Gate Control Theory

Pain is a unique subjective experienced that is influenced by factors such as cultural learning, personal significance of the situation and attention (Melzack 2001). When pain is experienced, it usually indicates injury, disease and threats to body tissues (Mosley 2003 & Butler & Moseley 2013). However, complexity of pain perception increases when considering chronic or phantom limb pain. Simply, these types of pain are indicative of the neural mechanisms gone awry, thus, alter perception of what is occurring in the tissues (Moseley 2003). For example, chronic pain can be ongoing years after an injury has been healed by the body, so the pain felt is not physical damage but rather what the brain perceives as pain signals (Melzack 2001). Additionally,
The Specificity Theory proposes that pain impulses are transmitted along linear pathways to pain centres in the brain. The intensity of the pain is determined by the number of impulses along a neuron (Moayedi & David 2013). This theory fails to consider psychological effects such as past experiences and anxiety that can act to alter pain perception (Melzack and Katz 2006). The Gate Control Theory emphasised a ‘gate mechanism’ at the dorsal horns of the spine to modulate synaptic input to the brain for processing (Melzack 2003). The gates opening is determined by the diameter of the active peripheral axons whilst the dynamic action of the brain acts to ‘close’ the gate (Keefe et al. 1996). This theory is effective in combining peripheral sensory information with top-down information from the brain, but does not provide a sufficient explanation for phantom limb pain (Melzack and Katz
The defining feature of chronic pain is the duration of suffering and the resultant psychological stress which increases the pain experienced more than the physical disability alone (Moseley 2003). With persistent pain, the nociceptive system and the virtual body undergo changes which strengthens the neuromatrix and increases the sensitivity to inputs, thus less input results in pain (Melzack 2001). The most effective tool a clinician can use is education on the complexity of pain mechanisms. Studies show that even basic understanding of the principals and theories associated with pain have positive influences on patient’s pain levels, function and healing times (Louw et al. 2011). By understanding the factors that make up inputs into the neuromatrix the patient is equipped with the necessary information to alter their own pain perception (McAllister 2015). For example, the patient is able to reduce negative input from the cognitive-related brain area by giving new meaning to an old memory that once negatively affected their chronic pain. By reducing a ‘threatening’ input, a reactive response changes pain perception in a cognitive dimension (Melzack 2001). Furthermore, distraction has been shown to be an effective tool in decreasing pain for both acute and chronic pain sufferers (McAllister 2015). Cognitive intervention draws the patient’s attention away from the pain which they are experiencing,