The effects of skin temperature on the detection and discrimination of tactile stimulation.

Detection thresholds and intensity-difference thresholds were measured on four subjects ranging in age from 19 to 22 years. The stimuli were 250-Hz bursts of vibration applied through a 3.0 cm2 contactor to the thenar eminence of the right hand. Detection thresholds were substantially higher at 20 degrees C than at 30 degrees or 40 degrees C and were only slightly higher at 40 degrees C than 30 degrees C. When the intensity-difference threshold was expressed in relative terms, as the proportion by which two stimuli must differ in amplitude to be discriminated (delta phi/phi), discrimination capacities were unaffected by surface-skin temperature. The results are consistent with the hypothesis that surface-skin temperature alters the sensitivity of tactile receptors, and that, because of the 'near miss' to Weber's law, the relative difference threshold is unaffected substantially by skin temperature. It was concluded that, at least a partial explanation of the 'near miss' lies in the fact that, at low to moderate sensation levels, the P channel is exclusively activated whereas, at moderate to high sensation levels, because of recruitment of activity in Non-Pacinian channels, neural information for intensity discrimination is additionally provided by channels with superior discriminative capacities.