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Free keywords:
Ageing; Biological parametric mapping; Cognitive speed; Dopamine
Abstract:
Purpose
Age-related decline in cognitive speed has been associated with prefrontal dopamine D1 receptor availability, but the contribution of presynaptic dopamine and noradrenaline innervation to age-related changes in cognition is unknown.
Methods
In a group of 16 healthy participants aged 22–61 years, we used PET and the radioligand FDOPA to measure catecholamine synthesis capacity (K in app; millilitres per gram per minute) and the digit symbol substitution test to measure cognitive speed, a component of fluid IQ.
Results
Cognitive speed was associated with the magnitude of K in app in the prefrontal cortex (p < 0.0005). Both cognitive speed (p = 0.003) and FDOPA K in app (p < 0.0005) declined with age, both in a standard voxel-wise analysis and in a volume-of-interest analysis with partial volume correction, and the correlation between cognitive speed and K in app remained significant beyond the effects of age (p = 0.047). MR-based segmentation revealed that these age-related declines were not attributable to age-related alterations in grey matter density.
Conclusion
Our findings indicate that age-related changes in the capacity of the prefrontal cortex to synthesize catecholamines, irrespective of cortical atrophy, may underlie age-related decline in cognitive speed.
