Down syndrome is accompanied by significantly reduced cortical grey–white matter tissue contrast

Abstract

Increased cortical thickness (CT) has been reported in Down syndrome (DS) during childhood and adolescence, but it remains unclear, which components of the neural architecture underpin these increases and if CT remains altered in adults. Among other factors, differences in CT measures could be driven by reduced tissue contrast between grey and white matter (GWC), which has been reported in neurodegenerative disorders, such as Alzheimer's disease. Using structural magnetic resonance imaging, we therefore examined differences in CT and GWC in 26 adults with DS, and 23 controls, to (1) examine between-group differences in CT in adulthood, (2) establish whether DS is associated with significant reductions in GWC, and (3) determine the influence of GWC variability on between-group differences in CT. As hypothesized, we observed that DS was accompanied by wide-spread increases in CT, and significantly reduced GWC in several large clusters distributed across the cortex. Out of all vertices with a significant between-group difference in CT, 38.50% also displayed a significant reduction in GWC. This percentage of overlap was also statistically significant and extremely unlikely to be obtained by chance (p = .0002). Differences in GWC thus seem to explain some, although not all, of the differences in CT observed in DS. In addition, our study is the first to extend previous in vivo reports of altered CT in DS during childhood and adolescence to older adults, implying that the regional pattern of neuroanatomical differences associated with DS remains stable across the lifespan.

High resolution structural and functional MRI of the hippocampus in young adults with Down syndrome

“…We did find increased cortical thickness in the DS group, in agreement with previous reports, 58 , 59 although we did not account for the impact of grey–white matter contrast, previously reported as altered in DS. 60 Of note, both groups showed relationships of a similar magnitude between age and increased WM and decreased cortical GM. These relationships are in line with reported age-related volume changes in the general population, 61 , 62 and suggest that, despite potential differences in baseline level, whole-brain volume measures in young, non-demented individuals with DS may follow a similar trajectory as those in the general population.…”

Brain morphometry in 22q11.2 deletion syndrome: an exploration of differences in cortical thickness, surface area, and their contribution to cortical volume

“…number of vertices with differences in CT and SA) was then assessed in each of the 5000 overlapping patterns to derive a probability value of obtaining a given percentage of overlap based on randomly varying patterns of differences. These statistical analyses were previously published by our group 11 , 21 .…”

The effect of age on vertex-based measures of the grey-white matter tissue contrast in autism spectrum disorder

“…Next, we examined between-group differences and age-by-group interactions by applying a general linear regression model (GLM) at each vertex i for subject j , with (1) group (G) as categorical fixed-effects factor and (2) linear, quadratic, or cubic terms for age, as well as their interactions with group. Based on previous reports suggesting that there is a significant negative association between the GWC and general cognitive abilities [ 28 – 31 ], FSIQ was included as continuous covariate, so that GWC i = β 0 + β 1 G j + β 2 age j + β 3 age j 2 + β 4 age j 3 + β 5 (age j × group j ) + β 6 (age j 2 × group j ) + β 7 (age j 3 × group j ) + β 8 IQ j + ε i , where ε denotes the residual error. Corrections for multiple comparisons across the whole brain were performed as outlined above (i.e.…”