Impairment of Recent Memory by Marihuana and THC in Rhesus Monkeys

Abstract

SEVERAL studies with humans have indicated that marihuana and its active ingredient, delta-9-tetrahydro cannabinol (THC), have disruptive effects on short term memory^1–3. Of the few animal studies on THC, only that of Scheckel et al.⁴ addressed the question of memory impairment. The results of that study were attributed to lack of motivation. The study described here was designed to elucidate the effects of marihuana on short term memory in rhesus monkeys using an automated delayed matching-to-sample task. In our laboratory, monkeys have been trained to puff cigarettes for a water reward, and thus we are able to study the effects of marihuana smoke while avoiding the set problems associated with human subjects. Another group of monkeys, trained on a similar memory task, was administered oral THC. Significant memory impairment was established with both modes of administration.