On the role of astrocytes in synchronization of two coupled neurons: a mathematical perspective

Abstract

Based on recent findings, astrocytes, a subtype of glial cells, dynamically regulate the synaptic transmission of neuronal networks. In this research, a biologically inspired neuronal network model is constructed by connecting two Morris-Lecar neuron models. In this minimal network model, neuron-astrocyte interactions are considered in a functional-based procedure. Utilizing the developed model and according to the theoretical analysis carried out in the article, it is confirmed that, the astrocyte increases the threshold value of synchronization and provides appropriate feedback control in regulating the neural activities. Therefore, the healthy astrocyte has the potential to desynchronize the synchrony between two coupled neurons. Next, we investigate malfunction of the astrocyte in the regulatory feedback loop. Mathematically, we verify that pathologic astrocyte is no longer able to increase the synchronization threshold and therefore, it cannot compensate excessive increase in the excitation level. The main reason behind this is the fact that healthy astrocyte can optimally increase the input current of the individual neurons, while the so-called pathological astrocyte is unable to modify correctly the amount of this current. Consequently, disruptions of the signaling function of astrocyte initiate the hypersynchronous firing of neurons. In other words, reduction in neuron-astrocyte cross-talk will lead to synchronized firing of neurons. Therefore, our results propose that the astrocyte could have a key role in stabilizing neural activity.

An analog astrocyte–neuron interaction circuit for neuromorphic applications

“…Neuronal firing activity, which includes both the frequency and the timing of action potentials, is an essential component in information processing in the brain [57,61]. In addition, over the past decade, the knowledge about the diverse role of astrocytes in many facets of synaptic transmission has considerably expanded [62][63][64]. The present study puts forward a new perspective to analyze neuron-astrocyte interactions from hardware point of view.…”

Does deficits in place field formation cause spatial navigation impairment in Alzheimer's disease?

“…They act as regulators and inspect synaptic dynamics and control extracellular fluid content and electrolyte homeostasis. Their pivotal role in synaptic activities is to release gliotransmitters including glutamate and ATP to modulate synaptic activities [12], [13]. These facts demand for including astrocytes in our model in order to gain a deeper understanding of hippocampal neural circuitry and the role of astrocytes in place field formation.…”

“…In [12] neuronal dynamics are described through Morris-Lecar equations (equations (4) to (8)) and dynamics of the astrocytes are described through the Li-Rinzel model (equations (9) to (19)). …”

Analog implementation of neuron–astrocyte interaction in tripartite synapse

“…The input of an astrocyte (Z ) is concentration of the neurotransmitter ([T ] i ) released by activated neuron, and it triggers the IP 3 production [43]. It is defined as:…”

“…We used g se2 to change the excitation level. Increase in g se2 leads to enhancement of the coupling strength between neurons and thereby influences the neural synchrony [43]. The synaptic interactions are modeled in the same way as suggested by Terman, et al [44].…”