602 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY I 



FIG. 8. A. Lateral view of monkey brain, the sylvian fissure spread to show area responsive to 

 clicks Cshaded') according to Pribram et at. (.Ti)- ^- Enlarged view of shaded part of ^. SL, short latency 

 area; PO, parietal operculum. 



that the simian posterior supratemporal plane corre- 

 sponds to the feline A I inasmuch as in each case 

 destruction of the area leads to severe degeneration 

 of all but the caudal portion of the principal part of 

 the medial geniculate body. Pribram et al., however, 

 contrary to the findings of Rose & VVoolsey, are 

 quite positive in asserting that such a lesion and 

 consequent thalamic degeneration effectively elimi- 

 nates all conduction, not only to the simian counter- 

 part of S II but also to the other normally responsive 

 cortex of the ipsilateral hemisphere. From this they 

 conclude that the pathway to S II follows collaterals 

 from medial geniculate to some thalamic nucleus 

 which projects to S II. This impression gains credi- 

 bility from their oJKervation that the negating effect 

 of the lesion is not seen acutely (i.e. before conse- 

 quent geniculate degeneration has taken place) 

 but only some weeks later (i.e. after the effects have 

 been felt in the medial geniculate). This conflict, 

 except in the unlikely event it represents a species 

 difference, can be resolved only by full analysis of 

 the retrograde consequences of all combinations of 

 suspected subareas in each species combined with 

 electrophysiological delineation of responsive cortex 

 in each instance after time lapse to allow degenera- 

 tion and just before sacrifice. This is a large order, 

 but it is both legitimate and feasible. 



The reader will note that in the discussion of the 

 primate auditory cortex, no functional counterparts 

 of the feline insular and temporal regions have 



emerged. This probably represents merely a relative 

 shortage of information on the monkey, a lack which 

 may be filled in part by the additional information 

 we hope will accrue from the arduous future study 

 suggested in the last paragraph and in part from be- 

 havioral studies comparable to those in the cat. The 

 behavioral studies on the monkey so far available 

 are of little use inasmuch as they show no positive 

 loss of auditory capacity and the lesions are incom- 

 plete (26, 27). At the least, in the outlook on the 

 insular and temporal regions of the monkey, there is 

 reason to hope becau.se, if we accept the total area of 

 Pribram et al., a portion of the insula and all of the 

 lateral surface of the posterior superior temporal 

 gyrus are responsive to clicks but have not yet been 

 claimed for any other anatomical, electrical or func- 

 tional counterpart in the cat. 



Finally, we may note that the definition of A II 

 in the monkey rests in part on published data (107, 

 116) but in even larger part on logical though less 

 well supported extension of that data. This is due, 

 at least in part, to relative inaccessibility. In this 

 connection, it may have been noted that of all the 

 subdivisions in the cat's auditory cortex, A II seems 

 to be the least firmly established. At no time since 

 the initial definition of A II has it been as clearly 

 valid an area as it was at that time. The experiments 

 of Kiang (49), which explore the whole region in 

 the cat by a combination of techniques, make the 

 distinction between A I and A II more nebulous 



