NEUROPHYSIOLOGICAL BASIS OF HIGHER FUNCTIONS OF NERVOUS SYSTEM 



■445 



Psychical responses may be produced occasionally 

 in conscious man by gentle stimulation of the cortex of 

 the temporal lobe. The response is ordinarily physio- 

 logical and does not outlast the application of the 

 electrode to the gray matter. The responses are of 

 two types: illusion of comparative interpretation of 

 the present, and hallucination of re-enactment of 

 previous experience. 



Thus, the first type of response, if interpretive, 

 gives the patient a sudden sense of alteration in the 

 meaning of things being seen or heard or experienced 

 at the moment. He finds them suddenly familiar, or 

 strange, or more distant, nearer, fearful, etc. In nor- 

 mal life we assume that such feelings must result from 

 comparison of the present experience with similar 

 past experiences, although this comparison of present 

 with past is carried out subconsciously. 



If the response to stimulation is hallucinatory, it 

 proves to be a re-enactment, or 'flash back," of previ- 

 ous experience. The patient is aware of all those 

 things to which he paid attention in some previous 

 period of time. The experience unfolds for him at the 

 former rate of speed as long as the electrode is held in 

 place. He is aware of the present and of the past .is 

 well. If he hears music, it is ,1 specific rendition as he 

 heard it years ago, perhaps. He ma) sec the orchestra 

 or the piano or the singer, and he may feel again the 

 emotion roused in him by the music during that 

 distant strip of time. 



Thus it is clear that the temporal cortex has some 

 sort of selective connection with a detailed flash-back 

 record of the past, most of which has been forgotten 

 as far as the individual's ability for voluntary recall is 

 concerned. 



HIGHER FUNCTIONAL MECHANISMS 



It would seem that, under normal circumstances, 

 this flash-back record is reopened when similar experi- 

 ence presents itself. For example, the reappearance of 

 a long-forgotten friend makes available his previous 

 records so that he seems familiar at once, and minor 

 changes in him are obvious. Take another example: 

 the set of present circumstances is compared with 

 similar experiences from the past which may have 

 been dangerous or painful and the subject feels a fear 

 that calls for action. 



By inference, therefore, one may surmise that the 

 temporal cortex normally plays some role in a sub- 

 conscious scanning mechanism that opens the flash- 

 back memory file and provides a signal of compara- 

 tive interpretation (familiar, fearful, etc.) which rises 

 without warning into consciousness. 



This scanning of the flash-back memory forms one 

 partially separable mechanism in the higher functions 

 of the brain. The use of words in symbolic thinking, 

 so well described in Chapter LXYIII by Zangwill, is 

 another such mechanism. Some degree of localization 

 of the cortical portion of these mechanisms is possible 

 now, but not the centrencephalic portions. Neverthe- 

 less this is a beginning of the delineation of functional 

 units closely related to conscious thinking. 



Hughlings Jackson pointed out that there were 

 levels of integration in the nervous system and at- 

 tempted to assign an ascending "representation" and 

 're-representation' to spinal cord, cerebral cortex and 

 frontal lobes. But it is clear now that, although there 

 are advancing stages in the progressive organization 

 that make conscious thinking possible, these stages 

 cannot lie assigned 10 separable major areas of the 

 brain. 



A neurophysiologist might well attempt to separate 

 the levels . > t organization invoked in normal volun- 

 tary activity on the basis oi the progressive lapse of 

 time, the period of afferent conduction, the period of 

 organization and integration, the period of efferent 

 conduction. From a functional point of view the 

 mechanisms of that middle period of time are the 

 highest and seem the most complicated. They form 

 the physical basis of the mind. Doubtless, many of 

 the mechanisms that are usable in this middle period 

 .ire .ilso v.iiiuuslv employed during aimless conscious 

 states and in constructive abstract thinking. 



Ihe neuron circuits of these functional mechanisms 

 are to be found in the higher brain stem and in the 

 cerebral cortex, joined together in action patterns 

 lli.it form themselves and vanish and form anew, 

 making combinations never twice the same. Genera- 

 tions of workers must employ the scientific method to 

 Study man in health and in disease 



Thus the shadowy outlines we perceive today will 

 take clear form in a neurophysiology of higher func- 

 tions. And if man comes to understand himself in 

 mind and body he will have made his greatest con- 

 quest. Perhaps then he will recall the prediction that 

 "the truth shall make vou free." 



