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Noise-enhanced vibrotactile sensitivity in older adults, patients with stroke, and patients with diabetic neuropathy,☆☆,,★★,,♢♢

https://doi.org/10.1053/apmr.2002.28025Get rights and content

Abstract

Liu W, Lipsitz LA, Montero-Odasso M, Bean J, Kerrigan DC, Collins JJ. Noise-enhanced vibrotactile sensitivity in older adults, patients with stroke, and patients with diabetic neuropathy. Arch Phys Med Rehabil 2002;83:171-6. Objective: To test the hypothesis that vibrotactile detection thresholds in older adults, patients with stroke, and patients with diabetic neuropathy can be significantly reduced with the introduction of mechanical noise. Design: A randomized controlled study. Setting: A university research laboratory. Participants: Twelve healthy elderly subjects (age range, 67-85y), 5 patients with stroke (age range, 24-64y), and 8 patients with diabetic neuropathy (age range, 53-77y). Interventions: Each subject's detection thresholds (ie, minimum level of stimulus to be detected) for a vibrotactile stimulus without and with mechanical noise (ie, random vibration with a small intensity) were determined by using a 4-, 2-, and 1-stepping algorithm. The stimuli were applied to the fingertip and/or to the first metatarsal of the foot. Main Outcome Measure: Detection threshold for a vibrotactile stimulus. Results: The detection threshold at the fingertip for the vibration stimulus with mechanical noise was significantly lower than that without mechanical noise for all 12 elderly subjects, for 4 of the 5 patients with stroke, and all 8 patients with diabetic neuropathy. For the 8 patients with diabetes, mechanical noise also significantly reduced the vibrotactile detection threshold at the foot. Conclusions: Reduced vibrotactile sensitivity in older adults, patients with stroke, and patients with diabetic neuropathy can be significantly improved with input mechanical noise. Noise-based techniques and devices may prove useful in overcoming age- and disease-related losses in sensorimotor function. © 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Section snippets

Methods

Twelve healthy elderly subjects (6 men, 6 women; age range, 67-85y; mean, 74y), 5 patients with stroke (3 men, 2 women; age range, 24-64y; mean, 44y), and 8 patients with diabetic neuropathy (4 men, 4 women; age range, 53-77y; mean, 67y) participated in the study. The diagnoses of stroke and diabetic neuropathy were both made clinically, not by electrodiagnostic testing. Informed consent was obtained from each subject before their participation. This study was approved by the Boston University

Results

The detection threshold at the fingertip for the vibration stimulus with mechanical noise was lower than that for the vibration stimulus without mechanical noise in all 9 trials for all 12 elderly subjects. This effect for a representative elderly subject is shown in figure 4A.

. Detection thresholds for the vibration stimulus without and with mechanical noise for 3 representative subjects. Shown are results from (A) the 9 fingertip trials for an elderly subject, (B) the 9 fingertip trials for a

Discussion

The results of the present study show that vibrotactile detection thresholds in older adults, patients with stroke, and patients with diabetic neuropathy can be significantly reduced by adding mechanical noise to the site of application of the vibratory stimuli. These novel findings suggest that age- and disease-related sensory loss may be reversible by exploiting stochastic resonance–type effects. The experiment's design reduced the possibility of subject bias because subjects were unaware of

Conclusion

This study showed that input noise can enhance sensory detection in healthy elderly people as well as in patients with central or peripheral nerve damage from stroke or diabetes. These findings are potentially important, insofar as impaired sensation leads not only to serious secondary medical complications, but also to impaired dexterity and coordination. Because sensation is an integral component of motor function, impaired sensation significantly hinders an individual's ability to perform

Acknowledgements

The authors thank Subashan Perera, PhD, for help with the statistical analyses.

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    Supported by the US National Science Foundation, the National Institutes of Health, the Partners HealthCare System Center for Innovative Minimally Invasive Therapy, a Teaching Nursing Home Award (grant no. AG04390), and Claude D. Pepper Older Americans Independence Center Grant (grant no. AG08812) from the National Institute on Aging, and the Argentinian Ministry of Education.

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    No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated.

    Reprint requests to James J. Collins, PhD, Center for BioDynamics and Dept of Biomedical Engineering, Boston University, 44 Cummington St, Boston, MA 02215, e-mail: [email protected].

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