Laboratory of Signal Processing and Motor Control, University of Brasïlia, College of Physical Education Brasïlia, Brazil ; Rehabilitation Neuroscience Laboratory, School of Exercise Science, Physical, and Health Education, University of Victoria Victoria, BC, Canada.
Rehabilitation Neuroscience Laboratory, School of Exercise Science, Physical, and Health Education, University of Victoria Victoria, BC, Canada ; Department of Integrative Physiology, Kyorin University School of Medicine Mitaka, Tokyo, Japan.
Front Hum Neurosci. 2014 Mar 11;8:136. doi: 10.3389/fnhum.2014.00136. eCollection 2014.
after stroke a typical presentation is exaggerated stretch reflexes (SRs) on the more affected (MA) side. The present study evaluated the contribution of presynaptic inhibition (PSI) induced by arm cycling and homosynaptic depression (HD) to the modulation of hyperreflexia at the ankle after stroke. Possible asymmetry of these effects between the MA and less affected (LA) legs was also assessed.
soleus SR was conditioned by: arm cycling at 1 Hz (to increase Ia PSI); or, a preceding conditioning tendon tap applied 1 s before the test stimulus (to induce HD). The extent of conditioning effects was compared between the MA and the LA legs.
for both MA and LA legs, rhythmic arm movement induced a bidirectional effect in different participants, either increasing or decreasing SR amplitude (p < 0.05). HD had a significant effect in both legs (p < 0.05), however, the effect of both a previous muscle stretch and arm cycling was not different between the MA and the LA legs.
our data reveal a bidirectional reflex modulation induced by arm cycling that produced facilitation in some and suppression in other participants after stroke. Relative SR amplitude modulation did not differ between the LA and MA legs. We speculate that alterations in SR amplitude modulation after stroke may reflect specific changes in both presynaptic afferent transmission mechanisms and fusimotor control.
the present findings open new perspectives on the characterization of pathophysiology of stroke during the performance of functionally relevant motor tasks.
脑卒中后，患侧肢体常出现反射亢进（SRs）。本研究评估了手臂循环诱发的突触前抑制（PSI）和同突触抑制（HD）对脑卒中后踝关节反射亢进的调节作用，并评估了这些作用在患侧（MA）和非患侧（LA）下肢之间的可能不对称性。
用以下方法对比目鱼肌 SR 进行条件反射：以 1 Hz 的频率进行手臂循环（增加 Ia PSI）；或者，在测试刺激前 1 秒施加先前的条件反射肌腱轻叩（以诱导 HD）。比较 MA 和 LA 下肢之间的条件反射效应。
对于 MA 和 LA 两条腿，节律性手臂运动在不同参与者中产生了双向效应，要么增加要么减少 SR 幅度（p<0.05）。HD 在两条腿上均有显著影响（p<0.05），但肌肉拉伸和手臂循环的先前效应在 MA 和 LA 腿之间没有差异。
我们的数据揭示了手臂循环诱导的双向反射调节，在脑卒中后，一些参与者产生了易化作用，而另一些则产生了抑制作用。LA 和 MA 腿之间的相对 SR 幅度调制没有差异。我们推测，脑卒中后 SR 幅度调制的改变可能反映了传入性传入传输机制和梭内肌控制的特定变化。
本研究结果为在进行功能相关运动任务时，对脑卒中的病理生理学特征的研究提供了新的视角。
