School of Population Health, Curtin University, Perth, Western Australia, Australia.
Department of Psychology, University of Warwick, Coventry, UK.
Psychophysiology. 2023 Jul;60(7):e14267. doi: 10.1111/psyp.14267. Epub 2023 Feb 7.
During preparation for action, the presentation of loud acoustic stimuli (LAS) can trigger movements at very short latencies in a phenomenon called the StartReact effect. It was initially proposed that a special, separate subcortical mechanism that bypasses slower cortical areas could be involved. We sought to examine the evidence for a separate mechanism against the alternative that responses to LAS can be explained by a combination of stimulus intensity effects and preparatory states. To investigate whether cortically mediated preparatory processes are involved in mediating reactions to LAS, we used an auditory reaction task where we manipulated the preparation level within each trial by altering the conditional probability of the imperative stimulus. We contrasted responses to non-intense tones and LAS and examined whether cortical activation and subcortical excitability and motor responses were influenced by preparation levels. Increases in preparation levels were marked by gradual reductions in reaction time (RT) coupled with increases in cortical activation and subcortical excitability - at both condition and trial levels. Interestingly, changes in cortical activation influenced motor and auditory but not visual areas - highlighting the widespread yet selective nature of preparation. RTs were shorter to LAS than tones, but the overall pattern of preparation level effects was the same for both stimuli. Collectively, the results demonstrate that LAS responses are indeed shaped by cortically mediated preparatory processes. The concurrent changes observed in brain and behavior with increasing preparation reinforce the notion that preparation is marked by evolving brain states which shape the motor system for action.
在准备行动期间，响亮的声音刺激（LAS）的呈现可以在称为 StartReact 效应的现象中引发非常短潜伏期的运动。最初提出的是，可能涉及一种特殊的、单独的皮质下机制，该机制可以绕过较慢的皮质区域。我们试图在替代理论的背景下，检验是否存在单独的机制来解释对 LAS 的反应，该替代理论认为对 LAS 的反应可以通过刺激强度效应和预备状态的组合来解释。为了研究皮质介导的预备过程是否参与介导对 LAS 的反应，我们使用了听觉反应任务，在该任务中，我们通过改变强制性刺激的条件概率来改变每个试验中的预备水平，从而操纵预备水平。我们对比了非强烈音调与 LAS 的反应，并检查了皮质激活和皮质下兴奋性以及运动反应是否受到预备水平的影响。预备水平的增加表现为反应时间（RT）逐渐减少，同时伴随着皮质激活和皮质下兴奋性的增加——无论是在条件水平还是试验水平。有趣的是，皮质激活的变化影响了运动和听觉区域，但不影响视觉区域——突出了预备的广泛但选择性的性质。LAS 的 RT 比音调短，但两种刺激的预备水平效应的总体模式是相同的。总的来说，这些结果表明，LAS 反应确实受到皮质介导的预备过程的影响。随着预备的增加，大脑和行为中观察到的并发变化强化了这样一种观点，即预备的特点是不断发展的大脑状态，这些状态为运动系统的行动做好了准备。
