Persistent tactile P3 in long-term brain-computer interface home use by a patient in locked-in state

P3-based brain-computer interfaces (BCIs) allow for communication via non-muscular, non-invasive electroencephalography (EEG) signals. They have been applied successfully in various contexts with users in the locked-in state (LIS). A current challenge lies in overcoming the limitations of the commonly used visual stimulation. To this end, vision-independent P3-based BCIs have been developed, for example by using auditory or tactile stimuli. Despite promising findings with healthy participants, studies with severely paralyzed users remain scarce. Here, we present a long-term case study of a user with LIS due to amyotrophic lateral sclerosis (ALS) to evaluate a tactile P3-based BCI over the course of two years at the user’s home. The user preferred the tactile over the auditory modality and a multi-class over a two-class BCI. After using four classes for 30 sessions, he preferred upgrading to six classes for 39 additional sessions. Over the course of the entire study, we consistently found distinct P3 patterns and BCI performances significantly above chance level, despite disease progression. Our findings demonstrate the persistence of the tactile P3 and the feasibility of a tactile P3-based BCI for LIS end-users. This merits further user-centered research in combination with technical adjustments for BCI optimization and expanded applications with end-users.