The phase of pre‐stimulus brain oscillations correlates with cross‐modal synchrony perception

Abstract

In everyday life multisensory events, such as a glass crashing on the floor, the different sensory inputs are often experienced as simultaneous, despite the sensory processing of sound and sight within the brain are temporally misaligned. This lack of cross‐modal synchrony is the unavoidable consequence of different light and sound speeds, and their different neural transmission times in the corresponding sensory pathways. Hence, cross‐modal synchrony must be reconstructed during perception. It has been suggested that spontaneous fluctuations in neural excitability might be involved in the temporal organisation of sensory events during perception and account for variability in behavioural performance. Here, we addressed the relationship between ongoing brain oscillations and the perception of cross‐modal simultaneity. Participants performed an audio‐visual simultaneity judgement task while their EEG was recorded. We focused on pre‐stimulu activity, and found that the phase of neural oscillations at 13 ± 2 Hz 200 ms prior to the stimulus correlated with subjective simultaneity of otherwise identical sound‐flash events. Remarkably, the correlation between EEG phase and behavioural report occurred in the absence of concomitant changes in EEG amplitude. The probability of simultaneity perception fluctuated significantly as a function of pre‐stimulus phase, with the largest perceptual variation being accounted for phase angles nearly 180º apart. This pattern was strongly reliable for sound‐flash pairs but not for flash‐sound pairs. Overall, these findings suggest that the phase of ongoing brain activity might underlie internal states of the observer that influence cross‐modal temporal organisation between the senses and, in turn, subjective synchrony.

The Common Rhythm of Action and Perception

“…One recent study by Benedetto et al (2018) further shows that audio-visual temporal order judgments (TOJs) undergo rhythmic fluctuations (at around 7-8 Hz) time-locked to a button press action (figure 4). The modulation does not affect temporal sensitivity (precision of the judgements) but the temporal bias, i.e., whether the visual stimulus is perceived ahead or behind of the auditory stimulus (in line with the neuronal phase effects on audio-visual perceived simultaneity reported by Ikumi et al, 2018;and Kösem et al, 2014). This suggests that processing resources and\or speed may rhythmically alternate between the visual and the auditory modality and this alternation may be temporally synchronized to the ongoing motor processing.…”

Single trial prestimulus oscillations predict perception of the sound-induced flash illusion

“…Interestingly, the optimal delay between flashes is correlated with the subject-specific impulse response frequency, pointing to a contribution of oscillatory reverberation to illusory visual perception. Similarly, the phase of ongoing alpha band oscillations influences crossmodal synchrony perception 24 . A phase reset of ongoing slow oscillations in unisensory areas is a likely mechanism for the modulation of activity following heteromodal input 13,25,26 .…”

Quantitative Personality Predictions From a Brief EEG Recording

“…While the ERP signals recorded before the onset of stimuli have traditionally been considered as "baseline" and not included in data analysis, there is emerging evidence to suggest that there are functional implications for pre-stimulus activity (Falkenstein, Hoormann, Christ, & Hohnsbein, 2000;Lazzaro, Gordon, Whitmont, Meares, & Clarke, 2001). The inter-trial variability of the pre-stimulus activity has been repeatedly been reported as being related to one's cognitive states (Bode et al, 2012;Ikumi, Torralba, Ruzzoli, & Soto-Faraco, 2019;Lou, Li, Philiastides, & Sajda, 2014;Polich & Kok, 1995). As the mean amplitude of the pre-stimulus period was subtracted before the analysis, our results suggest a possible contribution from the fluctuation of the baseline activity rather than its absolute amplitude.…”