Grasping at Illusions: Stimulating the skin to investigate the cutaneous contribution to kinesthesia in the human hand

• Author / Creator

  Leverett, Jessica A.

• How do you know your hand is moving without looking at it? This “movement sense”, known as kinesthesia, is thought to be primarily informed by receptors in muscles; specifically, the muscle spindles. As we move, muscle spindles discharge when muscles lengthen and, thus, most research has focussed on these receptors. However, receptors in the skin, known as cutaneous receptors, also discharge when we move, although their role in kinesthesia remains less clear. This thesis project was designed to investigate the role of cutaneous receptors in kinesthesia by using electrical stimulation to create illusory hand movements; namely, flexion of the index finger. The frequency and intensity of the stimulation were modulated, separately and simultaneously, to test hypotheses regarding how the central nervous system may use frequency coding and population coding from cutaneous receptors in kinesthesia. Thirty-four healthy participants (22 females, 12 males; aged 18-33) with no neurological or musculoskeletal impairments that affect the movement or sensation in the hands were recruited. Stimulation was applied to the superficial branch of the radial nerve on the dorsum of the right hand. A total of 10 trials were delivered in a random order. Each trial consisted of one of four stimulation patterns: 1) frequency-modulated: the frequency of the stimulation was sinusoidally increased and decreased with intensity held at perceptual threshold; 2) intensity-modulated: stimulation intensity was sinusoidally increased and decreased with frequency held at 55 Hz; 3) combined-modulation: stimulation frequency and intensity were synchronously increased and decreased; 4) sham: stimulation frequency was held at 55 Hz and intensity was held at perceptual threshold throughout the trial. If participants perceived movement, they were instructed to keep their right (stimulated) hand relaxed and to mimic the movements with their left (unstimulated) hand. Prevalence of illusory movements and movement amplitudes of the index finger were quantified using passive motion capture cameras. In total 25/34 (74%) of participants perceived illusory movements, with the mean amplitude of movement ranging from 1-25. There were no significant differences between the amplitudes of the frequency-modulated, intensity-modulated, or combined-modulation trials. However, the amplitudes of all three modulated trials were significantly larger than the sham trial. These results suggest that cutaneous receptors play a role in kinesthesia, and that the CNS uses frequency coding and population coding from cutaneous receptors to inform kinesthesia. The simple method used in this project may have applications for the investigation of other basic research questions, or integration with other sensory stimuli such as virtual reality.

• Subjects / Keywords

  • kinesthesia
  • proprioception
  • electrical stimulation

• Graduation date

  Fall 2024

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-24ps-9483

• License

  This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.