Communication aid device utilizing event-related potentials for patients with severe motor impairment

The purpose of the present study was to develop a communication aid device utilizing event-related potentials (ERPs) for patients with severe motor disabilities. Preliminary experiments were performed on eight healthy volunteers to determine the optimal methods of presentation of visual stimuli and an off-line analysis of electroencephalography signals. Three clinical experiments were performed online on 17 healthy volunteers, 5 patients with amyotrophic lateral sclerosis, and 1 patient with olivopontocerebellar atrophy. First, one of four vertically aligned short expressions ("yes definitely," "yes," "no," and "don't know") was presented in a random sequence to determine the target. Second, a systematic table of 50 Japanese syllables, and third, 16 pictorial symbols in four columns were presented, with each column presented at random. The target was identified by the maximum sum of the 2-5 Hz power spectrum after fast Fourier transform of averaged ERPs. A high correct response rate was obtained in the clinical experiments of almost 100% in "yes or no" and pictorial symbol paradigms using seven averaged samples. These results indicate that such devices may be used to communicate with patients who have lost all ability to interact other than directly via the brain.