(HealthDay News) – Differences in white matter integrity in the brain account for some of the variation in general intelligence in elderly individuals, with their effect mediated by information-processing speed.

Lars Penke, PhD, from the University of Edinburgh in the United Kingdom, and colleagues performed structural brain magnetic resonance imaging in 420 adults (71–73 years old), measuring fractional anisotropy and two biomarkers of white matter integrity: magnetization transfer ratio and longitudinal relaxation time. They also measured general intelligence, cognitive information-processing speed, and reaction times.

The researchers found that the three imaging biomarkers were strongly associated with the integrity of 12 major white matter tracts. Each parameter was independently associated with general intelligence and together accounted for 10% of the variation in intelligence. The effect was completely due to information-processing speed.

“Unlike most previously established neurostructural correlates of intelligence, these findings suggest a functionally plausible model of intelligence, where structurally intact axonal fibers across the brain provide the neuroanatomical infrastructure for fast information processing within widespread brain networks, supporting general intelligence,” Penke and colleagues conclude.

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