Conduction velocity along a key white matter tract is associated with autobiographical memory recall ability

Abstract

Conduction velocity is the speed at which electrical signals travel along axons and is a crucial determinant of neural communication. Inferences about conduction velocity can now be made in vivo in humans using magnetic resonance (MR) imaging and a measure called the MR g-ratio. Here, in the first application to cognition, we found that increased MR g-ratio, and by inference faster conduction velocity, specifically in the parahippocampal cingulum bundle, which connects the hippocampus with a range of other brain areas, was associated with better memory recall ability in 217 healthy adults. Moreover, two tract features seemed to favour better memory retrieval – large inner axon diameters and coherently organised neurites, both of which facilitate speedy signalling. These results offer a new perspective on drivers of individual differences in memory recall ability. More broadly, they show that MR g-ratio can provide novel insights into how the human brain processes and integrates information.

Taking stock of the past: A psychometric evaluation of the Autobiographical Interview

“…The study of trait-level AM has fostered a deeper understanding of how AM and non-mnemonic cognition interact. It has also moved the field toward uncovering how individual variation in brain structure and function shape the way in which humans recall the personal past, at scales ranging from the biophysical properties of axons (Clark et al, 2022) resting-state functional connectivity (Setton et al, 2022a), and temporal lobe volumetry (Setton et al, 2022b). However, several open questions remain, such as the appropriate factor structure for the AI and how it covaries with other related domains such as perception, language, and attention.…”

“…Some studies have gone beyond group differences to examine the individual difference properties of AM (Palombo et al, 2013; Palombo et al, 2018; Sheldon et al, 2016). Doing so has shed light on how brain structure and function shape the episodic quality of recollection on the AI (e.g., Sheldon et al, 2016; Clark et al, 2022). Yet the reliability of trait-level AM has not been formally evaluated.…”