Gender effects on cortical thickness and the influence of scaling

Abstract

Using magnetic resonance imaging and well-validated computational cortical pattern matching methods in a large and well-matched sample of healthy subjects (n = 60), we analyzed the regional specificity of gender-related cortical thickness differences across the lateral and medial cortices at submillimeter resolution. To establish the influences of brain size correction on gender effects, comparisons were performed with and without applying affine transformations to scale each image volume to a template. We revealed significantly greater cortical thickness in women compared to men, after correcting for individual differences in brain size, while no significant regional thickness increases were observed in males. The pattern and direction of the results were similar without brain size correction, although effects were less pronounced and a small cortical region in the lateral temporal lobes showed greater thickness in males. Our gender-specific findings support a dimorphic organization in male and female brains that appears to involve the architecture of the cortical mantle and that manifests as increased thickness in female brains. This sexual dimorphism favoring women, even without correcting for brain size, may have functional significance and possibly account for gender-specific abilities and/or behavioral differences between sexes.

Regional volumes and spatial volumetric distribution of gray matter in the gender dysphoric brain

“…Previous studies investigating sex differences in the human brain have also detected increased volume or cortical thickness in the GM comprising the superior frontal and more medial sections of the frontal cortex in women compared to men (Goldstein et al, 2001;Good et al, 2001;Lombardo et al, 2012;Luders et al, 2006Luders et al, , 2009a. It should be noted that in this study we did not obtain information regarding the menstrual cycle in the girls, and therefore we cannot exclude subtle cycle-related effects on GM volumes.…”

Cortical surface complexity in a population-based normative sample

“…Rate of change in surface complexity S estimated by finite differencing at visit 2 in all the subjects who provided MRI data for a total of 3 visits. Other studies that have investigated the cortical surface area have reported that male brains have greater cortical surface area than female brains when measured in their native space [22][23][24], but when area measurements were normalized by volume, females actually had more surface area than males [23], though not significantly. However, an investigation of cortical surface area did show highly significant sex differences after image scaling [24].…”

“…Other studies that have investigated the cortical surface area have reported that male brains have greater cortical surface area than female brains when measured in their native space [22][23][24], but when area measurements were normalized by volume, females actually had more surface area than males [23], though not significantly. However, an investigation of cortical surface area did show highly significant sex differences after image scaling [24]. Two other studies also provided evidence for direct sex effects of cortical complexity in which the female brain revealed greater cortical complexity compared to males [2,24].…”

“…Luders et al [2] estimated cortical complexity in the superior frontal, inferior frontal, temporal, parietal, and occipital lobar regions and found that female brains were more complex in the frontal and parietal lobes compared to males [2]. In a later study, Luders et al (2006) used the mean curvature to quantify cortical convolution at multiple surface points, confirming findings of greater cortical surface complexity in the frontal and parietal lobes of females compared to males. Another study that estimated cortical complexity used a spatial resolution and regression model [25] and found significant sex-by-age interaction in children and adolescents for frontal brain regions with cortical complexity only increasing with age in females [26].…”

“…However, an investigation of cortical surface area did show highly significant sex differences after image scaling [24]. Two other studies also provided evidence for direct sex effects of cortical complexity in which the female brain revealed greater cortical complexity compared to males [2,24]. Luders et al [2] estimated cortical complexity in the superior frontal, inferior frontal, temporal, parietal, and occipital lobar regions and found that female brains were more complex in the frontal and parietal lobes compared to males [2].…”