LIMBIC NETWORKS AND ASSOCIATIVE LEARNING .2. ENTORHINAL CONTRIBUTIONSTO SPONTANEOUS-ALTERNATION, PASSIVE-AVOIDANCE, AND TASTE-AVERSION LEARNING

The hippocampus plays an important role in learning and memory, but th e precise nature of that involvement remains uncertain. Transection of the perforant path, a primary input pathway to the hippocampus, has b een shown to produce changes in reaction to novelty and acquisition of active avoidance; the nature and magnitude of these changes vary with lateral or medial perforant path damage. In a series of experiments o n adult rats, the role of these pathways in spontaneous alternation, e xploration, acquisition and extinction of conditioned responses, passi ve avoidance, and conditioned taste aversion was investigated. Lateral transection reduced exploration while medial transection facilitated acquisition of an active avoidance response; no effects were observed on any other measure. Results are discussed in terms of what perforant path damage might reveal regarding the interactions of the hippocampu s with other brain regions.