Task preparation and neural activation in stimulus-specific brain regions: an fMRI study with the cued task-switching paradigm.

To investigate the role of posterior brain regions related to task-relevant stimulus processing in task preparation, we used a cued task-switching paradigm in which a pre-cue informed participants about the upcoming task on a trial: face discrimination or number comparison. Employing an event-related fMRI design, we examined for changes of activity in face- and number-related posterior brain regions (right fusiform face area (FFA) and right intraparietal sulcus (IPSnum), respectively), and explored the functional connectivity of these areas with other brain regions, during the (preparation) interval between cue onset and onset of the (to-be-responded) target stimulus. The results revealed task-relevant posterior brain regions to be modulated during this period: activation in task-relevant stimulus-specific regions was selectively enhanced and their functional connectivity to task-relevant anterior brain regions strengthened (right FFA - face task, right IPSnum - number task) while participants prepared for the cued task. Additionally, activity in task-relevant posterior brain regions was influenced by residual activation from the preceding trial in the right FFA and the right IPSnum, respectively. These findings indicate that, during task preparation, the activation pattern in currently task-relevant posterior brain regions is shaped by residual activation as well as preparatory modulation prior to the onset of the critical stimulus, even without participants being instructed to imagine the stimulus.