From quiescence to self-sustained activity: How astrocytes reshape neural dynamics

Astrocytes are currently gaining attention from the neuroscience community due to their contribution to a multitude of functions, which includes but are not limited to their ability to change the neuron's spiking frequency, their capacity to alter neuron's firing activity, and their involvement in memory formation and synaptic plasticity regulation. To date, many computational models describing the dynamics of astrocytes, together with their complex interaction with neurons, were proposed, however, these could still be improved since the exploration of their functions and mechanisms was way later than neurons. Hence, in this paper, investigation of the steady state behavior of the neuron-astrocyte interaction through a presentation of phase plane analysis and one parameter bifurcation were primarily performed. Adaptive Exponential Integrate-and-Fire model was utilized to describe the firing dynamics of the neuron while the model from the work of Postnov and collaborators was used to describe the calcium dynamics of the astrocyte. The findings demonstrate that astrocytic modulation can significantly shape neuronal activity, including initiating spikes, inducing self-sustained oscillations, and exerting both inhibitory and excitatory effects depending on synaptic strength. These highlight the crucial role that the contribution of astrocytes to the synapse plays in regulating neuronal activity and producing a range of neuronal firing behaviors within the neuron-astrocyte ensemble. They may impact neuronal synchronization, an attribute of several neurological illnesses, including epilepsy, and, on the other hand, may enhance brain information processing.