Pain Perception, Affective Mechanisms, and Conscious Experience
Pain has afflicted humankind since the dawn of human self-awareness, yet we are still struggling to understand its nature. Young physicians in training, whose job it will be to prevent or relieve pain in myriad medical settings, listen to instructors who teach about pain receptors, pain pathways, and mechanisms that gate pain at the dorsal horn of the spinal cord. Continuing medical education efforts sustain and enhance the same message, implying that pain is a primitive sensory signal. Specific sensory end organs transduce injury and transmit "pain," and along the pathway from the periphery to the brain, descending modulatory pathways gate this transmission. Curiously, these same lecturers and teachers are quick to agree that pain is subjective and that it exists only in the brain and when the perceiver is conscious. They point out that they merely equate nociception, the transduction and signal transmission of tissue injury, with pain itself. Surely, they reason, when injury occurs, some message of tissue trauma moves from the periphery to the somatosensory cortex, and when that message reaches the somatosensory cortex, something "realizes" it and pain happens. They further reason that, because pain is intrinsically unpleasant, it causes negative emotional responses that we recognize as emotional reactions to pain.