Giboin Louis-Solal, Sangari Sina, Lackmy-Vallée Alexandra, Messé Arnaud, Pradat-Diehl Pascale, Marchand-Pauvert Véronique
Sensorimotor Performance Lab, Sport Science Department, Universität Konstanz, Konstanz, Germany.
Sorbonne Universités, Laboratoire d'Imagerie Biomédicale (LIB), UPMC Univ Paris 06, INSERM, CNRS, Paris, France.
Physiol Rep. 2017 Nov;5(20). doi: 10.14814/phy2.13387. Epub 2017 Oct 29.
Inhibitory propriospinal neurons with diffuse projections onto upper limb motoneurons have been revealed in humans using peripheral nerve stimulation. This system is supposed to mediate descending inhibition to motoneurons, to prevent unwilling muscle activity. However, the corticospinal control onto inhibitory propriospinal neurons has never been investigated so far in humans. We addressed the question whether inhibitory cervical propriospinal neurons receive corticospinal inputs from primary motor (M1) and ventral premotor areas (PMv) using spatial facilitation method. We have stimulated M1 or PMv using transcranial magnetic stimulation (TMS) and/or median nerve whose afferents are known to activate inhibitory propriospinal neurons. Potential input convergence was evaluated by studying the change in monosynaptic reflexes produced in wrist extensor electromyogram (EMG) after isolated and combined stimuli in 17 healthy subjects. Then, to determine whether PMv controlled propriospinal neurons directly or through PMv-M1 interaction, we tested the connectivity between PMv and propriospinal neurons after a functional disruption of M1 produced by paired continuous theta burst stimulation (cTBS). TMS over M1 or PMv produced reflex inhibition significantly stronger on combined stimulations, compared to the algebraic sum of effects induced by isolated stimuli. The extra-inhibition induced by PMv stimulation remained even after cTBS which depressed M1 excitability. The extra-inhibition suggests the existence of input convergence between peripheral afferents and corticospinal inputs onto inhibitory propriospinal neurons. Our results support the existence of direct descending influence from M1 and PMv onto inhibitory propriospinal neurons in humans, possibly though direct corticospinal or via reticulospinal inputs.
利用外周神经刺激，在人类中发现了对上肢运动神经元具有弥散投射的抑制性脊髓 propriospinal 神经元。该系统被认为介导对运动神经元的下行抑制，以防止不必要的肌肉活动。然而，迄今为止，尚未在人类中研究皮质脊髓对抑制性脊髓 propriospinal 神经元的控制。我们使用空间易化方法探讨了抑制性颈脊髓 propriospinal 神经元是否接受来自初级运动区（M1）和腹侧运动前区（PMv）的皮质脊髓输入。我们使用经颅磁刺激（TMS）和/或正中神经刺激 M1 或 PMv，已知正中神经传入纤维可激活抑制性脊髓 propriospinal 神经元。通过研究 17 名健康受试者在单独和联合刺激后腕伸肌肌电图（EMG）中产生的单突触反射变化，评估潜在的输入汇聚情况。然后，为了确定 PMv 是直接控制脊髓 propriospinal 神经元还是通过 PMv-M1 相互作用来控制，我们在通过配对连续 theta 爆发刺激（cTBS）使 M1 功能破坏后，测试了 PMv 与脊髓 propriospinal 神经元之间的连接性。与单独刺激所诱导效应的代数和相比，M1 或 PMv 上的 TMS 在联合刺激时产生的反射抑制明显更强。即使在降低 M1 兴奋性的 cTBS 之后，PMv 刺激所诱导的额外抑制仍然存在。这种额外抑制表明外周传入纤维和皮质脊髓输入在抑制性脊髓 propriospinal 神经元上存在输入汇聚。我们的结果支持在人类中存在从 M1 和 PMv 到抑制性脊髓 propriospinal 神经元的直接下行影响，可能是通过直接的皮质脊髓或经由网状脊髓输入。
