A method of communication for a patient in a completely locked-in state, using a computer to decode letters from brain signals, is demonstrated in Nature Communications this week. The findings suggest that verbal communication using a brain-computer interface (BCI) may be possible for patients in a completely locked-in state.
BCIs can restore communication to people who have lost the ability to move or speak. A major focus of research in this field has been maintaining the ability to communicate for patients with amyotrophic lateral sclerosis (ALS) — also known as motor neurone disease — a neurodegenerative disorder that leads to the progressive loss of voluntary muscular control. Several approaches have already been developed to allow patients with ALS to communicate using eye movements or facial muscles. However, once control over these muscles is lost, these patients also lose their ability to communicate.
Using an auditory neurofeedback system, a type of BCI, which was implanted into the patient’s brain, Ujwal Chaudhary and colleagues found that a 34 year old, male patient with ALS and in a completely locked-in state, with no voluntary muscular control, could form words and phrases to communicate at an average rate of about one character per minute. The patient was provided with auditory feedback of his neural activity and the authors instructed the patient to match the frequency of a feedback tone to the target tone by controlling the firing rates of neurons in his brain. If the firing rate changes lasted for longer than 250ms, at the high or low end of a given range, this was interpreted as a “yes” or “no”, respectively. The patient was also able to modulate neural firing rates based on auditory feedback to select letters to form words and phrases to communicate their needs.
The findings may allow for patients who are currently unable to communicate, to communicate verbally. Further demonstrations of the longevity, applicability in other patients, safety and efficacy of the BCI are required before widespread clinical use.
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