Auditory Attention Implements Complementary but Independent Cortical Mechanisms of Enhancement and Suppression

Abstract

In noisy environments, goal-directed behavior requires the brain to prioritize task-relevant sound and to suppress distraction. While mechanisms of proactive attention in the presence of foreknowledge about targets and distractors are well-characterized, the neural dynamics governing reactive auditory attention in the absence of foreknowledge remain less understood. To fill this gap, we recorded the electroencephalogram (EEG) from N = 34 participants performing an auditory search task. Participants identified an amplitude-modulated spoken target number amid distractor numbers of varying salience. Presenting stimuli from three spatial locations enabled isolation of lateralized electrophysiological responses to targets and distractors. We quantified selection of targets versus distractors by continuously tracking participants cursor movements on a virtual response pad. Behaviorally, the target-directedness of cursor movements (i.e., towardness) increased for target repetitions (positive priming) and decreased when the target was a distractor from the previous trial (negative priming), indicating respective enhancement and suppression. Neurally, lateral targets evoked an N2ac component reflecting reactive enhancement. Importantly, we here demonstrate for the first time in an auditory attention task that distracting sounds evoke an auditory distractor positivity (PD) component. Target enhancement and distractor suppression were largely independent: their neural and behavioral markers were not significantly correlated and they originated from distinct cortical sources. Furthermore, shorter N2ac-but not PD-latencies related to higher towardness. By dissociating neural signatures and behavioral relevance of enhancement and suppression, our findings refine biased-competition models of attention, demonstrating that reactive selection relies on separable mechanisms rather than a single competitive gain process. Significance statementEveryday listening requires the rapid selection of relevant sounds and ignoring distraction, even when there is no prior knowledge of what will be heard. Here, we reveal the neural mechanisms that enable such reactive auditory attention. Combining electroencephalography with continuous measures of behavior, we show that target enhancement and distractor suppression are supported by distinct neural processes, indexed by the N2ac and the auditory PD component. These processes are largely independent, with only enhancement predicting behavior. This dissociation challenges unitary accounts of attentional selection and instead supports models in which separable mechanisms of enhancement and suppression operate in parallel. Our findings provide a mechanistic framework for understanding how the human brain flexibly prioritizes information in complex listening environments.