2 (A) A person severely disabled by amyotrophic lateral sclerosis (ALS) using the Wadsworth brain-computer interface (BCI) system in his home. He wears a modifi ed eight-channel electrode cap. (B) Monitor display used by caregiver to check electrode impedance. Red dots are the locations of the eight recording electrodes. When all the locations become green, electrode impedance is suffi ciently low, and the caregiver can begin the BCI session.