Abstract
Brain–computer interfaces (BCIs) enable communication with others and allow machines or computers to be controlled in the absence of motor activity. Clinical studies evaluating neural prostheses in amyotrophic lateral sclerosis (ALS) patients have been performed; however, to date, no study has reported that ALS patients who progressed from locked-in syndrome (LIS), which has very limited voluntary movement, to a completely locked-in state (CLIS), characterized by complete loss of voluntary movements, were able to continue controlling neural prostheses. To clarify this, we used a BCI system to evaluate three late-stage ALS patients over 27 months. We employed steady-state visual evoked brain potentials elicited by flickering green and blue light-emitting diodes to control the BCI system. All participants reliably controlled the system throughout the entire period (median accuracy: 83.3%). One patient who progressed to CLIS was able to continue operating the system with high accuracy. Furthermore, this patient successfully used the system to respond to yes/no questions. Thus, this CLIS patient was able to operate a neuroprosthetic device, suggesting that the BCI system confers advantages for patients with severe paralysis, including those exhibiting complete loss of muscle movement.
Highlights
Brain−computer interface (BCI) technology is employed as neural prostheses for communication and control[1,2]
We used a bedside BCI system to analyze state visually evoked potentials (SSVEPs) recorded over the visual cortex while the participant focused his/her visual attention on flickering stimuli[15]
We observed for the first time that an Amyotrophic lateral sclerosis (ALS) patient who progressed from locked-in syndrome/state (LIS) to completely locked-in state (CLIS) continued to operate the visual EEG/BCI system with high accuracy
Summary
Brain−computer interface (BCI) technology is employed as neural prostheses for communication and control[1,2]. Vansteensel et al reported the successful use of a fully implanted BCI to read the electrocorticography (ECoG) signals of an ALS patient with LIS12 It remains unclear whether ALS patients who progress from LIS to CLIS can continue to control neural prostheses using neuroelectric activity. We applied our in-house BCI system; we used steady-state visually evoked potentials (SSVEPs)[15] of scalp EEG to allow three late-stage ALS patients to communicate over a period of 27 months. One of these patients progressed to CLIS but continued to operate the system accurately. In contrast to a previous study[14], we demanded only covert attention shifts to flickering light sources; the CLIS patient obviously retained some visual function with light–dark discrimination
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