cortex must be intact in order for a person to be aware of 3-dimensional space. Moreover, the anatomy of the human brain contains fractal structures [
Information processing by the human brain is not intended to be accurate nor is it. Rather, the human brain evolved to be biologically adaptive. As a consequence, waking consciousness necessarily includes such errors as optical illusions [20-23], pareidolia [24-26], change blindness [27-32] and plastic memories [33-36]. Indeed, even blind people experience optical illusions [
In looking at
conduct the following experiment.
1) Print two copies of the page containing
2) Use one copy to cut out the two squares labeled A and B.
3) Place the cutout squares labeled A and B next to each other. It will be seen that, despite appearances that seem certain, they are exactly the same color.
4) Place the cutout square labeled B over the square labeled A in
Even after you have learned that the two labeled squares are the same color, and moving one to the position of the square labeled A makes it appear much darker, you will not be able to see
Orientation in linear time is limited to waking consciousness [37-40]. Indeed, when awake, a person is only conscious of the neurological present. From a neurologic standpoint, “nowness” can be defined as that which is perceived when a person is awake (although the physical definition is different). A person may remember the past and can anticipate the future by remembering that tomorrow is a holiday or that he has an appointment next week. But these recollections are not perceived in the same way that the present is perceived when a person is awake.