A Word Communication System with Partner Assist for Amyotrophic Lateral Sclerosis Patients in Late Stages

People with severe 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 partner assist, in which partners play an active role in helping patients express a word. We report here that five ALS patients in late stages (one in CLIS and four almost in CLIS) succeeded in expressing their own words (in Japanese) in response to wh-questions that could not be answered “yes/no.” Each subject sequentially selected vowels (maximum three) contained in the word that he or she wanted to express, by using a “yes/no” communication aid based on near-infrared spectroscopy. Then, a partner entered the selected vowels into a dictionary with vowel entries, which returned candidate words having those vowels. When there were no appropriate words, the partner 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. Two subjects confirmed the selected word six times out of eight (credibility of 91.0% by a statistical measure); two subjects, including the one in CLIS, did so five times out of eight (74.6%); and one subject did so three times out of four (81.3%). We have thus taken the first step toward a practical word communication system for such patients.