Objective: Engagement in tasks requiring vigilant attention is susceptible to modulation by exogenous stimulation, reflected in changes in performance accuracy and speed. The shift from endogenous to exogenous control may be observed not only when the external cue is meaningful to the task, but also when it holds no information about the task or performance. The purpose of this study was to examine how the shift to exogenous engagement is reflected in changes to the well-documented, right-lateralized, frontal-parietal-thalamic vigilant attention network.
Method: Using functional magnetic resonance imaging , healthy participants were scanned as they performed the Sustained Attention to Response Task (SART) in 60-s blocks, some of which were presented with brief, random, auditory tones. The SART requires participants to overcome the tendency to respond in an automatic, task-driven manner in response to infrequent no-go stimuli.
Results: Despite no overall effect on performance, and only a transient increase in response times immediately following the tones, the SART with alerting tones was associated with a diminished pattern of activation in key nodes of the network. The pattern of right-lateralized activity observed with the SART was attenuated with the tones, and activity in the right middle frontal gyrus was significantly diminished, as revealed by region-of-interest analyses.
Conclusions: Alerting tones provided the stimulation to cue the maintenance of the goal-state, reducing reliance on prefrontal control mechanisms and demonstrating the shift from endogenous top-down control to exogenous control. These findings suggest a neural mechanism for the facilitatory effects of exogenous engagement for patients with damaged top-down attentional brain systems.
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