'444 



II VNDIHMlK nl I'HVSIOI.OCV 



NEUROPHYSIOLOGY III 



make at these junction points. It does prove something 

 • ihciut i!h- dromic connections of each area. 



The electrode, applied to a sensory area, produces 

 seeing or hearing or feeling, depending upon which 

 area is stimulated. The sensation, if somatic, is ting- 

 ling, Dumbness or a sense of movement in some 

 part; if visual, it is moving lights or colors or stars; 

 if auditory, it is a buzzing, ringing, whispering or 

 thumping sound. These are the elements of the sen- 

 sory input. 3 



The exploratory electrode, delivering, for example, 

 60 pulses per sec. lasting a msec, with an intensity of 

 3 v., produces these three different categories of 

 sensation because the cortical areas are connected 

 with three different receiving stations in the higher 

 brain stem. That same electrode, when it applies the 

 same current to the precentral gyrus, produces move- 

 ment because of the corticofugal connections with 

 motor mechanisms in the cord or lower brain stem. 



However, under normal functional conditions, the 

 How of impulses that activates the precentral gyrus 

 for voluntary movement must arise in subcortical 

 hi, iv matter since excision of cortex in front of the 

 gyrus or behind it does not prevent a man from carry- 

 ing out voluntary action based on sensory informa- 

 tion.' 



CENTR1 \< I PHALIC ORGANIZA1 H in 



Therefore, the hypothesis presents itself that much 

 of the organizing neuronal activity between sensory 

 input ,ind motor oulpul must depend upon circuits 

 and ganglionic structures within the higher brain 

 stem, if the brain stem as defined by Herrick is under- 

 stood to include the thalamic nuclei ot the two hemi- 

 spheres. This old centra] structure, including the 

 diencephalon, mesencephalon and at leasl part of 

 the metencephalon, is connected by symmetrical 

 projection tracts to the various functional areas of the 

 i erebral 1 01 tea on either side. 



Tims bv means of these connections each area oi 



ould, it seems, be employed in common 



integrated action. There is no oilier obvious set of 



essential inlei < oiinecl ions for one cortex with the 



othei 1 ortex and "in- cortical area with iis neighboring 



In Chapter l.\. William Nefl points out .ilso thai the 

 "input "I the tensor) systems may be controlled at .1 numba ol 

 levels . . 1 ntrifugal pathways " 



In I haptei I \\ II [acques Paillard h.is summarized the 

 cortical origin ol the voluntai \ 

 ind ih- stud) hi the patterning ol skilled movements 

 is stimulating. 



cortical areas. Direct transcortical connections can 

 be interrupted with relative impunity. Even com- 

 plete section of the corpus callosum by a number of 

 intrepid neurosurgeons has had astonishingly little 

 effect on the intellectual activity of man. 



One-sided removal of, or injury to, any area of 

 cerebral cortex does not abolish conscious thinking. 

 It may change the content of awareness, interfere 

 with voluntary acts, render less effective planned ac- 

 tion, deprive the patient of word symbols — but he 

 still thinks and weeps, perhaps, at his own pitiful 

 incapacity. 



On the other hand, interference with the centren- 

 cephalic svstem of the higher brain stem produces 

 loss of consciousness. In the presence of deep coma 

 due to a small critically placed local lesion in the 

 higher brain stem, the motor mechanisms may seem 

 to remain intact. The patient lies in bed and move- 

 occasionally as in deep sleep, like the enchanted 

 'sleeping beauty' of the French nursery tale. 



It is accepted by those familiar with epilepsv that 

 epileptic discharge originates in gray matter, never 

 in white matter. When epileptic discharge occurs in 

 the gray matter of the centrenccphalic system of the 

 higher brain stem, the patient is initially unconscious 

 because the discharge interferes with local ganglionic 

 function. On the other hand, a partial seizure, due to 

 restricted epileptic discharge in any area of gray 

 matter of the cerebral cortex, is no( associated with 

 initial unconsciousness. 



The system of nerve fibers and ganglionic centers 

 within the brain stein may be called centrenccphalic 

 since, because of iis central position, it provides 

 symmetrical connections with the whole brain 

 Through it, one may suppose that this part of the 

 cortex, or that part, could be used simultaneous!) or 

 in sequence, depending upon the pattern and the 

 requirements of the existing stale ol consciousness. 



11 VSH-BACK VIIVHiKV v\l) COMPARATIV] 



IN I I RPR] I V I n IN 



From the temporal cortex of either side, electrical 

 stimulation or local epileptic discharge mav produce 

 phenomena ol an entirely different order from the 

 motor and sensory responses previously produced in 

 animals and man These responses are 'psychical,' 

 to borrow an adjective from Hughlings Jackson. 1 1<- 

 described such phenomena as they were experienced 

 l>v his epileptic patients during small his. "Dreamy 

 states," be called them, "as ii I went back to all thai 



mi lined in mv childhood." 



