Abstract
Current studies support the belief that high levels of performance and intellectual abilities are associated with increased brain size or volume. With few exceptions, this conclusion is restricted to studies of post-adolescent subjects and to cerebral cortex. There is evidence that “bigger is better” may not pertain to children and further, that there are areas of the brain in which larger structures are associated with cognitive deficits. In 50 preadolescent children (21 girls) a structural survey of the brain (VBM) was conducted to determine and locate areas in which gray matter volume was associated with poor cognitive performance. Only increased gray matter volume in particular areas of the basal ganglia and specifically the putamen was significantly associated with poor performance on tests of memory, response speed and a general marker and subtests of intelligence. Based on the VBM findings, volumetric analysis of basal ganglia structures was performed using FSL/FIRST. However, no significant changes in total volume of putamen or other basal ganglia structures were detected with this analysis. The disagreement between measures of localized gray matter differences and volumetric analysis suggested that there might be local regional deformity rather than widespread volumetric changes of the putamen. Surface analysis with FSL/FIRST demonstrated that bilateral outward deformation of the putamen, but especially the left, was associated with poor performance on several cognitive tests. Expansion of the globus pallidus and caudate nucleus also was associated with poor performance. Moreover a significant association was detected between a reliable test of language-free intelligence and topographically distinct outward and inward deformation of the putamen. Expansion and contraction of the putamen as a predictor of intelligence may explain why this association was not observed with measures of total volume. These results suggest that deformity is a sensitive measure of function, and that distortion of the basal ganglia may be a neurophenotype for risk of developmental impairment.
Highlights
Inward displacement of subcortical areas including the putamen and caudate nucleus, especially in the right hemisphere, were associated with intellectual abilities
Voxel Based Morphometry (VBM) analysis of gray matter morphology initially was implemented to address the central question of whether specific areas of increased gray matter volume were associated with impaired cognitive performance in typically developing preadolescent children
Regression analyses indicated that only areas of increased gray matter volume in the basal ganglia and the putamen were significantly associated with impaired performance
Summary
Inward displacement of subcortical areas including the putamen and caudate nucleus, especially in the right hemisphere, were associated with intellectual abilities. But not all, studies suggest that increased size and outward deformity of structures in the basal ganglia, especially the caudate nucleus and putamen are linked to poor performance in healthy subjects and to clinical conditions with behavioral and cognitive impairments. These effects, with one exception (Estes et al, 2011), have been reported in post-adolescent subjects. Significant associations will be further assessed with specific topographical measures of size and shape
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