Pupil-linked arousal is sensitive to subconscious processing of auditory novelty

Abstract

AbstractThe ability to detect novelty in sensory stimuli is at the base of autonomic and goal-directed behavior. Pupil size, a proxy of the Locus Coeruleus-Norepinephrine system, is sensitive to auditory novelty. However, whether this response reliably reflects conscious processing of novelty remains contentious. Here, we characterized pupil and electrophysiological responses during conscious and subconscious processing of auditory novelty by presenting participants deviant stimuli that were below and above their discriminatory thresholds. We found higher pupil responses to subthreshold targets that were not consciously perceived as deviant stimuli. Larger pupil size and dilation rates were associated to more negative Event-Related Potential values extracted from temporal, prefrontal and anterior cingulate regions. We suggest that increased phasic responses to deviant targets that escape conscious perception reflect Norepinephrine-mediated adaptation of arousal levels in order to meet the perceptual and behavioral demands imposed by the task at hand.