RADIATION-CONDITIONED BEHAVIOR 689 



posure and, therefore, were not involved in motivating behavior during 

 the conditioning phase. One functional disturbance in the conscious 

 rat was found to fulfill the criteria for a response coincident with exposure 

 and sensitive to small doses of radiation. In a study of gastrointestinal func- 

 tion, radiation exposure throughout a transit period of 2.5-20 minutes 

 decreased the gastric transit rate by a factor of at least three with no latent 

 period or minimum efTective dose observable (Jones and Kimeldorf, 

 1959). Conard (1951) has reported an intestinal disturbance during ex- 

 posure, namely an increase in motility with exposure doses of 100 r and more 

 after a latency of approximately 1 minute. However, the relationship between 

 gastrointestinal dysfunction during low dose exposure and conditioning re- 

 mains obscure since prior adrenalectomy profoundly reduced the gastric 

 retention effect during radiation exposure, but the same operation did not 

 inhibit saccharin conditioning. 



In summary, it has been possible to demonstrate that radiation exposure 

 can instigate learning and that stimuli associated with exposure can become 

 determinants of postirradiation behavior in several species of mammals. Thus 

 far, it has not been possible to delineate the perceptual properties of the 

 stimulus in terms of a specific receptor mechanism, endocrine state, or 

 anatomic region whose exposure to radiation is critical for the event. The 

 motivational strength of the radiation stimulus is indicated by the relatively 

 small dose which is sufficient to condition a taste aversion in the rat and by 

 the persistence of the conditioned response. 



With the demonstration of radiation-conditioned behavior, there is im- 

 plied at least a transient alteration in neural function contingent upon the 

 radiation. It has not been established whether neural involvement is the 

 result of direct action of radiation on a component of the nervous system or 

 is the result of neural mediation of radiation eflfects in other systems. The 

 use of radiation as a stimulus in the conditioning situation provides a tool 

 for eliciting neural activity at radiation dose levels well below those available 

 with other methods and should contribute to the analysis of the role of the 

 nervous system in the radiation syndrome. 



References 



Andrews, H. L., and Cameron, L. M. 1960. Radiation avoidance in the mouse. Proc. 



Soc. Exptl. Biol. Med. 103, 565-567. 

 Arbit, J. 1959a. Spatial avoidance behaviour in the rat as a result of exposure to 



ionizing radiation. Brit. J. Radiol. 32, 214. 

 Arbit, J. 1959b. Autonomic block and avoidance conditioning using x-radiation as the 



UnCS. Paper read at Midwestern Psychol. Assoc. Meetings, Chicago. 

 Conrad, R. A. 1951. Effect of x-irradiation on intestinal motility of the rat. Am. J. 



Physiol. 165, 375-385. 



