Poster Title

Prefrontal Cortex in Spatial Learning

Institution

Morehead State University

Abstract

The rat medial prefrontal cortex (mPFc) is hypothesized to be involved in spatial learning, behavioral flexibility or inhibition, and attention. Animal lesion studies that characterize specific functions of mPFc have yielded conflicting results. One factor varied across these experiments is lesion sites within mPFc (dorsal, ventral, or both). The present study examined functional differences between the dorsal and ventral mPFc in simple spatial discrimination, using reversible lesions. We hypothesized that the ventral, but not the dorsal mPFc, is critical for successful performance. Wistar rats were trained on a spatial discrimination task, which required a correct barpress matching the cue location. Upon reaching criterion (³ 85% correct, 3 sessions), rats were implanted with bilateral cannulae aimed at mPFc (dorsal or ventral). Postsurgery training resumed after a 5-7 day recovery period. Once performance reached a pre-surgery criterion, either lidocaine (2%) or saline was infused (0.5 ml/site), 5 min prior to testing on the task. Lidocaine and vehicle infusions were counterbalanced within subjects, allowing 2-3 days between infusions. We found that lidocaine infusions into the ventral mPFc, but not the dorsal mPFc, de-creased correct responses. Vehicle infusions in neither region affected performance. This was consistent with our preliminary observation that permanent, excitotoxic lesions in the ventral mPFc disrupt acquisition of spatial discrimination. The present findings support our hypothesis, and suggest that the integrity of the ventral, but not the dorsal mPFc, is required in spatial discrimination.

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Prefrontal Cortex in Spatial Learning

The rat medial prefrontal cortex (mPFc) is hypothesized to be involved in spatial learning, behavioral flexibility or inhibition, and attention. Animal lesion studies that characterize specific functions of mPFc have yielded conflicting results. One factor varied across these experiments is lesion sites within mPFc (dorsal, ventral, or both). The present study examined functional differences between the dorsal and ventral mPFc in simple spatial discrimination, using reversible lesions. We hypothesized that the ventral, but not the dorsal mPFc, is critical for successful performance. Wistar rats were trained on a spatial discrimination task, which required a correct barpress matching the cue location. Upon reaching criterion (³ 85% correct, 3 sessions), rats were implanted with bilateral cannulae aimed at mPFc (dorsal or ventral). Postsurgery training resumed after a 5-7 day recovery period. Once performance reached a pre-surgery criterion, either lidocaine (2%) or saline was infused (0.5 ml/site), 5 min prior to testing on the task. Lidocaine and vehicle infusions were counterbalanced within subjects, allowing 2-3 days between infusions. We found that lidocaine infusions into the ventral mPFc, but not the dorsal mPFc, de-creased correct responses. Vehicle infusions in neither region affected performance. This was consistent with our preliminary observation that permanent, excitotoxic lesions in the ventral mPFc disrupt acquisition of spatial discrimination. The present findings support our hypothesis, and suggest that the integrity of the ventral, but not the dorsal mPFc, is required in spatial discrimination.