BEHAVIOR AND CNS INTEGRATION 221 



SUMMARY 



Recent advances in the sensory biology and neuroanatomy of elasmobranchs 

 have enhanced the chances for success in studying the brain— behavior rela- 

 tionship in sharks. The advantages of such an analysis are discussed in rela- 

 tion to past efforts to understand shark behavior and specifically in terms of 

 learning more about shark central visual mechanisms. The morphology of the 

 shark's central visual system is reviewed in light of new findings compared 

 with the still prevalent traditional views of comparative neuroanatomy. Fol- 

 lowing a discussion of various methods to assess visual function in sharks, 

 behavioral results are presented which indicate that the optic tectum does 

 not exert exclusive control over visually guided behavior in sharks. The 

 participation of the telencephalon in central visual processing is supported 

 by a combination of anatomical, electrophysiological, and behavioral data. 

 Nurse sharks with experimental lesions of the visual portion of the central 

 telencephalic nucleus have difficulty learning, or are unable to learn, simple 

 visual discrimination tasks. The fact that earlier workers reported no visual 

 deficits following telencephalic ablations may have been due to their ex- 

 clusive use of dogfish, the thalamotelencephalic pathways of which have no 

 visual function. The exact nature of any functional differences between the 

 midbrain and forebrain components of the shark central visual system re- 

 mains a matter for conjecture. 



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