The Evolutionary and Organizational Bases of Active Affordance.

The vertebrate brain must balance internally generated predictions with constraints of environmental affordances. This balance constitutes a fundamental principle of neural organization that underwrites cortical computation. Using the prosomeric model of the neuraxis, we show how dorsalizing and ventralizing morphogenetic gradients specify excitatory and inhibitory lineages during development, establishing the functional architecture of active affordance. These developmental asymmetries are elaborated through telencephalic expansion, pallial-subpallial integration, and laminar differentiation of the neocortex, as described by the structural model. We demonstrate that motor control emerges within a sensory-predictive architecture due to the alar origin of the telencephalon and that increasing excitatory-inhibitory complementarity within the mammalian neocortex enables selective, context-sensitive action. Subpallial and diencephalic systems provide inhibitory governance over cortical action tendencies, supporting policy evaluation and selection in the framework of active inference. At the base of this hierarchy, the hypothalamus integrates homeostatic and allostatic signals to bias the landscape of affordances, shaping the likelihood of action policies. Together, these findings establish active affordance as a developmental and evolutionary framework linking prosomeric neurodevelopment, cortical architecture, subcortical control, and adaptive behavior. Active inference is thereby situated as the mature cortical expression of a conserved biological solution to acting in an uncertain world.