Heterarchy in the Brain: Control as a Spectrum, Not a Chain of Command

Neuroscience treats the brain as a control hierarchy, with cortical systems governing subcortical mechanisms. We argue that this mistakes a configuration for an architecture. Local asymmetries of influence are real, but control is relational and process-specific; because neural elements constrain one another across concurrent processes, relations can form cycles that resist a stable ranking. Evidence from learned action, cortico-cerebellar and thalamocortical loops, and defensive behavior shows that control changes with practice, task phase, urgency, viability demands, and affordances. Hierarchical order therefore characterizes time-bounded configurations, whereas heterarchy characterizes the architecture's repertoire across occasions. We propose a spectrum of control indexed by dynamical decoupling: how far behavior can depend on history, internal state, and anticipated consequences. The account yields experimentally testable predictions.