Astrocyte modulation of neural activity during intracortical microstimulation

Electrical manipulation of neural circuits has advanced our understanding of brain function, but the mechanisms that shape neural activity during stimulation remain incompletely understood. This gap reflects a persistent neuron-centric view of stimulation that overlooks the regulatory influence of glial cells, especially for long-duration stimuli. Here we investigated whether astrocytes actively shape the brain's response to different patterns of stimulation. Using two-photon and mesoscale calcium imaging of the visual cortex in awake mice, we bidirectionally manipulated astrocyte calcium signaling during intracortical microstimulation (ICMS) via chemogenetic (hM3Dq) and optogenetic (melanopsin) tools. We show that astrocytes respond to stimulation in a pattern-dependent manner and shape ongoing neural activity rather than simply following it. Near the electrode, neurons responded to astrocyte modulation in mixed directions, some increasing and some decreasing. Instead of uniformly raising or lowering activity, modulating astrocyte calcium pulled neuronal responses toward an intermediate state, with the direction determined by each neuron's starting response and its distance from the electrode. Our results identify astrocytes as a modulator of sustained neuronal activity during electrical stimulation and highlight the need to consider neuron-glia dynamics in the design of therapeutic neurostimulation.