Consciousness and Pain

Pain, by definition, is a sensory and emotional experience. Response to noxious stimuli in the absence of consciousness is nociception, not pain. Knowledge that a stimulus is tissue threatening (noxious) is available in the pain system with minimal signal processing. This contrasts with vision, for example, where extensive cortical processing is required to extract meaning. Indeed, effects of lesions, epileptic auras, and response to direct brain stimulation suggest that the conscious perception of pain may not require cortical processing at all. The recent discovery of a brainstem cell group capable of rapidly switching consciousness (including pain) on and off provides a new experimental lead into the circuitry that subserves the conscious experience of pain. In general, understanding transitions between consciousness and unconsciousness may be a more tractable near-term goal for neurobiological study of the hard problem than the usual focus on the contents of consciousness.