Morehead State University

Poster Title

Differential Involvement of the Prefrontal Cortex and the Nucleus Accumbens in Visuospatial Learning

Institution

Morehead State University

Abstract

The medial prefrontal cortex (mPFc) and the nucleus accumbens (NAc) are thought to play an important role in spatial learning. Neuroanatomical studies indicated a topographical organization: NAc-core region projects to the dorsal mPFc and NAc-shell region projects to the ventral mPFc. The present study examined differential involvement of subregions within mPFc and NAc during two visuospatial tasks using reversible lesions with lidocaine. Lidocaine produces a temporal blockade of neural transmission. Wistar rats were trained on two tasks; one required a correct barpress on cue location (matching); the other required a correct barpress opposite to cue location (non-matching). Upon reaching a criterion (>85% correct, 3 consecutive sessions), rats were cannulated in mPFc (dorsal/ventral) or NAc (core/shell). After recovery, rats were retrained until their performance reached the pre-surgery criteria, and received lidocaine and saline infusions into each subregion of mPFc or NAc. Lidocaine infusions into neither subregion of mPFc affected performance on the matching task. Lidocaine infusions into the ventral, not dorsal, mPFc decreased correct responses on the nonmatching task. Interestingly, lidocaine infusions into either shell or core decreased performance on both tasks. Our preliminary data indicate that activation of D1-dopamine receptors within shell, but not core, is critical for successful performance during the nonmatching task. Our data suggest that visuospatial discrimination requires both mPFc and NAc, and that involvement of each subregion within mPFc and NAc depends on the nature of behavioral tasks.

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Differential Involvement of the Prefrontal Cortex and the Nucleus Accumbens in Visuospatial Learning

The medial prefrontal cortex (mPFc) and the nucleus accumbens (NAc) are thought to play an important role in spatial learning. Neuroanatomical studies indicated a topographical organization: NAc-core region projects to the dorsal mPFc and NAc-shell region projects to the ventral mPFc. The present study examined differential involvement of subregions within mPFc and NAc during two visuospatial tasks using reversible lesions with lidocaine. Lidocaine produces a temporal blockade of neural transmission. Wistar rats were trained on two tasks; one required a correct barpress on cue location (matching); the other required a correct barpress opposite to cue location (non-matching). Upon reaching a criterion (>85% correct, 3 consecutive sessions), rats were cannulated in mPFc (dorsal/ventral) or NAc (core/shell). After recovery, rats were retrained until their performance reached the pre-surgery criteria, and received lidocaine and saline infusions into each subregion of mPFc or NAc. Lidocaine infusions into neither subregion of mPFc affected performance on the matching task. Lidocaine infusions into the ventral, not dorsal, mPFc decreased correct responses on the nonmatching task. Interestingly, lidocaine infusions into either shell or core decreased performance on both tasks. Our preliminary data indicate that activation of D1-dopamine receptors within shell, but not core, is critical for successful performance during the nonmatching task. Our data suggest that visuospatial discrimination requires both mPFc and NAc, and that involvement of each subregion within mPFc and NAc depends on the nature of behavioral tasks.