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Cereb Cortex. 2016 May;26(5):1965-74. doi: 10.1093/cercor/bhv013. Epub 2015 Feb 6.

A Working Memory Buffer in Parahippocampal Regions: Evidence from a Load Effect during the Delay Period.

Author information

1
Department of Psychological and Brain Sciences, Center for Memory and Brain Graduate Program for Neuroscience CELEST, Center of Excellence for Learning in Education, Science, and Technology, Boston University, Boston, MA 02215, USA Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA.
2
Department of Psychological and Brain Sciences, Center for Memory and Brain Graduate Program for Neuroscience CELEST, Center of Excellence for Learning in Education, Science, and Technology, Boston University, Boston, MA 02215, USA Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA.
3
Department of Psychological and Brain Sciences, Center for Memory and Brain CELEST, Center of Excellence for Learning in Education, Science, and Technology, Boston University, Boston, MA 02215, USA Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA.

Abstract

Computational models have proposed that the entorhinal cortex (EC) is well suited for maintaining multiple items in working memory (WM). Evidence from animal recording and human neuroimaging studies show that medial temporal lobe areas including the perirhinal (PrC), EC, and CA1 hippocampal subfield may contribute to active maintenance during WM. Previous neuroimaging work also suggests CA1 may be recruited transiently when encoding novel information, and EC and CA1 may be involved in maintaining multiple items in WM. In this study, we tested the prediction that a putative WM buffer would demonstrate a load-dependent effect during a WM delay. Using high-resolution fMRI, we examined whether activity within the hippocampus (CA3/DG, CA1, and subiculum) and surrounding medial temporal cortices (PrC, EC, and parahippocampal cortex-PHC) is modulated in a load-dependent manner. We employed a delayed matching-to-sample task with novel scenes at 2 different WM loads. A contrast between high- and low-WM load showed greater activity within CA1 and subiculum during the encoding phase, and greater EC, PrC, and PHC activity during WM maintenance. These results are consistent with computational models and suggest that EC/PrC and PHC act as a WM buffer by actively maintaining novel information in a capacity-dependent manner.

KEYWORDS:

encoding; high-resolution fMRI; hippocampus; maintenance; matching-to-sample

PMID:
25662713
PMCID:
PMC4830282
DOI:
10.1093/cercor/bhv013
[Indexed for MEDLINE]
Free PMC Article

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