Prefrontal cortex and episodic memory retrieval mode

TLDR

Prior neuroimaging studies have consistently shown frontal activations during episodic memory retrieval, but their functional significance has remained unclear, suggesting a possible role for retrieval mode (REMO). The authors aim to test whether REMO activations explain the frontal hemispheric asymmetry observed in episodic retrieval, as posited by the hemispheric encoding‑retrieval asymmetry model. PET analysis across multiple studies revealed that activity in three right prefrontal sites (near BA10, BA47/45, BA8/9) and two left prefrontal sites, along with an anterior cingulate region, is specifically correlated with maintenance of REMO, with no other cerebral regions showing such a pattern.

Abstract

A multistudy analysis of positron emission tomography data identified three right prefrontal and two left prefrontal cortical sites, as well as a region in the anterior cingulate gyrus, where neuronal activity is correlated with the maintenance of episodic memory retrieval mode (REMO), a basic and necessary condition of remembering past experiences. The right prefrontal sites 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 sites were homotopical with the right frontal pole and opercular sites. The same 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 signaled their involvement in REMO. We propose that REMO activations largely if not entirely account for the frontal hemispheric asymmetry of retrieval as described by the original hemispheric encoding retrieval asymmetry model.