Sensitivity to cutaneous warm stimuli varies greatly in the human head

The head has been known as the most sensitive area to temperature changes but the values are limited to the face. The purpose of this study was to examine cutaneous warm thresholds on the scalp and face of young males. Eight males participated in this study (24 ± 3 yrs in age, 178.2 ± 5.3 cm in height, and 90.0 ± 15.4 kg in body mass). All measurements were conducted in an environmental chamber (27 ± 1 °C air temperature and 53 ± 1% relative humidity). Cutaneous warm thresholds were measured on nine areas of the following regions: the frontal (two points on the right), parietal (a point on the right and the vertex, respectively), temporal (two points on the right), and occipital region (on the right) along with the forehead using a thermal stimulator (rate of temperature increase 0.1 °C s−1). Skin temperatures on the nine head regions were monitored during the threshold test. The results showed that 1) no significant differences were found in initial skin temperatures among the nine head regions; 2) cutaneous warm detecting temperatures were significantly greater on the vertex (38.2 ± 3.5 °C) than on the forehead (34.8 ± 1.4 °C) and the other seven scalp regions (P < 0.05); 3) subjects detected the increase of 1.2 ± 1.0 °C on the forehead and 1.5 ± 1.2 °C on the occipital region as the first warmth while the vertex was the most insensitive to the increase of temperature (4.0 ± 3.2 °C) (P < 0.05). In summary, the scalp region of young males was less sensitive to the temperature change when compared to the forehead, and the vertex was the most insensitive among the eight scalp regions to the temperature increase. We conclude that the entire head should be considered as a binary topography with the face and the scalp in terms of cutaneous thermal sensitivity.