Some Behavioral Effects of Ionizing 

 Radiation on Primates* 



Arthur J. Riopelle 



Yerkes Laboratories of Primate Biology, 

 Orange Park, Florida 



For the past eight years, Yerkes Laboratories have been engaged in a 

 survey of the behavioral effects of ionizing radiation in chimpanzees. These 

 studies were begun by Henry W. Nissen and continued under his direction 

 until his death in 1958. They are now being continued in collaboration with 

 C. M. Rogers. Only a small portion of the results are as yet published, and 

 a review of the findings seems appropriate at this time. 



The chimpanzees were given 375 or 400 r whole body gamma radiation. 

 Although this dose is less than that usually believed to cause early pathologic 

 changes in the central nervous system, there have been reports of functional 

 changes following irradiation with this amount (Livshits, 1953, reported by 

 Stahl, 1959). 



In another investigation, the heads of cynomolgus monkeys (Ai. irus) were 

 irradiated with 2,000 r, a dose which, if given to the whole body, would have 

 killed the animals quickly. 



This latter investigation was begun in the hope that it would contribute 

 toward the development of techniques to study the role played by various 

 parts of the brain in the elaboration of certain behavioral patterns, without 

 the artifacts of more conventional methods. Numerous studies of brain 

 functions and behavior made use of the methods of surgical ablation, elec- 

 trical stimulation, or administration of drugs, most of which reported definite 

 behavioral changes. By eliminating the need for entry into the cranium, the 

 effects of infection, displacement and distortion of tissue, and electrical 

 damage are avoided. Side effects are doubtlessly minimal with irradiation, 

 and the vascular system is left uninterrupted. 



In general, the more techniques employed to study the problem, the more 

 surely can we isolate the real from the artifacts, especially where indirect 

 effects are significant. Should behavioral changes be manifested, the sensi- 



* This work was performed under contract with the U. S. .Atomic Energy Com- 

 mission. 



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