Ca²⁺ Activity Patterns Emerging from Neuronal-Astrocytic Interactions: A Critical Brain Perspective

Astrocytes constitute the majority of cells in the human central nervous system. While they do not conduct electrical signals like neurons, they communicate via calcium (Ca²⁺) signaling and are more recently recognized as active participants in neural network dynamics. Beyond their metabolic support, astrocytes influence—and are influenced by—neuronal activity.

In this study, we introduce an experimentally validated mathematical model of a multilayer neuron–astrocyte network to investigate the reciprocal effects between neuronal firing patterns and astrocytic calcium dynamics. By simulating different network configurations—such as uncoupling astrocytes from neurons, from each other, or maintaining full coupling—we identify conditions that enable astrocytes to initiate and propagate Ca²⁺ signals, determine the universality class of this spreading process, and assess whether Ca²⁺ events contribute to or modify neuronal activity propagation. Our results show that neuronal bursts are essential to both trigger the initiation of calcium (Ca²⁺) activity in astrocytes and to sustain its propagation across the astrocytic network over time.

To evaluate the broader implications of these interactions, we assess whether they give rise to critical behavior consistent with the critical brain hypothesis, which proposes that the brain operates as a self-organized dynamical system optimized for information processing and storage. Specifically, we characterize the scale-invariant features of both neuronal and astrocytic avalanches. Our analysis indicates that avalanche size distributions follow a power law, in line with predictions of the critical brain hypothesis.