Prefrontal cortex lesions augment the location-related firing properties of area TE/perirhinal cortex neurons in a working memory task

It has previously been proposed that prefrontal cortex may have some role i n keeping temporal cortex-based representations 'on-line' during a working memory task. To test this hypothesis, the effects of electrolytic prefronta l cortex lesions on the firing of area TE and perirhinal cortex (PRC) neuro ns were examined while rats performed a delayed non-match to position task in the T-maze. The behavioural performance of control (n = 4) and lesioned (n = 4) animals were similar during this task, and many neurons displayed a statistically significant location-related variation in firing rate during the sample (44/56 neurons) and test (39/56 neurons) phases. Units from pre frontal-lesioned animals (82%) were more likely to display a significant va riation in firing across the maze compared to controls (50%; P < 0.01), and to have more discrete location-related properties (50% of neurons) compare d to the control (5%) group (P < 0.0005). This finding suggests that prefro ntal cortex normally modulates the transmission and/or processing of spatia l information in area TERN during a working memory task. Modulation could b e mediated through direct connections between the structures or via prefron tal control of subcortical structures. This finding has im plications for o ur understanding of prefrontal-temporal involvement in memory and cognitive disorders.