Regional sensitivity and spatial summation in the warmth sense.

Abstract The magnitude of warmth sensation aroused by heat irradiation and assessed by the method of magnitude estimation depends on the level of the irradiation, its areal extent, and the particular region of the body stimulated. Within a given body region, area and irradiation level both contribute to the magnitude of the warmth sensation (signifying generous spatial summation of neural signals), except that the proportional contribution of area diminishes gradually with increasing level of warmth and finally becomes negligible as the pain threshold is approached. Some regions of the body are far more responsive than others to low-level heating, but all regions respond more or less uniformly when the level of heating is high enough.