(don’t worry, that’s the biggest word in this article)
and the Gate Control Theory of Pain
The brain is bombarded with tens of thousands of pieces of information every second, information about body movement, input from the sense organs (eyes, ears, nose, etc.), from the internal organs, from thermal and chemical detectors… the list goes on and on. 88% of this information belongs to our subconscious; we are unaware of it. Everything else, everything we sense, ponder, feel, and experience is only 12% of what the brain is processing at any given moment. The combined input from our peripheral nervous system, both conscious and unconscious, is called afferent flow.
Not surprisingly, the brain needs to sort this information. It filters, prioritizes and responds to what it has learned. Once it has finished sorting, it transmits a response called efferent flow. In approximate terms, for every 10 bits of afferent information the brain receives, it responds with 1 bit of efferent information.
Part of this sorting and prioritizing happens at the spinal cord level, before signals even reach the brain. Information about movement flows up one type of nerve, and information about pain flows up another. If information about both movement and pain happen at the same time, the two signals compete with each other to see who actually gets to project up the spinal cord to the brain. This is known as the Gate Control Theory of Pain.
Because nerve fibres that convey information about body position are faster than the ones that convey information about pain, they usually win the battle to project up the spinal cord to the brain. Therefore, the more information the brain receives about changes in body position, the less information it receives about pain.
The Four Dogs of the Apocalypse: Gluttony, Hyperactivity, Barking, and Stick Chewing
This is why you rub your leg after banging your shin; the sensation of skin being touched outpaces the sensation of pain and reduces the amount of discomfort perceived by the brain. Similarly, this is why people who have an illness or injury might not feel too bad when they are up and moving about, but then once they just lie immobile in bed at night, they really notice their aches and pains.
The same goes for arthritic pets. If all they do is lie on a blanket, then there is little information travelling to the brain to compete with the sensation of pain. Dysafferentation is the word used to describe this imbalance in which the brain receives a large amount of afferent flow relating to pain, and little information about movement. This triggers a downward spiral: reduced movement allows the perception of more pain, which makes the patient reluctant to move, which allows the perception of more pain, which makes the patient reluctant to move….
We’re used to the notion that “practise makes perfect”, that the more we repeat an action, the better we get at it, whether it’s catching a ball or balancing on a narrow beam. This occurs because the nervous system is constantly rewiring itself for greater efficiency. The problem is, this phenomenon happens at both a conscious and unconscious level. In the same way that the nervous system can learn to catch a ball more efficiently, it can become more efficient at slouching, or at having a seizure, or at experiencing pain. The more pain you feel, the easier it becomes to feel that pain. This goes back to the downward spiral described in the paragraph above.
Both chiropractic adjustments and acupuncture needles trigger neurologic responses that help reduce dysafferentation, as well as provide temporary relief and the comfort needed to start moving, but the best way to prevent dysafferentation is to remain active. Encourage your arthritic dog to participate in controlled exercise. Distract them with activity. Circulate that joint fluid to disperse inflammatory mediators. Prescription pain control might be needed – whatever it takes to maintain activity. The longer they keep active, the happier they will be and the longer their arthritic joints will last.
As was mentioned before in a previous blog on exercising old dogs, any exercise that doesn’t flare them up afterward was good for them. If you are unsure of how much your dog is capable of doing, consult a professional with experience in developing rehabilitation exercise programs.