Functional parcellation of the hippocampus based on its layer-specific connectivity with default mode and dorsal attention networks

Gopikrishna Deshpande; Xinyu Zhao; Jennifer Robinson

doi:10.1016/j.neuroimage.2022.119078

Functional parcellation of the hippocampus based on its layer-specific connectivity with default mode and dorsal attention networks

Neuroimage. 2022 Jul 1:254:119078. doi: 10.1016/j.neuroimage.2022.119078. Epub 2022 Mar 9.

Authors

Gopikrishna Deshpande¹, Xinyu Zhao², Jennifer Robinson³

Affiliations

¹ AU MRI Research Center, Department of Electrical and Computer Engineering, Auburn University, 560 Devall Dr, Suite 266D, Auburn, AL 36849, USA; Department of Psychological Sciences, Auburn University, Auburn, AL, USA; Alabama Advanced Imaging Consortium, Birmingham, AL, USA; Center for Neuroscience, Auburn University, Auburn, AL, USA; Key Laboratory for Learning and Cognition, School of Psychology, Capital Normal University, Beijing, China; Department of Psychiatry, National Institute of Mental Health and Neurosciences, Bangalore, India; Centre for Brain Research, Indian Institute of Science, Bangalore, India. Electronic address: gopi@auburn.edu.
² AU MRI Research Center, Department of Electrical and Computer Engineering, Auburn University, 560 Devall Dr, Suite 266D, Auburn, AL 36849, USA; Quora Inc., Mountain View, CA, USA.
³ AU MRI Research Center, Department of Electrical and Computer Engineering, Auburn University, 560 Devall Dr, Suite 266D, Auburn, AL 36849, USA; Department of Psychological Sciences, Auburn University, Auburn, AL, USA; Alabama Advanced Imaging Consortium, Birmingham, AL, USA; Center for Neuroscience, Auburn University, Auburn, AL, USA.

PMID: 35276366
DOI: 10.1016/j.neuroimage.2022.119078

Abstract

Recent neuroimaging evidence suggests that there might be an anterior-posterior functional differentiation of the hippocampus along the long-axis. The HERNET (hippocampal encoding/retrieval and network) model proposed an encoding/retrieval dichotomy with the anterior hippocampus more connected to the dorsal attention network (DAN) during memory encoding, and the posterior portions more connected to the default mode network (DMN) during retrieval. Evidence both for and against the HERNET model has been reported. In this study, we test the validity of the HERNET model non-invasively in humans by computing functional connectivity (FC) in layer-specific cortico-hippocampal microcircuits. This was achieved by acquiring sub-millimeter functional magnetic resonance imaging (fMRI) data during encoding/retrieval tasks at 7T. Specifically, FC between infra-granular output layers of DAN with hippocampus during encoding and FC between supra-granular input layers of DMN with hippocampus during retrieval were computed to test the predictions of the HERNET model. Our results support some predictions of the HERNET model including anterior-posterior gradient along the long axis of the hippocampus. While preferential relationships between the entire hippocampus and DAN/DMN during encoding/retrieval, respectively, were observed as predicted, anterior-posterior specificity in these network relationships could not be confirmed. The strength and clarity of evidence for/against the HERNET model were superior with layer-specific data compared to conventional volume data.

Keywords: Default mode network; Dorsal attention network; HERNET model; Hippocampus; Layer-specific connectivity; Parcellation; Resting state functional connectivity.

MeSH terms

Brain Mapping* / methods
Hippocampus* / diagnostic imaging
Humans
Magnetic Resonance Imaging / methods
Nerve Net / diagnostic imaging
Temporal Lobe