Visual acuity performance of normal and chronic irradiated monkeys.

Abstract

Abstract : Six normal, 10 low-dose irradiated (77-154 rep), 9 intermediate-dose irradiated (308 rep), and 4 high-dose irradiated rhesus monkeys (616 rep) were tested to a criterion of 21 correct responses (24 trials a day) for two successive days on each of eight visual acuity problems presented in order of increasing difficulty. Each problem required the subject to choose between circles and circles with breaks in order to procure a food reward. Previous visual acuity testing had shown a deficit only in the high-dose irradiated group during the first year following the radiation exposure to which the experimental animals had been subjected three years prior to the initiation of the present study. The results of the present study demonstrated that: (1) The visual acuity deficit noted during the first year after exposure in the high-dose irradiated monkeys (616 rep) was still manifested three years after exposure. (2) Monkeys in the intermediate-dose group (308 rep), that had shown no visual acuity deficit during the first year after exposure, manifested such a deficit three years after exposure. (3) An interpretation of the results in terms of a basic deficit in learning ability for the monkeys of these two groups is contraindicated by their superiority over normal and low-dose irradiated monkeys on the initial and easiest problem. (Author)