Neuromatrix theory of pain
Melzack (1999) extended his gate-control theory of pain during the 1980s and 1990s.
The primary reason for this was the original theory’s inability to explain the phenom -
enon known as phantom limb pain (i.e. experiencing pain in a limb that no longer
exists). This new model has suggested a stronger and more dominant role for the brain.
The central tenets of the theory are:
1 The areas of the brain linked to particular parts of the body continue to be active
and receive inputs even if a body part no longer exists.
2 We can still experience the qualities of the human condition, including pain,
without receiving input from the body, indicating that the origins of the patterns
of activation that bring about these qualities of experience must be located in neural
networks in the brain.
3 Conscious awareness of ‘body’ and ‘self’ is generated in the brain via patterns of
input that can be modified by different perceptual inputs.
4 A network of neurons, known as the neuromatrix, is distributed throughout the
brain to process all incoming sensory information including pain signals (known
as the body–self neuromatrix). This neural network consists of cyclical, feedback
loops between three of the brain’s main neural circuits: the thalamus, limbic system
and the cortex. The neuromatrix can process ‘experiences’ such as pain without
receiving direct input from the body.
5 When the neuromatrix receives sensory inputs, they are processed (synthesized)
and become imprinted on the matrix creating what is known as a neurosignature.
The neurosignature is projected to areas of the brain – the sentient neural hub –
where the flow of nerve impulses is transformed into a constantly changing stream
of awareness.
6 An action neuromatrix is then activated to signal appropriate movements when
pain is experienced (e.g. remove hand from hot iron).
7 The neuromatrix is genetically determined, however, it is modified through
sensory inputs such as pain experiences.
As you will have gathered, this is a complicated theory and further work is required
before researchers fully understand phantom limb pain. For example, recent advances
of the theory have suggested that exploration of how the stress response systems interact
and provide additional inputs into the neuromatrix is required. Nevertheless, the
developments presented by Melzack’s neuromatrix theory of pain have provided
valuable insights into the mechanisms underlying this phenomenon (Giummarra et al.,
2007; Jensen and Turk, 2014).
PSYCHONEUROIMMUNOLOGY
Have you ever wondered why a relatively large number of students report having the
common cold around the time of important examinations? Is this simply bad luck, all
in the mind, or is there a biological explanation? A growing body of evidence indicates
that there is a link between social and psychological factors and susceptibility to
BIOPSYCHOSOCIAL PATHWAYS 31