Evaluation of the Feasibility and Efficacy of a Chronic Brain-computer Interface for Speech Rehabilitation in Patients With Locked-in-syndrome (LIS) (SpeechBCI)
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About
Eighteen million people worldwide are affected by speech disorders. Locked-in syndrome (LIS) represents the most extreme form of communication disability resulting from motor impairment. In France, the Association du Locked-In Syndrome (ALIS) reports approximately 500 individuals with LIS, most of whom live at home. The quality of life of people with LIS depends strongly on their ability to communicate, and speech synthesis is the mode of communication restoration most desired by individuals with LIS. Several surveys have shown that improving communication abilities in these individuals leads to a significant improvement in their quality of life as well as that of their caregivers.
Natural speech allows the production of an average of 150 words per minute. Non-invasive communication methods, whether based on residual motor function (eye-blink code) or on brain-machine or brain-computer interfaces (Brain-Computer Interface, BCI) using scalp electroencephalographic (EEG) signals, involve a high cognitive load and have low efficiency (spelling only a few letters per minute). Invasive BCIs for speech rehabilitation aim to overcome the limitations of non-invasive devices (cognitive overload and slow speech rate). The intention to act (the act of speaking) is predicted by an algorithm based on the direct decoding of neuronal activity from the sensorimotor cortex (the area where articulatory muscles are represented).
To date, studies testing speech rehabilitation BCIs in humans remain rare. A subdural electrocorticographic (ECoG) invasive BCI enabled speech decoding (words and sentences from a limited repertoire) for chronic use (2 years). Real-time control of an on-screen cursor allowing spelling of up to 90 letters per minute (equivalent to text messaging) has also been achieved using an intracortical invasive BCI (Utah Array). Very recently, up to 60 words per minute were produced using an intracortical invasive BCI (Utah Array) implanted in the ventral premotor cortex, although with a connector potentially contaminated by acoustic audio feedback. Furthermore, these devices still rely on transcutaneous connectors, which may be sources of infection and prevent routine daily-life use.
In summary, there is currently no fully implantable, wireless invasive "speech BCI" with real-time speech synthesis suitable for long-term home use. The present study will use an intracranial extradural invasive BCI combined with a speech synthesizer, with the aim of developing a communication tool suitable for everyday use. More specifically, the SpeechBCI protocol will propose two complementary BCI approaches in the same subject: a speech BCI (primary objective, BCI_PAROLE device) and a cursor BCI (secondary objective). Both BCIs will use the WIMAGINE intracranial epidural system, enabling ECoG signal acquisition with a very limited risk of infection and brain injury and providing signals that are more stable over time compared with intracortical or subdural ECoG devices that retain transcutaneous connectors. These systems will allow long-term and ecological use, as the WIMAGINE implant is wireless and offers excellent long-term signal stability. The WIMAGINE implant has already been successfully tested for controlling an exoskeleton in a tetraplegic subject (operational for over 6 years) and very recently for controlling walking in real-life conditions via a spinal cord stimulator in a paraplegic individual.
The BCI_PAROLE device will integrate a speech synthesizer providing real-time auditory feedback to the speaker. The BCI-CURSEUR device will allow the subject to control an on-screen cursor to access various communication functionalities (web access, emails, chats, etc.). This will provide a complementary communication solution to real-time speech production.
The hypothesis of this stydy is that the intention to speak (attempted speech) will be decoded by the BCI_PAROLE device in individuals with LIS because, as with limb paralysis, paralysis of articulatory and phonatory muscles does not prevent the corresponding cortical map from producing specific signals. Similarly, the BCI-CURSEUR device will decode the intention to move a cursor and perform actions on a computer screen.
Neuronal electrical signals will be recorded bilaterally from the ventral motor cortex (representation of lips, cheeks, tongue, palate, and larynx-the vocal tract) and from the dorsal part of the motor cortex (larynx and hand, the latter for controlling a two-degree-of-freedom cursor), using a total of 128 electrodes (64 on each cerebral hemisphere). The implant will be optimally positioned over speech motor areas using preoperative functional imaging in order to optimize speech decoding by the BCI_PAROLE device.
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Inclusion criteria
a. Male or female between 18 and 65 years old b. French speaking person c. Person in locked in syndrome with a severe speech disorder following either: i. A subcortical stroke ii. Amyotrophic Lateral Sclerosis. d. Person with stable clinical state (esp. regarding respiratory state) e. Person able to read on a screen (sufficient eye movement control) f. Negative plasma pregnancy test for women of childbearing potential* g. Highly effective or at least acceptable** contraception for women of childbearing potential.
h. Persistence of localizing signals of language function proven by functional MRI.
i. Person able to perform a simple BCI task with MEG j. Person with a neuropsychological profile evaluated by psychiatrist as compatible with sustain BCI training k. Informed consent to participate in the obtained using their usual means and code of communication (residual vocalizations, eye-blinking code, pictograms, eye tracking, alphabet chart, etc.), in the presence of their trusted person or curator who is accustomed to communicating with them using this means.
l. Person affiliated to the French social security system or beneficiary of such a system
Exclusion criteria
Patients with any of the following criteria cannot be included in this investigation:
- Severe cognitive disorders assessed after a neuropsychological evaluation
- Deafness
- Continuous assisted ventilation
- Contraindication to intracranial surgery
- Contra-indication to MRI (1.5T), CT-scan or their related contrast agent injection or MEG examinations.
- Anatomical brain MRI showing structural abnormalities in the cortical areas of language
- Functional impairment of language cortical areas on MRI
- Auditory evoked potential showing hearing impairment
- Person with a skull shape incompatible with one WIMAGINE implant on each hemisphere
- Persons referred to in Articles L1125-7 of the Public Health Code and article 64 of MDR(corresponding to all protected persons: pregnant women, women in labor, breastfeeding mothers, minors, persons deprived of liberty by judicial or administrative decision.
Trial design
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Interventional model
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3 participants in 1 patient group
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Central trial contact
Amina FONTANELL; Blaise YVERT
Data sourced from clinicaltrials.gov
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