Single unit responses of human cutaneous mechanoreceptors to air-puff stimulation

Objective: To investigate responsiveness of human cutaneous mechanoreceptor to selective tactile stimuli produced by brief air-puff stimulation. Methods: Using percutaneous microneurography, activities of single sensory units innervating glabrous skin of the hand were recorded, and air-puff stimuli with a short rise time (0.5 ms), generated by a high-speed air control system, were applied to the receptive field. Receptor activation time was estimated as the latency difference between electrically and air-puff evoked responses. Results: Thirty units were analyzed: all 4 kinds of mechanoreceptors of human glabrous skin (fast adapting type 1 [FA I, n=7], fast adapting type 2 [FA II, n=4], slowly adapting 1 [SA I, n=5] and slowly adapting 2 [SA II, n=14]) were activated by air-puff stimulation. Estimated receptor activation times were 0.6–6.2 ms (mean 2.2 ms). FA II units occasionally responded twice or more to a single air-puff stimulus. Conclusions: Brief air-puffs can activate all 4 human cutaneous mechanoreceptors, and the receptor transduction time is estimated as approximately 2.0 ms. Properties of human mechanoreceptors can be studied using air-puff stimulation and microneurography.