Vibrotactile thresholds in non-Pacinian mechanoreceptive afferents: the importance of temporal parameters.

Vibrotactile thresholds of non-Pacinian mechanoreceptive afferents (RA, SAI, SAII) were determined as a function of stimulus duration (100-800 ms) at three frequencies (20-240 Hz). Altogether 64 units innervating the hairy skin of the cat were tested. At all frequencies SAII units had the lowest thresholds whereas SAI units had the highest thresholds. At all frequencies and in all unit populations the absolute thresholds (1 impulse/stimulus train) were independent of stimulus duration, whereas the tuning thresholds (1 impulse/cycle) were elevated as a function of increasing stimulus duration. The present results suggest that the detection threshold decreases as a function of increasing stimulus duration are not based on peripheral properties of non-Pacinian mechanoreceptors.