Before using the Tongue Drive system, the subjects trained the computer to understand how they would like to move their tongues to indicate different commands. A unique set of specific tongue movements was tailored for each individual based on the user's abilities, oral anatomy and preferences.
For the first computer test, the user issued commands to move the computer mouse left and right. Using these commands, each subject played a computer game that required moving a paddle horizontally to prevent a ball from hitting the bottom of the screen.
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After adding two more commands to their repertoire--up and down--the subjects were asked to move the mouse cursor through an on-screen maze as quickly and accurately as possible.
Then the researchers added two more commands--single and double mouse clicks--to provide study participants with complete mouse functionality. When a randomly selected symbol representing one of the six commands appeared on the computer screen, the subject was instructed to issue that command within a specified time period. Each participant completed 40 trials for each time period.
An Obstacle Course
After the computer sessions, patients were ready for the wheelchair driving exercise. Using forward, backward, right, left and stop/neutral tongue commands, they maneuvered a powered wheelchair through an obstacle course.
The collision course contained 10 turns and was longer than a professional basketball court. Throughout the exercise, the users had to perform navigation tasks such as making a U-turn, backing up and fine-tuning the direction of the wheelchair in a limited space. Subjects were asked to navigate through the course as fast as they could, while avoiding collisions.
Continuous Mode for Curves
Each patient operated the powered wheelchair using two different control strategies: discrete mode, which was designed for novice users, and continuous mode for the more agile crowd.
In discrete mode, if the user issued the command to move forward and then wanted to turn right, the user would have to stop the wheelchair before issuing the command to turn right. The stop command was selected automatically when the tongue returned to its resting position, bringing the wheelchair to a standstill.
In continuous mode, the user is allowed to steer the powered wheelchair to the left or right as it is moving forward and backward, making it possible to navigate a curve.
Each patient completed the course at least twice using each strategy while the researchers recorded the navigation time and number of collisions incurred. Using discrete control, the average speed for the five subjects was 5.2 meters per minute and the average number of collisions was 1.8. Using continuous control, the average speed was 7.7 meters per minute and the average number of collisions was 2.5.