Asymmetries of cortical thickness: effects of handedness, sex, and schizophrenia

Abstract

Sex, handedness, and disease processes in schizophrenia may affect the magnitude and/or direction of structural brain asymmetries. Using MRI data from 67 healthy (30 men, 10 nondextral) and 84 schizophrenia patients (60 men, 16 nondextral), cortical thickness asymmetries were compared at high spatial resolution. Within-group asymmetries were observed in sensorimotor, perisylvian, and parahippocampal cortices (leftward) and in anterior mesial frontal cortices (rightward). Asymmetry patterns were similar across diagnosis and sex, although some regional asymmetry increases were observed in men. Hand preference (dextrality) significantly influenced regional asymmetries in parietal association and dorsomedial frontal cortices (false discovery rate-corrected), where medial-frontal regions showed diagnosis by dextrality effects (uncorrected). Thus, dextrality relates to cortical thickness asymmetries, although schizophrenia may differentially affect asymmetry patterns across handedness.

Fig. 1

Significant cortical thickness asymmetries mapped within dextral healthy male and female participants (top); dextral male and female schizophrenia patients (second row); nondextral male and female participants collapsed across diagnosis (third row); and nondextral patients and controls collapsed across sex (bottom). Significance and direction of regional cortical thickness asymmetries are indexed by the color bar.

Fig. 2

(a) Statistical maps (uncorrected) show significant diagnosis (top left), dextrality (top center), and sex (top right) effects for cortical thickness asymmetry indices compared at thousands of hemispheric surface locations. Regional interactions between diagnosis and dextrality (left) and sex and dextrality (right) are mapped in the second row. The color bars encode the probability and direction of effects. (b) Average asymmetry indices mapped within dextral and nondextral participants. Cool colors indicate leftward (positive) asymmetries; hot colors indicate rightward (negative) asymmetries.