Title: An Evaluation of Cortical Preparatory Activity and Peripheral Muscle Activity in Movement-evoked pain
Thesis Supervisors: Dr. John Kramer and Dr. Michael Berger
Committee member: Dr. Tim Inglis
Defence Chair: Dr. Tania Lam
Abstract: Pain is a significant contributor to the development and potential persistence of motor dysfunction. However, the influence of movement-evoked pain on motor system function during the different stages of movement generation in movements that solely evoke pain is not well known. To determine whether brief movement-evoked nociceptive pain inhibits the motor system during submaximal activation, cortical preparatory processes and indexes of peripheral muscle activation were assessed. Cortical preparatory activity was assessed with both the event-related desynchronization of beta (13-30 Hz) oscillatory activity and the movement-related cortical potential (MRCP) using electroencephalography (EEG) while peripheral activity was assessed using surface electromyography (EMG), torque, and the rate of force development (RFD). In addition, the persistence of change was evaluated in subsequent pain-free movement. In all studies cortical activity as well as first dorsal interosseous muscle activity (FDI) and torque were recorded. Experimental nociceptive laser pain induced mild-moderate pain on the skin overlaying the dorsal aspect of the hand (pain-rating ~4 on a scale from 0 to 10). Movement-evoked pain increased MRCP peak negativity at the vertex and contralaterally (p=0.010, p=0.03, respectively), but no change in beta ERD modulation depth was observed. Furthermore, movement-evoked nociceptive pain caused a significant reduction (~11%) in submaximal muscle torque output (p = 0.044), without altering EMG activity and RFD. Any observed changes in cortical and peripheral activity reverted back to baseline levels during subsequent-pain free movement, which suggests that inhibitory mechanisms were not persistent. Thus, the present study suggests that brief experimental movement-evoked pain in the FDI affects central motor pathways, and collectively, these effects can be observed at multiple levels of the motor system during motor performance.