Kida Tetsuo, Wasaka Toshiaki, Nakata Hiroki, Akatsuka Kosuke, Kakigi Ryusuke
Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki, 444-8585, Japan.
Exp Brain Res. 2006 Sep;173(4):733-41. doi: 10.1007/s00221-006-0448-0. Epub 2006 Apr 25.
A warning signal followed by an imperative signal generates anticipatory and preparatory activities, which regulate sensory evoked neuronal activities through a top-down centrifugal mechanism. The present study investigated the centrifugal regulation of neuronal responses evoked by a task-relevant somatosensory signal, which triggers a voluntary movement without a warning signal. Eleven healthy adults participated in this study. Electrical stimulation was delivered to the right median nerve at a random interstimulus interval (1.75-2.25 s). The participants were instructed to extend the second digit of the right hand as fast as possible when the electrical stimulus was presented (ipsilateral reaction condition), or extend that of the left hand (contralateral reaction condition). They also executed repetitively extension of the right second digit at a rate of about 0.5 Hz, irrespective of electrical stimulation (movement condition), to count silently the number of stimuli (counting condition). In the control condition, they had no task to perform. The amplitude of short-latency somatosensory evoked potentials, the central P25, frontal N30, and parietal P30, was significantly reduced in both movement and ipsilateral reaction conditions compared to the control condition. The amplitude of long-latency P80 was significantly enhanced only in the ipsilateral reaction condition compared to the control, movement, contralateral reaction, and counting conditions. The long-latency N140 was significantly enhanced in both movement and ipsilateral reaction conditions compared to the control condition. In conclusion, short- and long-latency neuronal activities evoked by task-relevant somatosensory signals were regulated differently through a centrifugal mechanism even when the signal triggered a voluntary movement without a warning signal. The facilitation of activities at a latency of around 80 ms is associated with gain enhancement of the task-relevant signals from the body part involved in the action, whereas that at a latency of around 140 ms is associated with unspecific gain regulation generally induced by voluntary movement. These may be dissociated from the simple effect of directing attention to the stimulation.
一个警告信号之后紧接着一个命令信号会引发预期和准备活动，这些活动通过自上而下的离心机制调节感觉诱发的神经元活动。本研究调查了由与任务相关的体感信号诱发的神经元反应的离心调节，该信号在没有警告信号的情况下触发自主运动。11名健康成年人参与了本研究。以随机的刺激间隔（1.75 - 2.25秒）对右侧正中神经进行电刺激。当出现电刺激时，参与者被指示尽可能快地伸展右手的食指（同侧反应条件），或者伸展左手的食指（对侧反应条件）。他们还以约0.5赫兹的频率重复伸展右手食指，而不考虑电刺激（运动条件），以便默默地数刺激的次数（计数条件）。在对照条件下，他们没有任务要执行。与对照条件相比，在运动和同侧反应条件下，短潜伏期体感诱发电位的波幅，即中央P25、额叶N30和顶叶P30，均显著降低。与对照、运动、对侧反应和计数条件相比，长潜伏期P80的波幅仅在同侧反应条件下显著增强。与对照条件相比，长潜伏期N140在运动和同侧反应条件下均显著增强。总之，即使信号在没有警告信号的情况下触发自主运动，由与任务相关的体感信号诱发的短潜伏期和长潜伏期神经元活动也通过离心机制受到不同的调节。潜伏期约80毫秒时活动的促进与来自参与动作的身体部位的与任务相关信号的增益增强有关，而潜伏期约140毫秒时的促进与通常由自主运动诱导的非特异性增益调节有关。这些可能与将注意力导向刺激的简单效应相分离。
