BEHAVIORAL EFFECTS OF RADIATION ON PRIMATES 



727 



100 



Fig. 5. Performance of normal and head-irradiated monkeys on a series of dis- 

 crimination learning problems presented consecutively. 



to undergo testing on a series of consecutively presented discrimination 

 problems. The learning curves of the normal and the combined irradiated 

 groups for successive blocks of 50 problems are shown in Fig. 5. Although 

 both groups had received identical preirradiation training, their capabilities 

 after treatment were markedly dissimilar. The normal monkeys retained the 

 ability to perform the test during inactivity. The irradiated monkeys showed 

 loss on the first block of problems and further loss on the second and third 

 blocks of problems. There was no o\erlap of scores between the two groups. 



Both of these tests were conducted after the edema had subsided some- 

 what, and the animals were not tested if there was any doubt as to clarity 

 of vision. At no time was the behavior of the subjects indicative of impeded 

 vision, nor was it ever inappropriate. Food was always eaten when offered, 

 and responses, although somewhat slower than those of the normal subjects, 

 were suggestive of high motivation. 



In contrast to the chimpanzee data, the monkey data clearly indicate that 

 2,000 r administered within 40 minutes produces profound behavioral 

 changes which are probably not transient. The tests described are of proven 

 usefulness for the detection of experimental brain damage in macaques and 

 may be of assistance in identifying those organ systems within the brain which 

 are the more sensitive to irradiation. Although w^e regret that our macaques 

 did not live long enough to undergo a more extensive battery of tests, the 

 results obtained do suggest that some functional derangement has occurred 

 at least in the so-called "posterior association"' areas. Probably the temporal 



