Astrocytes connect specific brain regions through plastic gap junctional networks.

Traditionally, neuronal axons have been considered the primary mediators of functional connectivity among brain regions. However, the role of astrocyte-mediated communication has been largely underappreciated. While astrocytes communicate with one another through gap junctions, the extent and specificity of this communication remain poorly understood. Astrocyte gap junctions are necessary for memory formation(1,2), synaptic plasticity(3-5), coordination of neuronal signaling(6), and closing the visual and motor critical periods(7,8). These findings indicate that this form of communication is essential for proper central nervous system development and function. Despite their significance, studying astrocyte gap junctional networks has been challenging. Current methods like slice electrophysiology disrupt network connectivity and introduce artifacts due to tissue damage. To overcome these limitations, we developed a vector-based approach that labels molecules as they are fluxed by astrocyte gap junctions in awake, behaving animals. We then used whole-brain tissue clearing(9,10) to image these intact, three-dimensional astrocyte networks. We show that multiple astrocyte networks traverse the mouse brain. These networks selectively connect specific regions, rather than diffusing indiscriminately, and vary in size and organization. We observe local networks are confined to single brain regions and long-range networks robustly interconnecting multiple regions across hemispheres, often exhibiting patterns distinct from known neuronal networks. Further, we demonstrate that astrocyte networks undergo structural reorganization in adult brain following sensory deprivation. These discoveries reveal a previously unrecognized mode of communication between distant brain regions, mediated by plastic networks of gap junction-coupled astrocytes.