Diversity of the P3 in the task-switching paradigm

Abstract

Electrophysiological studies investigating task switching usually reveal results of the parietal P3. In this study we investigated the frontal and parietal P3 after cues, targets and responses in a combined go/no-go task switch paradigm. We confirm behavioral findings showing reduction of switch costs after no-go trials. This was accompanied by a number of P3 findings: first, the cue-locked parietal P3 was increased after a switch relative to a repetition, regardless whether a go or no-go was previously required but the frontal counterpart was less positive after inhibited responses. Secondly, in the target-locked ERPs task-set switching decreased the P3 at parietal sites, while persisting inhibition from no-go in n-1 was associated with an attenuation of the frontal P3 relative to go in n-1. No impact of task set on the frontal P3 and response mode in n-1 on the parietal P3 was found, suggesting functional dissociation between task set switch and response mode in n-1. Thirdly, exactly the same pattern was observed in the response locked frontal and parietal P3. Fourthly, the task switch related parietal P3 attenuation after targets was also observed in current no-go trials, indicating task and response selection without response execution. No task switch effect on the frontal “no-go P3” was found. In sum, these results suggest that the cue-locked long-lasting P3 reflects task-set updating, whereas the post-target frontal P3 is associated with persisting response inhibition and parietal P3 is related to an after-effect of task-set activation in terms of response selection as it appears both in the target- as well as response-locked ERPs. Furthermore, the post-target parietal P3 effects are most likely due to N2 effects as a more pronounced N2 in switch trials the smaller the P3. A fronto-parietal network for an adaptive control of response requirements and task sets is proposed.