EEG alpha power predicts the temporal sensitivity of multisensory perception

Pre-stimulus electroencephalogram (EEG) oscillations, especially in the alpha range (8-13 Hz), can affect the sensitivity to temporal lags between modalities in multisensory perception. The effects of alpha power are often explained in terms of alpha's inhibitory functions, whereas effects of alpha frequency have bolstered theories of discrete perceptual cycles, where the length of a cycle, or window of integration, is determined by alpha frequency. Such studies typically employ visual detection paradigms with near-threshold or even illusory stimuli. It is unclear whether such results generalize to above-threshold stimuli. Here, we recorded EEG, while measuring temporal discrimination sensitivity in a temporal-order judgement task using above-threshold auditory and visual stimuli. We tested whether the power and instantaneous frequency of pre-stimulus oscillations predict audiovisual temporal discrimination sensitivity on a trial-by-trial basis. By applying a jackknife procedure to link single-trial pre-stimulus oscillatory power and instantaneous frequency to psychometric measures, we identified a posterior cluster where lower alpha power was associated with higher temporal sensitivity of audiovisual discrimination. No statistically significant relationship between instantaneous alpha frequency and temporal sensitivity was found. These results suggest that temporal sensitivity for above-threshold multisensory stimuli fluctuates from moment to moment and is indexed by modulations in alpha power.

Automated summary

In this study, the relationship between pre-stimulus alpha oscillations and temporal discrimination sensitivity was examined. The results showed that lower alpha power was associated with higher temporal sensitivity of audiovisual discrimination for above-threshold stimuli. No significant relationship was found between instantaneous alpha frequency and temporal sensitivity. This suggests that temporal sensitivity for multisensory stimuli fluctuates and can be indexed by alpha power modulation.