The StartReact test, increasingly popular for assessing cortico‐reticular functioning, is a valid method to influence the firing of reticulospinal tract neurons noninvasively. However, there remains limited evidence on how different stimuli employed in the StartReact test impact motor output in humans. The present study tested elbow flexor responses of 33 adults (aged 26–48 years) to visual stimuli only (LED light), audio‐visual (80 dB) stimuli, and startle‐inducing audio‐visual (120 dB) stimuli sitting with the arm supinated in an electromechanical dynamometer. Surface electromyogram (EMG) recorded muscle activity from the right biceps brachii muscle. Participants were presented with 20 stimuli for each of the three conditions in pseudorandom order with interstimulus intervals of ~8 s. Reaction times were calculated from the stimulus trigger to the initial rise in the EMG signal above 7 × SD from baseline. Rate of torque development (RTD) and EMG signals were recorded throughout and analyzed over their initial 50 ms and 100 ms time‐windows. Reaction times were reduced from visual (169 ± 23) to audio‐visual (140 ± 23) and further reduced to startle‐inducing audio‐visual stimuli (108 ± 19, p < 0.001). While RTD and EMG were consistently greatest following startle‐inducing stimuli (p < 0.001), they were also enhanced following all audio‐visual stimuli over 100 ms (p < 0.05). It appears that startle‐inducing audio‐visual stimuli result in shorter reaction times, increased RTD, and enhanced muscle activity within the initial 50 ms, likely from subcortical upregulation. However, the 100 ms time‐window suggests cortical upregulation following all audio‐visual stimuli considering the longer transmission times.

中文翻译：

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StartReact 对反应时间、力量发展速率和肱二头肌肌肉活动的影响


StartReact 测试越来越流行用于评估皮质网状功能，是一种无创影响网状脊髓束神经元放电的有效方法。然而，关于 StartReact 测试中采用的不同刺激如何影响人类运动输出的证据仍然有限。本研究测试了 33 名成年人（年龄 26-48 岁）对仅视觉刺激（LED 灯）、视听 (80 dB) 刺激和坐在椅子上的惊吓视听 (120 dB) 刺激的肘屈肌反应。手臂在机电测力计中旋后。表面肌电图（EMG）记录了右侧肱二头肌的肌肉活动。参与者在三种情况下分别接受 20 个刺激，以伪随机顺序进行，刺激间隔约为 8 秒。反应时间是从刺激触发到 EMG 信号初始上升到基线以上 7 × SD 以上的时间计算的。全程记录扭矩发展率 (RTD) 和 EMG 信号，并在最初的 50 毫秒和 100 毫秒时间窗口内进行分析。反应时间从视觉 (169 ± 23) 减少到视听 (140 ± 23)，并进一步减少到引起惊吓的视听刺激 (108 ± 19，p < 0.001)。虽然 RTD 和 EMG 在惊吓刺激后始终保持最大 (p < 0.001)，但在超过 100 毫秒的所有视听刺激后，它们也得到增强 (p < 0.05)。似乎引起惊吓的视听刺激会导致反应时间缩短、RTD 增加以及最初 50 毫秒内的肌肉活动增强，这可能是由于皮质下上调所致。然而，考虑到较长的传输时间，100 毫秒的时间窗口表明所有视听刺激后皮质都会上调。