Physiological variations of warm and cool sense with shift of environmental temperature.

In order to obtain control data on the temperature sense (warm and cool threshold values) of fingertips, the relationships between room temperature and either skin temperature, warm threshold or cool threshold of the middle fingertips were investigated in healthy subjects (6 males), using our thermo-esthesiometer. The skin temperature changes in a sigmoidal response with the variation of room temperature. A point of inflection for this response was observed at the room temperature of 15 degrees C, at which the greatest standard deviation of skin temperature occurred. The warm and cool thresholds, on the other hand, were also affected by variations of room temperature. Warm threshold and skin temperature or cool threshold and skin temperature bore a linear relation to each other, and the correlation coefficient was 0.854 in the former, and 0.925 in the latter, respectively. The disorder of temperature sensitivity (warm and cool thresholds) must always be considered together with the room temperature or skin temperature. On the other hand, the width of the neutral zone between warm and cool thresholds was affected by neither the changes of room temperature nor the changes of skin temperature. Hence, the width of the neutral zone was approximately constant, especially, at the room temperatures in the vicinity of 15 degrees C to 25 degrees C.