Complex body movements require complex dynamics and coordination among neurons in motor cortex. Conversely, a long-standing theoretical notion supposes that if many neurons in motor cortex become excessively synchronized, they may lack the necessary complexity for healthy motor coding. However, direct experimental support for this idea is rare and underlying mechanisms are unclear. Here we recorded three-dimensional body movements and spiking activity of many single neurons in motor cortex of rats with enhanced synaptic inhibition and a transgenic rat model of Rett syndrome (RTT). For both cases, we found a collapse of complexity in the motor system. Reduced complexity was apparent in lower-dimensional, stereotyped brain–body interactions, neural synchrony, and simpler behavior. Our results demonstrate how imbalanced inhibition can cause excessive synchrony among movement-related neurons and, consequently, a stereotyped motor code. Excessive inhibition and synchrony may underlie abnormal motor function in RTT.

复杂的身体运动需要运动皮层神经元之间复杂的动态和协调。相反，一个长期存在的理论认为，如果运动皮层中的许多神经元过度同步，它们可能缺乏健康运动编码所需的复杂性。然而，对这一想法的直接实验支持很少见，并且潜在的机制尚不清楚。在这里，我们记录了具有增强的突触抑制和 Rett 综合征 (RTT) 转基因大鼠模型的大鼠运动皮层中许多单个神经元的三维身体运动和尖峰活动。对于这两种情况，我们发现运动系统的复杂性崩溃了。在低维、刻板的脑-身交互、神经同步和更简单的行为中，复杂性的降低是显而易见的。我们的研究结果表明，不平衡的抑制如何导致与运动相关的神经元过度同步，从而导致刻板的运动代码。过度抑制和同步可能是 RTT 运动功能异常的基础。