Dissociations in cortical morphometry in youth with down syndrome: Evidence for reduced surface area but increased thickness

Abstract

Detailed descriptions of cortical anatomy in youth with Down syndrome (DS), the most common genetic cause of intellectual disability (ID), are scant. Thus, the current study examined deviations in cortical thickness (CT) and surface area (SA), at high spatial resolution, in youth with DS, to identify focal differences relative to typically developing (TD) youth. Participants included 31 youth with DS and 45 age-and sex-matched TD controls (mean age ?16 years; range = 5-24 years). All participants completed T1-weighted ASSET-calibrated magnetization prepared rapid gradient echo scans on a 3-T magnetic resonance imaging scanner. Replicating prior investigations, cortical volumewas reduced in DS compared with controls. However, a novel dissociation for SA and CTwas found-namely, SAwas reduced (predominantly in frontal and temporal regions) while CTwas increased (notably in several regions thought to belong to the default mode network; DMN). These findings suggest that reductions in SA rather than CTare driving the cortical volume reductions reported in prior investigations of DS. Moreover, given the link betweenDMNfunctionality and Alzheimer's symptomatology in chromosomally typical populations, future DS studies may benefit from focusing on the cortex in DMN regions, as such investigations may provide clues to the precocious onset of Alzheimer's disease in this at-risk group.