Integrated brain activity in medial temporal and prefrontal areas predictssubsequent memory performance: Human declarative memory formation at the system level

After an era in which lesion studies have identified the declarative memory system and its essential anatomical structures, functional imaging and eve nt-related potential studies have begun to delineate the neural underpinnin gs of declarative memory formation at the system level. By memory formation , we refer to those mnemonic processes present during encoding that transfo rm perceptual representations into enduring memories. Recent studies have r evealed that distinct regions in medial temporal and prefrontal areas exhib it more neural activity during successful than unsuccessful memory formatio n. We attempt to identify the nature of the processes underlying these subs equent memory effects, Reviewed data suggest specific mnemonic operations i n the medial temporal lobe that may be integrated with semantic/perceptual operations and subserving operations in the prefrontal cortex. The formatio n of relational and non-relational memories may be supported by distinct su bregions within these two brain regions. While the medial temporal lobe may have a serial organizational structure, with a processing hierarchy, inter actions between medial temporal and prefrontal areas seem to occur in a par allel and bi-directional fashion. Interacting with this system, emotionally arousing events enhance neural activity in the amygdala, which in turn may modulate processing in other brain regions responsible for declarative mem ory formation. (C) 2001 Elsevier Science Inc.