Magnitude of dopamine release in medial prefrontal cortex predicts accuracy of memory on a delayed response task

Modulation of neural function in the prefrontal cortex (PFC) by dopamine (DA) is essential for higher cognitive processes related to attention, working memory, and planning of future behavior. The present study demonstrates that DA efflux in the PFC is increased in a phasic manner when a rat engages in search behavior for food reward on an eight arm radial maze guided by memory, independent of whether or not reward is obtained for making the correct choice. Furthermore, disruption of accurate recall of the correct pattern of arms induced by increasing the delay period from 30 min to 1 or 6 hr, is associated with attenuated DA efflux during the retrieval phase of the task. The observed increase in DA efflux in the absence of reward at a 30 min delay and the minimal increase during consumption of the same quantity of food during poor performance after an unexpected 6 hr delay, argue against a simple relationship between DA function in the PFC and reward processes. Instead, these data demonstrate a close functional relationship between the release of DA from terminals within the PFC and the retrieval of specific trial unique memories; furthermore, the magnitude of mesocortical DA efflux is predictive of the accuracy of this form of memory.