Bilateral spatial summation of cooling of symmetrical sites

The possibility of spatial summation of conducted ??Ts (temperature decrements from the adapted skin temperature) was tested when the ??Ts were presented simultaneously and individually at symmetrical sites on either side of the body. The use of a signal detection rating method yielded data that indicate that spatial summation is complete (area and intensity trade reciprocally) for ??s near threshold and at clearly suprathreshold intensities of stimulation is invariant of the adapted skin temperature (AT), and the intensity of stimulation within the range of stimuli used (from as little as ?0.05?C to as much as ?1.25?C). In view of the characteristics ascribed to the thermosensory apparatus in humans, it is postulated that spatial summation occurs in the central nervous system.