Data from: Modulation of the cutaneous silent period in the upper-limb with whole-body instability

The silent period induced by cutaneous electrical stimulation of the digits has been shown to be task-dependent, at least in the grasping muscles of the hand. However, it is unknown if the cutaneous silent period is adaptable throughout muscles of the entire upper limb, in particular when the task requirements are substantially altered. The purpose of the present study was to examine the characteristics of the cutaneous silent period in several upper limb muscles when introducing increased whole-body instability. The cutaneous silent period was evoked in 10 healthy individuals with electrical stimulation of digit II of the right hand when the subjects were seated, standing, or standing on a wobble board while maintaining a background elbow extension contraction with the triceps brachii of ~5% of maximal voluntary contraction (MVC) strength. The first excitatory response (E1), first inhibitory response (CSP), and second excitatory response (E2) were quantified as the percent change from baseline and by their individual durations. The results showed that the level of CSP suppression was lessened (47.7 ± 7.7% to 33.8 ± 13.2% of baseline, p = 0.019) and the duration of the CSP inhibition decreased (p = 0.021) in the triceps brachii when comparing the seated and wobble board tasks. For the wobble board task the amount of cutaneous afferent inhibition of EMG activity in the triceps brachii decreased; which is proposed to be due to differential weighting of cutaneous feedback relative to the corticospinal drive, most likely due to presynaptic inhibition, to meet the demands of the unstable task.已有研究表明，对指部实施皮肤电刺激所诱导的皮肤静默期（cutaneous silent period, CSP）具有任务依赖性，该现象至少在手部抓握肌中得到验证。然而目前仍不清楚，皮肤静默期是否可在整个上肢的肌肉中产生适应性改变，尤其是当任务要求发生显著变化时。本研究旨在探究受试者处于全身不稳定状态时，上肢多块肌肉内皮肤静默期的特征。实验共纳入10名健康受试者，分别令其采取坐位、站立位以及站在晃动平衡板上的姿势，同时维持肱三头肌约5%最大自主收缩（maximal voluntary contraction, MVC）强度的肘关节伸展背景收缩，并通过电刺激右手第二指诱发出皮肤静默期。研究者对首个兴奋性反应（E1）、首个抑制性反应（CSP）及第二个兴奋性反应（E2）进行了量化分析，量化指标包括其相对于基线的变化百分比以及各自的持续时长。结果显示，相较于坐位任务，在晃动平衡板任务中，肱三头肌的CSP抑制程度有所降低（从基线的47.7±7.7%降至33.8±13.2%，p=0.019），且CSP抑制的持续时长也显著缩短（p=0.021）。针对晃动平衡板任务，肱三头肌肌电活动所受的皮肤传入抑制程度有所下降；该现象被认为是由于相对于皮质脊髓驱动，皮肤感觉反馈的权重发生了调整，而这一调整最可能由突触前抑制介导，以适应不稳定任务的动作需求。