Abstract
Selective attention can be deployed under the observer's control (goal-directed) or be captured by novel or salient events in the environment (stimulus-driven). These two types of selection are generally regarded as dissociable and rely on mostly distinct neural circuits, with a dorsal parieto-frontal network primarily involved in goal-directed selection and a ventral parieto-frontal network processing stimulus-driven information. However, it has also been argued that the two forms of selective attention must ultimately interact, although the neural mechanisms by which they do so are not understood. Using fMRI, here we show that the inferior frontal junction (IFJ), located at the posterior portion of the inferior frontal sulcus and a core brain region of the ventral attention network, may represent a neural site of convergence for goal-directed and stimulus-driven selection. In the goal-directed aspect of the experimental task, subjects searched for and responded to a target letter embedded in a rapid serial visual presentation (RSVP) of distractor letters. Stimulus-driven attention was elicited by presenting an unexpected and task-irrelevant distractor stimulus (face) before the target in a small percentage of the trials. The sudden appearance of the surprise stimulus provoked a strong BOLD response in the ventral network, namely the IFJ and temporo-parietal junction (TPJ). By contrast, activity in IFJ, but not TPJ, was in phase with the dorsal brain regions during the goal-driven behavior of searching for and responding to the target. Correlation analysis further supported the result that IFJ's co-activation switches from dorsal brain regions to ventral brain regions with the presentation of an unexpected stimulus in the midst of goal-directed behavior. These findings suggest that the IFJ acts as a central hub for stimulus-driven and goal-directed selection.