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

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.