Basic Study on Tongue Movement as a Control Command for Functional Electrical Stimulation (FES) System

Functional electrical stimulation (FES) has been developed in order to restore paralyzed motor functions of patients who have injured their upper motor neurons. Use of tongue movement was proposed as a control command for an FES system, because even quadriplegic patients can move their tongue voluntarily and generate much information easily. In this paper, we investigated the tongue movement by using a simple measurement system that simulated an input part of control commands in an FES system. The measurement system consisted of a 16-key membrane switch array, and a personal computer. The switch array detected the tongue movement as shift of touching area of the buccal region. We measured and discussed recognition rates by which the measurement system could recognize direction of tongue movement correctly. In this discussion, we assumed the following command-rules; transverse and longitudinal direction were accepted as a command, and reentry was required if oblique direction or undetected condition occurred. Five healthy subjects operated the system by their tongue in experiments, and the recognition rates were calculated. The rates within three entries were more than 85% even by less-experienced subjects; more than 95% by some subjects. The results of experiments during 5 days indicated that the repeatability of the recognition of the tongue movement was high. It implied that a precise calibration of a relative position between the system and a subject was not necessary. The results of this paper verified the fundamental feasibility of the use of tongue movement as a control command for an FES system.