Effortful Listening Produces Both Enhancement and Suppression of Alpha in the EEG

ABSTRACTABSTRACTIntroduction Adverse listening conditions can drive increased mental effort during listening. Neuroelectromagnetic alpha oscillations (8–13 Hz) may index this listening effort, but inconsistencies regarding the direction of the relationship are abundant. We performed source analyses on high-density EEG data collected during a speech-on-speech listening task to address the possibility that opposing alpha power relationships among alpha-producing brain sources drive this inconsistency.Methods Listeners (N = 20) heard two simultaneously presented sentences of the form: Ready go to now. They either reported the color/number pair of a "Baron" call sign sentence (active: high effort), or ignored the stimuli (passive: low effort). Independent component analysis (ICA) was used to segregate temporally distinct sources in the EEG.Results Analysis of independent components (ICs) revealed simultaneous alpha enhancements (e.g., for somatomotor mu ICs) and suppressions (e.g., for left temporal ICs) for different brain sources. The active condition exhibited stronger enhancement for left somatomotor mu rhythm ICs, but stronger suppression for central occipital ICs.Discussion This study shows both alpha enhancement and suppression to be associated with increases in listening effort. Literature inconsistencies could partially relate to some source activities overwhelming others in scalp recordings.KEYWORDS: Listening effortEvent-related desynchronization (ERD)Event-related synchronization (ERS)speech-in-noisetau rhythm Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingResearch reported in this publication was supported by the Cognitive and Neurobiological Approaches to Plasticity (CNAP) Center of Biomedical Research Excellence (COBRE) of the National Institutes of Health under grant number P20GM113109. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health