Experimental Pain Decreases Corticomuscular Coherence in a Force- But Not a Position-Control Task.

Differences in neural drive could explain variation in adaptation to acute pain between postural and voluntary motor actions. We investigated whether cortical contributions, quantified by corticomuscular coherence, are affected differently by acute experimental pain in more posturally focused position-control tasks and voluntary focused force-control tasks. Seventeen participants performed position- and force-control contractions with matched loads (10% maximum voluntary contraction) before and during pain (injection of hypertonic saline into the infrapatellar fat pad of the knee). Surface electromyography (EMG) of right knee extensor and flexor muscles was recorded. Electroencephalography (EEG) was recorded using a 128-channel sensor net. Corticomuscular coherence was calculated between 4 EEG electrodes that approximated the contralateral motor cortical area, and EMG. Coherence, EEG, EMG, and target performance accuracy were compared between task types and pain states. Before pain, coherence EEG and EMG did not differ between tasks. During pain, EMG increased in both tasks, but the force-control task showed greater pain interference (decreased coherence, higher EEG frequencies, and increased force fluctuations). Neural substrates of motor performance of postural functions are changed uniquely by experimental pain, which might be explained by differences in cortical demands. Our results provide new insights into the mechanisms of motor adaptations during acute pain. PERSPECTIVE: Understanding of the mechanisms underlying adaptations to motor function in acute pain is incomplete. Experimental work almost exclusively focuses on voluntary motor actions, but these adaptations may be inappropriate for postural actions. Our results show less pain-related interference in brain activity and its relationship to muscle activation during position-control tasks.