Mu Laiyong, Ritzmann Roy E
Department of Biology, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106-7080, USA.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2008 Mar;194(3):283-98. doi: 10.1007/s00359-007-0307-x. Epub 2007 Dec 20.
Tethered cockroaches turn from unilateral antennal contact using asymmetrical movements of mesothoracic (T2) legs (Mu and Ritzmann in J Comp Physiol A 191:1037-1054, 2005). During the turn, the leg on the inside of the turn (the inside T2 leg) has distinctly different motor patterns from those in straight walking. One possible neural mechanism for the transformation from walking to inside leg turning could be that the descending commands alter a few critical reflexes that start a cascade of physical changes in leg movement or posture, leading to further alterations. This hypothesis has two implications: first, the descending activities must be able to influence thoracic reflexes. Second, one should be able to initiate the turning motor pattern without descending signals by mimicking a point farther down in the reflex cascade. We addressed the first implication in this paper by experiments on chordotonal organ reflexes. The activity of depressor muscle (Ds) and slow extensor tibia muscle (SETi) was excited and inhibited by stretching and relaxing the femoral chordotonal organ. However, the Ds responses were altered after eliminating the descending activity, while the SETi responses remain similar. The inhibition to Ds activity by stretching the coxal chordotonal organ was also altered after eliminating the descending activity.
被束缚的蟑螂利用中胸（T2）腿的不对称运动，从单侧触角接触状态转身（Mu和里兹曼，《比较生理学杂志A》191:1037 - 1054，2005年）。在转身过程中，转向内侧的腿（内侧T2腿）具有与直线行走时明显不同的运动模式。从行走转变为内侧腿转身的一种可能神经机制是，下行指令改变一些关键反射，这些反射引发腿部运动或姿势的一系列物理变化，进而导致进一步的改变。该假说有两个含义：第一，下行活动必须能够影响胸部反射。第二，通过模拟反射级联中更靠下的一个点，可以在没有下行信号的情况下启动转身运动模式。我们在本文中通过对弦音器反射的实验探讨了第一个含义。通过拉伸和放松股弦音器，抑制肌（Ds）和胫节慢伸肌（SETi）的活动会被激发和抑制。然而，消除下行活动后，Ds的反应发生了改变，而SETi的反应保持相似。消除下行活动后，通过拉伸髋节弦音器对Ds活动的抑制也发生了改变。
