Age-related changes in neural recruitment for cognitive control.

The dual mechanisms of control (DMC; Braver, Gray, & Burgess, 2007) framework postulates a distinction between proactive and reactive modes of cognitive control. Event-related brain potentials (ERPs) were used to examine age differences in the neural correlates of proactive and reactive control for task-switching. Whereas proactive control is associated with brain activity for anticipatory task preparation, reactive control is accompanied by reduced preparatory activity, but increased activation during task execution. Switching between tasks was based on feedback-based transition cueing which places particularly high demands on mechanisms for cognitive control. Older adults maintained good performance accuracy at the expense of slower response times. No age-related increase in behavioral switching costs was observed. The cue-locked ERP (P3a) data revealed an age-related decrease in neural activity related to the processing of switch cues. In the target-locked ERPs, there was an increased frontal focus of the P3b in older adults. These ERP data indicate an age-related neural under-recruitment for proactive cognitive control and an age-related neural over-recruitment for reactive cognitive control. They are consistent with the idea that older adults may not fully implement task settings before target onset, after which they need to catch up on the omitted preparatory task settings.