Brain activation during whole body cooling in humans studied with functional magnetic resonance imaging.

Regional activation of the brain was studied in humans using functional magnetic resonance imaging during whole body cooling that produced thermal comfort/discomfort. Eight normal male subjects lay in a sleeping bag through which air was blown, exposing subjects to cold air (8 degrees C) for 22 min. Each subject scored their degree of thermal comfort and discomfort every min. As the subjects reported more discomfort the blood oxygen level dependent response in the bilateral amygdala increased. There was no activation in the thalamus, somatosensory, cingulate, or insula cortices. This result suggests that the amygdala plays a role in the genesis of thermal discomfort due to cold.