The Critical Brain

The large view is labelled Living cortical sheet · spike-density field. One mesh covers a 128 by 128 grid. It bows upward where cells have just spiked. Excitatory activity is cyan. Inhibitory activity is pink. A faint floor grid sits underneath, and the camera orbits. The corner reads cortex 128×128 · 16,384 units, model Izhikevich · 80/20 E·I, and the current σ. A cell contributes a spike when its voltage crosses 30 mV and is then reset to −65 mV.

The slider is labelled Control parameter · synaptic gain g, with the note anaesthesia ↓ · edge of chaos · seizure ↑. It runs from g = 0.18 to g = 0.80 and opens at 0.46. The presets are Anaesthesia at 0.30, Critical at 0.46 and Seizure at 0.66. The badge Dynamical regime reads σ, in blue as SUBCRITICAL below 0.88, in green as CRITICAL from 0.88 to 1.12, and in pink as SUPERCRITICAL above 1.12.

The right column holds Avalanche size · P(S) and Avalanche duration · P(T), both log-log. Size is drawn in cyan with a dashed amber reference marked slope -1.5, and the fitted slope is reported as τ. Duration is drawn in purple with a dashed reference marked slope -2, and the corner of the sheet labels that fitted slope α. Under them, Branching ratio · σ carries the note criticality at σ=1. Four traces follow: population rate in cyan, branching σ(t) in amber with a mark at 1, active fraction in purple, and avalanche size in pink.

E / I balance opens at 4.0, on a slider from 1.5 to 6. Background σ opens at 0.55, on a slider from 0 to 1.5. Stimulate adds a short current to a small patch. Reset reseeds the sheet. Run and Pause gate the stepping, which advances at 70 steps a second.