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Brain white matter tract integrity as a neural foundation for general intelligence

Abstract

General intelligence is a robust predictor of important life outcomes, including educational and occupational attainment, successfully managing everyday life situations, good health and longevity. Some neuronal correlates of intelligence have been discovered, mainly indicating that larger cortices in widespread parieto-frontal brain networks and efficient neuronal information processing support higher intelligence. However, there is a lack of established associations between general intelligence and any basic structural brain parameters that have a clear functional meaning. Here, we provide evidence that lower brain-wide white matter tract integrity exerts a substantial negative effect on general intelligence through reduced information-processing speed. Structural brain magnetic resonance imaging scans were acquired from 420 older adults in their early 70s. Using quantitative tractography, we measured fractional anisotropy and two white matter integrity biomarkers that are novel to the study of intelligence: longitudinal relaxation time (T1) and magnetisation transfer ratio. Substantial correlations among 12 major white matter tracts studied allowed the extraction of three general factors of biomarker-specific brain-wide white matter tract integrity. Each was independently associated with general intelligence, together explaining 10% of the variance, and their effect was completely mediated by information-processing speed. Unlike most previously established neurostructural correlates of intelligence, these findings suggest a functionally plausible model of intelligence, where structurally intact axonal fibres across the brain provide the neuroanatomical infrastructure for fast information processing within widespread brain networks, supporting general intelligence.

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Acknowledgements

LP, SMM, MCVH and IJD were supported by the UK Medical Research Council (Refs 82800 and G0700704/84698). JMW is supported by the Scottish Funding Council (SFC) through the SINAPSE Collaboration (Scottish Imaging Network. A Platform for Scientific Excellence, http://www.sinapse.ac.uk/). MCVH is supported by the Row Fogo Charitable Trust. The Lothian Birth Cohort 1936 is funded by Age UK's Disconnected Mind Programme, including the Sidney De Haan Award for vascular Dementia. We thank the study secretary P Davies, and A Gow, J Corley and R Henderson for data collection and data entry, the nurses, radiographers and other staff at the Wellcome Trust Clinical Research Facility (http://www.wtcrf.ed.ac.uk/) and the Brain Research Imaging Centre (http://www.bric.ed.ac.uk/) where the data were collected; and the staff at Lothian Health Board and at the SCRE Centre, University of Glasgow. The Brain Research Imaging Centre is supported by the SINAPSE Collaboration. The work was undertaken within The University of Edinburgh Centre for Cognitive Ageing and Cognitive Epidemiology (G0700704/84698; http://www.ccace.ed.ac.uk/), part of the cross council Lifelong Health and Wellbeing Initiative. Funding from the BBSRC, EPSRC, ESRC and MRC is gratefully acknowledged.

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Correspondence to L Penke.

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Penke, L., Maniega, S., Bastin, M. et al. Brain white matter tract integrity as a neural foundation for general intelligence. Mol Psychiatry 17, 1026–1030 (2012). https://doi.org/10.1038/mp.2012.66

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