Hippocampal, but not parahippocampal, damage in a case of dense retrograde amnesia: a pathological study.

Damage limited to the hippocampus is believed to result in temporally graded retrograde amnesia (RA), with more severe RA occurring only as a result of additional damage to adjacent neocortical structures. Patient N.T. suffered dense, temporally ungraded, RA following a right temporal lobectomy for intractable epilepsy. Postmortem pathological examination revealed sclerosis of the unresected left hippocampus. Microscopic analysis of the parahippocampal areas and other temporal lobe regions undertaken in this study confirmed the absence of any significant pathology extending beyond the hippocampus. This further review of the pathological findings in N.T. is therefore not consistent with the postulated role of the hippocampus as a temporary memory store and suggests instead that the hippocampus is involved in the storage of remote memories as well as recent memories.