500 



BRAIN MECHANISMS AND LEARNING 



seen that these cats with maximal lesions gave indication cither of no 

 saving or only slight saving ni relearnuig through the second eye. 



In summary, transection of broad expanses of corpus callosum anteriorly 

 did not halt transfer while relatively much smaller lesions posteriorly 

 interfered completely, speaking for a clear-cut posterior localization of the 

 visual gnostic exchange activity. Further, a second important point 

 emerges from a close consideration of these cases. Cat Brd transferred 

 discrimination Ill-ab with only the posterior-most 4.0 mm. of the corpus 



^ 10 - 



Sets of twenty triols 



Sets of twenty trials 



Sets of twenty trials 



Fig. 9 



, 10 15 



Sets of twenty trials 



Graphs comparing rates of learning through the two eyes on discrimination Ill-ab in four cats. 

 Initial learning through the right eye is represented by the solid line and relearning through 

 the left eye by the broken line. Extent of destruction of corpus callosum in each case may be 

 seen by reference to Tables I and II. Gbh showed no saving in relearning with the untrained 

 eye while some slight saving is suggested from the curves of Gry, Blk, and Blc. Cat Ghh was 

 trained and tested by an individual different from the one handling Gry, Blk and Blc. 



callosum preserved. Cat Cto transferred the same discrimination with the 

 selfsame strand of posterior fibres severed but more anterior fibres 

 preserved. These latter two cases taken together point up an equipoten- 

 tiality or equivalence of function of different fibre strands within the 

 broader posterior segment of the corpus callosum given over to the realm 

 of visual gnostic intercommunication. 



PROBLEM V. WHAT ROLE CAN ENVIRONMENTAL INFLUENCES PLAY IN DEFINING 

 THE DEGREE OF INTEROCULAR TRANSFER IN THE CHIASMA-SECTIONED CAT? 



Earlier, several exceptional instances were seen of depressed level of 

 interocular transfer in the chiasma-sectioned cats. Examination of Table I 



