Diffusion tensor imaging of neurocognitive profiles in a community cohort living in marginal housing

Abstract

Objective We investigated white matter differences associated with distinct neurocognitive profiles derived from a large cohort of marginally housed persons with comorbid physical and mental illnesses. Our prior work identified three profile cluster groups: a high functioning group (Cluster 1), a low functioning group with relative strength in decision‐making (Cluster 3), and an intermediary group with a relative decision‐making weakness (Cluster 2). This study extends previous findings of cortical gray matter differences between these groups with evidence for putative neurodevelopmental abnormalities in the low cognitive functioning group (i.e., Cluster 3). We hypothesized that altered white matter diffusion would be associated with the lowest functioning neurocognitive profile and would be associated with previously observed gray matter differences. Method Participants from a socially impoverished neighborhood in Vancouver, Canada underwent neurocognitive evaluation and neuroimaging. We performed Tract‐Based Spatial Statistics using diffusion tensor imaging data from 184 participants to examine whole‐brain differences in white matter microstructure between cluster analytically derived neurocognitive profiles, as well as unitary neurocognitive measures. Correlations between frontal gray and white matter were also examined. Results Cluster 3 showed increased diffusion in predominately bilateral frontal and interhemisphere tracts (vs. Clusters 1 and 2), with relatively greater diffusion in the left hemisphere (vs. Cluster 1). Differences in radial diffusivity were more prominent compared with axial diffusivity. A weak association between regional frontal fractional anisotropy and previously defined abnormalities in gyrification was observed. Conclusions In a socially marginalized sample, we established several patterns in the covariation of white matter diffusion and neurocognitive functioning. These patterns elucidate the neurobiological substrates and vulnerabilities that are apt to underlie functional impairments inherent to this complex and heterogeneous population.

Cognitive profiles and associated structural brain networks in a multimorbid sample of marginalized adults

“…Total scores range from 12 (very fluent in English) to 60 (not at all fluent in English), and those with a score of 24 (much fluent in English) or lower were included in analyses. These details of the cognitive assessment protocol have been previously published [6,8,9].…”

“…Common co-occurring illnesses include psychosis, polysubstance use, HIV infection, and traumatic brain injury [2–4], which may reflect a set of genetic, environmental, and developmental vulnerabilities that predispose individuals to significant cognitive dysfunction. Previous studies in marginalized populations have shown substantial cognitive heterogeneity and impairment across domains [5–7] and this was linked with regional alterations in cortical thickness and gyrification [8], and to variation in white matter microstructure [9]. However, due to the scope of illness burden among marginalized persons, there are likely to be more widespread alterations to structural brain integrity, which warrants further exploration.…”