In a first experiment, we investigated whether temporal predictions auding auditory listening are robust to temporal variability, which that are naturally present in many auditory signals such as speech and music. We tested whether temporal expectations can be formed in no-fully predictable context, and how the temporal variability of sensory contexts affects perception. Participants were asked to discriminate a target deviant sound embedded in sound sequences. Auditory discrimination performance progressively declined as the temporal variability of the sound sequence increased. Altogether, these results suggests that temporal predictions can be set up quickly based on the temporal statistics of past sensory events, and are robust to a certain amount of temporal variability. This data was presented at two conferences (Cutting EEG 2021, Biomag 2022), and the article is in preparation.
Second, we tested the influence of neural oscillations on speech comprehension, by manipulating oscillations with continuous transcranial alternating current stimulation (tACS) above the auditory cortices. We show an effect of tACS frequency on the perception of ambiguous words, suggesting that neural oscillations causally influence word comprehension. Results were published in Journal of Cognitive Neuroscience. We further tested the link between neural entrainment and linguistic processing in a Cocktail party setting (i.e. in the presence of multiple speakers). Listening to speech is difficult in noisy environments, and is even harder when the interfering noise consists of intelligible speech as compared to unintelligible sounds. We asked whether neural oscillations tracking the attended speech reflects its comprehension, and/or the comprehension of the distracting speech signal. In this magnetoencephalography (MEG) experiment, the low-frequency neural oscillations followed less the dynamics of target speech, when the target was less intelligible. The results were published in Current Research in Neurobiology, and presented at the Rhythm Workshop (Lyon, 2022)
Third, we directly dissociated the contribution of neural oscillations in the processing of speech acoustic cues from that related to linguistic processing. We examined the neural changes associated with the comprehension of acoustically degraded speech using MEG. Significant changes in neural oscillations were observed in relation to the acoustic degradation of speech. However, we failed to find a direct effect of speech comprehension on the neural oscillatory response. This suggests that acoustics greatly influence the neural oscillatory response to speech signals. These results were presented at the conference Biomag (2022), a preprint has been published on BioRxiv.
