The role of the pre-commissural fornix in episodic autobiographical memory and simulation

Angharad N. Williams, Samuel Ridgeway, Mark Postans, Kim S. Graham, Andrew D. Lawrence, Carl J. Hodgetts

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Neuropsychological and functional magnetic resonance imaging evidence suggests that the ability to vividly remember our personal past, and imagine future scenarios, involves two closely connected regions: the hippocampus and ventromedial prefrontal cortex (vmPFC). Despite evidence of a direct anatomical connection from hippocampus to vmPFC, it is unknown whether hippocampal-vmPFC structural connectivity supports both past- and future-oriented episodic thinking. To address this, we applied a novel deterministic tractography protocol to diffusion-weighted magnetic resonance imaging (dMRI) data from a group of healthy young adult humans who undertook an adapted past-future autobiographical interview (portions of this data were published in Hodgetts et al., 2017a). This tractography protocol enabled distinct subdivisions of the fornix, detected previously in axonal tracer studies, to be reconstructed in vivo, namely the pre-commissural (connecting the hippocampus to vmPFC) and post-commissural (linking the hippocampus and medial diencephalon) fornix. As predicted, we found that inter-individual differences in pre-commissural - but not post-commissural - fornix microstructure (fractional anisotropy) were significantly correlated with the episodic richness of both past and future autobiographical narratives. Notably, these results held when controlling for non-episodic narrative content, verbal fluency, and grey matter volumes of the hippocampus and vmPFC. This study provides novel evidence that reconstructing events from one's personal past, and constructing possible future events, involves a distinct, structurally-instantiated hippocampal-vmPFC pathway.
Original languageEnglish
Pages (from-to)107457
JournalNeuropsychologia
Volume142
Early online date4 Apr 2020
DOIs
Publication statusPublished - May 2020

Keywords / Materials (for Non-textual outputs)

  • hippocampus
  • episodic memory
  • future thinking
  • mental time travel
  • vmPFC
  • white matter tractography

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