Sex Differences in Brain Gray and White Matter in Healthy Young Adults: Correlations with Cognitive Performance

Abstract

Sex-related differences in behavior are extensive, but their neuroanatomic substrate is unclear. Indirect perfusion data have suggested a higher percentage of gray matter (GM) in left hemisphere cortex and in women, but differences in volumes of the major cranial compartments have not been examined for the entire brain in association with cognitive performance. We used volumetric segmentation of dual echo (proton density and T2-weighted) magnetic resonance imaging (MRI) scans in healthy volunteers (40 men, 40 women) age 18-45. Supertentorial volume was segmented into GM, white matter (WM), and CSF. We confirmed that women have a higher percentage of GM, whereas men have a higher percentage of WM and of CSF. These differences sustained a correction for total intracranial volume. In men the slope of the relation between cranial volume and GM paralleled that for WM, whereas in women the increase in WM as a function of cranial volume was at a lower rate. In men the percentage of GM was higher in the left hemisphere, the percentage of WM was symmetric, and the percentage of CSF was higher in the right. Women showed no asymmetries. Both GM and WM volumes correlated moderately with global, verbal, and spatial performance across groups. However, the regression of cognitive performance and WM volume was significantly steeper in women. Because GM consists of the somatodendritic tissue of neurons whereas WM comprises myelinated connecting axons, the higher percentage of GM makes more tissue available for computation relative to transfer across distant regions. This could compensate for smaller intracranial space in women. Sex difference in the percentage and asymmetry of the principal cranial tissue volumes may contribute to differences in cognitive functioning.

Three-Dimensional Laser Surface Imaging and Geometric Morphometrics Resolve Frontonasal Dysmorphology in Schizophrenia

“…Recently, we have reported double dissociations between facial morphology and neuropsychological test performance in normal subjects: the shape of the anterior face covaried with spatial attention/visuomotor tracking in men but not women, and with verbal fluency in women but not men (Hennessy et al 2005(Hennessy et al , 2006; these findings complement evidence that men perform better than women on visuospatial tasks, while women perform better than men on verbal tasks (Caplan et al 1997;Gur et al 1999). Such relationships constitute strong evidence that the well established, intimate embryological relationship between facial and anterior brain morphogenesis extends to anterior brain function in adults, in a sex-specific manner.…”

Hemodynamics and brain blood flow during posture change in younger women and postmenopausal women compared with age-matched men

“…diastolic MCA velocity) compared with men, which has been well documented (9,43,64,67). It has also previously been shown that premenopausal women have greater resting brain blood flow compared with age-matched men (despite a smaller brain mass) (19,20). This could be a result of the vasodilatory effects of estrogen on the cerebrovascular endothelium (47).…”

Computerized Neurocognitive Scanning: II. The Profile of Schizophrenia

“…This differs from some reports of less neurocognitive impairment in women than men with schizophrenia (Goldstein et al 1998;Hoff et al 1996), or more impairment in women than men (Lewine et al 1996), but is consistent with earlier reports from our center reporting similar impairment in male and female patients. The difference favoring women with schizophrenia for verbal memory and men for spatial processing may reflect normal sex differences in these domains (Bleecker et al 1988;Gur et al 1999aGur et al ,2001Kimura and Harshman 1984;Kramer et al 1988). Thus, it seems that although clinical measures favoring women do correlate with neurocognitive functioning, the effect is not sufficient to produce a group difference in neuropsychological performance.…”