The brain that controls itself

The brain is a complex adaptive system that is organized across broad spatiotemporal scales. This multiscale architecture poses unique computational challenges, as the brain must balance the segregation of specialized functions with their cooperative integration into broader cognitive processes, while also simultaneously remaining both stable yet flexible enough to robustly rapidly adapt to new challenges. Systems poised near critical points reflect this same trade-off, however they are typically coordinated by external control parameters. Here, we argue that diffuse projections from the subcortex act as intrinsic control parameters that allow the brain to control its own coherence and flexibility. We review biophysical computational models that demonstrate how diffuse projections enforce low-dimensional neural dynamics promoting system-wide coherence while maintaining a susceptibility to external changes. The findings suggest that these systems underlie the brain’s capacity for complex, adaptive behavior, providing a foundation for exploring how diffuse projections influence higher-level cognitive processes and consciousness. • Diffuse projections modulate brain-wide activity by targeting multiple areas. • Diffuse projections act as a control parameter for critical dynamics. • Computational models reveal that diffuse projections facilitate neural integration. • Quasicritical brain states induced by diffuse projections support adaptive behavior. • This suggests a scale-invariant mechanism for control in the brain.