Sex differences in the IQ-white matter microstructure relationship: a DTI study - PubMed (original) (raw)

Sex differences in the IQ-white matter microstructure relationship: a DTI study

Beate Dunst et al. Brain Cogn. 2014 Nov.

Abstract

Sex differences in the relationship between general intelligence and brain structure are a topic of increasing research interest. Early studies focused mainly on gray and white matter differences using voxel-based morphometry, while more recent studies investigated neural fiber tracts using diffusion tensor imaging (DTI) to analyze the white matter microstructure. In this study we used tract-based spatial statistics (TBSS) on DTI to test how intelligence is associated with brain diffusion indices and to see whether this relationship differs between men and women. 63 Men and women divided into groups of lower and higher intelligence were selected. Whole-brain DTI scans were analyzed using TBSS calculating maps of fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD). The results reveal that the white matter microstructure differs between individuals as a function of intelligence and sex. In men, higher intelligence was related to higher FA and lower RD in the corpus callosum. In women, in contrast, intelligence was not related to the white matter microstructure. The higher values of FA and lower values of RD suggest that intelligence is associated with higher myelination and/or a higher number of axons particularly in men. This microstructural difference in the corpus callosum may increase cognitive functioning by reducing inter-hemispheric transfer time and thus account for more efficient brain functioning in men.

Keywords: Corpus callosum; DTI; Intelligence; Sex; TBSS.

Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

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Figures

Fig. 1

Fig. 1

(A) Result of the whole-brain TBSS analysis comparing men of lower and higher IQ in their Fractional Anisotropy (FA). More intelligent men showed higher FA in the genu and body of the corpus callosum (p < .05 FWE-corrected). Blue means higher FA in more intelligent men. The figure is presented in radiological convention (X = 105, Y = 153, Z = 91). (B) TBSS result of the significant T-contrast between less and more intelligent men in Radial Diffusivity (RD) with a significant cluster in the corpus callosum (p < .05 FWE-corrected). Red means lower RD in more intelligent men. (C) Scatterplot depicting the correlation between intelligence and FA values in the significant cluster, separately for men (blue) and women (orange). (D) Scatterplot depicting the correlation between intelligence and RD values in the significant cluster, separately for men (blue) and women (orange). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

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