Redundant Control of Motor Systems in Arthropods

1)在完整的小龙虾中，不同的感觉输入通过直接的兴奋和抑制通路汇聚到大脑的三对非尖峰巨型中间神经元(G1，G2，G3；NGI)上，尽管他汀囊输入可能对NGI反应有更大的影响，但反应的平衡必须取决于不同的感觉输入在神经元整合中的权重。此外，研究还发现，行走过程中眼柄的补偿性运动不仅受到重力、视觉和基质输入等方位线索的影响，而且还受到行走运动中枢输出的影响。2)在腿部接触水面的成人中，向腹神经节末端上升的4个背侧巨型中间神经元(DGI)和从大脑下降的18个已识别的中间神经元(触发神经元)中的任何一个细胞内注射去极化电流引发游泳行为。当腿不接触水面时，同样的电流注入会引发飞行行为。在大脑和食道下神经节被切除的成年人中，细胞内向这些中间神经元中的任何一个注入去极化电流，启动了在水面上的飞行行为。与单个DGI内注射电流相比，同时向两个DGI内注射电流可引起潜伏期短、持续时间长的飞行或游泳行为。这些结果表明，食道下神经节整合了腿部本体感觉输入，以选择最适合当前外部条件的行为运动模式。3)上述结果提示，节肢动物运动控制的神经机制可能涉及大量的功能重叠或“冗余”，以利用在“假安全”和“协同作用”模式下操作的公共肌肉组，并选择特定的运动模式。

1)In the intact crayfish, the diverse sensory inputs converge onto the three pairs of nonspiking giant interneurons (G1, G2, G3 ; NGIs) of the brain through both direct excitatory and inhibitory pathways, and that although statocyst inputs potentially have more of an effect on NGI responses, the balance of the response must depend on how different sensory inputs are weighted in neuronal integration. Furthermore, it was found that the compensatory eyestalk movements during walking are not only under the influence of orientation cues, such as gravitational, visual, and substrate inputs, but also under the influence of outputs from walking motor center. 2)In adults with leg contact with the surface of water, intracellular injection of depolarizing current into any one of four dorsal giant interneurons (dGIs) ascending from the terminal abdominal ganglion and eighteen identified interneurons (trigger neurons) descending from the brain initiated swimming behavior. When the legs were not contact with the surface of water, the same current injection initiated flying behavior. In adults whose the brain and suboesophageal ganglion were removed, intracellular injection of depolarizing current into any one of these interneurons initiated flying behavior on the surface of water. Compared with the current injection into a single dGI,the current injection into two dGIs at the same time initiated flight or swimming behavior with short latency and long duration. These results suggest that the suboesophageal ganglion integrates the leg proprioceptive inputs to select the behavioral motor pattern most appropriate to the current external condition. 3)The above-mentioned results imply that the neuronal mechanism of motor control in arthropods might involve considerable functional overlap or "redundancy" to utilize common sets of muscles while operating in "false safe" and "synergic action" modes, and to select specific motor pattern.