Fluid intelligence – the ability to solve novel, complex problems – declines steeply during healthy human aging. Despite consensus that fluid intelligence is associated with particular frontoparietal brain regions, little research has investigated suggestions that under-responsiveness of these regions mediates age-related decline.
Using fMRI data collected for the Cambridge Centre for Ageing and Neuroscience (Cam-CAN), scientists at the MRC CBU first replicated a recent demonstration of such mediation. They then precisely localised the mediating brain regions, finding that mediation was specifically associated with regions most activated by cognitive demand, but not with regions suppressed by cognitive demand. The scientists quantified the robustness of the mediation result to potential unmodelled confounders, and estimated the causal direction of the effects, which they found to be consistent with the hypothesised model. Specification of such a neuro-cognitive mechanism may facilitate design of targeted interventions to maintain fluid intelligence into healthy old age. As one example, they investigated whether the mediation pathway depended on individual differences in regular physical activity and found that the link between reduced brain response and poorer performance on intelligence tasks was weaker in people who reported more varied, regular, physical activities. Thus identifying a widely applicable lifestyle strategy that might buffer age-related cognitive decline, by decoupling one link in this putative causal pathway, and so help to promote successful aging.
The full paper can be read here: