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Task switching is regularly required in our everyday life. To succeed in switching, it is important to inhibit the most recently performed task and instead activate the currently relevant task. The process that inhibits a recently performed task when a new task is to be performed is referred to as 'backward inhibition' (BI). While the BI effect has been subject to intense research in cognitive psychology, little is known about the neuronal mechanisms that are related to the BI effect and those that relate to differences in the magnitude of the BI effect. In the current study, we examined the system neurophysiological basis of BI processes using event-related potentials (ERPs) and sLORETA by also taking inter-individual differences in the magnitude of the BI into account. The results suggest that BI processes and inter-individual differences in them strongly depend upon attentional selection mechanisms (reflected by N1-ERP modulations in the current task/trial) mediated via networks consisting of extrastriate occipital areas, the temporo-parietal junction and the inferior frontal gyrus. Other processes and mechanisms related to conflict monitoring, response selection, or the updating, organization and implementation of a new task-set (i.e. N2 and P3 processes) were not shown to be modulated by BI processes and differences in their magnitude, as evoked with a common BI paradigm. [ABSTRACT FROM AUTHOR]

Switching between tasks requires individuals to inhibit mental representations of the previous task demands and to activate representations of the new demands. To date, investigators have identified only one way to measure task set inhibition-that is, through a backward inhibition (BI) paradigm. In this paradigm, participants take more time to return to a task set that was recently abandoned (e.g., 'A' in an AB A task sequence) than to a nonrecently abandoned task set (e.g., CB A), and investigators have demonstrated that this time cost reflects time needed to overcome the inhibition of the recently abandoned task set. To date, however, investigators have not been able to use this paradigm, or any other, to isolate brain activity related to task set inhibition. For example, contrasting the brain activity elicited by AB A and CB A trials will not isolate activity related to task set inhibition, because inhibition occurs during the initial switch away from task A (i.e., A BA). Given that there is currently no way to directly isolate the brain activity related to task set inhibition, we decided instead to examine how brain activity during task switching varies in individuals who are better than others at inhibiting the previous task set. We found that participants who were good at inhibiting previous task sets, as measured with the BI paradigm, exhibited more activity in the basal ganglia and supplementary motor area/premotor area when task switching, as measured via functional magnetic resonance imaging. These findings suggest that activity in these regions plays a role in task set inhibition. [ABSTRACT FROM AUTHOR]

In their recent review article, Koch, Gade, Schuch, & Philipp, (Psychonomic Bulletin & Review, 17, 1-14, 2010) present compelling evidence for the role of inhibition in task switching, as measured by n-2 repetition costs. They promote the view that inhibition targets response-related processes of task performance rather than cue-based preparatory stages. In support of this distinction, they cite the finding in the literature that n-2 repetition costs are not reduced given longer preparation intervals. In this article, we advocate the analysis of whole reaction time distributions for investigating the influence of task preparation on task inhibition. We present such analyses from two of our published experiments that support the view that n-2 repetition costs can be reduced given sufficient preparation. The results suggest that cue-based processes do contribute to inhibition in task switching. [ABSTRACT FROM AUTHOR]