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VISION 



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60 H NS-186 POST TELEN 

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TRAINING SESSIONS 



Figure 7 Postoperative learning curves on the BW and HV tasks for two 

 sharks with bilateral posterior telencephalic lesions that subsequently 

 damaged areas of the central telencephalic nucleus receiving visual input. 

 Upper function in each pair indicates median daily response latency, from 

 leaving start pen to making correct response. 



as indicated by their quickly turning away from a light source suddenly 

 switched on during darkness. In addition, they all exhibited normal pupillary 

 responses to changes in ambient light intensity. 



These findings offer the first behavioral evidence for telencephalic visual 

 mechanisms in sharks and differ significantly from the results of similar 

 studies with teleost fish, in which no postoperative visual deficits have been 

 found (Bernstein 1962, Iwai et al. 1970, Nolte 1932, Savage 1968a, Savage 

 and Swingland 1969). The reported decreases in spontaneous activity and in- 

 creases in response latency and variability in teleosts (Aronson and Herber- 

 man 1960, Dewsbury and Bernstein 1969, Kaplan and Aronson 1967, 

 Overmier and Curnow 1969) were not observed in the sharks with posterior 

 telencephalic lesions and therefore cannot be used to explain their poor 



