Cracklin' Fish Brains

Abstract

Whole-Brain Neuronal Activity Displays Crackling Noise Dynamics Ponce-Alvarez A, Jouary A, Privat M, Deco G, Sumbre G. Neuron. 2018;100(6):1446-1459.e6. Previous studies suggest that the brain operates at a critical point in which phases of order and disorder coexist, producing emergent patterned dynamics at all scales and optimizing several brain functions. Here, we combined light-sheet microscopy with GCaMP zebrafish larvae to study whole-brain dynamics in vivo at near single-cell resolution. We show that spontaneous activity propagates in the brain's 3-dimensional space, generating scale-invariant neuronal avalanches with time courses and recurrence times that exhibit statistical self-similarity at different magnitude, temporal, and frequency scales. This suggests that the nervous system operates close to a nonequilibrium phase transition, where a large repertoire of spatial, temporal, and interactive modes can be supported. Finally, we show that gap junctions contribute to the maintenance of criticality and that, during interactions with the environment (sensory inputs and self-generated behaviors), the system is transiently displaced to a more ordered regime, conceivably to limit the potential sensory representations and motor outcomes.

Figure 1.

Neural activity patterns show signs of criticality. A, (1) Spinning of electrons within a magnet as described by the Ising model. The spinning of an electron is influenced by nearby electrons. At cooler temperatures (eg, left), such interactions dominate such that spin orientation is similar across all electrons within the magnet. If the temperature is raised (eg, right), then local electron interactions are disrupted and electron spins become random. At the critical temperature (eg, middle), local and dynamic clusters of spatially contiguous electrons with similar spin orientations emerge. Each circle represents an electron. Each arrow represents the orientation of the electron. (2) Schematic representing neural activity patterns operating at subcritical (left), critical (middle), and supracritical (right) regimes. Local clusters of spatially contiguous active neurons emerge at criticality. Active neurons are represented by filled cell bodies. B, Neuronal avalanche. A cluster of active neurons at different time points (t) transiently emerges and then disappears. The statistics of neuronal avalanches is similar to those observed during sandpile avalanches. C, Power law relationships plotted on linear (left) and log (right) scales. As an example, the volume of a cube is plotted as a function of the cube’s length. This relationship appears linear when using a log scale. D, Ponce-Alverez et al (2) show that several features of neuronal avalanches recorded in the entire zebrafish brain follow the power law.