The study suggests that older people with robust brain “wiring” – the nerve fibres that connect different, distant brain areas – can process information quickly and this makes them generally smarter.
According to the findings, joining distant parts of the brain with better wiring improves mental performance, suggesting that intelligence is not found in a single part of the brain.
However, a loss of condition of this wiring, or “white matter”, can impair intelligence by altering these networks and slowing processing speed.
The research, funded by the charity Age UK, has shown for the first time that the deterioration of white matter with age is likely to be a significant cause of cognitive decline.
The researchers examined scans and results of thinking and reaction time tests from 420 people in the Lothian Birth Cohort of 1936, a group of nearly 1100 people whose intelligence and health have been tracked since they were aged 11.