The spatio-temporal dynamics of the earliest stages of attentional control: how and when is control triggered in different task situations

Adaptations to environmental changes critically depend on selective attention or the ability to focus on relevant stimuli and actions. Since transient shifts in selective attention are covert, brain-imaging techniques are pre-eminently suitable to provide more insight into the mechanisms underlying behavioral adaptations. However, the relatively low temporal resolution of imaging techniques makes it difficult to link particular brain regions to specific sub-processes involved in attentional control, such as the disengagement from current focus, orientation to new focus, and modulation of sensory input reflecting the result of attentional control. The disentanglement of these sub-processes critically depends on the availability of time information. The time course of brain activations has been studied by combining imaging techniques with event-related potentials (ERP) or by using cue-target paradigms, which allow for the dissociation between cue-related directing of attention and resulting changes in target processing. Previous results have indicated that a fronto-parietal network exerts top-down control by biasing sensory processing in corresponding cortices. The question remains, however, how attentional control is triggered. A partial answer to this question is provided by the conflict-monitoring hypothesis, which states that the detection of (response) conflict, associated with activity in the anterior cingulate cortex (ACC), triggers compensatory adjustments in control mediated by the dorsolateral prefrontal areas (DLPFC). In line with this notion, ACC activity on incongruent trials has been found to correlate with DLPFC activity on immediately succeeding incongruent trials. Current studies do not reveal (1) whether the joint activation of ACC and DLPFC is critical for control in a wide variety of situations or specifically related to conflict-triggered control, and (2) how and when conflict-detection invokes control. The present study aims at uncovering the spatio-temporal dynamics of the earliest stages of attentional control in a variety of task situations. First, cue-target paradigms will be administered to identify brain regions responsible for attentional control in different task situations. Then, the focus will be on how and when diverse factors trigger adjustments in control in these regions. As for conflict-monitoring, activity in control regions (e.g. DLPFC) is expected to follow conflict detection (ACC). Rather than comparing succeeding trials, analysis will concern processes during the entire interval, starting from the conflict events. Different time segments will be separated to determine whether the triggering of attentional control is time-locked to the presentation of the current stimulus or rather associated with the expected arrival of the next stimulus. When these processes are better understood, it will be examined how factors other than conflict detection, such as arousal state, overall expectancy, and task switching, influence the triggering of attentional control.