Event-related potentials reveal multiple components of proactive and reactive control in task switching

Task-switching performance relies on both proactive control processes that contribute to preparation during the cue-target interval and reactive control processes that contribute to interference control after target onset. Event-related potentials (ERPs) have excellent temporal resolution that is unmatched by other neuroimaging methods. In the context of task-switching paradigms, ERPs offer a unique approach for temporally distinguishing between proactive and reactive control processes that contribute to variability in task-switching performance. In this chapter, we highlight findings from the ERP task-switching literature that inform theoretical models of task-switching and cognitive control. Within the cue-target interval, we focus primarily on the cue-locked 'switch-positivity', a parietally-maximal increase in positivity for switch than for repeat trials. We present evidence that proactive control during task-switching involves both general and switch-specific preparation, and that switch-specific preparation itself consists of multiple processes. After target onset, we review evidence for switch-related modulation of frontocentral N2 and centroparietal P3b components that are related to conflict control and decision processes, as well as the lateralised readiness potential (LRP), which indexes processes associated with response preparation and implementation. We discuss evidence that reactive control in task-switching involves resolution of target-related interference and difficulty of task implementation processes, and that both response selection and response activation are modulated by the need to switch tasks. Finally, we present emerging evidence from studies that combine ERP measures with other techniques, such as formal cognitive modeling, functional and structural magnetic resonance imaging (MRI), and imaging genetics. We conclude that these multi-modal approaches enhance our understanding of individual differences in cognitive control and refine current neural models of cognitive control.