IEEE Trans Biomed Circuits Syst. 2015 Apr;9(2):175-87. doi: 10.1109/TBCAS.2015.2417580.
Neuromorphic circuits are designed and simulated to emulate the role of astrocytes in phase synchronization of neuronal activity. We emulate, to a first order, the ability of slow inward currents (SICs) evoked by the astrocyte, acting on extrasynaptic N-methyl-D-aspartate receptors (NMDAR) of adjacent neurons, as a mechanism for phase synchronization. We run a simulation test incorporating two small networks of neurons interacting with astrocytic microdomains. These microdomains are designed using a resistive and capacitive ladder network and their interactions occur through pass transistors. Upon enough synaptic activity, the astrocytic microdomains interact with each other, generating SIC events on synapses of adjacent neurons. Since the amplitude of SICs is several orders of magnitude larger compared to synaptic currents, a SIC event drastically enhances the excitatory postsynaptic potential (EPSP) on adjacent neurons simultaneously. This causes neurons to fire synchronously in phase. Phase synchrony holds for a duration of time proportional to the time constant of the SIC decay. Once the SIC decay has completed, the neurons are able to go back to their natural phase difference, inducing desynchronization of their firing of spikes. This paper incorporates some biological aspects observed by recent experiments showing astrocytic influence on neuronal synchronization, and intends to offer a circuit view on the hypothesis of astrocytic role on synchronous activity that could potentially lead to the binding of neuronal information.
神经形态电路被设计和模拟，以模拟星形胶质细胞在神经元活动的相位同步中的作用。我们首先模拟星形胶质细胞引发的缓慢内向电流（SICs）的能力，该电流作用于相邻神经元的突触外 N-甲基-D-天冬氨酸受体（NMDAR），作为一种相位同步的机制。我们运行了一个模拟测试，其中包含两个与星形胶质细胞微域相互作用的神经元小网络。这些微域使用电阻和电容梯网络设计，它们的相互作用通过传输晶体管发生。在足够的突触活动下，星形胶质细胞微域相互作用，在相邻神经元的突触上产生 SIC 事件。由于 SIC 的幅度比突触电流大几个数量级，因此 SIC 事件会同时大大增强相邻神经元的兴奋性突触后电位（EPSP）。这导致神经元同步相位放电。相位同步持续时间与 SIC 衰减的时间常数成正比。一旦 SIC 衰减完成，神经元就能够回到它们的自然相位差，导致它们的尖峰发射失步。本文结合了最近的实验观察到的一些生物学方面，这些实验表明星形胶质细胞对神经元同步的影响，并旨在提供一个关于星形胶质细胞在同步活动中的作用的假设的电路观点，这可能导致神经元信息的绑定。
