The brain is like a multi-story building: lower floors process simple signals, while upper floors assemble them into complex perceptions. Scientists have long suspected that this order is tied to how neurons work together. But exactly how has remained a puzzle.
Researchers recorded the electrical activity of thousands of neurons in the mouse visual cortex and hippocampus. They then applied a method akin to viewing a map at different magnifications: first you see fine details, then larger regions. This approach, called renormalization, reveals how a system's properties change with scale.
When the mouse performed a visual task, these signatures changed markedly. Furthermore, by examining the interrelations among critical markers across different brain regions during active behavior, the researchers could reconstruct the anatomical hierarchy. This means that neuron dynamics directly reflect brain architecture.
This approach opens a path to understanding how brain structure gives rise to complex behavior — from perception to memory.
Brain criticality is often compared to the phase transition of water into ice: at the critical point, the system is most sensitive to small changes, allowing the brain to respond rapidly to stimuli.