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Centre de Recherche Cerveau & Cognition (CerCo)
CNRS
Université de Toulouse
We are part of the CerCo team "Neuromodulation in Cognition" (directors: Benedikt Zoefel & Florence Rémy).
We leverage rhythmic brain activity to study cognitive functions and their interactions with other bodily systems. Historically, our research has focused on the auditory system.
Below are some recent highlights from our research. You can click on the images to access the corresponding article.
We found that attention to sensory information alternates regularly with other, possibly "internal" processes, at a rate of ~0.07 Hz.
These slow fluctuations in "attentional modes" seemed to reflect interactions between sensory brain regions and those associated with attentional control.
We used Magnetoencephalography (MEG) to discover "entrainment echoes" in the cerebellum. These echoes are rhythmic responses that are first produced by a rhythmic stimulus but then persist when the stimulus has stopped.
The cerebellum was the only brain region with such echoes, and they were only visible after intelligible (but not unintelligible) speech. During the echo (but not during the stimulus itself), the cerebellum drove activity in the left inferior frontal gyrus (IFG).
As the stimulus rhythm induced temporal expectations and these had to be updated after stimulus offset, we suggest that cerebellar entrainment echoes reflect the updating of temporal predictions, relayed to cortical regions.
We found that neural responses to irrelevant but not to relevant auditory targets depend on the preceding phase of neural oscillations. This is a critical difference to the visual system, where the phasic modulation of perception is amplified (rather than abolished) by attention.
Oscillatory mechanisms in audition therefore seem to depend on the degree of possible information loss during the oscillation’s low excitability phase, revealing a mechanism to cope with the rapid sensory dynamics that audition is normally exposed to.
One line of our research applies transcranial alternating current stimulation (tACS) to phasically modulate speech perception. We found that some of the effects might be driven by cutaneous stimulation.
We explored a novel form of transcranial magnetic stimulation: amplitude-modulated kTMP (collab UC Berkeley) and achieved similar phasic modulation despite strongly reduced cutaneous stimulation.
We used a novel type of neurofeedback - based on "temporal response functions" (TRF) - that allows the user to train attention to speech in challenging scenarios. We found that this training enhances a neural signature of selective attention to speech, with corresponding effects on a measure of speech recognition.
We found that the temporal predictability of an auditory event accelerates reaction times and aligns the phase of beta oscillations in stimulus anticipation. Aligned phases were opposite for relevant versus distracting stimuli, and phase opposition re-emerged before pitch discrimination.
We therefore show that oscillatory phase alignment underlies anticipation of sensory information in time. However, our results are more consistent with phase-based event encoding that facilitates subsequent behavioural responses, rather than with a mechanism of attentional selection, for reasons that we explain in the article.
Other research is dedicated to the development of methods to test for phasic effects in perception and neural responses, and the identification of "true" (endogenous) oscillations in rhythmic brain responses.
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