Del Santo Francesco, Gelli Francesca, Spidalieri Raffaele, Rossi Alessandro
Unit of Clinical Neurophysiology, Department of Neurological and Behavioural Sciences, University of Siena, Viale Bracci 1, 53100 Siena, Italy.
Brain Res. 2007 Jan 12;1128(1):91-8. doi: 10.1016/j.brainres.2006.09.039. Epub 2006 Nov 28.
In the voluntary contractions, output force can be maintained constant although the inhibitory influences exerted by pain on muscle activity. We investigated changes in the spontaneous and evoked activity of the abductor digiti minimi muscle (ADM) and the biceps brachii muscle (BIC) in healthy volunteers during constant force noxious contraction, resulting from chemically activated nociceptive afferents. EMG-force relationship, motor-evoked response (MEP) to transcranial magnetic stimulation and determinism (DET) of surface EMG signals during constant force contraction was analyzed before, during and after chemically induced tonic activation of their nociceptive afferents. Under constant force contraction, amplitude of surface EMG signal decreased in BIC and increased in ADM during pain with respect to control condition. In both muscles, the size of motor-evoked potential (MEP) induced by transcranial magnetic stimulation (TMS) of the primary motor cortex was significantly higher during pain than in control. Level of determinism extracted from surface EMG signal by non-linear method was similarly and significantly increased in both muscles during pain stimulation. Finally, nociceptive stimulation caused a decline in steadiness of the force exerted by ADM and BIC. These results are interpreted in terms of increased corticospinal synchronizing inputs. The possibility that it may play a role in governing force production to counteract pain inhibitory influences on motor system is considered.
在自主收缩过程中，尽管疼痛对肌肉活动存在抑制作用，但输出力仍可保持恒定。我们研究了健康志愿者在化学激活伤害性传入神经引起的恒力伤害性收缩过程中，小指展肌（ADM）和肱二头肌（BIC）的自发活动和诱发活动的变化。在化学诱导其伤害性传入神经的紧张性激活之前、期间和之后，分析了恒力收缩过程中的肌电图-力关系、经颅磁刺激的运动诱发电位（MEP）以及表面肌电图信号的确定性（DET）。在恒力收缩下，与对照条件相比，疼痛期间BIC的表面肌电图信号幅度降低，ADM的表面肌电图信号幅度增加。在两块肌肉中，疼痛期间经颅磁刺激（TMS）初级运动皮层诱发的运动诱发电位（MEP）大小均显著高于对照。通过非线性方法从表面肌电图信号中提取的确定性水平在疼痛刺激期间在两块肌肉中同样显著增加。最后，伤害性刺激导致ADM和BIC施加的力的稳定性下降。这些结果可根据皮质脊髓同步输入增加来解释。还考虑了其可能在控制力量产生以抵消疼痛对运动系统的抑制影响中发挥作用的可能性。
