Duysens J, Tax A A, Nawijn S, Berger W, Prokop T, Altenmüller E
Department of Medical Physics and Biophysics, University of Nijmegen, The Netherlands.
Exp Brain Res. 1995;105(3):423-31. doi: 10.1007/BF00233042.
To investigate how gait influences the perceived intensity of cutaneous input from the skin of the foot, the tibial or sural nerves were stimulated at the ankle during walking or running on a treadmill. As compared to standing, the detection threshold for these stimuli was raised by more than 30% during the locomotion tasks. During walking, there was a phase-dependent modulation in perceived intensity of suprathreshold stimuli (1.5, 2, or 2.5 x PT). Stimuli given just prior to footfall were perceived as significantly above average (Wilcoxon signed-rank test). In contrast there was a significant phasic decrease in sensitivity for shocks delivered immediately after ipsi- and contralateral footfall. The amplitude of somatosensory evoked potentials (P50-N80 complex), simultaneously evoked from pulse trains to the sural nerve and recorded at scalp level, was, on average, 62% of the level during standing. During gait, the amplitude of this complex was significantly smaller just after footfall than the amplitude during late swing (MANOVA). It is suggested that the reduced sensation and the decreased evoked potentials after touchdown may be due to occlusion or masking by concomitant afferent input from the feet. On the other hand, the phasic increase in sensitivity at the end of swing is thought to result from a centrally generated facilitation of sensory transmission of signals in anticipation of foot-placing.
为了研究步态如何影响来自足部皮肤的皮肤输入的感知强度，在跑步机上行走或跑步时，在脚踝处刺激胫神经或腓肠神经。与站立相比，在运动任务期间，这些刺激的检测阈值提高了30%以上。在行走过程中，阈上刺激（1.5、2或2.5倍PT）的感知强度存在相位依赖性调制。在足部落地前给予的刺激被认为明显高于平均水平（Wilcoxon符号秩检验）。相反，同侧和对侧足部落地后立即施加的电击的敏感性出现明显的相位性降低。从腓肠神经的脉冲序列同时诱发并在头皮水平记录的体感诱发电位（P50-N80复合波）的幅度，平均为站立时水平的62%。在步态期间，足部落地后该复合波的幅度明显小于摆动后期的幅度（多变量方差分析）。有人认为，着陆后感觉降低和诱发电位降低可能是由于来自足部的伴随传入输入的遮挡或掩盖。另一方面，摆动末期敏感性的相位性增加被认为是由于中枢产生的对预期足部放置信号的感觉传递促进作用。
