Makihara Yukiko, Segal Richard L, Wolpaw Jonathan R, Thompson Aiko K
Helen Hayes Hospital, New York State Department of Health, West Haverstraw, New York; Program in Human Movement Science, Department of Allied Health Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina;
Program in Human Movement Science, Department of Allied Health Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; Department of Health Professions, Medical University of South Carolina, Charleston, South Carolina;
J Neurophysiol. 2014 Sep 15;112(6):1439-46. doi: 10.1152/jn.00225.2014. Epub 2014 Jun 18.
In normal animals, operant conditioning of the spinal stretch reflex or the H-reflex has lesser effects on synergist muscle reflexes. In rats and people with incomplete spinal cord injury (SCI), soleus H-reflex operant conditioning can improve locomotion. We studied in normal humans the impact of soleus H-reflex down-conditioning on medial (MG) and lateral gastrocnemius (LG) H-reflexes and on locomotion. Subjects completed 6 baseline and 30 conditioning sessions. During conditioning trials, the subject was encouraged to decrease soleus H-reflex size with the aid of visual feedback. Every sixth session, MG and LG H-reflexes were measured. Locomotion was assessed before and after conditioning. In successfully conditioned subjects, the soleus H-reflex decreased 27.2%. This was the sum of within-session (task dependent) adaptation (13.2%) and across-session (long term) change (14%). The MG H-reflex decreased 14.5%, due mainly to task-dependent adaptation (13.4%). The LG H-reflex showed no task-dependent adaptation or long-term change. No consistent changes were detected across subjects in locomotor H-reflexes, EMG activity, joint angles, or step symmetry. Thus, in normal humans, soleus H-reflex down-conditioning does not induce long-term changes in MG/LG H-reflexes and does not change locomotion. In these subjects, task-dependent adaptation of the soleus H-reflex is greater than it is in people with SCI, whereas long-term change is less. This difference from results in people with SCI is consistent with the fact that long-term change is beneficial in people with SCI, since it improves locomotion. In contrast, in normal subjects, long-term change is not beneficial and may necessitate compensatory plasticity to preserve satisfactory locomotion.
在正常动物中，对脊髓牵张反射或H反射进行操作性条件反射对协同肌反射的影响较小。在大鼠和不完全脊髓损伤（SCI）的人中，比目鱼肌H反射操作性条件反射可改善运动能力。我们在正常人体中研究了比目鱼肌H反射下行性条件反射对内侧腓肠肌（MG）和外侧腓肠肌（LG）H反射以及对运动的影响。受试者完成了6次基线测试和30次条件反射训练。在条件反射试验期间，鼓励受试者借助视觉反馈减小比目鱼肌H反射的大小。每六次训练后，测量MG和LG H反射。在条件反射训练前后评估运动能力。在成功建立条件反射的受试者中，比目鱼肌H反射下降了27.2%。这是训练期间（任务依赖性）适应性变化（13.2%）和训练间（长期）变化（14%）的总和。MG H反射下降了14.5%，主要是由于任务依赖性适应性变化（13.4%）。LG H反射未显示出任务依赖性适应性变化或长期变化。在受试者的运动H反射、肌电图活动、关节角度或步幅对称性方面未检测到一致的变化。因此，在正常人体中，比目鱼肌H反射下行性条件反射不会引起MG/LG H反射的长期变化，也不会改变运动能力。在这些受试者中，比目鱼肌H反射的任务依赖性适应性变化比脊髓损伤患者更大，而长期变化则较小。与脊髓损伤患者的结果不同，这一差异与长期变化对脊髓损伤患者有益这一事实相符，因为它可改善运动能力。相比之下，在正常受试者中，长期变化并无益处，可能需要代偿性可塑性来维持满意的运动能力。
