Division of Brain Circuits, National Institute for Basic Biology Okazaki, Japan ; CREST, Japan Science and Technology Agency Saitama, Japan ; Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, University of Tokyo Tokyo, Japan.
Front Neural Circuits. 2013 Apr 1;7:55. doi: 10.3389/fncir.2013.00055. eCollection 2013.
Interactions between distinct motor cortical areas are essential for coordinated motor behaviors. In rodents, the motor cortical forelimb areas are divided into at least two distinct areas: the rostral forelimb area (RFA) and the caudal forelimb area (CFA). The RFA is thought to be an equivalent of the premotor cortex (PM) in primates, whereas the CFA is believed to be an equivalent of the primary motor cortex. Although reciprocal connections between the RFA and the CFA have been anatomically identified in rats, it is unknown whether there are functional connections between these areas that can induce postsynaptic spikes. In this study, we used an in vivo Channelrhodopsin-2 (ChR2) photostimulation method to trace the functional connections between the mouse RFA and CFA. Simultaneous electrical recordings were utilized to detect spiking activities induced by synaptic inputs originating from photostimulated areas. This method, in combination with anatomical tracing, demonstrated that the RFA receives strong functional projections from layer 2/3 and/or layer 5a, but not from layer 5b (L5b), of the CFA. Further, the CFA receives strong projections from L5b neurons of the RFA. The onset latency of electrical responses evoked in remote areas upon photostimulation of the other areas was approximately 10 ms, which is consistent with the synaptic connectivity between these areas. Our results suggest that neuronal activities in the RFA and the CFA during movements are formed through asymmetric reciprocal connections.
不同运动皮质区域之间的相互作用对于协调的运动行为至关重要。在啮齿动物中，运动皮质前肢区域至少分为两个不同的区域：前肢皮质的背侧区域（CFA）和前肢皮质的腹侧区域（RFA）。RFA 被认为是灵长类动物的前运动皮质（PM）的等价物，而 CFA 被认为是初级运动皮质的等价物。尽管在大鼠中已经在解剖学上确定了 RFA 和 CFA 之间的相互连接，但尚不清楚这些区域之间是否存在可以诱导突触后峰的功能连接。在这项研究中，我们使用体内 Channelrhodopsin-2（ChR2）光刺激方法来追踪小鼠 RFA 和 CFA 之间的功能连接。同时进行电记录以检测源自光刺激区域的突触输入引起的尖峰活动。这种方法与解剖学追踪相结合，表明 RFA 从 CFA 的第 2/3 层和/或第 5a 层接收强的功能投射，但不接收第 5b 层（L5b）的投射。此外，CFA 从 RFA 的 L5b 神经元接收强的投射。在对其他区域进行光刺激时，在远程区域诱发的电反应的起始潜伏期约为 10ms，这与这些区域之间的突触连接一致。我们的结果表明，在运动过程中 RFA 和 CFA 中的神经元活动是通过不对称的相互连接形成的。
