BRAIN AND CONSCIOUSNESS

The purpose of the following paper is to consider what light has been thrown on the problem of consciousness by recent researches on the brain, particularly those carried out by the many new techniques which have become available during the last fifteen years. It appears (i) that the nerve cell differs in no essential way, either in its basic structure or in its metabolic processes, from other gland‐like cells, though, like all cells, it is differentiated for its specific function; (ii) that conduction in the nerve fibre is a relatively simple electro‐chemical process; (iii) that the transmission of the nerve impulse across the synapse is chemical, and the transmitter substances are of a familiar hormonal character; and (iv) that, apart from the greater complexity and the greater instability of the synaptic thresholds, there are no essential differences between those parts of the neuronal network (n.g. the cortex) which are accompanied by consciousness and those parts (e.g. the spinal cord) which are not. A comparison of the specific micro‐neural situations in which consciousness does and does not arise suggests that the brain functions, not as a generator of consciousness, but rather as a two‐way transmitter and detector; i.e. although its activity is apparently a necessary condition, it cannot be a sufficient condition, of conscious experience.