Group III and IV muscle afferents differentially affect the motor cortex and motoneurones in humans.

摘要: The influence of group III and IV muscle afferents on human motor pathways is poorly understood. We used experimental pain to investigate their effects at cortical spinal levels. In two studies, electromyographic (EMG) responses in elbow flexors extensors stimulation the cortex (MEPs) corticospinal tract (CMEPs) were evoked before, during, after infusion hypertonic saline into biceps brachii evoke deep pain. study 1, MEPs CMEPs relaxed muscles during contractions a constant flexion force. 2, extension level or triceps EMG, respectively. During pain, size increased (by ∼47% ∼56%, respectively; P < 0.05). did not change with but relative CMEPs, they decreased ∼34%) ∼43%; force, ongoing background EMG for ∼14% 15%; level, ∼30% ∼26%, 0.05) both ∼20% ∼17%; For extension, ∼22%) whereas ∼15%; Activity produced by facilitates motoneurones innervating flexor extensor depresses cells projecting these muscles.