White Matter Correlates of Spoken Discourse in Cerebrovascular Disease

Abstract

BackgroundSpoken discourse (language beyond single words or sentences) performance can be used to detect cognitive impairment in cerebrovascular disease (CVD) [Roberts A, et al. (2021). Top Lang Disord 41(1):73‐98]. However, the neurological basis for altered spoken discourse in CVD is poorly defined. This study examined the association between spoken discourse and indicators of white matter microstructural integrity provided by diffusion tensor imaging (DTI) to better define the link between CVD‐related neurodegeneration and altered spoken discourse.MethodSpoken discourse and 3T DTI data (30‐32 directions, b=1000) were obtained from the CVD cohort of the Ontario Neurodegenerative Disease Research Initiative (n=133). Spoken discourse analyses were completed previously [Roberts, 2021]. A DTI analysis pipeline [Hassan SMH, et al. (2019) PLoS One 14(12):e0226715] was used to generate brain maps of fractional anisotropy (FA) and mean diffusivity (MD) and calculate mean FA and MD values for the inferior longitudinal fasciculus (ILF), superior longitudinal fasciculus – parietal (SLFp) and temporal (SLFt) endings, and uncinate fasciculi (UNC) in each hemisphere. Canonical correlation analyses examined associations between DTI metrics and 10 spoken discourse measures separately for FA in left hemisphere, MD in left hemisphere, FA in right hemisphere, MD in right hemisphere.ResultCanonical correlations were significant in the left hemisphere (FA: r=0.47, p<0.05; MD: r=0.51, p<0.01) but not the right (FA: r=0.34, p=0.90; MD: r=0.40, p=0.15)(Figure 1). Among the white matter tracts, the strongest canonical loadings were seen for the SLFp (FA: 0.81; MD: ‐0.59) and SLFt (FA: 0.71; MD: ‐0.40) compared to the ILF (FA: 0.44; MD: 0.03) and UNC (FA: ‐0.34; MD: 0.10). Higher FA in the SLFp and SLFt was associated with better performance on measures of fluency and information content. Lower MD in these tracts was associated with better performance on measures of fluency, information content, and syntax.ConclusionSpoken discourse performance was associated with white matter microstructural integrity in the left hemisphere of the brain. Of the white matter tracts investigated in this study, impaired spoken discourse performance in CVD was most strongly linked to altered tissue microstructure in the parietal and temporal endings of the superior longitudinal fasciculus.