Psychological models have proposed that valence, how pleasant or unpleasant a stimulus is perceived, and intensity, the strength with which a stimulus is perceived, constitute two primary dimensions that describe affective experience. However, the inherent relationship between valence and intensity has limited imaging studies of these models and the neural substrates are poorly understood. For example, it is not known if the neural representations for each dimension are discrete or shared. To overcome these limitations, we applied properties of alliesthesia, the phenomenon where the valence of a stimulus is dependent upon the physiological state of the body, using thermal stimuli to the hand in combination with whole-body warming and cooling. In this way, we were able to manipulate the hedonic aspect of our thermal stimuli independent of their perceived intensity. Brain regions correlating with stimulus valence included the medial orbitofrontal cortex, subgenual anterior cingulate cortex and amygdala, whereas stimulus intensity was correlated with activity in the insula, thalamus and striatum, among others. Our results suggest segregated patterns of neural activity underlying perceptions of valence and intensity, consistent with dimensional models of emotion.
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