Sensory Feedback for Upper-Limb Amputees by Noninvasive Electrical Stimulation and Its Performance Assessment

Area of Science:

• Biomedical Engineering
• Neuroscience
• Rehabilitation Technology

Background:

• Commercial prostheses often lack natural sensory feedback, leading to high abandonment rates.
• Transcutaneous Electrical Nerve Stimulation (TENS) is a viable method for evoking sensations in amputees.

Purpose of the Study:

• To investigate how TENS parameters influence sensory feedback.
• To evaluate TENS performance using behavioral and electroencephalography (EEG) data.

Main Methods:

• Recruited three transradial amputees and seven able-bodied subjects.
• Systematically varied TENS parameters (amplitude, width, frequency) to evoke sensations.
• Collected behavioral responses and EEG data to assess sensation perception and cortical activity.

Main Results:

• Sensation thresholds and intensity were primarily affected by stimulus amplitude and width.
• Stimulus frequency influenced sensation type, with 10 Hz for vibration and 100 Hz for pressure.
• Amputees demonstrated high accuracy (94.4% type, 77.8% intensity) in discriminating TENS-evoked sensations.
• EEG analysis revealed reliable sensory feedback with distinct ERP components (N1) correlating with sensation type and intensity.

Conclusions:

• TENS parameters can be optimized to provide specific sensory feedback (e.g., pressure for grasp force).
• TENS-based sensory feedback is reliable and discriminable for amputees, though with slower responses and reduced cortical activation compared to able-bodied individuals.
• This study supports TENS as a key technology for closed-loop prosthetic systems and bionic robots.