Cholinergic Drug Effects on Reaction Speed and Short-Term Memory of Primates

Abstract

Abstract : The effects of four cholinergic drugs on the speed and accuracy of performance of a short-term memory (STM) task by rhesus monkeys were measured. The drugs and doses studied were atropine sulfate and atropine methylnitrate (0. 044, 0.140, and 0.440 mg/kg), physostigmine sulfate (0.05, 0.10, and 0.15 mg/kg) , pyridostigmine bromide (0.15, 0.20, and 0.25 mg/kg), and all possible combination doses of atropine sulfate (0.0, 0.14, and 0.44 mg/kg) and physostigmine sulfate (0.0, 0.75, and 0.10 mg/kg). The STM task was a three- alternative delayed match-to-sample paradigm with hue the relevant stimulus dimension and delay (retention interval) titrated so as to maintain performance at approximately 75% correct. The following performance measures were examined: median retention interval (the measure of STM), speed of response to sample stimulus, speed of response to match stimuli when the correct match was chosen, and speed of response to match stimuli when the incorrect match was chosen. There were no significant effects of any drug on STM, although there were suggestions that physostigmine can facilitate and atropine can interfere with STM. These suggestive findings are in agreement with results from other laboratories. At high doses, physostigmine completely disrupted performance of the STM task. Atropine reversed this effect.