Feed-forward motor control of ultrafast, ballistic movements

To circumvent the limits of muscle, ultrafast movements achieve high power through the use of springs and latches. The timescale of these movements is too short for control through typical neuromuscular mechanisms, thus ultrafast movements are either invariant or are controlled prior to movement. We tested whether mantis shrimp (Stomatopoda: Neogonodactylus bredini) vary their ultrafast smashing strikes and, if so, how this control is achieved prior to movement. We collected high speed images of strike mechanics and electromyograms of the extensor and flexor muscles that control spring compression and latch release. During spring compression, lateral extensor and flexor units were co-activated. The strike initiated several milliseconds after the flexor units ceased, suggesting that flexor activity prevents spring release and determines the timing of strike initiation. We used linear mixed models and Akaike Information Criterion to serially evaluate multiple hypotheses for control mechan...为突破肌肉的生理极限，超快运动通过借助弹簧与锁扣结构实现高功率输出。此类运动的时程极短，无法通过典型神经肌肉机制完成调控，因此超快运动要么为固定不变的模式，要么需在运动启动前完成调控。本研究以螳螂虾（Stomatopoda: Neogonodactylus bredini）为实验对象，探究其超快锤击动作是否存在变异，若存在变异，则其运动前调控机制是如何实现的。我们采集了锤击动作力学过程的高速影像，以及调控弹簧压缩与锁扣释放的伸肌与屈肌的肌电图（electromyogram）。在弹簧压缩阶段，外侧伸肌单元与屈肌单元被共同激活。锤击动作于屈肌单元活动停止数毫秒后启动，这表明屈肌活动可阻止弹簧释放，并决定锤击启动的时机。我们采用线性混合模型与赤池信息准则（Akaike Information Criterion）对运动调控机制的多项假设进行序贯评估……