Pain is conventionally viewed as a pattern of convergent activity within the somatosensory system that represents the exteroceptive sense of touch. Accumulating functional, anatomical and imaging findings indicate that pain is generated by specific sensory channels that ascend in a central homeostatic afferent pathway. Phylogenetically new thalamocortical projections in primates provide a sensory image of the physiological condition of the body and, in addition, direct activation of limbic motor cortex. These findings indicate that the human feeling of pain is both a distinct sensation and a motivation - that is, a specific emotion that reflects homeostatic behavioral drive, similar to temperature, itch, hunger and thirst.