Department for Animal Physiology, Institute for Zoology, Biocenter Cologne, University of Cologne, Cologne, Germany.
J Neurophysiol. 2019 Nov 1;122(5):2173-2186. doi: 10.1152/jn.00436.2019. Epub 2019 Sep 25.
Feedback from load and movement sensors can modify timing and magnitude of the motor output in the stepping stick insect. One source of feedback is stretch reception by the femoral chordotonal organ (fCO), which encodes such parameters as the femorotibial (FTi) joint angle, the angular velocity, and its acceleration. Stimulation of the fCO causes a postural resistance reflex, during quiescence, and can elicit the opposite, so-called active reaction (AR), which assists ongoing flexion during active movements. In the present study, we investigated the role of fCO feedback for the difference in likelihood of generating ARs on the inside vs. the outside during curve stepping. We analyzed the effects of fCO stimulation on the motor output to the FTi and the neighboring coxa-trochanter and thorax-coxa joints of the middle leg. In inside and outside turns, the probability for ARs increases with increasing starting angle and decreasing stimulus velocity; furthermore, it is independent of the total angular excursion. However, the transition between stance and swing motor activity always occurs after a specific angular excursion, independent of the turning direction. Feedback from the fCO also has an excitatory influence on levator trochanteris motoneurons (MNs) during inside and outside turns, whereas the same feedback affects protractor coxae MNs only during outside steps. Our results suggest joint- and body side-dependent processing of fCO feedback. A shift in gain may be responsible for different AR probabilities between inside and outside turning, whereas the general control mechanism for ARs is unchanged. We show that parameters of movement feedback from the tibia in an insect during curve walking are processed in a body side-specific manner, and how. From our results it is highly conceivable that the difference in motor response to the feedback supports the body side-specific leg kinematics during turning. Future studies will need to determine the source for the inputs that determine the local changes in sensory-motor processing.
负载和运动传感器的反馈可以修改步进竹节虫的电机输出的定时和幅度。反馈的一个来源是股索音器官（fCO）的拉伸接收，它编码了诸如股胫（FTi）关节角度、角速度及其加速度等参数。fCO 的刺激会在静止时引起姿势抵抗反射，并可能引发相反的所谓主动反应（AR），这有助于在主动运动中持续弯曲。在本研究中，我们研究了 fCO 反馈在曲线行走过程中内侧与外侧产生 AR 的可能性差异的作用。我们分析了 fCO 刺激对中间腿的 FTi 及相邻的髋关节和胸节-髋关节的电机输出的影响。在内侧和外侧转弯中，随着起始角度的增加和刺激速度的降低，AR 的概率增加；此外，它与总角位移无关。然而，无论转弯方向如何，站立和摆动运动活动之间的转换总是在特定的角位移之后发生。fCO 的反馈对外侧转弯中的提转节肌运动神经元（MNs）也有兴奋作用，而相同的反馈仅在外侧步骤中影响外侧髋关节 MNs。我们的结果表明，fCO 反馈的关节和身体侧处理方式不同。增益的变化可能是内侧和外侧转弯之间 AR 概率不同的原因，而 AR 的一般控制机制保持不变。我们表明，在昆虫的曲线行走过程中，来自胫骨的运动反馈的参数以特定于身体侧的方式进行处理，以及如何处理。从我们的结果可以高度想象，对反馈的运动反应的差异支持转弯过程中特定于身体侧的腿部运动学。未来的研究将需要确定确定感觉运动处理局部变化的输入源。
