Preparatory brain activity in dual-tasking.

Task preparation in dual-tasking is more complex than preparation for single tasks and involves additional factors such as task prioritization. Utilizing event-related potentials, we sought to disentangle preparatory processes involving preparation on the subtask level and the superordinate dual-task level. Participants worked on a psychological refractory period paradigm in which two temporally overlapping tasks have to be completed in a specified order. Whereas dual-task-related preparation was measured by comparing task-order switches and repetitions, subtask preparation was isolated through error precursors for the individual subtasks. We found that a switch-related posterior positivity was linked to the preparation of the superordinate dual-task set. In contrast, an early frontal modulation and a stimulus-preceding negativity were markers of subtask preparation of Task 1 and Task 2, respectively. Our study provides neural evidence for a hierarchical system of control processes in dual-tasking and confirms assumptions from earlier behavioral and computational studies on strategic task prioritization.