While area CA1 of the hippocampal formation has long been regarded as the final stage of processing in the so-called """"""""trisynaptic circuit"""""""", it projects mainly to the subiculum. This suggests that the subiculum, rather than area CA1, is the main output of hippocampal processing. However, while physiological studies have evaluated neurons in areas adjacent to and in connection with the subiculum such as the hippocampus proper and parahippocampal cortex, subicular neurons have received little attention with respect to their response properties. The main objective of the proposed series of experiments is to investigate using multiple and single unit recording studies, the role of the subiculum as a relay station and/or processing area which connects the hippocampal formation and other areas of the brain. These areas include subcortical and neocortical structures which may play a role in learning and memory. Response characteristics of subicular neurons will be compared to characteristics of cells in the hippocampus and parahippocampal neocortex to determine the functional role of the subiculum as (1) a waystation for the transfer of hippocampal information to the neocortex, or (2) a parallel- or co-processor that can function independently of the hippocampus and work with the entorhinal cortex.
