Thompson Aiko K, Gill Christina R, Feng Wuwei, Segal Richard L
Department of Health Sciences and Research, College of Health Professions, Medical University of South Carolina, Charleston, SC, United States.
Department of Neurology, College of Health Professions, Duke University School of Medicine, Durham, NC, United States.
Front Rehabil Sci. 2022 Jul 22;3:859724. doi: 10.3389/fresc.2022.859724. eCollection 2022.
Through operant conditioning, spinal reflex behaviors can be changed. Previous studies in rats indicate that the sensorimotor cortex and corticospinal tract are essential in inducing and maintaining reflex changes induced through conditioning. In people with incomplete spinal cord injury (SCI), an operant down-conditioning protocol decreased the soleus H-reflex size and improved walking speed and symmetry, suggesting that a partially preserved spinal cord can support conditioning-induced plasticity and benefit from it. This study examined whether down-conditioning can decrease the soleus H-reflex in people with supraspinal injury (i.e., cortical or subcortical stroke). Operant down-conditioning was applied to the soleus H-reflex in a cohort of 12 stroke people with chronic spastic hemiparesis (>12 months from stroke onset of symptoms). Each participant completed 6 baseline and 30 conditioning sessions over 12 weeks. In each baseline session, 225 control H-reflexes were elicited without any feedback on H-reflex size. In each conditioning session, 225 conditioned H-reflexes were elicited while the participant was asked to decrease H-reflex size and was given visual feedback as to whether the resulting H-reflex was smaller than a criterion value. In six of 12 participants, the conditioned H-reflex became significantly smaller by 30% on average, whereas in other 6 participants, it did not. The difference between the subgroups was largely attributable to the difference in across-session control reflex change. Ten-meter walking speed was increased by various extent (+0.04 to +0.35, +0.14 m/s on average) among the six participants whose H-reflex decreased, whereas the change was 0.00 m/s on average for the rest of participants. Although less than what was seen in participants with SCI, the fact that conditioning succeeded in 50% of stroke participants supports the feasibility of reflex down-conditioning in people after stroke. At the same time, the difference in across-session control reflex change and conditioning success rate may reflect a critical role of supraspinal activity in producing long-term plasticity in the spinal cord, as previous animal studies suggested.
通过操作性条件反射，脊髓反射行为可以发生改变。先前对大鼠的研究表明，感觉运动皮层和皮质脊髓束对于诱导和维持通过条件反射引起的反射变化至关重要。在不完全性脊髓损伤（SCI）患者中，一种操作性下行条件反射方案减小了比目鱼肌H反射的大小，并提高了步行速度和对称性，这表明部分保留的脊髓可以支持条件反射诱导的可塑性并从中受益。本研究调查了下行条件反射是否能降低脊髓上损伤（即皮质或皮质下卒中）患者的比目鱼肌H反射。对12名患有慢性痉挛性偏瘫（卒中症状发作超过12个月）的卒中患者的比目鱼肌H反射进行操作性下行条件反射。每位参与者在12周内完成6次基线测试和30次条件反射训练。在每次基线测试中，诱发225次对照H反射，且不提供关于H反射大小的任何反馈。在每次条件反射训练中，诱发225次条件化H反射，同时要求参与者减小H反射大小，并给予关于所产生的H反射是否小于标准值的视觉反馈。12名参与者中有6名的条件化H反射平均显著减小了30%，而其他6名参与者则没有。亚组之间的差异很大程度上归因于各次训练中对照反射变化的差异。在H反射减小的6名参与者中，10米步行速度有不同程度的提高（+0.04至+0.35，平均提高0.14米/秒），而其余参与者的变化平均为0.00米/秒。尽管不如脊髓损伤患者明显，但条件反射在50%的卒中参与者中取得成功这一事实支持了卒中后患者进行反射性下行条件反射的可行性。同时，各次训练中对照反射变化和条件反射成功率的差异可能反映了脊髓上活动在脊髓产生长期可塑性中的关键作用，正如先前的动物研究所示。
