Morphology of rodent proprioceptors and their implications in motor control. (A) The anatomical structure of rodent proprioceptors. Two main proprioceptive neurons, muscle spindle (MS) and Golgi tendon organ (GTO) have their sensory afferent endings in the middle of the muscle and the tendon, respectively. (B) Beha-vioral deficits observed in the mutant mice lacking proper proprioception. Top panel: abnormal limb postures in hanging. Bottom panel: Error-prone stepping in walking test.