NEUROPHYSIOLOGICAL BASIS OF HIGHER FUNCTIONS OF NERVOUS SYSTEM 



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It might be considered hypothetically that that 

 mechanism is highest which is functionally the closest 

 to the zone of departure of the stream of potentials 

 which, flowing outward, determines voluntary action. 

 In the ganglionic zone of departure the pattern of the 

 plan must become the pattern of the emerging motor 

 stream. On arrival at the muscles, the pattern of that 

 stream is translated into act or word. 



Abstract thinking, which has no outward expres- 

 sion, differs no doubt from that which produces con- 

 tinuous voluntary action such as talking, or writing or 

 playing football, and yet many of the functional units 

 of integration must be the same. 



CLINICAL SURMISES 



There are many inferences that come to a clinician. 

 Perhaps it may serve a useful purpose to sel down a 

 few observations and thoughts which seem to shadow 

 forth the outlines of functional organization in the 

 human brain. Substantiation of most of these state- 

 ments may be found in previous publications else- 

 where. 



Many patients have been operated upon under 

 local anesthesia to cure them of recurring attacks of 

 focal epilepsy. In the course of such operations, 

 nearly all areas of the cerebral cortex have been 

 excised at one lime or another, all except the most 

 precious, the major speech areas of the dominant 

 hemisphere. Furthermore, all areas, including; those 

 devoted to speech, have been stimulated repeatedly 

 since this is one way of discovering the abnormal zone 

 which must In- excised if the sufferer is 10 Ik- relieved 

 of his fits. 



These subjects, who help the surgeon with so much 

 steadfast courage, have reported to him movements, 

 sensations and certain psychical phenomena that are 

 produced by application of ,i gentle electric current 

 to the cortex. These constitute- data that no laboratory 

 'preparation' can provide 



Electrical stimulation of the cerebral cortex of a 

 fully conscious man produces positive 'physiological' 

 responses, but onK in certain areas. These excitable 

 areas yield, when conditions are favorable and the 

 stimulating current is at a threshold level, three prin- 

 cipal types of physiological responses: a) motor, h) 

 sensory and c) psychical. 



2 Over the years, these data have been recorded carefully in 

 the Montreal Neurological Institute with the invaluable as- 

 sistance of Herbert Jasper, Theodore Rasmussen, Theodore 

 Erickson, Edwin Boldrey, Lamar Roberts, Anne Dawson and 

 a succession of brilliant assistants. 



SENSORY AND MOTOR RESPONSES 



There are 'sensory' and 'motor' areas that may be 

 considered secondary or supplementary. These areas 

 yield responses, when stimulated, that seem to the 

 patient just as compelling as those obtained from the 

 better known primary areas. But I shall refer here only 

 to the latter: the excitable motor strip on the Rolandic 

 or precentral gyrus, the somatic sensory area on the 

 postcentral gyrus, the visual sensory area in the 

 calcarine fissure and the auditory sensory area that 

 carpets Heschl's transverse gyrus deep in the fissure 

 of Sylvius. 



One conclusion is clear: these sensorv areas, that 

 occupy homologous positions in each hemisphere, are 

 way stations in the afferent streams of impulses that 

 lead from the periphery to some deep subcortical 

 target. The precentral gyrus, on the other hand, is a 

 way station in the efferent pathway that arises in sub- 

 cortical gray matter and passes outward to the muscles 

 of voluntary action. 



Circumexcision of conical areas, sparing these 

 sensor) or the motor areas, does not stop functional 

 conduction through these wa\ stations, for example, 

 when the parietal cortex of the right hemisphere is 

 excised the subject is still able to guide the left hand 

 in voluntary movement according to the information 

 received from the left visual field that entered the 

 brain through the right visual cortical area. The 

 guidance is obviousl) not provided by direct cortical 

 interconnection. 



It seems lair to conclude that corticocortical 

 'association 1 connections between one functional 

 of cortex and another are of comparatively minor 

 importance. This contradicts a long-cherished hy- 

 pothesis that the cortex was somehow invested with 

 miraculous mechanisms of integration. 



Electrical stimulation of die cortex, which produces 

 sensor) or motor responses, does so l>\ producing 

 neuronal conduction in the direction of the normal 

 flow through the particular way station to which the 

 electrode is applied. This neuronal conduction ma\ 

 therefore be considered dromic, and the effect is pro- 

 duced by activation of nerve cell stations farther along 

 in the stream of normal flow 



The electrode applied to the precentral gyrus thus 

 produces simple movement of the opposite fingers by 

 conduction to the anterior horn cell clusters in the 

 cervical spinal cord; or, if applied elsewhere, it pro- 

 duces vocalization, by conduction to the vocalization 

 and respiratory mechanisms in the lower brain stem. 



Thus, the electrode provides no direct information 

 as to what functional contribution the cortex may 



