Brain science on the way to solving the problem of consciousness

Abstract

article Four issues are discussed: the possible mechanism of subjective events, conscious versus unconscious brain functions, the rhythmic coding of mental operations and the possible brain basis of understanding. i. Several approaches have been developed to explain how subjective experience emerges from brain activity. One of them is the return of the nervous impulses to the sites of their primary projections, providing a synthesis of sensory information with memory and motivation (Ivanitsky, A.M., 1976. Brain Mechanisms of the Signal Evaluation. Medicina, Moscow 264 pp. (in Russian)). Support for the existence of such a mechanism stems from studies upon the brain activity that subserves perception (visual and somato-sensory) and thought (verbal and imaginative). The cortical centres for information synthesis have been found. For perception, these are located in projection areas; for thinking — in frontal and temporal-parietal associative cortex. Closely related ideas were also developed by G. Edelman (Edelman, G.M., 1978. Group selection and phasic reentrant signaling: A theory of higher brain function. In: Eds. Edelman, G.M., Mountcastle, V.B. The Mindful Brain. Cortical Organization and the Group-selective Theory of Higher Brain Function. Cambridge, MA, MIT Press, pp 51-100.) in his re-entry theory of consciousness. Both theories emphasize the key role of memory and motivation in the origin of conscious function. ii. Conscious experience elucidates not all, but only salient brain functions. As a rule, voluntary control is switched onwhen additional cognitive resources are needed. Even a rathercomplicated mental operation, such as the discrimination between concrete and abstract words, could be executed very rapidly and implicitly; explicit analysis being engaged only in more difficult tasks. Furthermore, these two different kinds of mental operations, i.e., automatic and conscious, are predominantly associated with two different kinds of memory: a recognition memory for implicit analysis, and an episodic memory for explicit functions. iii. Rearrangements of EEG rhythms underlie mental functions. Certain rhythmical patterns are related with definite types of mental activity. The dependence of one upon the other is rather pronounced and expressive, so it becomes possible to recognize the type of mental operation being performed in mind with few seconds of the ongoing EEG, provided that the analysis of rhythms is accomplished using an artificial neural network.