KAO LIANG CHOW 523 



bi-temporal after-discharges, but performed perfectly under uni-temporal 

 after-discharges. 



As a control, they were also tested either immediately after bilateral 

 shocks to the visual areas, or during the shock period. Because of the 

 difficulty of eliciting consistent seizure after-discharges in the visual areas 

 (the EEG tracings usually flattened out for a short period after shocks to 

 the visual areas), the latter procedure w2ls used. The results w^ere entirely 

 negative. The animals performed the discriminations correctly under these 

 conditions. Thus, electric shocks to the visual areas do not affect the 

 monkey's retention of visual habits. 



Several investigators have reported that electrical stimulation of sub- 

 cortical structures rendered cats and rats incapable of learning (Buchwald 

 and Ervin, 1957; Glickman, 1958; Ingram, 1958; Thompson, 1958). The 

 data presented here show that only bilateral temporal EEG after-discharges 

 prevent a monkey from learning or from retaining visual discriminations. 

 Whatever neural circuits may be responsible for these discriminations, 

 they are located in the two temporal lobes and can be temporarily dis- 

 rupted by abnormal neuronal discharges. These results may be relevant to 

 elucidating the effects of unilateral stimulation of the temporal cortex in 

 conscious human patients. Such stimulations have been variously reported 

 to elicit illusions, hallucinations, recall, and to cause transient amnesia 

 (Penfield and Jasper, 1954; Bickford cr ai, 1958; Mullen and Pentield, 

 1959)- 



SUMMARY 



Previous investigations have established that a restricted area of tem- 

 poral neocortex in the monkey concerns with the learning and remem- 

 bering of visual discriminations. This paper reports four studies illustrating 

 how this problem is analysed at the present time. These studies are far 

 from uncovering the mechanisms of learning and retention at a neuronal 

 level, but they show what specihc questions may be asked and answered 

 experimentally. To ask meaningful questions about learning phenomena 

 that can be identified behaviourally and tested empirically, constitutes one 

 approach to the understanding of the neural mechanisms of learning. 



GROUP DISCUSSION 



Galambos. Dr Chow has referred to 'brain-disorganization' experiments from 

 which much, I feel, is to be learned. Besides his anatomical methods there are two 

 physiological ways in which these disorganizations can be created. Shocks applied 

 to the temporal lobes and elsewhere create after-discharges, highly abnormal 



