Modulation of task-related neural activity in task-switching: an fMRI study.

Task-switching paradigms, in which subjects are typically asked to switch between different S-R mappings, can be considered operationalizations of executive control. Such paradigms are therefore potentially useful in investigating the neural bases of control functions. Here, we present the results of an fMRI study intended to examine two separable components of task-switching: preparation, and the residual shift cost identified by Rogers and Monsell [13]. In analyses restricted to functionally identified regions of interest, we found robust evidence of greater activity for switch trials, compared to repeat trials. This pattern was present both at the time of stimulus presentation and prior to the switch trial. In analyses of the entire brain, we were able to identify one area in the superior parietal lobule that was active during switching but was not part of the apparent network of task-related regions. We conclude that switch trials are neurally distinct from repeat trials in eliciting generally greater neural activity both before and during the performance of a trial.