An inter-segmental network model and its use in elucidating gait-switches in the stick insect
An inter-segmental network model and its use in elucidating gait-switches in the stick insect
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DOI：
10.1007/s10827-010-0300-1
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发表时间：
2011-08-01
影响因子：
1.2
通讯作者：
Toth, Tibor Istvan
中科院分区：
文献类型：
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作者：
Daun-Gruhn, Silvia;Toth, Tibor Istvan
动物的运动需要控制肢体运动的节段神经元网络的高度协调工作。实验表明，来自四肢的感觉信号通过作用于中枢网络，在控制运动模式方面发挥着关键作用。基于竹节虫运动的结果，我们构建了一个节间模型，包括所有三条腿的局部网络，即前胸、中胸和后胸，它们的相互连接和修改它们活动的主要感觉输入。在该模型中，局部网络是统一的，每个网络由一个中央模式发生器（CPG）提供的节律性振荡的前伸肌-后缩肌运动系统，相应的运动神经元（MN），和本地抑制性中间神经元（IIN）之间的CPG和MN。在节段之间，CPG通过由上述感觉输入调制的兴奋性和抑制性通路循环连接。用我们的网络模型进行的模拟表明，它能够再现基本的运动模式，例如在三足动物和四足动物步态中发生的运动模式。该模型进一步揭示了一些基本的神经元过程（例如突触抑制，或改变特定神经元的突触驱动），这些过程在模拟中是必要的，并且在整体上足以实现从一种步态到另一种步态的过渡。这项模拟研究的主要结果是，完全相同的机制是两种类型的步态之间的过渡，无论方向的变化。此外，该模型表明，这些过程中的大多数可以归因于直接的感觉影响，和变化只需要在中央控制的突触驱动器的CPGs。
Animal locomotion requires highly coordinated working of the segmental neuronal networks that control the limb movements. Experiments have shown that sensory signals originating from the extremities play a pivotal role in controlling locomotion patterns by acting on central networks. Based on the results from stick insect locomotion, we constructed an inter-segmental model comprising local networks for all three legs, i.e. for the pro-, meso- and meta-thorax, their inter-connections and the main sensory inputs modifying their activities. In the model, the local networks are uniform, and each of them consists of a central pattern generator (CPG) providing the rhythmic oscillation for the protractor-retractor motor systems, the corresponding motoneurons (MNs), and local inhibitory interneurons (IINs) between the CPGs and the MNs. Between segments, the CPGs are connected cyclically by both excitatory and inhibitory pathways that are modulated by the aforementioned sensory inputs. Simulations done with our network model showed that it was capable of reproducing basic patterns of locomotion such as those occurring during tri- and tetrapod gaits. The model further revealed a number of elementary neuronal processes (e.g. synaptic inhibition, or changing the synaptic drive at specific neurons) that in the simulations were necessary, and in their entirety sufficient, to bring about a transition from one type of gait to another. The main result of this simulation study is that exactly the same mechanism underlies the transition between the two types of gait irrespective of the direction of the change. Moreover, the model suggests that the majority of these processes can be attributed to direct sensory influences, and changes are required only in centrally controlled synaptic drives to the CPGs.