Internally generated and directly cued task sets: an investigation with fMRI

It is widely acknowledged that the prefrontal cortex (PFC) plays a major role for goal-directed behaviour. In this context it is usually necessary to coordinate environmental information and internally represented intentions. Such goal-directed "endogenous control processes" can be investigated with the task-switching paradigm in which participants are required to alternate between different tasks. In the present study, we aimed at investigating different degrees of endogenous control by introducing two cue types with varying directness of the cue-task association. The "transition cues" informed the participants about repeating or switching the task but not about the task identity. Contrary to that, the "task cues" were directly associated with the upcoming task set. Since the transition cues are not directly associated with the task set they should require a higher demand of endogenous control than the task cues. The comparison of both cue types revealed frontolateral as well as frontomedian activations for the transition cue. We assume that the frontolateral activation reflects the coordination of information within working memory (WM) and the frontomedian cortex reflects the higher demand for endogenous control. Furthermore, regions of interest (Rots) analyses indicate an important role for anterior regions along the left inferior frontal sulcus and frontomedian wall. This is suggested to reflect a functional gradient in anterior-posterior direction which is linked to the relative degree of required endogenous control. (c) 2004 Elsevier Ltd. All rights reserved.