THE MOTOR AND SENSORY CORTICAL AREAS 659 



1. THE SIGNIFICANCE OF THE MOTOR AND SENSORY 

 CORTICAL AREAS 



We have seen that the motor cortical areas constitute the place of origin 

 of the long-fibered motor pathways, and that the sensory pathways terminate 

 in different cortical areas. What then is the physiological and psychological 

 significance of these areas? 



Theoretically, the simplest psychical events probably take place in the 

 cortical areas of the higher senses, for in such events the bodily movements 

 play but a relatively subordinate part, or at least do not occupy so prominent 

 a place in consciousness as do the sensory components of our experiences. We 

 shall therefore begin with the sensory areas. 



The conception most widely held at present is, that the excitation of these 

 cortical fields itself produces the appropriate simple, special sensations; that 

 the simple visual sensations, for example, arise in the visual area of the 

 occipital lobe; the simple auditory sensations* in the auditory area of the 

 temporal lobe, etc. 



But this cannot be looked upon as actually proved. If, for example, we 

 follow in our imagination the conducting pathway of optical impressions from 

 the periphery to the cerebral cortex it is evident at once that any complete 

 interruption of that pathway, no matter where it might occur, would cause 

 total blindness; also that any partial interruption, wherever it might occur, 

 would necessarily produce partial blindness. From this point of view it is 

 a matter of indifference whether the interruption take place by a peripheral 

 lesion or by a lesion in the corresponding part of the optical cortex. If only we 

 can assume that the activity of any part of the cerebrum, be it never so small, 

 will occasion a conscious process, then one can say that the simplest visual 

 impression is produced by excitation of the optical area in the cortex. But 

 this is only an unproved postulate. 



Moreover, our simplest conscious states are always very complicated. With 

 the simplest optical impression that, for example, of a luminous point we 

 observe not only the strength of the light and the color, but its position in the 

 field of vision, its apparent distance from the eye, its apparent size. All this 

 is given at the first glance, and it is at least very difficult to suppose that all 

 this can come into consciousness by the activity of the optical cortex alone. 



It would appear to be justifiable therefore to assume that pathways pass 

 out from the optical cortex and connect this field with others, and that even 

 the simplest visual sensations require the cooperation of several different 

 cortical regions. The excitation furnished the optical cortical area is of 

 course an important, perhaps the most important, component of the whole 

 process. And with Flechsig we would especially emphasize the point that 

 what gives the sensation its active character, what makes it essentially clear 

 and distinct, is brought about by this very component. 



The manifold ways in which the different sensory areas are connected 

 together and the great importance of such connection for the objective valua- 

 tion of our sense impressions are beautifully illustrated by the following 

 observation on successfully operated patients born blind. Such persons learn 

 to recognize an external object presented to them by feeling "it with the fingers 



