Active Suppression of Visual Distracters during difficult auditory discrimination: Effects of intensity and congruency

Simon Kelly, Cognitive Neurophysiology Lab, City College of New York

Abstract
In many situations attention must be focused on a single relevant modality while an irrelevant modality must be suppressed. Previous work has uncovered an electrophysiological correlate of suppression: increased visual alpha-band (8-14 Hz) power in anticipation of an audio-visual stimulus in which the visual part is irrelevant. In spatial attention studies we further showed that the effect is retinotopically specific. It remains to be seen whether it is sensitive to aspects of distracter salience. In the present study we employ visually-cued auditory discrimination tasks and manipulate both the intensity of the visual distracter and its response compatibility, i.e. its propensity to cause interference through incongruity. A sequence of two tones is presented 800ms post-cue, ascending or descending in pitch with both panned slightly to the left or right. In different runs the subject discriminates either the direction of pan (“LR” task), or whether the tones are ascending or descending (“UD” task). Simultaneous with the tones, a large disc is flashed in the left or right hemifield, at low or high contrast in different runs. Preliminary results indicate that anticipatory alpha power may be greater during the LR task when distracters are high-contrast, compared with all 3 other conditions. Thus, greater active suppression is invoked when distracters are highly salient on both dimensions of basic intensity and propensity for response interference. This underscores the role of alpha-mediated suppression as an active and adaptable mechanism.

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