Short-term memory in the rhesus monkey: effects of dopamine blockade via acute haloperidol administration

The effects of dopaminergic blockade on recent or short-term memory (STM) were evaluated in test-sophisticated rhesus monkeys. Each monkey was tested under several doses of the antidopaminergic haloperidol (0.006 to 0.05 mg/kg), in an automated, delayed-response procedure. The same procedure and test apparatus had previously been used to demonstrate profound STM impairments in aged rhesus monkeys and strikingly similar deficits in young monkeys given the anticholinergic scopolamine. The results of this study do not support the notion that dopaminergic mechanisms play a critical role in primate STM. Although significant impairments in delayed-response accuracy were observed with the higher doses of haloperidol, this impairment was unrelated to the duration of the retention interval, implying a more general, non-mnemonic dysfunction. Since the qualitative nature of this deficit to dissimilar to, and not as specific as that previously found in aged rhesus monkeys (or young monkeys given scopolamine), it is suggested that age-related changes observed in the dopaminergic system are less likely to be responsible for the aged STM impairments than comparable age-related changes in the cholinergic system.