Hao Yaoyao, Riehle Alexa, Brochier Thomas G
Institut de Neurosciences de la Timone, CNRS - Aix-Marseille Université, UMR7289 Marseille, France.
Institut de Neurosciences de la Timone, CNRS - Aix-Marseille Université, UMR7289Marseille, France; RIKEN Brain Science InstituteSaitama, Japan; Institute of Neuroscience and Medicine, Forschungszentrum JülichJülich, Germany.
Front Neural Circuits. 2016 Dec 16;10:104. doi: 10.3389/fncir.2016.00104. eCollection 2016.
Anatomical studies have demonstrated that distant cortical points are interconnected through long range axon collaterals of pyramidal cells. However, the functional properties of these intrinsic synaptic connections, especially their relationship with the cortical representations of body movements, have not been systematically investigated. To address this issue, we used multielectrode arrays chronically implanted in the motor cortex of two rhesus monkeys to analyze the effects of single-pulse intracortical microstimulation (sICMS) applied at one electrode on the neuronal activities recorded at all other electrodes. The temporal and spatial distribution of the evoked responses of single and multiunit activities was quantified to determine the properties of horizontal propagation. The typical responses were characterized by a brief excitatory peak followed by inhibition of longer duration. Significant excitatory responses to sICMS could be evoked up to 4 mm away from the stimulation site, but the strength of the response decreased exponentially and its latency increased linearly with the distance. We then quantified the direction and strength of the propagation in relation to the somatotopic organization of the motor cortex. We observed that following sICMS the propagation of neural activity is mainly directed rostro-caudally near the central sulcus but follows medio-lateral direction at the most anterior electrodes. The fact that these interactions are not entirely symmetrical may characterize a critical functional property of the motor cortex for the control of upper limb movements. Overall, these results support the assumption that the motor cortex is not functionally homogeneous but forms a complex network of interacting subregions.
解剖学研究表明，远距离的皮质点通过锥体细胞的长轴突侧支相互连接。然而，这些内在突触连接的功能特性，尤其是它们与身体运动的皮质表征之间的关系，尚未得到系统研究。为了解决这个问题，我们使用长期植入两只恒河猴运动皮质的多电极阵列，来分析在一个电极上施加单脉冲皮质内微刺激（sICMS）对在所有其他电极上记录的神经元活动的影响。对单单位和多单位活动诱发反应的时间和空间分布进行量化，以确定水平传播的特性。典型反应的特征是短暂的兴奋性峰值，随后是持续时间更长的抑制。在距离刺激部位4毫米远的地方，对sICMS仍可诱发明显的兴奋性反应，但反应强度呈指数下降，其潜伏期随距离呈线性增加。然后，我们根据运动皮质的躯体定位组织量化了传播的方向和强度。我们观察到，在sICMS之后，神经活动的传播在中央沟附近主要沿前后方向，但在最前面的电极处沿中外侧方向。这些相互作用并非完全对称，这一事实可能是运动皮质控制上肢运动的关键功能特性。总体而言，这些结果支持这样一种假设，即运动皮质在功能上并非均匀一致，而是形成了一个由相互作用的子区域组成的复杂网络。
