Complete Locked-in and Locked-in Patients: Command Following Assessment and Communication with Vibro-Tactile P300 and Motor Imagery Brain-Computer Interface Tools

Abstract

Many patients with locked-in syndrome (LIS) or complete locked-in syndrome (CLIS) also need brain-computer interface (BCI) platforms that do not rely on visual stimuli and are easy to use. We investigate command following and communication functions of mindBEAGLE with 9 LIS, 3 CLIS patients and three healthy controls. This tests were done with vibro-tactile stimulation with 2 or 3 stimulators (VT2 and VT3 mode) and with motor imagery (MI) paradigms. In VT2 the stimulators are fixed on the left and right wrist and the participant has the task to count the stimuli on the target hand in order to elicit a P300 response. In VT3 mode an additional stimulator is placed as a distractor on the shoulder and the participant is counting stimuli either on the right or left hand. In motor imagery mode the participant is instructed to imagine left or right hand movement. VT3 and MI also allow the participant to answer yes and no questions. Healthy controls achieved a mean assessment accuracy of 100% in VT2, 93% in VT3, and 73% in MI modes. They were able to communicate with VT3 (86.7%) and MI (83.3%) after 2 training runs. The patients achieved a mean accuracy of 76.6% in VT2, 63.1% in VT3, and 58.2% in MI modes after 1–2 training runs. 9 out of 12 LIS patients could communicate by using the vibro-tactile P300 paradigms (answered on average 8 out of 10 questions correctly) and 3 out of 12 could communicate with the motor imagery paradigm (answered correctly 4,7 out of 5 questions). 2 out of the 3 CLIS patients could use the system to communicate with VT3 (90 and 70% accuracy). The results show that paradigms based on non-visual evoked potentials and motor imagery can be effective for these users. It is also the first study that showed EEG-based BCI communication with CLIS patients and was able to bring 9 out of 12 patients to communicate with higher accuracies than reported before. More importantly this was achieved within less than 15–20 min.

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“…We showed that two of three patients with CLIS could communicate using the mindBEAGLE system [8]. This is an exciting development, because BCI technology had not yet been well validated with persons with CLIS.…”

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“…Structural patterns will underlie it all, but dynamic patterns are essential for NCC. This is particularly important because it opens the way for direct communication with persons with severe disabilities …”

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“…ej., Ron-Angevin, Varona-Moya, y Silva-Sauer (2015)), ya que tienden a ofrecer un mejor rendimiento en accuracy y podrían ser un objetivo más realista para los futuros pacientes. Se debe recordar que, hasta la fecha, ningún BCI basado en P300 visual ha sido controlada por el paciente en CLIS (Guger et al, 2017). Además, el beneficio de una gran cantidad de elementos disponibles para la obtención de un buen ITR podría no ser suficiente para compensar la pérdida en accuracy, como puede verse en la sección de discusión de este artículo cuando se compara con otros trabajos.…”