KAO LIANG CHOW 



509 



projects to the temporal region). It can be argued that a small remnant 

 of tissue may be responsible for the lack of detrimental effects, thus 

 illustrating the great plasticity of the system. 



In order to remedy the inadequacy of the lesions described above, three 

 other types of surgery were carried out in a series of monkeys. First, both 

 the parastriatc cortex and the pulvinar were ablated in two monkeys. 

 This was done in the hope that these two lesions would overlap enough to 

 prevent effective communication between the visual and temporal areas. 

 Second, the temporal cortex was undercut parallel to the surface to 



NO. 3 



Fig. I 

 Reconstruction of lesions of monkey No. 3 who had ablations of both the parastriatc cortex 

 and the posterior n. pulvinaris inedialis. Solid black, area of destruction; hatching, surrounding 

 degenerated zone; R, right; L, left; PM, n. pulvinaris niedialis; PL, n. pulvinaris lateralis; 

 MD, n. niedialis dorsalis; LG, lateral geniculate body; MG, medial geniculate body. 



eliminate all subcortical projection fibres in four animals. Third, in another 

 four monkeys, the temporal cortex was cross-hatched to eliminate the 

 intracortical and the arcuate fibres. This last operation was applied after 

 failure to circumscct the temporal region. Two monkeys with ablation of 

 the temporal cortex were included to serve as controls. 



Pre-operatively all animals were adapted to the testing situation by 

 applying a red and green discrimination. They were then trained on two, 

 siiiiukaiicoiis visual pattern discriminations: black circle v. black square; 

 and black and white vertical striations i>. horizontal striations. The animals 

 were required to choose the positive stimulus to receive a food reward, 

 and to disregard the negative stimulus. The non-correction method was 



