大脑皮质神经元及其网络的兴奋

Excitability of cortical neurons and their neural network

大脑皮质中神经元的种类丰富多样,它们通过突触彼此连接,形成了能实现感觉、运动、学习、语言和决策等各种功能的神经网络。网络中信息的传递需要单个神经元及其交互神经网络的激活,即产生动作电位(AP)和网络电活动。AP首先在轴突产生,由轴突上各种离子通道和自身的生物物理特性所决定。交互神经网络的兴奋除了由各类神经元的兴奋性决定外,还被兴奋性和抑制性突触的递质释放模式所调控。传统观念认为,拥有"全或无"爆发特征的AP是信息传递的唯一方式,即数字信号编码模式。近期研究表明,阈下膜电位的波动也能调节由AP引发的突触传递,即模拟信号编码模式。在网络活动中,由谷氨酸能神经元提供的兴奋性信号和由γ-氨基丁酸(GABA)能神经元提供的抑制性信号往往是相辅相成的,从而达到兴奋和抑制的平衡。各类GABA能神经元所组成的抑制性微环路对平衡的维持十分重要,神经元间特异的突触传递模式可调控这些微环路的功能,如模拟信号传递模式和非同步化递质释放模式等。综上,本文阐述了大脑皮质中多种神经元及其网络的兴奋和调控机制。

The cerebral cortex contains a large variety of neuronal cells, which connect with each other via synapses to form different neural networks and fundamental elements for brain functions such as sense, movement, learning, language and decision making. Information processing in the cerebral cortex requires the activation of individual neurons and their recurrent networks, that is, the generation of action potential（AP）（excitability of single neurons） and network activity（excitability of neural networks）. Initiation of AP occurs at the axon and is determined by axonal ion channels as well as intrinsic biophysical properties. The excitability of recurrent networks is not only determined by the excitability of different types of neurons, but also regulated by the unique properties of neurotransmitter release in distinct synapses including excitatory and inhibitory ones. Traditionally, it is believed that the all-or-none AP is the only mode of information transmission-digital mode. Recent studies have shown that the subthreshold membrane potential fluctuations regulate AP-induced the synaptic transmission-analog mode. At the network level, the network activity is relatively stable, resulting from a dynamic balance of excitation and inhibition. The microcircuits of recurrent inhibition mediated by distinct inhibitory interneuron types and the modes of synaptic transmission, such as the analog mode of signal communication and asynchronous neurotransmitter release, play critical roles in maintaining the excitation and inhibition balance.Together, we present here some new insights into the mechanisms underlying the excitability of distinct types of cortical neurons and their interconnected networks.