General cognitive ability and pericortical contrast

Individual differences in general cognitive ability have been associated with various brain structure metrics. A relatively novel metric referred to as pericortical Gray-White Contrast (GWC) describes the sharpness of the pericortical gray-white boundary. GWC, which is hypothesized to be at least partly influenced by the degree to which myelinated axons invade the lower layers of cortex, is believed to be significantly associated with the dynamics of signal transmission across the brain and hence, with cognitive ability. The current work explores the association between GWC and IQ across the surface of the cortex. Subject data were retrieved from the NIH MRI Study of Normal Brain Development (Evans & Brain Development Cooperative, 2006). 376 subjects with a total of 742 scans were included in the longitudinal analyses. Mixed-effects regression analyses were used to map the relation between cortical contrast and each of full-scale, performance, and verbal IQ derived from the Wechsler Abbreviated Scale of Intelligence, while covarying for scanner, sex, and age effects. Significant associations were shown with FSIQ, PIQ, but not VIQ. We discuss the interpretation of these results and how they may relate to previously published results on structural cortical associations.