Research reportThe neural bases of proactive and reactive control processes in normal aging

•We administered the Stroop test to young and older subjects during fMRI acquisitions.•We examined BOLD signal changes linked to reactive and proactive cognitive control.•Aging differentially affects neural networks associated with both kind of control.•Very similar changes to those observed in young people with low brain dopamine level.•Prefrontal dopamine availability may be a brain modulator of cognitive control.

IntroductionResearch on cognitive control suggests an age-related decline in proactive control abilities (anticipatory control), whereas reactive control (following conflict detection) seems to remain intact. As proactive and reactive control abilities are associated with specific brain networks, this study investigated age-related effects on the neural substrates associated with each kind of control.MethodsIn an event-related fMRI study, a modified version of the Stroop task was administered to groups of 20 young and 20 older healthy adults. Based on the theory of dual mechanisms of control, the Stroop task has been built to induce proactive or reactive control depending on task context.ResultsBehavioral results (p < 0.05) indicated faster processing of interfering items in the mostly incongruent (MI) than the mostly congruent (MC) context in both young and older participants. fMRI results showed that reactive control is associated with increased activity in left frontal areas for older participants. For proactive control, decreased activity in the bilateral anterior cingulate cortex was associated with more activity in the right middle frontal gyrus in the older than the younger group.ConclusionThese observations support the hypothesis that aging affects the neural networks associated with reactive and proactive cognitive control differentially. These age-related changes are very similar to those observed in young adults with low dopamine availability, suggesting that a general mechanism (prefrontal dopamine availability) may modulate brain networks associated with various kinds of cognitive control.