Delayed-matching and delayed-response deficit from cooling dorsolateral prefrontal cortex in monkeys.

The hypothesis that the functional integrity of the dorsolateral prefrontal cortex is important for short-term memory of both spatial and nonspatial information was examined. Monkeys were tested in delayed matching-to-sample (DMS) and delayed-response (DR) tasks with delays of 0-32 sec. Testing was carried out under three different conditions: frontal cooling (FC), parietal cooling (PC), and normal temperature (noncooling, NC). Errors, reaction time, and motor activity were recorded. The proportion of correct responses decreased in NC as a function of the delay. This decrease was significantly accentuated by FC, whereas it was not modified by PC. At each delay, the decrement elicited by FC was as large in DR as in DMS. Reaction time and activity normally increased as a function of delay; these changes were enhanced by FC. The FC-induced decrements in proportion of correct responses suggest a faster loss from short-term memory of both spatial and nonspatial information.