Comparison scanning generalized eigendecomposition separates temporal dynamics of alpha oscillations during inhibition of spatialized acoustic distractors

Lateralized alpha-band oscillations are thought to reflect distractor inhibition through suppression of cortical regions processing spatially-localized distracting stimuli. Standard lateralization indices (LI) quantify hemispheric asymmetries in spectral power over large time windows, while characterizations of the time-varying dynamics of alpha-mediated distractor inhibition are lacking. Here we evaluate comparison scanning generalized eigendecomposition (csGED), a multivariate signal processing technique, for its efficacy in addressing questions related to alpha-mediated distractor inhibition using a simulation of same-frequency sources at symmetric cortical locations adapted from Zuure and Cohen (2021). We show that while LI accurately captures topographic power asymmetries, csGED is effective at recovering source-projections for bilateral, same-frequency activity across a wide range of signal-to-noise ratios (SNRs). We further extend these models to a pilot sample (N = 11) performing a speech-in-noise task using spatialized naturalistic distractors through individualized head-related transfer functions (HRTFs). Our results demonstrate the efficacy of GED to characterize source projections during spatialized distractors, and provide preliminary evidence for shifts in oscillatory activity in both the alpha (7 - 13 Hz) and beta frequency ranges (15 - 25 Hz) during spatialized speech-in-noise tasks. Together, these results demonstrate the feasibility of csGED for investigating temporal dynamics of lateralized distractor inhibition and motivate larger confirmatory studies.