The effects of static indentation on vibrotactile threshold.

Vibrotactile thresholds were measured on the thenar eminence and the volar forearm at different static depths of skin indentation. Three stimulus frequencies (1, 20, and 200 Hz) were delivered through either a 0.008- or a 2.9-cm2 contractor. The indentation depths ranged from 0 to 1 mm (0.25-mm steps) relative to the point of skin contact with the stimulator. There was a significant effect of indentation in all stimulus combinations of contactor size, location, and frequency. These results resolve an apparent discrepancy in the literature regarding threshold reduction with increasing contactor size observed on the forearm at low frequencies.