Controlling hippocampal output: the central role of subiculum in hippocampal information processing.

The subiculum has a central position between the hippocampus proper and entorhinal and other cortices, as well as a range of subcortical structures. The functional role of subiculum within the hippocampal formation circuit remains largely unexplored and a theoretical and experimental consensus on its functions has yet to emerge. Presented here is a simple and speculative model of the functions of the subiculum, based partly on anatomical, behavioural and neurophysiological considerations. The model suggests, firstly, that the subiculum acts to amplify hippocampal output, given the prominent bursting behaviour of its neurons and, secondly, that there is a dorso-ventral segregation of function within the subiculum. The dorsal component appears principally concerned with the processing of information about space, movement and memory, whereas the ventral component appears to play a major regulatory role in the inhibition of the HPA axis.