The P300 ‘face’ speller is resistant to cognitive decline in ALS

Three different P300 paradigms, the classic matrix-based speller, one employing faces as stimuli, and one with serial stimulus presentation, were used to assess the effects of cognition and visual function on brain–computer interface (BCI) use in 22 patients with amyotrophic lateral sclerosis (ALS) and 13 control participants. The patients in the study, on average, demonstrated lower accuracy than the matched control participants. Patients had a slightly greater incidence of oculomotor limitations, but this did not translate to a measurable difference in task-specific gaze control or performance on any of the tasks. Lower cognitive screen scores were the only clinical characteristic to consistently reduce evoked responses and P300 accuracies across individuals. The late portion of the evoked potential, 500–800 ms after the stimulus, was most strongly associated with cognitive score. The early evoked potential around 170 ms, generated by the face speller, was not as strongly associated with cognition. The results indicate that patients with neurodegenerative disease may fare better using an oddball-based BCI task employing face stimuli due in part to the early evoked response that is less hindered by cognitive impairment.