There appear to be at least two pain transmission circuits in humans. Some data suggests that a spinal cord-thalamic-frontal-cortex-anterior singulate pathway plays a role in the subjective psychological and physiological responses to pain, whereas a spinal cord-thalamic-somatosensory cortex pathway plays a role in pain sensation A descending pathway involving the periaquaductal gray region of the brain modulates pain signals (pain modulation circuit). This system can augment or inhibit pain transmission at the level of the dorsal spinal cord. Endogenous opioides are particularly concentrated in this pathway. At the level of the spinal cord, seratonin and norepinephrine also appear to play important roles.
Relaxation techniques as a group generally alter sympathetic activity as indicated by decreases in oxygen consumption, respiratory and heart rate, and blood pressure. Increased electroencephalographic slow wave activity has also been reported. Although the mechanism for the decrease in sympathetic activity is clear, one may infer that decreased arousal (due to alterations in catecholamines or other neurochemical systems) plays a role.
Hypnosis, biofeedback, cognitive behavioral therapy, and various relaxation procedures have all been shown to be effective in treating pain. A typical complementary medicine protocol for addressing acute and chronic pain may include all of the above procedures and in addition, use of aromatherapy (oil of lavender), acupuncture, magnetotherapy, massage reflexology or polarity therapy, hydrotherapy, and the use of standardized herbs.
Hypnosis in particular has been hypothesized to block pain from entering consciousness by activating the frontal-limbic attention system to inhibit pain impulse transmission from thalamic to cortical structures. Cognitive behavioral techniques may decrease transmission of pain through this pathway also.
Source: Journal of the American Medical Association, July 24/31, 1996 - Volume 276. No 4
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