674 WILLIAM J. ARNOLD 



results, it seems clear that brain-irradiated rats and rats starved to match 

 the weight loss of brain-irradiated rats perform significantly better than 

 control rats. The leg-irradiated rats tend to perform better than the controls, 

 but the difference is not reliable. Finally, the starved rats tend to perform 

 better than the brain-irradiated rats, but the difference is not statistically 

 reliable. Unfortunately, no definite conclusion can be drawn as to whether 

 there were detrimental effects from brain irradiation which were masked by 

 increased hunger motivation, but the possibility of such detrimental effects 

 remains. 



Maze Learning as a Function of Age When Irradiated 



Subjects were 90 albino rats grouped according to age at the time of ir- 

 radiation into 60-, 90-, and 120-day-old groups. Each group contained 15 

 males and 15 females. Dosage was 5,000 r to the brain. Sixty days after 

 irradiation and 7 days prior to the preliminary maze training, the rats were 

 placed on a 24-hour feeding schedule. After the preliminary training, they 

 were given one training trial per day on a 14-unit multiple T-maze until 

 they reached a criterion of 3 consecutive trials with a total of 3 errors or 

 less. On the 60th and 90th days after reaching the criterion, the rats were 

 given one retention test trial. After the 90-day retention test, the rats were 

 retrained on the maze, one trial per day until they again reached the 

 criterion. 



Results 



In the acquisition phase of the experiment, the irradiated animals in the 

 60 and 90 day groups tended to learn the maze faster than their controls. 

 The differences, however, were not statistically significant. The direction of 

 the differences was reversed for the 120 day group, where the control 

 animals tended to learn faster than the experimentals. Again, this difference 

 was not significant. None of the differences on the 60 and 90 day retention 

 tests or on the relearning trials was significant. These findings indicate that, 

 within the time limits involved in this experiment, irradiation at different 

 ages does not produce significant decrements in maze performance. This is 

 noteworthy in view of the fact that we have shown that the same dosage 

 produces close to 100% mortality in rats 30 days of age. 



Maze Learning As a Function of Higher Dosages 



This experiment was designed to test the effects of 6,000, 7,000, 8,000, 

 9,000, and 10,000 r. Unfortunately, a breakdown of the x-ray machine and 



