Distinct contributions of the fornix and inferior longitudinal fasciculus to episodic and semantic autobiographical memory

Cortex. 2017 Sep:94:1-14. doi: 10.1016/j.cortex.2017.05.010. Epub 2017 Jun 20.


Autobiographical memory (AM) is multifaceted, incorporating the vivid retrieval of contextual detail (episodic AM), together with semantic knowledge that infuses meaning and coherence into past events (semantic AM). While neuropsychological evidence highlights a role for the hippocampus and anterior temporal lobe (ATL) in episodic and semantic AM, respectively, it is unclear whether these constitute dissociable large-scale AM networks. We used high angular resolution diffusion-weighted imaging and constrained spherical deconvolution-based tractography to assess white matter microstructure in 27 healthy young adult participants who were asked to recall past experiences using word cues. Inter-individual variation in the microstructure of the fornix (the main hippocampal input/output pathway) related to the amount of episodic, but not semantic, detail in AMs - independent of memory age. Conversely, microstructure of the inferior longitudinal fasciculus, linking occipitotemporal regions with ATL, correlated with semantic, but not episodic, AMs. Further, these significant correlations remained when controlling for hippocampal and ATL grey matter volume, respectively. This striking correlational double dissociation supports the view that distinct, large-scale distributed brain circuits underpin context and concepts in AM.

Keywords: Hippocampus; Individual differences; Mental time travel; Structural connectivity; Temporal lobe; White matter tractography.

MeSH terms

  • Adolescent
  • Brain / diagnostic imaging
  • Brain / physiology*
  • Brain Mapping
  • Diffusion Magnetic Resonance Imaging
  • Female
  • Fornix, Brain / diagnostic imaging
  • Fornix, Brain / physiology*
  • Gray Matter / diagnostic imaging
  • Gray Matter / physiology
  • Humans
  • Image Processing, Computer-Assisted
  • Individuality
  • Male
  • Memory, Episodic*
  • Nerve Net / diagnostic imaging
  • Nerve Net / physiology
  • Neuropsychological Tests
  • Organ Size / physiology
  • White Matter / diagnostic imaging
  • White Matter / physiology*
  • Young Adult