Spatiotemporally distinctive astrocytic and neuronal responses to repetitive intracortical microstimulation

Abstract

Astrocytes are increasingly recognized as active modulators of neuronal synaptic transmission. Intracortical microstimulation (ICMS) is widely used to manipulate neuronal activity, yet the accompanying astrocytic responses remain poorly characterized. Using dual-color in vivo two-photon calcium imaging to simultaneously monitor neurons and astrocytes, we show that ICMS elicits astrocytic activation with spatiotemporal features that diverge from those of neurons. Astrocytes were recruited at stimulation intensities as low as 10A, thresholds sufficient to activate neurons, indicating that astrocytes robustly sense electrical perturbation. Unlike neurons, however, astrocytic responses were spatially heterogeneous and temporally variable across trials. At higher stimulation intensities (>=50A), astrocytic responsiveness, i.e., response peak amplitude, and number of responsive trials, progressively attenuated across repeated trials, in contrast to the stable and consistent neuronal responses. Although neuronally driven, astrocytes exhibited a distinct response profile under the same stimulation parameter, revealing a unique component of electrically evoked cortical activity that underscores the importance of incorporating glial physiology into future neuroprosthetic strategies.