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, Kim S. Graham

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)97-110
Number of pages14
JournalCortex
Volume124
DOIs
StatePublished - Mar 2020

Keywords

  • Diffusion MRI
  • Episodic memory
  • Hippocampus
  • Spatial learning
  • Spatial navigation

ASJC Scopus subject areas

  • Neuropsychology and Physiological Psychology
  • Experimental and Cognitive Psychology
  • Cognitive Neuroscience

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