Centripetal integration of past events by hippocampal astrocytes

Abstract

AbstractAn essential feature of neurons is their ability to centrally integrate information from their dendrites. The activity of astrocytes, on the other hand, has been described to be mostly uncoordinated across the cellular compartments and therefore without central integration. Here, we describe conditional centripetal integration, a principle how astrocytes integrate calcium signals from their distal processes. We performed calcium imaging of hippocampal astrocytes and neurons in head-fixed mice, together with monitoring of body movements and pupil diameter. Global astrocytic activity was well explained by the concurrent pupil diameter as a proxy for arousal, but equally well as leaky integration of past neuronal and behavioral events on a timescale of seconds. This integration of past events occurred in a centripetal pattern in individual astrocytes, starting in distal processes followed by a slow propagation towards the soma. Centripetal propagation was facilitated by high levels of arousal but impeded when pre-event calcium levels were high. Together, our results establish astrocytes as computational units of the brain that slowly and conditionally integrate information about the past.