Delayed match-to-sample performance decrement in monkeys following cobalt- 60 irradiation

Abstract : The report presents findings on the behavioral effects of Cobalt-60 gamma irradiation on monkeys performing a complex delayed match-to-sample (DMTS) task or a simpler visual memorization task. It was found that the DMTS group reflected clear performance decrement at lower doses (e.g., several hundred rads midbody) than previously reported, while the memorization animals tended to show either no decrement or, in a few cases, response cessation (i.e., early transient incapacitation). The latter result has been characteristic of simple visual discrimination tasks when radiation doses of approximately 1000 rads have been employed. The differences between the two present groups, and the contrasts drawn with previous studies, were explained as a function of greater complexity of the DMTS task and an improved scoring procedure for performance decrement.