EFFECTS OF SCOPOLAMINE ON LEARNING AND MEMORY IN MONKEYS

The effects of scopolamine were evaluated in monkeys responding under operant procedures designed to evaluate drug effects on learning and m emory. In one procedure, responding was maintained by food presentatio n under a multiple schedule. One component of the multiple schedule wa s a repeated-acquisition task in which the discriminative stimuli for left- and right-key responses changed each session (learning). In the other component, the discriminative stimuli for responses were the sam e each session (performance). In both components of the multiple sched ule, scopolamine produced dose-related decreases in responding; there was little evidence of differential rate-decreasing effect between com ponents. Percent errors in learning were increased in a dose-related m anner, whereas percent errors in performance were generally unaffected except at high doses, which also produced substantial decreases ill r esponse rate. These results suggest that acquisition is more sensitive to the disruptive effects of scopolamine than is performance. The sec ond procedure utilized repeated acquisition and delayed performance as a technique to study the effects of scopolamine on memory. In this pr ocedure, each session was divided into three phases: acquisition, dela y and performance. After a 24-h delay, scopolamine had little or no ef fect on retention, accuracy or rate of responding. In contrast, after a 60-min delay, scopolamine decreased retention in a dose-related mann er. These data suggest that scopolamine produces a greater disruptive effect on short (60-min) versus long (24-h) delays.