Abstract
Previous studies have demonstrated that attentional processing of visual stimuli is facilitated when stimulus onset is triggered by a voluntary action. However, little is known about the neurobiological mechanisms underlying this facilitation effect. Here we showed that the locus coeruleus-noradrenaline (LC-NA) system activating before the voluntary action is involved in the facilitation of attentional processing. We focused on pupil dilation that reflects the function of LC-NA system. We measured participants pupil size when the participant performed a rapid serial visual presentation task at the rate of 20 items/s. Under the voluntary conditions, after participants key press, the items in the task were switched from numerals of nontargets to letters of targets with temporal delays: 0-50, 100-150, 200-250, 300-350, 400-450, 600-650, and 800-850 ms. The switch occurred automatically without the key press under the control condition. These conditions were blocked. Participants were asked to report the first four successive letters as targets. The second target was reported significantly more under the 600-650 ms delay condition than under the control condition. This indicates the facilitation of attentional processing of the second target triggered by the action. The facilitation effect is tightly linked with the activation of the LC-NA system: pupil size from the stimulus onset to the key press increased in the 600-650 ms delay condition than in the automatic condition. This pupil dilation occurred only at the end of the condition block, suggesting that the LC-NA system activates after participants learn the delay between the voluntary action and the onset of targets. We conclude that the LC-NA system plays an important role in the facilitation of transient attention for visual stimuli triggered by the voluntary action.
Meeting abstract presented at VSS 2014