BEHAVIOR AND CNS INTEGRATION 



213 



1 B W 



-i 1 1 t 1 1 r 



5 10 15 20 25 30 35 



H V 



t 1 1 1 r 



5 10 15 20 25 30 



TRAINING SESSIONS 



Figure 6 Postoperative learning curves on the BW 

 and HV tasks for two sharks with bilateral lesions 

 in the posterior telencephalon. "P" indicates 

 attempt to correct position habit by placing cor- 

 rect target on nonpreferred side for all daily trials. 



of BW training the shark developed a position habit that persisted into HV 

 training despite attempts to correct it. The visual nature of this shark's post- 

 operative learning deficit is confirmed by its subsequent performance on a 

 nonvisual, position task in which the correct target of the HV pair was 

 always located on the left, or nonpreferred, side. The shark reached criterion 

 quickly, after 54 trials. It is clear that the shark did not depend on visual tar- 

 get cues to learn this later task, because it continued to choose the left-hand 

 target when the positions of the horizontally and vertically striped targets 

 were reversed after criterion was achieved. 



NS-191 required more training than NS-186 before its median daily res- 

 ponse latency decreased to a stable, low level, even though it had received 

 14 days of pretraining before undergoing surgery. The improvement in 

 response latency coincided with the appearance of vicarious trial-and-error 

 behavior and sudden swerving from one side of the approach alley to the 

 other before choosing a target. Upon the failure of any stable performance to 

 develop on the BW task, the shark was switched to the more difficult HV 

 task. Here training was finally halted after the subject became uncooperative, 

 frequently circling just before the targets and refusing to swim through parts 

 of the conditioning apparatus. 



The histological findings for these two sharks are reconstructed in Figure 

 8. They both received substantial damage to the portions of the central 

 telencephalic nucleus receiving input from the thalamic visual areas. Despite 

 their poor performances on the visual discrimination tasks, subjects NS-186 

 and NS-191, like the other sharks, were able to detect the presence of light, 



