RONALD E. MYERS 



491 



of pattern visual learning resides within or is dependent upon cortex, and 

 (2) transection of corpus callosum completely removes one hemisphere 

 from the sway of the other as regards aid and abetment in visual gnosis. 

 The consequence of 'trained' cortical ablation on contralateral mne- 

 monics may be dealt with first. Fourteen chiasma-sectioned cats were 

 monocularly taught one or both of the two discriminations, Ill-ab and 

 Il-ab. Discrimination Ill-ab is an 'easy' discrimination while discrimination 

 Il-ab is relatively much more 'difficult' as determined by the number of 

 trials needed for the animals to learn, the general level of sustained pcr- 



Table III 



PERFORMANCE WITH UNTRAINED EYE ON DISCRIMINATION III-AB AFTER 

 DESTRUCTION OF CONTRALATERAL 'tRAINEd' CORTEX 



Nkm refused to run after 10 test trials, having erred in the last 3. 



formaiicc during overtraining, and the general behaviour of tlic aiumals 

 in the training situation. It may be stated parenthetically tliat the visual 

 capacity of the chiasma-sectioned cat as determined by the difficulty ot 

 discriminations that may be learned is vastly inferior to that of tlie normal 

 cat (sec Fig. 5). 



After the monocularly trained discriminations had been established and 

 stabilized by overtraining, cortex was surgically removed from the 

 'trained' hemisphere. The cortical removals were of three general types as 

 illustrated in Fig. 6. The minimal type lesion comprised removal of cortex 

 generally recognized as the striate or primary visual receptive cortex; the 



