Tan Andrew Q, Dhaher Yasin Y
Northwestern University Interdepartmental Neuroscience, Northwestern University, Chicago, IL, United States.
Searle Center for the Science of Walking, Shirley Ryan AbilityLab, Chicago, IL, United States.
Front Neurol. 2017 Aug 7;8:373. doi: 10.3389/fneur.2017.00373. eCollection 2017.
The neural constraints underlying hemiparetic gait dysfunction are associated with abnormal kinetic outflow and altered muscle synergy structure. Recent evidence from our lab implicates the lesioned hemisphere in mediating the expression of abnormally coupled hip adduction and knee extension synergy, suggesting a role of cortical networks in the regulation of lower limb motor outflow poststroke. The potential contribution of contralesional hemisphere (CON-H) in regulating paretic leg kinetics is unknown. The purpose of this study is to characterize the effect of CON-H activation on aberrant across-joint kinetic coupling of the ipsilateral lower-extremity muscles poststroke.
Amplitude-matched adductor longus motor-evoked potentials were elicited using single pulse transcranial magnetic stimulation (TMS) of the lesioned (L-H) and CON-Hs during an isometric adductor torque matching task from 11 stroke participants. For 10 control participants, TMS of the contralateral and ipsilateral hemisphere were given during the same task. TMS-induced torques were characterized at the hip and knee joints to determine the differential regulation of abnormal kinetic synergies by each motor cortices. The TMS-induced ratio of knee extension/hip adduction torques was quantified during 40 and 20% of maximum adduction torque.
For both the 40 and 20% target adduction tasks, we find that contralesional stimulation significantly reduced but did not eliminate the TMS-induced ratio of knee extension/hip adduction torques for the stroke group ( = 0.0468, = 0.0396). In contrast, the controls did not present a significantly different TMS-evoked torque following stimulation ( = 0.923) of the hemisphere ipsilateral to the test leg.
The reduced expression of abnormal across-joint kinetic coupling suggests that the CON-H may contribute an adaptive role in lower limb control poststroke. Future study of neuromodulation paradigms that leverage adaptive CON-H activation may yield clinically relevant gains in lower limb motor function poststroke.
偏瘫步态功能障碍背后的神经限制与异常的动力学输出和改变的肌肉协同结构有关。我们实验室最近的证据表明，受损半球在介导异常耦合的髋关节内收和膝关节伸展协同作用的表达中起作用，这表明皮质网络在中风后下肢运动输出的调节中发挥作用。对侧半球（CON-H）在调节患侧腿部动力学方面的潜在贡献尚不清楚。本研究的目的是描述CON-H激活对中风后同侧下肢肌肉异常跨关节动力学耦合的影响。
在11名中风参与者进行等长内收肌扭矩匹配任务期间，使用单脉冲经颅磁刺激（TMS）分别刺激受损半球（L-H）和CON-H，引出振幅匹配的长收肌运动诱发电位。对于10名对照参与者，在相同任务期间对其对侧和同侧半球进行TMS。通过对髋关节和膝关节处TMS诱发的扭矩进行特征分析，以确定每个运动皮层对异常动力学协同作用的差异调节。在最大内收扭矩的40%和20%时，对TMS诱发的膝关节伸展/髋关节内收扭矩比值进行量化。
对于40%和20%的目标内收任务，我们发现对侧刺激显著降低但并未消除中风组TMS诱发的膝关节伸展/髋关节内收扭矩比值（P = 0.0468，P = 0.0396）。相比之下，在对测试腿同侧半球进行刺激后（P = 0.923），对照组的TMS诱发扭矩没有显著差异。
异常跨关节动力学耦合表达的降低表明，CON-H可能在中风后下肢控制中发挥适应性作用。未来对利用适应性CON-H激活的神经调节模式的研究可能会在中风后下肢运动功能方面产生临床相关的改善。
