The role of sensorimotor incongruence in pathological pain

For any given movement, our brains generate a prediction of what the outcome should be. This prediction is then compared with the feedback that is received once the movement is initiated, enabling appropriate corrections to be made. Following immobilisation due to injury or over-training, the cortical representation of a body part may change. This seems to be the case in certain populations, such as professional typists, musicians and in amputees with phantom limb sensations, all of which are often associated with chronic pain. The sensorimotor theory of pain postulates that certain types of chronic pain arise because a mismatch in body representation leads to an incongruence between the actual and predicted sensory outcomes of movements. In turn, this triggers neural signals for pain to alert the individual of potential harm to their body. Such cortical origins of pain are thought to contribute to repetitive strain injury, back pain, whiplash and Complex Regional Pain Syndrome (CRPS), which is a disorder that can follow relatively minor injury. A better understanding of sensorimotor integration in pain could facilitate better prevention and treatment of painful conditions.

I will use a well-characterized measures of body representation, motor prediction and sensory-motor integration to test the sensorimotor theory of pain, by comparing CRPS patients with healthy controls. To further explore these phenomena, I will conduct further experiments where the controls will be exposed to two possible drivers of CRPS; pain and sensory disturbance. This will be done by administering pain inducing or anesthetizing cream to healthy controls hands.

After a few minutes of tool use, the cortical representation of our body is updated to include the tool. I will examined this using a robust measure of this phenomena, the crossmodal congruency task (Maravita et al., 2002), which will indicate whether patients with CRPS have difficulties in updating their body representation, due to pain or sensory disturbance.

Typically, imagined and real movement have a similar duration (Papaxanthis et al., 2002). This suggests that we recruit motor processes when imagining a movement. By comparing these imagined and actual movement in CRPS, research will be conducted to explore problems in generating predictive motor signals, which arise due to pain or sensory disturbance.

Manipulating participants vision can be used to evaluate the integration of motor predictions and sensory information. Using motion-tracking equipment, I will examine whether CRPS patients and controls, experiencing pain or sensory disturbance, show impaired adaptation to manipulated vision. If this is the case, it would indicate impaired sensory-motor integration.

As part of the GW4 MRC BioMed Doctoral Training Partnership, this project will address the area of neuroscience and mental health by investigating the cortical underpinnings of pathological pain.