Prefrontal neuronal activity in rhesus monkeys performing a delayed anti-saccade task

PATIENTS with damage to the dorsolateral prefrontal cortex are impaired on cognitive tasks such as the Wisconsin Card Sort Test¹, the Stroop Test2 and an anti-saccade paradigm³, in which sensory-guided habitual responses must be suppressed in favour of conceptually or memory-guided responses. We report here recordings from prefrontal neurons in rhesus monkeys trained to perform a delayed anti-saccade task based on tests that have been used with humans³. Activity in the same prefrontal neurons was recorded across conditions when saccades were made toward a remembered target, and also when this prepotent response was suppressed and a saccade in the opposite direction required. Our findings show that most prefrontal neurons code the location of the visual stimulus in working memory, and that this memory can be engaged to suppress as well as prescribe a response. These results establish, in a subset of prefrontal neurons, the iconic nature of the memory code, and suggest a role for visual memory in response suppression.