Evolution and Reorganization of the Hierarchical Brain-wide Neuronal Network Through Anesthesia.

The brain fluctuates across different states, such as anesthesia and wakefulness, which differ in sensory responses and inherent fluctuations. Although these have been intensively studied at the molecule-to-brain regional network level, the underlying mechanisms by which neuronal interactions across the brain generate global states, and the transitions between them, remain unclear. In the present study, we applied fast wide-field calcium imaging to track neuronal activity across the brains of freely swimming juvenile zebrafish during wakefulness and anesthesia. Herein, we developed a methodological pipeline to dissect the functional coordination of a brain-wide neuronal network and characterize neuronal participation in functional clusters over time. Our analyses showed that a dynamic population of local neurons supported stable inter-regional coordination and the hierarchical organization of neurons across the brain, which deteriorated upon anesthesia, but recovered along with swimming behavior. This paradigm may apply to deciphering the emergent principles underlying global information processing.