218 



VISION 



10 20 



TRAINING SESSIONS 



Figure 11 Performance of three sharks on the BW and 

 HV discrimination tasks before and after surgery (OP) 

 that damaged 10% to 50% of the central telencephalic 

 nuclei. 



-BW 

 --HV 



TRAINING SESSIONS 



Figure 12 Performance of three sharks on the BW and 

 HV discrimination tasks before and after surgery (OP) 

 that damaged less than 10% of the central telencephalic 

 nuclei. 



The results of this second experiment indicate that the discrimination 

 deficits seen so far are not due to disruption of visual learning mechanisms 

 alone, but can be attributed instead to some type of sensory loss or sensori- 

 motor loss that makes it difficult for them to orient to, or localize, a stimu- 

 lus in visual space. It is still difficult to decide exactly which type of loss is 

 responsible. The animals with severe central telencephalic damage can 

 detect light and are therefore not totally blind. This conclusion agrees with 

 Baru's finding that sharks with more complete telencephalic ablations are 



