Castellote J M, Valls-Solé J
National School of Occupational Medicine, Carlos III Institute of Health, Madrid, Spain; Department of Physical Medicine and Rehabilitation, School of Medicine, Complutense University of Madrid, Madrid, Spain.
Unidad de EMG y Control Motor, Servei de Neurologia, Hospital Clínico, Universidad de Barcelona, Barcelona, Spain.
Clin Neurophysiol. 2015 Oct;126(10):1879-85. doi: 10.1016/j.clinph.2015.01.028. Epub 2015 Feb 18.
Fast and accurate movements are often performed in response to a sensory signal. In reaction time tasks, execution of open loop movements is speeded up when a startling auditory stimulus (SAS) is applied together with the imperative signal (IS). In this study, we examined the effects of a SAS on the performance of a task that demands accuracy.
Nine subjects were asked to move a monitored pen to a target point located in a table at a fixed angular distance of 30 degrees from a start point. The target was a spot of three possible diameters: 5, 10, and 20mm. Finger force for pen holding, pen tip pressure against the table and kinematic variables of the forearm movement were measured for three conditions: control, SAS delivered at IS (SAS-IS trials) and SAS delivered during movement execution (SAS-MOV trials).
Two movement phases could be identified in the movement trajectory and force profile. The first phase, ballistic, was significantly shortened in SAS-MOV trials, with earlier and larger peak velocity and peak force with respect to control trials. The second phase, slow approach to target, was longer in SAS-IS trials but not in SAS-MOV trials. Accuracy was maintained throughout all conditions and stimulation modes.
A SAS speeds up only the first (ballistic) part of the movement in an accuracy task. Slower target approach compensates for the accelerated initial movement. No changes in the last part of the movement are seen when a SAS is delivered after movement onset.
The StartReact effect is restricted to the onset of a complex movement, when muscles are activated in a ballistic mode, without feedback.
快速而准确的动作通常是对感觉信号的反应。在反应时任务中，当将一个惊人的听觉刺激（SAS）与指令信号（IS）一起施加时，开环运动的执行速度会加快。在本研究中，我们研究了SAS对一项要求准确性的任务表现的影响。
九名受试者被要求将一支受监测的笔移动到位于桌子上的一个目标点，该目标点与起始点的固定角距离为30度。目标是一个有三种可能直径的点：5毫米、10毫米和20毫米。在三种条件下测量了握笔的手指力、笔尖对桌子的压力以及前臂运动的运动学变量：对照、在IS时给予SAS（SAS-IS试验）和在运动执行期间给予SAS（SAS-MOV试验）。
在运动轨迹和力分布中可以识别出两个运动阶段。第一阶段，弹道式的，在SAS-MOV试验中显著缩短，相对于对照试验，峰值速度和峰值力出现得更早且更大。第二阶段，缓慢接近目标，在SAS-IS试验中更长，但在SAS-MOV试验中并非如此。在所有条件和刺激模式下准确性都得以保持。
在一项准确性任务中，SAS仅加速运动的第一（弹道式）部分。较慢的接近目标过程补偿了加速的初始运动。当在运动开始后给予SAS时，运动的最后部分没有变化。
StartReact效应仅限于复杂运动开始时，此时肌肉以弹道模式激活，无反馈。
