fingertips touchingSending imperceptible white-noise vibrations through the wrist could increase the dexterity of those recovering from stroke, according to an article published in Physiological Results July 14.

Patients who have experienced a stroke can have lasting side effects, such as a diminished tactile response in their fingers and hands. A decrease in sensory feedback from the fingers can cause insufficient grip force control, decreased dexterity, decreased fine object manipulation, and an unstable grip, often causing patients to drop objects.

Na Jin Seo, Ph.D., Assistant Professor in the Division of Occupational Therapy at MUSC Health, was the senior investigator for this study, which applied perceptible and imperceptible white-noise vibrations at various intensities and in separate locations on patients’ extremities to determine the optimal level of white-noise vibration needed to improve signal detection. V. Ramesh Ramakrishnan, Ph.D., and Abigail W. Lauer, M.S., in the Department of Public Health Sciences at MUSC Health performed the statistical analyses for the study. The patients’ non-dominant hands were used for the test because it was postulated to be more sensitive to somatosensory feedback. The vibration was then applied to areas of the palm, back of the hand, and inner wrists an attempt to increase sensitivity in the finger pads. The intensities of the vibration varied from 0% to 120% of the threshold.

At 60% of the threshold, the imperceptible white-noise vibrations significantly improved finger tactile sensation in the thumb and index finger when compared to 0%. At 80% of the threshold, no significant changes were seen, and at 120% of the threshold degraded sensory feedback was observed in the fingers, conforming to stochastic resonance behavior.

While the vibration stimuli would quickly decrease as it moved away from the application site, not reaching the fingertips, each site reacted similarly to the same intensities. According to the study, these results indicate that neuronal activity in the fingers is influenced by the vibration.

“This finding suggests a potential for a sensory orthotic that can be worn at the wrist,” says Seo. “It would provide minute vibration and enhance patients’ touch sensation and dexterity, improving their ability for activities of daily living.” 

This study suggests that patients who have experienced an injury or a stroke could gain access to the neuronal network in their hands through imperceptible white-noise vibrations. Wearing a vibrating device on their wrists could help these patients gain back some of the control they may have lost.