Modulating Speech Perception With Current Stimulation

Study Overview
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Brief Summary
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This study aims to further develop tACS as a tool to improve speech perception, by manipulation of brain-speech synchronisation (entrainment), thereby transforming a promising approach into a technique that can benefit to society on a large scale.

Detailed Description
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Neural oscillations align their phase to the rhythm of speech. This phenomenon is termed neural entrainment and associated with successful speech comprehension. Importantly, we have demonstrated that transcranial alternating current stimulation (tACS) can be used to manipulate how neural activity aligns to speech rhythm, leading to changes in speech perception. The aim of Experiment 1 is to understand how tACS operates on the neural level. This aim will be reached by testing whether tACS produces rhythmic electroencephalography (EEG) responses that outlast the stimulation, indicating an involvement of endogenous oscillatory activity. The aim of Experiment 2 is to increase efficacy of tACS and, consequently, its potential to play an important role in research and everyday life applications. This aim will be reached by using brain imaging (fMRI) to predict optimal stimulation protocols for individual participants. The aim of Experiment 3 is to reveal how tACS can boost speech perception in a multi-speaker scenario. This aim will be reached by using tACS to enhance attended speech or suppress distracting speech, and by comparing these two approaches in their efficacy to boost speech perception. The aim of Experiment 4 is to combine established techniques to create novel opportunities to improve speech perception. This aim will be reached by using neurofeedback to teach participants to enhance their own neural entrainment, applying tACS to support them in this process.

Official Title
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Modulating Speech Perception With Current Stimulation (SPEECHSTIM)

Conditions
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Healthy

Intervention / Treatment
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* Procedure: transcranial alternating current stimulation (tACS)
* Procedure: electroencephalography (EEG)
* Procedure: brain imaging (fMRI)
* Procedure: electroencephalography (EEG) with neurofeedback


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Subject aged between 18 and 50 years old informed written consent Absence of pro-epileptogenic drugs Absence of visual or hearing impairment incompatible with participation in the study Exclusion Criteria: Pregnant or breastfeeding women, Persons protected by law adults under guardianship or curatorship Persons not affiliated to a Social Security scheme Subjects with progressive psychiatric or neurological pathology Subjects with a contraindication to tCS or MRI (history of epilepsy, severe head injury or brain/spinal cord surgery, cardiac pacemaker/defibrillator, implanted equipment activated by electrical, magnetic or mechanical system, hemostatic clip carriers of intracerebral aneurysms or carotid arteries, orthopedic implant carriers, claustrophobic, pregnancy).

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Experiment 1<br>The aim of Experiment 1 is to understand how tACS operates on the neural level | Procedure: transcranial alternating current stimulation (tACS)<br>* transcranial alternating current stimulation (tACS) used to manipulate how neural activity aligns to speech rhythm, leading to changes in speech perception<br>Procedure: electroencephalography (EEG)<br>* analyse rhythmic electroencephalography responses that outlast the stimulation<br>|
| Experimental: Experiment 2<br>The aim of Experiment 2 is to increase efficacy of tACS and, consequently, its potential to play an important role in research and everyday life applications | Procedure: transcranial alternating current stimulation (tACS)<br>* transcranial alternating current stimulation (tACS) used to manipulate how neural activity aligns to speech rhythm, leading to changes in speech perception<br>Procedure: brain imaging (fMRI)<br>* Using brain imaging (fMRI) to predict optimal stimulation protocols for individual participants<br>|
| Experimental: Experiment 3<br>The aim of Experiment 3 is to reveal how tACS can boost speech perception in a multi-speaker scenario. | Procedure: transcranial alternating current stimulation (tACS)<br>* transcranial alternating current stimulation (tACS) used to manipulate how neural activity aligns to speech rhythm, leading to changes in speech perception<br>|
| Experimental: Experiment 4<br>The aim of Experiment 4 is to combine established techniques to create novel opportunities to improve speech perception | Procedure: transcranial alternating current stimulation (tACS)<br>* transcranial alternating current stimulation (tACS) used to manipulate how neural activity aligns to speech rhythm, leading to changes in speech perception<br>Procedure: electroencephalography (EEG) with neurofeedback<br>* Using neurofeedback to teach participants to enhance their own neural entrainment<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| correctly identified words | percentage of correctly identified words during or after tACS who will permit to evaluate efficacy of tACS to modulate speech perception and neural responses in different experimental conditions (involving electrophysiological, brain imaging, and perceptual measures) | Day 1 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| correctly identified words with different modality | percentage of correctly identified words during or after tACS between different modality | day 1 | 
| oscillatory activities | measurement of oscillatory activities resulting from electrical stimulation: (frequency, power, and phase, latency) on the scalp and at the level of the sources and their synchronization with during or after tACS | Day 1 | 
| neural activity | measurement of neural activity that results from electrical stimulation: fMRI (BOLD response) during or after tACS | Day 1 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Transcranial alternating current stimulation (tACS),, speech, perception, neural oscillations, entrainment, phase, neurofeedback