Contributions of regional cortical thickness and surface area to cognitive functioning in psychosis-risk

Cognitive deficits in schizophrenia are detectable at the onset of illness and during the preceding prodromal period. Additionally, adolescents and young adults at clinical high risk for psychosis (CHR-P) demonstrate cognitive impairment regardless of future conversion. The cortical substrates of these deficits have yet to be established within CHR-P samples, including the differential relations of cortical thickness (CTh) versus surface area (SA) as they differ in underlying cytoarchitecture and genetic influences. Youth at CHR-P (N = 463) and healthy control participants (N = 210) from the second cohort of the North American Prodrome Longitudinal Study (ages 12-35) completed the two-subtest form of the Wechsler Abbreviated Scale of Intelligence and structural MRI scans at baseline. The associations between regional cortical morphometry and Full-Scale IQ (FSIQ-2) were examined using multiple linear regression. Increased CTh in frontoparietal regions (left lateral orbitofrontal cortex; left precentral gyrus; left postcentral gyrus; right supramarginal gyrus) and lateral occipital areas associated with better cognitive functioning in CHR-P. In contrast, among healthy control participants, no associations between CTh and cognitive functioning were observed. Additionally, increased SA across the cortex was associated with better cognitive functioning for both groups, though people at CHR-P demonstrated a more diffuse pattern of associations. These results underscore the importance of decomposing cortical volume into CTh and SA and how variation in cognitive functioning may be potentially supported by shared and group-specific substrates. Results generate hypotheses about how aberrant neurodevelopmental processes, such as cortical thinning, may disturb cognitive functioning in the early stage of psychosis.