A touch-guided neural circuit for dental alignment and motivated oral behavior

Abstract

Dental alignment is traditionally viewed as a passive mechanical consequence of tooth morphology and jaw structure. However, rodents continuously maintain their incisors through gnawing, a behavior required to offset lifelong tooth growth and preserve normal occlusion. How sensory signals arising from the teeth are integrated with motor and motivational systems to regulate this process remains poorly understood. Here, I will describe the identification of a brainstem circuit that links incisor mechanosensation to both jaw motor control and motivational drive. We found that somatostatin-expressing (SST+) neurons in the spinal trigeminal nucleus oralis (Sp5O) are essential for maintaining dental alignment. These neurons receive input from a genetically distinct population of S100b-positive Aβ low-threshold mechanoreceptors that innervate the incisor periodontium and selectively encode dynamic mechanical forces generated during gnawing. Sp5O SST+ neurons form direct excitatory connections with trigeminal motor neurons controlling jaw closure and are required for normal gnawing behavior. Disruption of this pathway leads to severe malocclusion characterized by incisor overgrowth and misalignment. In parallel, Sp5O SST+ neurons engage a parabrachial-midbrain pathway that drives dopamine release in the nucleus accumbens and promotes the motivational value of gnawing. Together, these findings reveal a touch-dependent sensorimotor-motivational circuit that actively regulates dental alignment through goal-directed oral behavior. More broadly, this work suggests that craniofacial function depends on the integration of sensory feedback, motor control, and motivational state, providing a neural framework for understanding oral motor dysfunction and malocclusion.