Neurosciences Program, Stanford University, Stanford, California, USA.
J Neurophysiol. 2013 Aug;110(4):817-25. doi: 10.1152/jn.00892.2011. Epub 2013 May 22.
The motor cortices exhibit substantial activity while preparing movements, yet the arm remains still during preparation. We investigated whether a subpopulation of presumed inhibitory neurons in primary motor cortex (M1) might be involved in "gating" motor output during preparation, while permitting output during movement. This hypothesis predicts a release of inhibition just before movement onset. In data from M1 of two monkeys, we did not find evidence for this hypothesis: few neurons exhibited a clear pause during movement, and these were at the tail end of a broad distribution. We then identified a subpopulation likely to be enriched for inhibitory interneurons, using their waveform shapes. We found that the firing rates of this subpopulation tended to increase during movement instead of decreasing as predicted by the M1 gating model. No clear subset that might implement an inhibitory gate was observed. Together with previous evidence against upstream inhibitory mechanisms in premotor cortex, this provides evidence against an inhibitory "gate" for motor output in cortex. Instead, it appears that some other mechanism must likely exist.
运动皮层在准备运动时会显示出大量的活动，但在准备过程中手臂仍然保持静止。我们研究了初级运动皮层（M1）中假定的抑制性神经元亚群是否可能参与运动准备期间的“门控”运动输出，同时允许运动期间的输出。该假设预测在运动开始前会释放抑制。在两只猴子的 M1 数据中，我们没有发现支持这一假设的证据：很少有神经元在运动过程中表现出明显的停顿，而且这些神经元处于广泛分布的末端。然后，我们使用它们的波形形状来识别可能富含抑制性中间神经元的亚群。我们发现，该亚群的放电率在运动过程中倾向于增加，而不是像 M1 门控模型所预测的那样减少。没有观察到可能实现抑制门的清晰子集。结合先前反对运动前皮层中上游抑制机制的证据，这为皮层中运动输出的抑制“门”提供了证据。相反，很可能存在其他机制。
