EFFECTS OF HYDRATION ON TACTILE SENSATION

The routine tasks of washing usually necessitates the immersion of pan s of the body in water, which causes hydration and changes in the mech anical properties of the superficial layer of skin. To determine how h ydration affects tactile sensations, the hydration and skin-surface te mperature of glabrous and hairy skin was first measured under normal c onditions (air), after submersion in distilled water alone and after s ubmersion in a surfactant-water solution. In these experiments, measur ements were made of the time to achieve complete hydration and the rec overy time to normal levels. The uptake of water in hairy skin was fou nd to be considerably greater than in glabrous skin, and retention was significantly prolonged by the surfactant additive. Subsequent experi ments on glabrous skin, based on the results of the preceding hydratio n studies, measured in-air and hydrated tactile thresholds and sensati on magnitudes to vibratory stimuli and to the roughness of textured su rfaces. Vibrotactile detection thresholds were not affected by skin hy dration, nor were sensation magnitudes to suprathreshold vibratory sti muli. However, suprathreshold perceptions of roughness were substantia lly altered by hydration. It is concluded that hydration and the mecha nics of the skin play a major role in the perception of spatiotemporal (i.e., textured) surfaces and, thus, must be taken into account in an y physiological/psychophysical model based on using such stimuli. This may not be required for models based on predominantly temporal (i.e., vibratory) stimuli.