Sutter Katrin, Nonnekes Jorik, Dibilio Valeria, Geurts Alexander C, Weerdesteyn Vivian
Radboud University Medical Centre, Donders Centre for Neuroscience, Department of Rehabilitation, Nijmegen, The Netherlands.
Department GF Ingrassia, Section of Neurosciences, University of Catania, Catania, Italy.
PLoS One. 2016 Apr 14;11(4):e0153129. doi: 10.1371/journal.pone.0153129. eCollection 2016.
StartReact is the acceleration of reaction time by a startling acoustic stimulus (SAS). The SAS is thought to release a pre-prepared motor program. Here, we investigated whether the StartReact effect is applicable to the very first trial in a series of repeated unpractised single-joint movements.
Twenty healthy young subjects were instructed to perform a rapid ankle dorsiflexion movement in response to an imperative stimulus. Participants were divided in two groups of ten. Both groups performed 17 trials. In one group a SAS (116 dB) was given in the first trial, whereas the other group received a non-startling sound (70 dB) as the first imperative stimulus. In the remaining 16 trials, the SAS was given as the imperative stimulus in 25% of the trials in both groups. The same measurement was repeated one week later, but with the first-trial stimuli counterbalanced between groups.
When a SAS was given in the very first trial, participants had significantly shorter onset latencies compared to first-trial responses to a non-startling stimulus. Succeeding trials were significantly faster compared to the first trial, both for trials with and without a SAS. However, the difference between the first and succeeding trials was significantly larger for responses to a non-startling stimulus compared to responses triggered by a SAS. SAS-induced acceleration in the first trial of the second session was similar to that in succeeding trials of session 1.
The present results confirm that the StartReact phenomenon also applies to movements that have not yet been practiced in the experimental context. The excessive SAS-induced acceleration in the very first trial may be due to the absence of integration of novel context-specific information with the existing motor memory for movement execution. Our findings demonstrate that StartReact enables a rapid release of motor programs in the very first trial also without previous practice, which might provide a behavioural advantage in situations that require a rapid response to a potentially threatening environmental stimulus.
起始反应（StartReact）是指由惊人的听觉刺激（SAS）导致的反应时间加速。人们认为这种惊人的听觉刺激会释放一个预先准备好的运动程序。在此，我们研究了起始反应效应是否适用于一系列重复的、未经练习的单关节运动的首次试验。
20名健康的年轻受试者被指示对命令刺激做出快速的踝关节背屈运动。参与者被分为两组，每组10人。两组都进行了17次试验。在一组中，首次试验给予一个惊人的听觉刺激（116分贝），而另一组则接受一个无惊人效果的声音（70分贝）作为首次命令刺激。在其余16次试验中，两组中25%的试验将惊人的听觉刺激作为命令刺激。一周后重复相同的测量，但两组之间首次试验的刺激进行了平衡处理。
当在首次试验中给予惊人的听觉刺激时，与对无惊人效果刺激的首次试验反应相比，参与者的起始潜伏期显著缩短。与首次试验相比，后续试验无论是有还是没有惊人的听觉刺激都显著更快。然而，与由惊人的听觉刺激引发的反应相比，对无惊人效果刺激的反应在首次试验和后续试验之间的差异显著更大。第二阶段首次试验中由惊人的听觉刺激引起的加速与第一阶段后续试验中的加速相似。
目前的结果证实，起始反应现象也适用于在实验环境中尚未练习过的运动。在首次试验中由惊人的听觉刺激引起的过度加速可能是由于缺乏将新的特定情境信息与现有的用于运动执行的运动记忆进行整合。我们的研究结果表明，起始反应能够在首次试验中也无需先前练习就快速释放运动程序，这可能在需要对潜在威胁的环境刺激做出快速反应的情况下提供行为优势。
