Neural mechanisms of advance preparation in task switching.

The preparation effect in task switching can be interpreted to reflect cognitive control processes during the interval between task-cue onset and the trial-stimulus onset which support the flexible and rapid configuration of response dispositions. However, it is an open issue what neural processes underlie this effect. In the present study, healthy volunteers underwent functional magnetic resonance imaging (fMRI) while performing a cued task switching paradigm, in which geometric objects had to be classified according to either color or shape. By manipulating the duration of the cue-target-interval (CTI) in the range between 0 and 1500 ms, we were able to dissociate brain activity changes related to the processing of either the cue or the target. A network of frontal and parietal brain areas was activated during advance preparation for the upcoming task independent of whether the task was switched or repeated. The same brain regions also showed increased neural activity in response to targets without advance preparation in contrast to targets with advance preparation which only elicited activations in areas involved in visual processing and motor execution. These findings strongly argue for a 'task-set activation perspective' on advance preparation in task switching [Altmann, E.M., 2004. Advance preparation in task switching: what work is being done? Psychol. Sci. 15, 616-622.], whereas no empirical support could be found for the 'mental gear changing model' of task switching as no significant brain activity changes were observable in association with task switches, switch costs, or the interaction effect of advance preparation on switch costs. Finally, in the light of previous behavioral studies on interference effects of articulatory suppression on task preparation in humans, the present findings are compatible with the assumption that verbalization mechanisms, e.g., the retrieval of a verbal task or goal representation into working memory may be a functional component of advance configuration of task-sets.