Criticality emerges within coherent functional organization in human forebrain organoids

Critical dynamics optimise information processing in neural systems, yet two-dimensional cortical cultures require structured external input to approach the critical point. Whether three-dimensional organoids achieve criticality autonomously, and whether this criticality reflects genuine functional organization, has not been systematically examined. Here we analyse spontaneous activity in 45 human forebrain organoids, revealing robust near-critical dynamics (branching ratio = 1.099 ± 0.052) that emerge without external input. Branching ratio correlates strongly with single-channel firing regularity (r = -0.816), functional connectivity, and network clustering, while small-world topology (σ = 8.26) co-emerges with near-critical dynamics. These results demonstrate that naive organoids self-organise to a computationally favourable state with coherent functional architecture, providing a validated baseline and identifying candidate biomarkers for organoid intelligence applications.