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 in keeping temporal cortex-based representations 'on-line' during a working memory task. To test this hypothesis, the effects of electrolytic prefrontal cortex lesions on the firing of area TE and perirhinal cortex (PRC) neurons 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 prefrontal-lesioned animals (82%) were more likely to display a significant variation in firing across the maze compared to controls (50%; P < 0.01), and to have more discrete location-related properties (50% of neurons) compared to the control (5%) group (P < 0.0005). This finding suggests that prefrontal cortex normally modulates the transmission and/or processing of spatial information in area TE/PRC during a working memory task. Modulation could be mediated through direct connections between the structures or via prefrontal control of subcortical structures. This finding has implications for our understanding of prefrontal-temporal involvement in memory and cognitive disorders.