The role of the fornix in human navigational learning

Hodgetts, Carl J. ORCID: https://orcid.org/0000-0002-0339-2447, Stefani, Martina, Williams, Angharad N. ORCID: https://orcid.org/0000-0001-9363-8537, Kolarik, Branden S., Yonelinas, Andrew P., Ekstrom, Arne D., Lawrence, Andrew D. ORCID: https://orcid.org/0000-0001-6705-2110, Zhang, Jiaxiang ORCID: https://orcid.org/0000-0002-4758-0394 and Graham, Kim S. ORCID: https://orcid.org/0000-0002-1512-7667 2020. The role of the fornix in human navigational learning. Cortex 124 , pp. 97-110. 10.1016/j.cortex.2019.10.017

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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.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Psychology Cardiff University Brain Research Imaging Centre (CUBRIC)
Additional Information:	This is an open access article under the terms of the CC-BY license.
Publisher:	Elsevier
ISSN:	0010-9452
Funders:	Wellcome Trust
Date of First Compliant Deposit:	12 November 2019
Date of Acceptance:	24 October 2019
Last Modified:	23 Feb 2024 03:48
URI:	https://orca.cardiff.ac.uk/id/eprint/126756

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