Human-machine interface for two-dimensional steering control with the auricular muscles

Area of Science:

• Biomedical Engineering
• Neuroscience
• Rehabilitation Technology

Background:

• Human-machine interfaces (HMIs) offer potential for individuals with motor disabilities, such as spinal cord injury, to regain control over external devices.
• Existing HMI solutions require improvements in decoding algorithms, hardware, and user learning.
• Auricular muscles (AMs) are vestigial muscles often preserved after neurological damage, making them a promising target for HMIs.

Purpose of the Study:

• To develop and evaluate a novel decoding and training paradigm for HMIs using auricular muscles.
• To enable naïve participants to control a two-dimensional virtual cursor with two degrees of freedom using their AMs.
• To assess the learning curve, performance, and cognitive load associated with this AM-based HMI.

Main Methods:

• Surface electromyographic (sEMG) signals from AMs were used to modulate cursor velocity and direction in a 2D space.
• A locking mechanism was implemented to allow independent control and stopping of cursor movement along each axis.
• A five-session training protocol with a center-out task was administered to five non-disabled volunteers, including a dual-task condition to assess cognitive load.

Main Results:

• Participants demonstrated significant improvement in task success rate (from 52.78% to 72.22%) and trajectory performance after training.
• The AM-based HMI was effective even under cognitively demanding dual-task conditions (66.67% success rate).
• Participants reported reduced mental demand and effort in later training sessions, as measured by the Nasa Task Load Index.

Conclusions:

• Naïve individuals can learn to effectively control a two-degrees-of-freedom cursor using their auricular muscles with minimal cognitive burden.
• This novel AM-based decoding and training paradigm represents a promising first step towards developing advanced HMIs for individuals with motor impairments.
• The preserved nature of AMs post-neurological injury highlights their potential for restoring functional control in assistive technologies.