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 a measure called the magnetic resonance (MR) g-ratio. This is the ratio of the inner axon diameter relative to that of the axon plus the myelin sheath that encases it. Here, in the first application to cognition, we found that variations in MR g-ratio, and by inference conduction velocity, of the parahippocampal cingulum bundle were associated with autobiographical memory recall ability in 217 healthy adults. This tract connects the hippocampus with a range of other brain areas. We further observed that the association seemed to be with inner axon diameter rather than myelin content. The extent to which neurites were coherently organised within the parahippocampal cingulum bundle was also linked with autobiographical memory recall ability. Moreover, these findings were specific to autobiographical memory recall and were not apparent for laboratory-based memory tests. Our results offer a new perspective on individual differences in autobiographical memory recall ability, highlighting the possible influence of specific white matter microstructure features on conduction velocity when recalling detailed memories of real-life past experiences.

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.…”

White matter integrity is associated with cognition and amyloid burden in older adult Koreans along the Alzheimer’s disease continuum

“…The CBH is part of the cingulum, which is a tract that is critically involved in interconnection of the frontal, medial temporal, and parietal cortices [11,12], as well as in the function of the limbic Papez Circuit [12]. Previously, disrupted integrity of this circuit, especially within the parahippocampal cingulum, has been demonstrated in AD [13,14,25,[27][28][29][30][31][32][33][34].…”

“…The cingulum bundle of the hippocampus (CBH), a posterior region of the cingulum [24] with proximity to the hippocampus, has been implicated in memory recall ability in CN adults [25]. Studies using diffusion tensor imaging (DTI), which measures the diffusion of water molecules, can provide information about WM microstructure [26].…”

Automated protocols for delineating human hippocampal subfields from 3 Tesla and 7 Tesla magnetic resonance imaging data

“…T2‐weighted partial volume images were acquired (voxel size = 0.52 × 0.52 × 0.50 mm) using a 3D turbo spin echo sequence. Full details of the sequence are available in previous publications (Clark et al, 2023; Clark & Maguire, 2023; Dalton et al, 2017, 2019). Of note, scans with isotropic voxels, such as those here, have equivalent resolution in all orientations, which is particularly important for convoluted structures like the hippocampus, which can contain undulations in the subfields.…”