High-resolution fMRI Reveals Match Enhancement and Attentional Modulation in the Human Medial Temporal Lobe

摘要

A primary function of the medial temporal lobe (MTL) isnto signal prior encounter with behaviorally relevant stimuli.nMTL match enhancement—increased activation when viewingnpreviously encountered stimuli—has been observed for goalrelevantnstimuli in nonhuman primates during delayed-matchto-nsample tasks and in humans during more complex relationalnmemory tasks. Match enhancement may alternatively reflect (a)nan attentional response to familiar relative to novel stimuli orn(b) the retrieval of contextual details surrounding the past encounternwith familiar stimuli. To gain leverage on the functionalnsignificance of match enhancement in the hippocampus, highresolutionnfMRI of human MTL was conducted while participantsnattended, ignored, or passively viewed face and scene stimulinin the context of a modified delayed-match-to-sample task. Onneach “attended” trial, two goal-relevant stimuli were encounterednbefore a probe that either matched or mismatched one of thenattended stimuli, enabling examination of the consequences ofnencountering one of the goal-relevant stimuli as a match probenon later memory for the other (nonprobed) goal-relevant stimulus.nfMRI revealed that the hippocampus was insensitive tonthe attentional manipulation, whereas parahippocampal cortexnwas modulated by scene-directed attention, and perirhinal cortexnshowed more subtle and general effects of attention. Byncontrast, all hippocampal subfields demonstrated match enhancementnto the probe, and a postscan test revealed more accuratenrecognition memory for the nonprobed goal-relevantnstimulus on match relative to mismatch trials. These data suggestnthat match enhancement in human hippocampus reflectsnretrieval of other goal-relevant contextual details surrounding anstimulusʼs prior encounter.