Performance-Related Sustained and Anticipatory Activity in Human Medial Temporal Lobe during Delayed Match-to-Sample Rosanna K. Olsen,1 Elizabeth A. Nichols,1 Janice Chen,1 Jack F. Hunt,1 Gary H. Glover,2,3 John D. E. Gabrieli,4 and Anthony D. Wagner1,

Introduction The relationship between short-delay memory performance and MTL While which with long delays is well established

Introduction fMRI data also reveal the importance of MTL in the short-delay recognition memory Ranganath and D’Esposito, 2001 Schon et al., 2004 Ranganath et al., 2005 7~13s DMS Nichols et al., 2006 Piekema et al., 2006 Axmacher et al., 2007

Introduction These study are Relatively short delay periods Trial-unique stimuli

Introduction Within the MTL, short-delay recognition memory may be differentially subserved by distinct subregions Ex. Persistent activity in entorhinal cortex May underlie active maintenance of goal-relevant stimuli Study of human brain deficits Study of rodent

Introduction The characterization of delay period response in specific human MTL requires higher spatial resolution fMRI

Materials and Methods 25 subjects Right handed Native English speakers 10 female 18-32 years old Paid 70$ for the participation 5 subjects data were excluded because 3 -> poor behavioral performance 2 -> functional data artifacts

Before the in-scanner DMS task A target detection task 330 face trials 30 DMS faces for 10times 2 “targets “(faces) for 15 times To make the stimuli non-trial-unique It means to make them familiarized

Procedure of DMS task

Behavioral data

fMRI analysis (Anatomical ROI) Sustained activity Differ from correct to incorrect

fMRI analysis (Anatomical ROI) Anticipatory effect (preparatory effect) Examine the linearity of delay-period activity WHY?

Across-region functional dissociations Pattern of delay-period activation Parahippocampal cortex Perirhinal and entorhinal cortex

Across-region functional dissociations Performance-independent interaction Perirhinal cortex  Entorhinal cortex Perirhinal cortex more active during study Entorhinal cortex more active during delay

Across-region functional dissociations Also, functional dissociation of hippocampus subregions Parallel previous studies of human hippocampus during declarative memory encoding and retrieval

fMRI voxel-level group analysis

fMRI voxel-level group analysis

Discussion Two patterns of delay-period acitivity across distinct MTL subregions Sustained anticipatory

Discussion Sustained delay period activity predicts DMS performance Further research Systematic investigation of the influence of stimulus novelty/familiarity

Discussion Stimulus class effects in MTL cortex Ventral visual cortex  perirhinal cortex Deficits studies Object recognition memory Visual discrimination of complex objects and faces fMRI studies Both object and location/scene encoding Dorsal visual cortex  parahippocampal cortex Memory for topographical and spatial stimuli Clear preference for location/scene encoding

Discussion Does the MTL mediate working memory?