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