Peripheral thermal responsivity to facial cooling during sleep

A recently developed technique for examining thermal sensitivity during sleep was used to assess whether skin and core temperature responses to thermal stimulation were altered by sleep state. The technique was designed to probe thermal responsivity without altering core body temperature or inducing awakening. Twenty-seven young men and women were studied during a sleep deprivation night and a sleep night three nights later. Cold water stimulation of the face alternated with an equal period of rewarming across a 40-min cycle throughout the night. Skin temperature from the finger and rectal temperature were continuously assessed. Sleep continuity and architecture were largely uninfluenced by the thermal stimulation. Finger skin temperature decreased during cold facial stimulation in both sleep and waking states. Skin temperature changes during sleep were approximately one-fifth the magnitude of those during waking. Core temperature was minimally influenced. REM sleep was associated with a greater amplitude decrease in finger temperature than was non-REM (NREM) sleep. The results support the utility of the technique as a probe of thermal responsivity during sleep and suggest a reduction of thermal responsivity during sleep and, more tentatively, an altered responsivity during REM versus NREM sleep.