Dual-task motor performance with a tongue-operated assistive technology compared with hand operations

Abstract

Background: To provide an alternative motor modality for control, navigation, and communication in individuals suffering from impairment or disability in hand functions, a Tongue Drive System (TDS) has been developed that allows for real time tracking of tongue motion in an unobtrusive, wireless, and wearable device that utilizes the magnetic field generated by a miniature disk shaped magnetic tracer attached to the tip of the tongue. The purpose of the study was to compare the influence of a concurrent motor or cognitive task on various aspects of simple movement control between hand and tongue using the TDS technology.

Methods: Thirteen young able-bodied adults performed rapid and slow goal-directed movements of hand and tongue (with TDS) with and without a concurrent motor (hand or tongue) or cognitive (arithmetic and memory) task. Changes in reaction time, completion time, speed, correctness, accuracy, variability of displacement, and variability of time due to the addition of a concurrent task were compared between hand and tongue.

Results: The influence of an additional concurrent task on motor performance was similar between the hand and tongue for slow movement in controlling their displacement. In rapid movement with a concurrent motor task, most aspects of motor performance were degraded in hand, while tongue speed during rapid continuous task was maintained. With a concurrent cognitive task, most aspects of motor performance were degraded in tongue, while hand accuracy during the rapid discrete task and hand speed during the rapid continuous task were maintained.

Conclusion: Rapid goal-directed hand and tongue movements were more consistently susceptible to interference from concurrent motor and cognitive tasks, respectively, compared with the other movement.

Figure 1

A subject using the tongue drive system (TDS) to perform tongue tasks. The major components of the TDS headset are depicted (a). The wireless control unit sits on top of the headset with the battery supply in the back. Two magnetic sensors are attached (one on each side) to detect the movement of the magnet on the subject's tongue (b).

Figure 2

Cartoon schematic to explain the experimental conditions for Session 1 (Rapid Discrete Movement), Session 2 part 1 (Rapid Continuous Movement), and Session 2 part 2 (Waveform Tracking Movement). A representative cursor trajectory for the waveform tracking a sinusoid is included for Session 2 part 2.

Figure 3

Main effects of task on reaction time, completion time, coefficient of variation (CV) of reaction time, and correctness during rapid discrete movement. The data in hand (a, c) and tongue (b, d) in Session 1 are presented. H, independent hand task; T, independent tongue task; HT, concurrent hand-tongue task; HC, concurrent hand-cognitive task; TC, concurrent tongue-cognitive task. *, P < 0.05; **, P < 0.01.

Figure 4

Main effects of task on the speed and correctness of movement during rapid continuous movement. The frequency of movement in hand (a, c) and tongue (b, d) in Part 1 of Session 2 is presented in counts/s. H, independent hand task; T, independent tongue task; HT, concurrent hand- tongue task; HC, concurrent hand-cognitive task; TC, concurrent tongue-cognitive task. *, P < 0.05; **, P < 0.01.

Figure 5

Effects of task and difficulty level on the coefficient of variation (CV) of time interval during rapid continuous movement. The data in hand (a) and tongue (b) in Part 1 of Session 2 are presented. H, independent hand task; T, independent tongue task; HT, concurrent hand-tongue task; HC, concurrent hand-cognitive task; TC, concurrent tongue-cognitive task. **, P < 0.01.

Figure 6

Main effects of task and difficulty level on the variability of displacement during slow waveform tracking. The root mean square error (RMSE) in hand (a, c) and tongue (b, d) in Part 2 of Session 2 are presented. Difficulty levels include square-wave and sine wave. H, independent hand task; T, independent tongue task; HT, concurrent hand-tongue task; HC, concurrent hand-cognitive task; TC, concurrent tongue-cognitive task. **, P < 0.01.