ABSTRACT
Introduction
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 <call sign> go to <color> <number> 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.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Notes
1. No coupler was used in this approximation. However, we were mainly concerned with safety for the subjects, and having sounds presented at what could be considered a normal listening level. Actual fit of earphones into the ear can vary among subjects, and we expected exact levels to vary as well. Note however, that this should not be concerning given our within-subjects design and the fact that this fitting should vary randomly.
2. We used a nonparametric test because of the non-normally distributed nature of the proportion correct data.