Your Brain and Phantom Limb Phenomenon
Why do we feel Pain?
Pain is a physical response which acts as an alert system. Put simply, feeling pain tells us there is something wrong within the body. It is a protective system of sorts. It alerts us to dangers to ensure we do not repeat behaviour or actions which are damaging to the body. If it hurts to do something you generally do not continue doing it.
Phantom Limb Pain
It is very common for people with amputated limbs to sense pain in the limb that is no longer there. This illusionary pain has intrigued researchers for a number of years as to how the pain is sensed and why. There are no pain receptors present to send the usual signals to the brain from the limb that there is physical pain, yet at least 90% of amputees experience phantom limb pain.
Research by Ramachandran in the 1990’s suggested that those who had paralysis in that limb before it was amputated experienced the most severe phantom limb pain. He suggested a theory based on the idea that when they tried to move their paralysed limb, their brain received sensory feedback that the limb was unable to move. This feedback continues even when the limb is no longer present. This evidence along with an understanding that children born without limbs also experience phantom limb sensation leads experts to believe that the perception of our limbs is hard-wired into the brain.
How do we sense Pain?
Pain is all to do with the central nervous system in the body which is comprised of our brain and spinal cord.
- tiny pain receptors called nociceptors are contained in your skin all over your body
- each receptor ends in a neurone which forms the ending of a nerve cell
- these are connected by nerve fibres directly to the spinal cord
- When pain receptors are activated, an electrical signal is sent up these nerve fibres, through the collective peripheral nerve, from the point of pain origin and into the spinal cord
Within the spinal cord these electrical signals are transported by neurotransmitters (chemical messages) from nerve cell to nerve cell across synapses or the junctions between the cells.
Once these neurotransmitters reach the brain they enter into the thalamus.
The thalamus acts as a junction box where nerve signals are sorted and fired off to the somatosensory cortex regarding sensation, the frontal cortex regarding thinking and the limbic system regarding emotional response.
When damage is detected, the nociceptors fire pain signals to the brain via the spinal cord and will continue to do so while the damage is present.
Once the damage has been fixed or healed these nociceptors stop firing and the pain we experiences ceases. In some cases, they do not stop activating which can result in long term pain conditions.
The Nervous System
Our nervous system is an incredibly complex web network of wiring that fans out through your spinal column and across into all areas of your body.
It is this network that transports signals, including pain signals into the brain and sends responses back to different parts of your body. This is an automatic and very fast process with signals passing in and out of the brain through this network in fractions of a second.
It is a completely unconscious process, the mind is totally unaware of this occurring and it is not something we have any conscious control over.
Pain and Your Brain
Your brain itself is a mass of white and grey matter and does not contain pain receptors, however your scalp and the covering around the brain which protects it does. Note your brain is a physical mass but within that we have the conscious mind which responds and reacts to physical experiences such as pain. Part of the brain’s role in pain reception is to understand why the pain receptors have activated. This information gets submitted to your memory and will be compared to previous memories of similar reactions. The thalamus within the brain has this role.
The thalamus can be thought of as the emotional centre of the brain where feelings and emotions are operated from and associations between feeling and emotions can be connected to pain. This in itself can create a physical response i.e. you may feel nauseous, your heart rate may increase, you may begin sweating. This is where the brain and the mind overlap.
The Theory of Pain
The most popular theory on how pain can be dealt with is the ‘gate theory’. This is based on the idea that there is a gate like system within the spinal cord where nerve signals go first when pain receptors are activated at the pain site. If the gate opens the signals will continue onto the brain, if the gate closes it blocks the signals from going any further.
This theory was suggested by Melzack and Wall in 1965 and they suggest such pain signals can be increased, decreased or even stopped within the spinal cord through this gate system before even reaching the brain and the various responses that come as a result.
Phantom Limb Pain and The Brain
It is thought that phantom limb pain is caused by your brain continuing to receive signals from the nerves that originally carried signals from the limb, or in the case of being born without a limb, were they would have carried the signals.
The brain does not recognize amputation very well. As far as your brain is concerned your limb is still there and it needs to learn that it has in fact been removed. Over time the brain does begin to recognise the limb is no longer present and reroutes the signals. However for some, this never fully completes meaning they have this pain for a long time and it can be very difficult to treat.
People can experience pain in the area of the amputated limb including different sensations such as tingling, cramping, shooting pain and sensitivity to heat and cold.
The Mirror Neuron
An Italian scientist in the 1990’s, Giacomo Rizzolatii, discovered nerons within the brains of macaque monkeys activated both when the monkey reaching out to grab something and when the monkey watched another monkey reach out. These findings were later replicated in humans, indicating that visual perception may be much more important within the sensation of movement than we first thought.
An amputees's experience of phantom limb pain
Ramachandran used this idea to test the effect of using mirrors to trick the brain into thinking the phantom limb was still present and could be controlled. When used with human subjects suffering phantom limb pain, he found many were relieved of their symptoms in the phantom limb.
The brain, it is believed, is tricked into thinking the limb is present through the visual information it receives from the reflection of the opposite limb in the mirror. Ramachandran named this treatment Visual Feedback Therapy (MVF).
Further evidence has been found in recent years for the effectiveness of using mirrors as treatment for phantom limb pain. A US medic, Dr Jack Tsao, used the technique with 22 amputee patients and found over the course of 4 weeks all patients reported a decrease in pain levels. Furthermore, it has been found those who use a prosthesis can also lower the levels of pain from the phantom limb. Again the visual feedback going to the brain suggests the limb is present which appears to intervene with the confused messages from the nervous system which are causing the original pain.
While our understanding of pain receptors and nerve signals is quite advanced, a different approach is required when pain is being felt from a limb which is no longer there. Visual perception is clearly very important within the phenomenon of phantom limb pain and can interfere with the confusing nerve signals the brain receives when a limb is amputated. the success of using a simple mirror to treat such pain is a considerable breakthrough for amputees struggling with this type of pain. Our brains are complex but clearly they can be tricked and the more advances we find in psychology and medicine, the more control we may be able to gain.
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