Semicircular Canal and Macular Influences on Neck Motoneurons

Publisher Summary This chapter highlights the influences of semicircular canal and macular on neck motoneurons. Synaptic potentials were recorded in cat dorsal neck motoneurons in response to stimulation of individual ampullary nerves or macular nerves. Disynaptic excitatory postsynaptic potential (EPSP) and inhibitory postsynaptic potential (IPSPs) were seen in dorsal neck motoneurons by stimulation of individual ampullary nerves. The early disynaptic potentials were usually followed by later components. Dorsal neck motoneurons are excited by stimulation of the two anterior canals, inhibited from the two posterior ampullae. A majority of these motoneurons were inhibited from the ipsilateral, excited from the contralateral horizontal canal. Splenius motoneurons are influenced most consistently from the horizontal canal. Stimulation of the saccular nerve usually evoked IPSPs in contralateral, EPSPs in ipsilateral neck motoneurons. Many of the potentials were probably disynaptic, though some were trisynaptic. The effects of utricular nerve were complex, perhaps because of contamination by canal afferents. The predominant effects consisted of ipsilateral inhibition and contralateral excitation.