To switch or to repeat? Commonalities and differences in the electrophysiological correlates of preparation for voluntary and forced task choices.

Abstract

When switching tasks in the laboratory, either the experimenter or the participant can decide which task comes next. So far, this kind of forced and voluntary task switching is usually investigated in isolation. However, in our everyday life, switching between different tasks and goals often depends both on current situational demands and on our intentions. While research has mainly focused on differences between forced and voluntary switching, it is still unclear whether, and if so, which neural processes are shared between both switch types. To identify these, we compared electrophysiological preparatory activity in blocks of randomly intermixed voluntary and forced task-switching trials. We further manipulated the forced switch rate (20% vs. 80%) between blocks to de-confound voluntariness with switch frequency and to investigate how switch frequency effects influence preparatory potentials. ERP analysis revealed an enhanced early parietal activity pattern in the P3b time window on voluntary trials, possibly reflecting early traces of a decision process. A later pre-target negativity was enhanced on forced as compared to voluntary trials. Multivariate pattern analyses revealed that a common preparatory activity on both forced and voluntary switch trials can be found in the switch positivity time window, which we interpreted as an index of a common endogenous task preparation process.