NEURAL CIRCUIT ANALYSIS OF SPATIAL WORKING-MEMORY - ROLE OF PRESUBICULUM AND PARASUBICULUM, MEDIAL AND LATERAL ENTORHINAL CORTEX

Using a continuous recognition memory procedure for spatial location i nformation, rats were given sequential presentation of individual arms on a 12-arm maze. Each arm contained a Froot Loop reinforcement the f irst time it was presented, and latency to traverse the arm was measur ed. A subset of the arms were repeated, but did not contain reinforcem ent. Repeated arms were presented with lags ranging from zero to six ( from zero to six different arm presentations occurred between the firs t and repeated presentation). After completion of acquisition training (significantly longer latencies for repeated arms in comparison with the first presentation of an arm), rats received lesions of the medial or lateral entorhinal cortex, pre- and parasubiculum, or served as sh am-operated controls. Based on continued postsurgery training and addi tional tests, the results indicated that rats with pre- and parasubicu lum or pre- and parasubiculum plus medial entorhinal cortex produced s ustained impairment in performing the task. Medial or lateral entorhin al cortex and control lesions did not display any sustained deficits. The data suggest that working memory for spatial location information is mediated primarily by the pre- and parasubiculum, but not medial en torhinal and lateral entorhinal cortex. Hippocampus 1998;8:416-423. (C ) 1998 Wiley-Liss, Inc.