Many neuropsychiatric disorders differ between the sexes in incidence, symptoms, and age at onset. To investigate the effects of X-chromosome aneuploidy and of sex steroid deficiency during childhood on brain structure and function, researchers, in one study, used neuropsychological tests and quantitative magnetic resonance imaging (MRI) to study the brains of 18 women with Turner's syndrome (TS) and 19 healthy control women of similar age.
Nine TS subjects had mosaic 45, X karyotypes, and nine had non-mosaic 45, X. The TS group had significantly lower scores than the controls for all the Wechsler adult intelligence scale tests, except those for verbal comprehension and reading level. The greatest difference was in the visuospatial construction. The TS subjects also had a greater discrepancy than the controls between verbal and performance intelligence quotients. The TS subjects also had significantly smaller values than the controls in MRI-measured volumes of hippocampus, caudate, lenticular, and thalamic nuclei, and parieto-occipital brain matter, on both sides.
From this study, researchers postulated that in human beings the X chromosome plays an important part in the development and ageing of gray matter in the striatum, diencephalon, and cerebral hemispheres. However, other studies have shown that female TS subjects compare favorably in areas of educational achievement, occupational status, and personal happiness. In addition, the controversy over TS cognitive deficits has generated other problems for females having this syndrome.
Various neuropsychiatric disorders show sex differences in incidence, age at onset, and symptoms. However, it is not clear whether these differences are due to the influence of sex steroids or of sex chromosomes on brain development. Sex steroids are critical for the organization of neuronal circuitry, and sex chromosomes aneuploidies are associated with cognitive abnormalities...