Evidence against a specific effect of cholinergic drugs on spatial memory in primates.

A scopolamine-like delay-dependent impairment in spatial delayed response performance in rhesus monkeys was induced by irrelevant interpolated activity or by using extended retention intervals. Physostigmine readily reversed the effects of scopolamine but had no effect on performance in young monkeys performing an irrelevant distractor task or in monkeys tested using extended retention intervals. Reducing stimulus control did not impair performance and did not alter the dose-response curve for induction of a deficit by scopolamine. Reducing the stimulus presentation time impaired performance across all retention intervals in a way which did not resemble the effect of scopolamine and which disappeared with practice. Our findings do not support the proposal that physostigmine interacts specifically with short-term spatial memory in primates.