A Word Communication System with Caregiver Assist for Amyotrophic Lateral Sclerosis Patients in Completely and Almost Completely Locked-in State

People with heavy physical impairment such as amyotrophic lateral sclerosis (ALS) in a completely locked-in state (CLIS) suffer from inability to express their thoughts to others. To solve this problem, many brain-computer interface (BCI) systems have been developed, but they have not proven sufficient for CLIS. In this paper, we propose a word communication system: a BCI with caregiver assist, in which caregivers play an active role in helping patients express a word. We report here that four ALS patients in almost CLIS and one in CLIS succeeded in expressing their own words (in Japanese) in response to wh-questions that could not be answered "yes/no." Each subject selected vowels (maximum three) contained in the word that he or she wanted to express in a sequential way, by using a "yes/no" communication aid based on near-infrared light. Then, a caregiver entered the selected vowels into a dictionary with vowel entries, which returned candidate words having those vowels. When there were no appropriate words, the caregiver changed one vowel and searched again or started over from the beginning. When an appropriate word was selected, it was confirmed by the subject via "yes/no" answers. Three subjects expressed "yes" for the selected word at least six times out of eight (reliability of 91.0% by a statistical measure), one subject (in CLIS) did so five times out of eight (74.6%), and one subject three times out of four (81.3%). We have thus taken the first step toward a practical word communication system for such patients.