School of Human Kinetics, University of Ottawa, 125 University Private, Ottawa, ON, K1N 6N5, Canada.
Sci Rep. 2023 Apr 21;13(1):6532. doi: 10.1038/s41598-023-33493-5.
Recent primate studies have implicated a substantial role of reticulospinal pathways in the production of various voluntary movements. A novel way to assess the relative reticulospinal contributions in humans is through the use of a "StartReact" paradigm where a startling acoustic stimulus (SAS) is presented during a simple reaction time (RT) task. The StartReact response is characterized by short-latency triggering of a prepared response, which is attributed to increased reticulospinal drive associated with startle reflex activation. The current study used a StartReact protocol to examine differences in reticulospinal contributions between proximal and distal effectors by examining EMG onset latencies in lateral deltoid and first dorsal interosseous during bilateral shoulder or finger abduction. The magnitude of the StartReact effect, and thus relative reticulospinal drive, was quantified as the difference in RT between startle trials in which startle-reflex related EMG activation in the sternocleidomastoid (SCM) was present (SCM +) versus absent (SCM -). A significantly larger StartReact effect was observed for bilateral shoulder abduction versus bimanual finger abduction and a higher incidence of SCM + trials occurred in the proximal task. Additionally, both startle reflex and response-related EMG measures were larger on SCM + trials for the shoulder versus finger task. These results provide compelling novel evidence for increased reticulospinal activation in bilateral proximal upper-limb movements.
最近的灵长类动物研究表明，网状脊髓通路在各种自主运动的产生中起着重要作用。一种评估人类网状脊髓相对贡献的新方法是使用“StartReact”范式，在这个范式中，在简单反应时间 (RT) 任务期间呈现一个令人惊讶的声刺激 (SAS)。StartReact 反应的特征是潜伏期短，触发准备好的反应，这归因于与惊吓反射激活相关的网状脊髓驱动增加。当前的研究使用 StartReact 协议通过检查在双侧肩部或手指外展期间，在外侧三角肌和第一背骨间肌的肌电图起始潜伏期，来检查近端和远端效应器之间的网状脊髓贡献差异。StartReact 效应的幅度，即与 SCM 中的惊吓反射相关的 EMG 激活（SCM+）与不存在（SCM-）相比，RT 之间的差异，从而相对网状脊髓驱动被量化。与双手手指外展相比，双侧肩部外展的 StartReact 效应明显更大，并且在近端任务中更频繁地出现 SCM+试验。此外，对于肩部任务，SCM+试验的惊吓反射和反应相关的 EMG 测量值均大于手指任务。这些结果为双侧近端上肢运动中增加的网状脊髓激活提供了令人信服的新证据。
