Comparing Two Different Cursor Control Methods which Use Single-Site Surface Electromyography*

Abstract

Electromyography (EMG) can be used as an input signal for Human-Computer Interfaces, which are used in the disabled community. Typically, both the user-condition and the end-goal application dictate the number and locations of EMG sensors. We developed two cursor control methods intended for high-level spinal cord injury patients, where available muscle sites are limited to the head and neck areas. For patient comfort, it is desirable to minimize the number of sensors and their intrusiveness while maximizing the functionality of the control method. Both our control methods use a single, noninvasive, surface, differential EMG sensor at the temporalis muscle that controls a cursor in two degrees of freedom (DOF). Fourteen inexperienced able-bodied subjects completed a Fitts’s law task-based cursor-to-target paradigm using both control methods ("auto-rotate" and "manual rotate"). Subjects evaluated and compared performance between the two control methods, which both enabled the cursor to move in 2-DOF. They differed in the level of user control, where one allowed direction manipulation in 1-DOF and 2-DOF in the other. Subjects also completed pre- and post-session surveys and the National Aeronautics and Space Administration Task Load Index for workload assessment. In general, subjects’ performance improved with subsequent sessions within each control method. Subjects achieved a higher throughput (better performance) in the auto-rotate method, had lower workload scores, and tended to prefer this control method. However, about half the subjects felt the manual rotate method allowed them more control over cursor behavior. Our results suggest that a viable cursor control method can be achieved with only a single muscle site.