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The role of the fornix in human navigational learning

Carl J. Hodgetts, Martina Stefani, Angharad N. Williams, Branden S. Kolarik, Andrew P. Yonelinas, Arne D. Ekstrom, Andrew D. Lawrence, Jiaxiang Zhang Orcid Logo, Kim S. Graham

Cortex, Volume: 124, Pages: 97 - 110

Swansea University Author: Jiaxiang Zhang Orcid Logo

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DOI (Published version): 10.1016/j.cortex.2019.10.017

Abstract

Experiments on rodents have demonstrated that transecting the white matter fibre pathway linking the hippocampus with an array of cortical and subcortical structures - the fornix - impairs flexible navigational learning in the Morris Water Maze (MWM), as well as similar spatial learning tasks. While...

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Published in: Cortex
ISSN: 0010-9452
Published: Elsevier BV 2020
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa61205
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Abstract: Experiments on rodents have demonstrated that transecting the white matter fibre pathway linking the hippocampus with an array of cortical and subcortical structures - the fornix - impairs flexible navigational learning in the Morris Water Maze (MWM), as well as similar spatial learning tasks. While diffusion magnetic resonance imaging (dMRI) studies in humans have linked inter-individual differences in fornix microstructure to episodic memory abilities, its role in human spatial learning is currently unknown. We used high-angular resolution diffusion MRI combined with constrained spherical deconvolution-based tractography, to ask whether inter-individual differences in fornix microstructure in healthy young adults would be associated with spatial learning in a virtual reality navigation task. To efficiently capture individual learning across trials, we adopted a novel curve fitting approach to estimate a single index of learning rate. We found a statistically significant correlation between learning rate and the microstructure (mean diffusivity) of the fornix, but not that of a comparison tract linking occipital and anterior temporal cortices (the inferior longitudinal fasciculus, ILF). Further, this correlation remained significant when controlling for both hippocampal volume and participant gender. These findings extend previous animal studies by demonstrating the functional relevance of the fornix for human spatial learning in a virtual reality environment, and highlight the importance of a distributed neuroanatomical network, underpinned by key white matter pathways, such as the fornix, in complex spatial behaviour.
Keywords: Hippocampus; Spatial navigation; Spatial learning; Episodic memory; Diffusion MRI
College: Faculty of Science and Engineering
Funders: This work was supported by funds from the Medical Research Council (G1002149; MR/N01233X/1), a Wellcome Strategic Award (104943/Z/14/Z), the National Institutes of Health (R01EY025999; R01NS076856), the National Institute of Neurological Disorders and Stroke (NSF BCS-1630296), the European Research Council ERC starting grant (716321), and the Wellcome Institutional Strategic Support Fund.
Start Page: 97
End Page: 110

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