Functional Modeling of Astrocytes in Synchronization of Neuronal Cells

Based on the neurophysiologic findings, astrocytes provide not only structural and metabolic supports for the nervous system but also they are active partners in neuronal activities and synaptic transmissions. In the present study, we improved two biologically plausible cortical and thalamocortical neural population models (CPM and TCPM), which were developed previously by Suffczynski and colleagues, by integrating the functional role of astrocytes in the synaptic transmission in the models. In other words, the original CPM and TCPM are modified to integrate neuronastrocyte interaction considering the idea of internal feedback proposed by Iasemidis and collaborators. Using the modified CPM and TCPM, it is demonstrated that healthy astrocytes provide appropriate feedback control for regulating the neural activities. As a result, we observed that the astrocytes are able to compensate for the variations in the cortical excitatory input and maintain the normal level of synchronized behavior. Next, it is hypothesized that malfunction of astrocytes in the regulatory feedback loop can be one of the probable causes of seizures. That is, pathologic astrocytes are not any more able to regulate and/or compensate the excessive increase of the cortical excitatory input. Consequently, disruption of the homeostatic or signaling function of astrocytes may initiate the hypersynchronous firing of neurons. Our results confirm the hypothesis and suggest that the neuronastrocyte interaction may represent a novel target to develop effective therapeutic strategies to control seizures.