Orofacial Central Pattern Generators: Neuroanatomical and Clinical Insights into Sensory, Motor, Emotional...

Orofacial behaviors such as mastication, swallowing, and phonation are not organized as simple reflex chains but are generated and coordinated by intrinsic brainstem networks known as central pattern generators (CPGs). Although the existence and organization of these circuits are well established in animal models, direct evidence for their microcircuit organization in humans remains limited, and current human interpretations rely largely on lesion-based, neurophysiological, and imaging-based inference. In this review, we synthesize neuroanatomical, neurophysiological, and clinical evidence to propose a network-centric framework for orofacial motor control. We describe the hierarchical organization of the orofacial CPG system across sensory input nuclei, premotor pattern-forming networks within the pontomedullary reticular formation, cranial motor output nuclei, and supranuclear modulation by cortical, basal ganglia, cerebellar, and limbic systems. Within this architecture, orofacial motor behaviors are conceptualized as a functional continuum in which somatic, visceral, and emotional signals converge to shape rhythmic and sequential motor output. Based on this circuit framework, we classify orofacial CPG dysfunction into four pathophysiological categories-sensory deafferentation, intrinsic pattern generator disturbances, motor output impairments, and supranuclear dysmodulation-emphasizing that failures of pattern generation are primarily expressed as deficits in timing and coordination rather than simple muscle weakness. Finally, we discuss circuit-informed implications for rehabilitation, highlighting how sensory priming, non-invasive brain stimulation, and rhythmic entrainment may promote functional recovery by reweighting residual brainstem-supranuclear networks. By reframing orofacial motor control as a distributed and hierarchically modulated network, this review provides a conceptual foundation for future experimental and translational studies of human brainstem motor systems.