Localization of proprioceptive reflexes in the splenius muscle of the cat.

Activity of the cat splenius muscle was modulated by sinusoidal rotation of the head around the C1-C2 joint in decerebrate cats with labyrinth intact or with all semicircular canals plugged, or, in one intact and alert cat, by rotation of the body with the head fixed in space. EMG modulation, recorded from the areas of splenius innervated by the C1-C4 nerves, was due to the cervicocollic reflex. Modulation was not uniform, but decreased with progressively more caudal recording locations; with stimuli of small amplitude it was often possible to obtain modulation of the rostral part of the muscle only. The results demonstrate localization of proprioceptive reflexes, including the stretch reflex, within the splenius muscle.