Switch probability context (in)sensitivity within the cognitive control network.

Cognitive control processes refer to the ability to flexibly adapt one's thoughts and actions in the pursuit of an internal goal. Task preparation is a central aspect of cognitive control and has generally been studied using explicitly cued task-switching paradigms. Over the last decade, numerous fMRI studies have identified a fronto-parietal network to exhibit greater activity during the preparation of task switches than during the preparation of task repetitions, which is assumed to reflect endogenous cognitive control processes. There is, however, a huge variability in preparatory switch-specific brain activity reported in the imaging literature on task-switching. One factor that might explain this heterogeneity is the difference in switch probability across studies. In the current fMRI study, we examined which preparation-related cognitive control areas are susceptible to such contextual differences by manipulating the switch probability within subjects. In the low switch probability (30% switch trials) blocks, we found the frequently observed switch-related preparatory activation in fronto-parietal areas. In the high switch probability (50% switch trials) blocks, however, only part of these areas (more particularly the (pre-) SMA, extending into the dorsal ACC and the superior parietal lobule) showed higher activation in switch compared to repeat trials. The activation levels in the other areas (the lateral prefrontal cortex, inferior parietal lobule and middle temporal gyrus) were very similar for switch and repeat trials. Our results suggest a functional dissociation within the cognitive control network with some brain areas being sensitive to the switch probability context while others are not.