Structural and functional correlates of behavioral pattern separation in the hippocampus and medial temporal lobe

ABSTRACT Structures of the medial temporal lobe (MTL) are known to be involved in declarative memory processes. However, little is known about how age‐related changes in MTL structures, white matter integrity, and functional connectivity affect pattern separation processes in the MTL. In this study,...

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Bibliographic Details
Published in:Hippocampus 2015-04, Vol.25 (4), p.524-533
Main Authors: Doxey, Christopher R., Kirwan, C. Brock
Format: Article
Language:English
Subjects:
Adolescent
Adult
Age Factors
Aged
Aged, 80 and over
aging
Diffusion Magnetic Resonance Imaging
diffusion tensor imaging
Female
Hippocampus - anatomy & histology
Hippocampus - physiology
Humans
Imaging, Three-Dimensional
Magnetic Resonance Imaging
Male
memory
Middle Aged
Neural Pathways - blood supply
Neural Pathways - physiology
Neuropsychological Tests
Oxygen - blood
pattern separation
Recognition (Psychology) - physiology
Rest
resting fMRI
Temporal Lobe - anatomy & histology
Temporal Lobe - physiology
Young Adult
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Summary:ABSTRACT Structures of the medial temporal lobe (MTL) are known to be involved in declarative memory processes. However, little is known about how age‐related changes in MTL structures, white matter integrity, and functional connectivity affect pattern separation processes in the MTL. In this study, we used magnetic resonance imaging (MRI) to measure the volumes of MTL regions of interest, including hippocampal subfields (dentate gyrus, CA3, CA1, and subiculum) in healthy older and younger adults. Additionally, we used diffusion tensor imaging to measure white matter integrity for both groups. Finally, we used functional MRI to acquire resting functional connectivity measures for both groups. We show that, along with age, the volume of left CA3/dentate gyrus predicts memory performance. Differences in fractional anisotropy and the strength of resting functional connections between the hippocampus and other cortical structures implicated in memory processing were not significant predictors of performance. As previous studies have only hinted, it seems that the size of left CA3/dentate gyrus contributes more to successful discrimination between similar mnemonic representations than other hippocampal sub‐fields, MTL structures, and other neuroimaging correlates. Accordingly, the implications of aging and atrophy on lure discrimination capacities are discussed. © 2014 Wiley Periodicals, Inc.
ISSN:1050-9631
1098-1063
DOI:10.1002/hipo.22389