Evaluation of the Feasibility and Efficacy of a Chronic Brain-computer Interface for Speech Rehabilitation in Patients With Locked-in-syndrome (LIS)

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 corte