WHICH BRAIN-REGIONS ARE CRITICALLY INVOLVED IN THE RETRIEVAL OF OLD EPISODIC MEMORY

Memory is two-sided like the head of Janus: it looks into the past (re trograde memory) and the future (anterograde memory). While current op inion assumes a strong anatomical interdigitation in the processing of either kind of memory, recent single case reports and results obtaine d with the positron emission tomographic subtraction method indicate t he likely existence of a dissociation: regions of the limbic system ar e primarily engaged in the encoding of autobiographical and semantic i nformation, while cortical areas in the orbitofrontal and anterolatera l temporo-polar regions are principally engaged in information retriev al. Within this retrieval system the right hemisphere may subserve epi sodic memory retrieval, and the left retrieval from the knowledge syst em (semantic memory).