Friday, February 18, 2011

The subiculum is the most inferior region of the hippocampus, lying between field CA1 of Ammon's horn and the parahippocampal gyrus. Located ventrally and medially to the dentate gyrus, it is a ventral continuation of the hippocampus. The subiculum is considered to be a gating structure for outputs originating from the hippocampus proper to the neocortex.

Mediating hippocampal-cortical interaction, the subiculum receives input from CA1 and entorhinal cortical layer III pyramidal neurons as it is the main output of the hippocampus. The pyramidal neurons of the subiculum send projections to the nucleus accumbens, septal nuclei, prefrontal cortex, lateral hypothalamus, nucleus reuniens, mammillary nuclei, entorhinal cortex and amygdala. The pyramidal neurons in the subiculum exhibit transitions between two modes of action potential output: bursting and single spiking. The transitions between these two modes is thought to be important for routing information out of the hippocampus.

Given the hypothesis that epileptic activity is triggered within the hippocampal formation when the CA3 and CA1 fields of Ammon's horn are damaged or even absent, it is feasible that the adjacent subiculum is uniquely responsible for the generation of limbic seizures.