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.
Competing Interest Statement
The authors have declared no competing interest.