The effect of experimental pain on neural function and motor learning

Abstract

This thesis investigated whether acute experimental pain interacts with motor learning acquisition to create adaptive and maladaptive changes in neural function. The first study consisted of two experiments where we determined the interactive effects of acute pain versus control (Experiment 1) and local versus remote acute pain (Experiment 2) on motor learning and sensorimotor processing and provided supportive evidence for early somatosensory evoked potential (SEP) peaks as markers for sensorimotor integration (SMI) and acute pain. Motor performance was better in the presence of pain pre-motor learning and motor learning retention improved in the presence of local pain. A limitation of this first study was that performance saturation occurred and therefore we used a more complex tracing task for the subsequent studies. Our second SEP study The interactive effect of acute pain and motor learning acquisition on sensorimotor integration and motor learning outcomes provides corroboration for the enhancement of motor learning while in acute pain. In addition, the changes in the amplitudes of SEP peaks suggests that SEP peak alterations reflect neurophysiological alterations accompanying both motor learning acquisition and mild acute pain. Improved motor learning acquisition during acute pain may be the result of increased attention or increased arousal, and therefore we concluded that it was important to compare the effects of local versus remote versus contralateral acute pain in conjunction with a complex motor learning task which was the focus of the third study. Our third study found that motor learning occurred in the presence of mild acute pain and there were no significant differences in motor learning acquisition or retention between three groups that had capsaicin applied at different locations. We hypothesized that improved motor learning acquisition during acute pain may have been caused through increased arousal. For the fourth study we explored the effect of acute pain on neuroplasticity of the motor cortex (MI) by using input-output curves elicited via transcranial magnetic stimulation (TMS). The acute pain in this study was shown to negate the increase in slope that was observed for the control group despite having a positive impact on motor learning acquisition.