1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 217 



and defmite structures. Nevertheless, some of the indisputably cor- 

 tical performances so far disclosed are localized in small portions of 

 the cortex. This is the case with certain functions of the projection 

 regions and with effector functions of the precentral and postcentral 

 regions, and of their corresponding afferent and efferent fiber systems. 

 For the precentral and postcentral regions this was demonstrated by 

 the physiological-histological experiments of Vogt (1919, Mitt. 4, 

 p. 399) . The same has been ascertained for the receptor function of the 

 postcentral region by Gushing (1909), Valkenburg (1914), Foerster 

 (1927), Mankowski (1920), Foerster-Penfield, and a great number of 

 other investigators, mostly clinicians (see bibliography), for the visual 

 system including the striate area by Wilbrand, Henschen, Minkowski, 

 Brouwer-Zeeman, Overbosch, Putnam, Foerster, Brouwer, Heuven, 

 Foerster-Penfield, R. A. Pf eifer 1930, and many others ; and for the 

 auditory system by Held-Kleinknecht, Quensel-Pf eifer, R. A. Pf eifer, 

 Kleist, Lorente de No et al. My previous and present investigations 

 justify admission of the existence of differences in functional signifi- 

 cance of various specific afferent paths of the cerebral cortex, and 

 even of the individual small neuronic units composing each of the 

 somatic sensory, auditory, and the visual systems together with their 

 respective cortical terminal areas. Moreover, it appears logical as 

 a next step to admit the existence of some kind of localization of 

 "higher" activities in the chain or sequence of events interposed 

 between initial afferent processes and final efferent acts. (This does not 

 necessarily preclude the co-existence of other paths with ill-defined and 

 more labile connections which would meet the requirements of the 

 Gestalt psychologists and would be in accord with Lashley's area! 

 "equipotentiality"; unfortunately these integrative mechanisms can 

 not at present be identified.)* Nor does it seem possible to avoid such 



4 To explain these two apparently contradictory statements we may use as an 

 example the visual projection cortex (striate area, field 17), especially its macular 

 portion. As is evident from the present experiments and other investigations, a 

 very strict or, better expressed, a point-to-point projection of the retina upon the 

 cortex with the corresponding- arrangement of afferent fibers can hardly be dis- 

 puted. Also it cannot be denied that the visual projection cortex participates in 

 a somewhat different way in cortical visual processes than the region immediately 

 contiguous to it. When we consider a far reaching "principle of localization" 

 with respect to the structures and functions of the afferent portion of the visual 

 system, we are struck by the comparatively small size of the main cortical receptor 

 apparatus, that is of the macular cortex, large as this cortex is in the brain of the 

 monkey. This region receives the bulk of the afferent impulses rapidly changing 

 in time. Therefore, it must be concluded that the same cortical apparatus, 

 in this case the macular cortex, is capable of rapid response to practically an 

 unlimited number of stimuli of a most varied kind. Although, according 

 to our conception, the "spatial" aiTangement of visual neurons exists and is, 



