594 



BRAIN MECHANISMS AND LEARNING 



group with an anterior lesion show a marked deficit. Differences from 

 the normal group arc significant both for the 'posterior' and the 'anterior 

 group' (p < G.ooi). 



The failure of the 'anterior group' is worth noticing, as until now 



Fig. 5 



Cortical lesions corresponding to the rats of the 'posterior t^roup' (sec legend 



Fig. 3). 



investigators have explored almost exclusively the effect of lesions in the 

 'cortical area' of the CS and only rarely the ci^cct of total decortication or 

 of extensive lesions of the non-visual cortex. 



The fact that four out of fourteen rats in the 'anterior group' learned 

 the CR might indicate that the average percentage (41 per cent) of ablated 



