Abstract
Intuitively, higher intelligence might be assumed to correspond to more efficient information transfer in the brain, but no direct evidence has been reported from the perspective of brain networks. In this study, we performed extensive analyses to test the hypothesis that individual differences in intelligence are associated with brain structural organization, and in particular that higher scores on intelligence tests are related to greater global efficiency of the brain anatomical network. We constructed binary and weighted brain anatomical networks in each of 79 healthy young adults utilizing diffusion tensor tractography and calculated topological properties of the networks using a graph theoretical method. Based on their IQ test scores, all subjects were divided into general and high intelligence groups and significantly higher global efficiencies were found in the networks of the latter group. Moreover, we showed significant correlations between IQ scores and network properties across all subjects while controlling for age and gender. Specifically, higher intelligence scores corresponded to a shorter characteristic path length and a higher global efficiency of the networks, indicating a more efficient parallel information transfer in the brain. The results were consistently observed not only in the binary but also in the weighted networks, which together provide convergent evidence for our hypothesis. Our findings suggest that the efficiency of brain structural organization may be an important biological basis for intelligence.
Highlights
Researchers have long studied the biological basis for intelligence and have found increasing evidence relating high performance on intelligence quotient (IQ) tests to the coordination of multiple brain regions, utilizing both structural and functional brain imaging techniques [1,2,3,4,5,6,7,8,9,10,11]
This connection pattern is generally comparable with previous brain anatomical network studies utilizing magnetic resonance imaging (MRI) and diffusion imaging data [20,30,31,32]
The filter ROIs for the corpus callosum were placed on the midsagittal planes; the ROIs for the cingulum were placed through the genutrunk junction and the trunk-splenium junction of the corpus callosum in coronal planes; the ROIs for the corticospinal tract were placed in the posterior limb of the internal capsule and the pre- and postcentral gyri respectively; and the ROIs for inferior frontooccipital fasciculus included large part of the entire frontal and occipital lobes [33,34]
Summary
Researchers have long studied the biological basis for intelligence and have found increasing evidence relating high performance on intelligence quotient (IQ) tests to the coordination of multiple brain regions, utilizing both structural and functional brain imaging techniques [1,2,3,4,5,6,7,8,9,10,11]. Recent progress has been made in the investigation of brain anatomical networks by He et al [20], who investigated patterns of anatomical connections in cerebral cortices in vivo using cortical thickness measured from structural magnetic resonance imaging (MRI) Their findings supported the view that human brain anatomical networks manifest small-world attributes. Only one binary anatomical network could be generated from a group of subjects by their method, which made it inapplicable for investigating the network properties of an individual brain In addition to He et al.’s cortical thickness measurements, an anatomical network was derived from the interregional covariation of the gray matter volume by Bassett et al using MRI data from 259 healthy volunteers [21].
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