Using advance information in dynamic cognitive control: an ERP study of task-switching.

Ensuring that behavior remains appropriate over time requires dynamic, flexible control. We used the task-switching procedure to investigate the mechanisms whereby advance information is used to control behavior under conditions of frequently changing task-rules. The color of target stimuli signaled which task-set (or behavioral 'rule') was required on each trial. We provided different forms of advance information in two conditions and found a double dissociation in their effects: visual precues ('precueing') facilitated task-switching, whereas a fixed task-sequence ('predictability') facilitated task-repetition. In addition, precueing was associated with a late parietal positive ERP which preceded target onset, whereas predictability produced an increase in the target-locked centro-parietal P3b ERP. We suggest that these results indicate the activity of two distinct mechanisms. The first, driven by a task-cue and indexed by the late parietal positivity, may drive efficient task-performance on precued switch trials but occurs too late on non-precued switch trials to index an anticipatory task-set reconfiguration process. The second may constitute active consolidation or maintenance of a particular task-set which occurs at least one trial ahead, when task-repetitions are predictable, and results in facilitation of target stimulus evaluation.