In vertebrates, specific command centers in the brain can selectively drive slow-explorative or fast-speed locomotion. However, it remains unclear how the locomotor central pattern generator (CPG) processes descending drive into coordinated locomotion. Here, we reveal, in adult zebrafish, a logic of the V2a interneuron rhythm-generating circuits involving recurrent and hierarchical connectivity that acts in tandem with pacemaker properties to provide an ignition and gear-shift mechanism to start locomotion and change speed. A comprehensive mapping of synaptic connections reveals three recurrent circuit modules engaged sequentially to increase locomotor speed. The connectivity between V2a interneurons of different modules displayed a clear asymmetry in favor of connections from faster to slower modules. The interplay between V2a interneuron pacemaker properties and their organized connectivity provides a mechanism for locomotor initiation and speed control. Thus, our results provide mechanistic insights into how the spinal CPG transforms descending drive into locomotion and align its speed with the initial intention.

中文翻译：

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多个节奏产生电路与起搏器特性协同作用，以控制运动的开始和速度。

在脊椎动物中，大脑中的特定指挥中心可以有选择地驱动缓慢探索或快速运动。但是，目前尚不清楚运动中央模式发生器（CPG）如何将降速驱动处理为协调运动。在这里，我们揭示了在成年斑马鱼中，V2a中神经元节律产生电路的逻辑，该逻辑涉及循环性和分级连接性，并与起搏器特性协同作用，以提供点火和换挡机制以开始运动并改变速度。突触连接的全面映射揭示了顺序地接合以增加运动速度的三个循环电路模块。不同模块的V2a内部神经元之间的连通性表现出明显的不对称性，有利于从较快模块到较慢模块的连接。V2a Interneuron起搏器特性与其有组织的连通性之间的相互作用为运动启动和速度控制提供了一种机制。因此，我们的结果为脊柱CPG如何将下降的驱动力转换为运动并将其速度与初始意图对齐提供了机械方面的见识。