Understanding Chronic Pain

The Painful Brain

[From Chapter 8 of Understanding Chronic Pain]

The experience of pain, as I have suggested before, is kindred to the experiences of thought and mood. They are housed in the same brain-places and controlled by the same brain chemicals (neurotransmitters). The other senses, those of vision, hearing, and touch, are housed in very different brain-places and controlled by different transmitters. Pain, therefore, is unique among the senses. Only occasionally do sight and sound provoke emotional and behavioral reactions. Pain always does.

It is time to pause and discuss, briefly, the manner in which our brains work. This is the necessary groundwork for understanding the case histories that follow. We actually have two brains. They are interactive, interdependent, and mutually supportive, but they are in a very real sense two separate organs. Our predominant brain, at least in size, is the cerebral cortex. The gray matter on the surface, it constitutes some 90 percent of the total brain's cellular volume. It employs in its operations two major neurotransmitters, glutamic acid, which is excitatory, and gamma-aminobutyric acid (GABA), which is inhibitory. Cortical neurons are vastly complicated in their aggregate, but individually they are rather simple mechanisms. They function as stop-go systems. Glutamic acid is go. GABA is stop. They are hard-wired and predictable in their function. The cortical activities of movement, vision, audition, and tactile (touch) sensation are pretty much constant. They don't change from day to day.

The cerebral cortex is divided by a cleft into left and right hemispheres. Each of these is further segmented into major lobes, the occipital dedicated to the function of vision, the parietal to the function of tactile sensation, the temporal to audition, and the frontal to motor function. It is a lateralized brain with each hemisphere subserving the perception of sensation and the control of movement in the opposite side of the body. Lateralization extends also into the faculty of speech and motor dominance, in most of us in the left hemisphere. The cortical brain is highly topographic. Specific areas of each lobe are dedicated to specific functions—the vocalization of speech to an area in the frontal lobe, and the comprehension of speech to the parietal. In the sensory and motor cortex there is a high degree of topography with different zones dedicated to sensation and movement in different parts of the body, with poor representation for the leg and foot, more for the arm and hand, and most for the face. This topographic anatomy, the dedication of certain areas to specific functions, is lacking only in two cortical areas, the extreme frontal, known as the prefrontal cortex, and the cingulate gyrus, cortical tissue tucked deep within the hemispheric cleft. These cortical areas have no clear-cut topographic anatomy nor do they demonstrate any specific executive function. They are the apex of our second brain.

The subcortical brain lacks the distinctive convoluted architecture of the cortex. It consists of aggregates of cell bodies deep beneath the surface. These extend from the brain stem, the point where the spinal cord enters the cranium, and expand in size and scope as they reach the cingulate and prefrontal cortex. It is, in cellular volume, less than the size of a woman's fist. The predominant neurotransmitters, quite unlike those of the cortex, are serotonin, noradrenaline, and dopamine. The subcortical brain is the vegetative, emotional, memorizing, thoughtful, and behavioral brain. It is soft-wired. Subcortical neurons are more complicated than those in the cortex. They are capable of many reactions. Their response to provocation is much less predictable than those in the cortex. Subcortical neurons have choice.

You can read the rest in Dr. Cochran's book, Understanding Chronic Pain

Last Updated: Nov 19, 08:16 AM

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