Electrophysiological indicators of decision uncertainty in task-switching

This event-related brain potential (ERP) study aimed at bridging two hitherto widely independently evolved domains of cognitive neuroscience. Specifically, we combined the analysis of cognitive control in a task-switching paradigm with the fundamental question of how uncertainty is encoded in the brain. The metacognitive model of Nelson and Narens (1990) served as a start to this investigation. It led to the prediction that meta-level processes contribute to task control to the degree that decisions about task-sets are uncertain. Specifically, we predicted that P3a waveforms are evoked by events which eliminate potential uncertainty about the effective task rule. In order to examine our hypothesis, we measured the EEG while sixteen healthy young participants performed task-switching paradigms closely modeled to the Wisconsin Card Sorting Test. We applied a factorial design, with number of task rules (two vs. three rules), cue explicitness (task cuing vs. transition cueing), and cue timing (prospective cuing vs. retrospective cueing) as independent variables. Switch cues evoked switch positivities with parietal topography on all experimental conditions. In contrast, frontally distributed P3a waveforms were evoked by those feedback stimuli which enabled resolution of uncertainty about the effective task rule. These results support our hypothesis that meta-level processes contribute to task control to the degree that decisions about task-sets are uncertain.