investigating sensory systems at the peripheral level. Typical has been 

 the emphasis on olfaction and vision and their roles in guiding behavior. 



Although these latter studies have led to some interesting and 

 worthwhile findings, it is our belief that in order to understand and 

 predict shark behavior, it will first be necessary to correct the lack of 

 emphasis which has been placed on studying the shark central nervous 

 system. It is here where the necessary integration of various sensory 

 inputs occurs and where the animal's motivational state and past experi- 

 ences exert their influence on behavior. By having dwelled on studies 

 of isolated physiological systems, shark research is at a point where we 

 now know a fair amount about both the effective stimulus modalities and 

 mechanisms of shark sensory physiology but almost nothing about how such 

 sensory information gets translated into actual response patterns. As a 

 result, the stage is set for a new, more molar type of research into the 

 psychobiology of shark behavior. The scope of this research program 

 should eventually encompass such topics as central cross-modal sensory 

 interaction, sensori-motor integration, and neural arousal mechanisms 

 with an emphasis on the behavioral implications of these central neural 

 processes. Hopefully, the following brief description of some such work 

 already begun in sharks and other fishes will help clarify the type of 

 research program we believe could be profitably pursued. 



1) Central Sensorimotor Integration 



As Ebbesson (1970, 1972) has pointed out, several of the revolutionary 

 developments in neuroantomical technology have recently been applied to 

 study elasmobranchs. Use of these methods, e.g., Nauta and Fink-Heimer 

 degeneration techniques, electron microscopical analysis, etc., has led to 

 a marked change in our understanding of the structure of the shark brain 

 and, in many instances, a complete reversal of traditional beliefs 

 (Ebbesson & Heimer, 1970; Ebbesson & Ramsey, 1968; Ebbesson & Schroeder, 

 1971; Graeber & Ebbesson, 1972). For instance, work on the olfactory 

 inputs to the brain has shown that only a relatively small portion of the 

 shark forebrain (formerly called the "smell brain") received any infor- 

 mation regarding olfactory stimuli (Ebbesson, 1972; Ebbesson & Heimer, 

 1970). However, due to the rather limited attention given to central 

 nervous system investigations in elasmobranchs, there is still a large 

 void to be filled concerning how the brain processes olfactory as well as 

 other sensory information. 



In this regard, there has been practically no work done since the 

 turn of the century on relating brain anatomy and physiology to actual 

 behavior. Nevertheless, a recent series of studies has demonstrated the 

 fruitfulness of this approach (Graeber & Ebbesson, 1972; Graeber, Ebbesson 

 & Jane, 1973; Graeber, e_t al, 1972). Here relatively standard methods of 

 behavioral analysis were used to study the contributions of various central 

 nervous system structures to visually guided behavior in the nurse shark, 

 Ginglymostoma cirratum . Contrary to traditional belief it was found that 

 the processing of visual information into action involved much more than 

 the midbrain optic tectum. Instead, by depending heavily on both thalamic 

 and telencephalic nuclei, the central processing of visual cues in sharks 

 may more closely resemble that in mammals and reptiles. 



These findings obviously suggest that the neural basis of visually 

 guided shark attack is more complicated that previously imagined. They 



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