Features of criticality are asymmetric in the zebrafish habenula

The habenula is an evolutionarily conserved structure of the vertebrate brain essential for behavioural flexibility and mood control. It is spontaneously active and is able to access diverse states upon exposure to stimulation. Information processing in the habenula can potentially be understood through criticality, which describes a system at the boundary between different dynamical states. Here we analyze two-photon calcium imaging time-series of a single plane of the dorsal habenula of larval zebrafish for statistical features of criticality, namely avalanche distributions and shape collapse. We find that the dorsal habenula, which has left-right asymmetry in connectivity and function, displays asymmetric features of criticality, with the left dorsal habenula being at or near a critical state, while the right side is not. Deviations from theoretical predictions were understood through a branching model to result from subsampling. These observations provide evidence that a sub-cortical region of the vertebrate brain operates at a critical state in the intact animal.