ABSTRACT
The most complex unconditioned reflexes or instincts — food, defense, orienting, sex, and parental — which are functions of adjacent subcortical centers, were regarded by Pavlov as the most important basis for the higher nervous activity of animals. He regarded the cerebral hemispheres as an instrument assuring delicate and precise adaptation of the activity of the subcortical centers to the conditions of the external environment. It would seem natural, by analogy with animals, to regard the highly complex subcortical reflexes, whose extraordinary significance in our lives is beyond question, as the foundation of higher nervous activity in man. However, for man, with his developed intellect, satisfaction of his instinctive needs is insufficient. Often he abandons a quiet environment, in which he lives under conditions that meet all his needs, and exchanges it for alarming, dangerous life situations in which deprivations are great; and he is driven to this by strivings that have been shaped under complex societal conditions. The very highly developed cerebral cortex of the human brain is so significant a superstructure influencing the subcortical centers that subcortical impulses are not always able to sustain cortical activity at a sufficiently high level to assure optimal excitability of its cells. Consequently, there are other physiological mechanisms, apparently in the cortex itself, that compensate for the inadequacy of the subcortical impulses. What is the essence of these physiological mechanisms ?
