The nature of recollection in behavior and the brain.

Long-term memory is widely believed to depend on either detailed recollection or nondetailed familiarity. Although familiarity is generally thought to be a continuous/graded process, the nature of recollection is currently under debate. The present review considers evidence bearing on three separate debates on recollection. The first debate has focused on whether each medial temporal lobe subregion is differentially or similarly engaged during recollection. A meta-analysis of 15 functional MRI studies indicated that the hippocampus and the parahippocampal cortex are associated with recollection, whereas the perirhinal cortex is associated with familiarity. The second debate has focused on whether recollection is a continuous process or a threshold/all-or-none process. A meta-analysis of seven studies with 30 conditions revealed that the large majority of source/context memory receiver operating characteristics are curved, which contradicts the linear receiver operating characteristic predicted by the threshold model of recollection and supports the continuous model of recollection. The third debate has focused on whether recollection and familiarity are separate processes or recollection and familiarity represent a single process. A meta-analysis of 37 studies with 230 conditions showed that "remember" and "know" response rates closely tracked the relationship predicted by a single-process continuous model, in which recollection and familiarity reflect strong memory and weak memory, respectively. Considered together, the body of evidence indicates that recollection represents a continuous process that is not distinct from familiarity and that this single cognitive process relies on multiple brain processes. However, much less is known about the nature of recollection in the brain.