Neurons in rat medial prefrontal cortex show anticipatory rate changes to predictable differential rewards in a spatial memory task.

The present study electrophysiologically examined the contribution of prelimbic and infralimbic neurons in the medial prefrontal cortex (mPFC) to integration of reward and spatial information while rats performed multiple memory trials on a differentially rewarded eight arm radial maze. Alternate arms consistently held one of two different reward amounts. Similar to previous examinations of the rat mPFC, few cells showed discrete place fields or altered firing during a delay period. The most common behavioral correlate was a change in neuronal firing rate prior to reward acquisition at arm ends. A small number of reward-related cells differentiated between high and low reward arms. The presence of neurons that anticipate expected reward consequences based on information about the spatial environment is consistent with the hypothesis that the mPFC is part of a neural system which merges spatial information with its motivational significance.