Conrad B, Aschoff J C
Electroencephalogr Clin Neurophysiol. 1977 Jan;42(1):107-116. doi: 10.1016/0013-4694(77)90155-9.
When the median nerve is stimulated at the wrist during voluntary contraction of m. abductor pollicis brevis (APB) EMG activity of this muscle contains different distinct responses: a direct muscular response (M response), a spinal reflex response (S response) and a third late reflex response, first described by Upton et al. (1971) as a second volitional reflex response (V2). Comparison of this very likely long-loop reflex involving pathways to and from the cortical level (therefore labelled C response) under isometric (hold) and isotonic (move) contraction revealed a strong facilitation of the response under the latter condition. Repetitive trains of stimuli had stronger facilitatory effect on the occurrence of this late reflex response than single stimuli. Cutaneous stimuli of the median nerve afferents did not exhibit M and S responses but definite late excitatory responses with similar latencies to the C responses. In cases of hemiparesis (mild to severe loss of sensorimotor control of finger movements) the C response was diminished, delayed or absent. These findings together with recent primate and human experimental work support the hypothesis of a transcortical stretch reflex. On the premise that muscular as well as cutaneous afferents contribute to the afferent cortical input the late C response can be interpreted as the efferent component. The C response may be a valuable aid in the diagnosis of small lesions of the sensorimotor cortex and internal capsule.
当在拇短展肌（APB）自主收缩期间在腕部刺激正中神经时，该肌肉的肌电图（EMG）活动包含不同的明显反应：直接肌肉反应（M反应）、脊髓反射反应（S反应）以及第三种延迟反射反应，Upton等人（1971年）首次将其描述为第二种自主反射反应（V2）。在等长（保持）和等张（移动）收缩条件下，对这种极有可能涉及往返皮质水平通路的长环反射（因此标记为C反应）进行比较，发现在后一种条件下反应有强烈的易化作用。重复刺激序列对这种延迟反射反应的出现具有比单次刺激更强的易化作用。正中神经传入纤维的皮肤刺激未表现出M和S反应，但具有与C反应相似潜伏期的明确延迟兴奋性反应。在偏瘫病例（手指运动的感觉运动控制轻度至重度丧失）中，C反应减弱、延迟或缺失。这些发现与最近的灵长类动物和人体实验工作一起支持了皮质脊髓牵张反射的假说。基于肌肉和皮肤传入纤维均对皮质传入输入有贡献这一前提，延迟的C反应可被解释为传出成分。C反应可能对感觉运动皮质和内囊小病变的诊断有重要帮助。
