1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 11 



Physiological and clinical studies present so many sources of error 

 that the conclusions dra^vn therefrom must be accepted with reserve ; 

 in the present state of our knowledge any physiological investigation 

 is hampered by our ignorance of the situation of the auditory pro- 

 jection cortex in lower primates. Yet the problem of whether the 

 auditory projection cortex is a small area with sharp boundaries or, 

 on the contrary, one which extends over a considerable portion of the 

 temporal cortex or even over that entire lobe, is of fundamental 

 importance for all further understanding of the physiology, psych- 

 ology, and pathology of auditory performances, including the highest 

 processes which manifest themselves as speech, understanding and 

 reproduction of music, and understanding of numberless biologically 

 important irregular acoustic stimuli of everyday life (noises). It is 

 evident that an attempted explanation of these liigher auditory pro- 

 cesses and localization thereof into special portions of the auditory 

 cortex will have, at most, only an approximate value or will remain 

 doubtful as long as the basic questions mentioned above are not 

 definitely settled. (Compare the uncertainty as to the finer localiza- 

 tion of various forms of aphasia and the confusion in its interpreta- 

 tion in Pick, Monakow, 1914 ; Head, 192*5, vol. 2, pp. 468, 474, 498 ; 

 Goldstein, 1927, p. 759, etc., but see also Henschen, 1918, 1919, 1927 ; 

 Isserlin, Niessl von Mayendorf, 1930, et al.) The experimental ana- 

 tomical method seems well adapted to help solve these problems and to 

 determine at least the comparatively gross features of the central audi- 

 tory mechanism. Everything here depends on the formulation of the 

 problems, on the choice of the material, and very considerably on the 

 technique. The first question to be settled is the exact origin, course, 

 and termination of the central portion of the auditory aiferent path. 

 If the auditory radiation after the destruction of the internal genic- 

 ulate body be found to terminate in a well delimitable, small cortical 

 area, this will permit the conclusion that there is, indeed, besides the 

 auditory projection cortex another portion of the cortex to which 

 functions higher than mere reception of auditory impulses must be 

 attributed. The conviction that only a small portion of the temporal 

 cortex serves as a ''gateway" for all cortico-petal auditory impulses 

 would be justified if in a suitable experiment all suggested afferent 

 pathways of the temporal cortex were severed, and only a single 

 degenerated afferent fiber system terminating in a small area were 

 actually found. If the auditory radiation, on the contrary, were 

 found to spread over the whole temporal lobe this would unavoidably 



