White Matter Microstructural Correlates of Swallowing Biomechanics: An Exploratory Pilot Study in Healthy Young Adults.

White matter (WM) enables complex brain connectivity by linking several cortical and subcortical regions. Most studies investigating the association between WM tracts and swallowing function have predominantly used a disease (lesion) based approach, and there is currently a paucity of research investigating the associations between swallowing physiology and WM microstructure in healthy individuals. Moreover, studies in healthy individuals are essential to understanding typical WM architecture and identifying any deviations caused by diseases or adaptations resulting from specific interventions or training regimes. The current study addresses this critical gap by investigating the association between quantitative metrics of WM microstructure and kinematic and temporal measures of swallowing biomechanics in healthy young adults. Diffusion-weighted magnetic resonance imaging (DW-MRI) was obtained from 17 right-handed healthy adults (males = 9; females = 8) aged 20 to 35 (mean age = 27.11 years). DW-MRI was pre-processed and analyzed using a custom-developed analysis pipeline to generate diffusion tensor image (DTI) derived scalar measures. Furthermore, videofluoroscopic data were collected from these participants and quantified using computational analysis of swallowing mechanics (CASM) and traditional pixel-based temporal and kinematic measures. We performed partial correlations to explore the association between swallowing biomechanics and WM diffusion metrics, with participants' age and sex as covariates. Our study revealed that the corpus callosum, cerebellar peduncle, thalamic radiation, corticospinal tract, cingulum, stratum, corona radiata, fornix, internal capsule, external capsule, and the superior frontal-occipital fasciculus showed significant bidirectional associations with the kinematic and temporal measures of swallowing biomechanics investigated in the current study. These findings are interpreted in relation to lesion studies and well-established functions of WM tracts. Future directions and limitations of our study are also discussed.