Prefrontal cortex and episodic memory retrieval mode

A multistudy analysis of positron emission tomography data identified three right prefrontal and two left prefrontal cortical sites, as well as a regi on in the anterior cingulate gyrus, where neuronal activity is correlated w ith the maintenance of episodic memory retrieval mode (REMO), a basic and n ecessary condition of remembering past experiences. The right prefrontal si tes were near the frontal pole [Brodmann's area (BA) 10], frontal operculum (BA 47/45), and lateral dorsal area (BA 8/9). The two left prefrontal site s were homotopical with the right frontal pole and opercular sites. The sam e kinds of REMO sites were not observed in any other cerebral region. Many previous functional neuroimaging studies of episodic memory retrieval have reported activations near the frontal REMO sites identified here, although their function has not been clear. Many of these, too, probably have signal ed their involvement in REMO, We propose that REMO activations largely if n ot entirety account for the frontal hemispheric asymmetry of retrieval as d escribed by the original hemispheric encoding retrieval asymmetry model.