Influence of stimulation of auditory and somatosensory systems on the activity of vestibular nuclear neurons in the frog.
In the frog, we have recorded extracellularly the activity of vestibular nuclear neurons driven by the horizontal semicircular canals. About 28% of the neurons recorded (n = 300) responded to auditory stimulation (clicks 150/s and pure tones 300-2,000 Hz, about 80 dB above threshold) or to somatosensory stimulation (electrical stimulation of the ipsilateral or contralateral sciatic nerve and vibratory stimulation of the ipsilateral gastrocnemius). Whatever the stimulus, the response was always an increase of the discharge frequency. Such a frequency increase was much more important for somatosensory stimulation (62-145%) than for auditory (20%) and sciatic nerve input was about twice as efficient as gastrocnemius input. Except for type IV units which were only exceptionally recorded, all the other neuronal types (according to Duensing and Schaefer 's classification, 1959) responded to auditory or somatosensory volleys. In particular, activation of type III units, which are partly efferent vestibular neurons ending at the base of the sensory hair cells, may result in a modulation of the peripheral vestibular discharges. The latencies of the responses varied over a wide range (5-40 ms); long latency responses are probably mediated by polysynaptic pathways including the reticular formation and/or the cerebellum, and short latency ones by oligosynaptic pathways. These pathways and the functional meaning of convergence of auditory and somatosensory input onto vestibular nuclei are discussed.
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001307:Auditory Perception / Q000502:physiology*; D004292:Dominance, Cerebral / Q000502:physiology; D005071:Evoked Potentials; D008465:Mechanoreceptors / Q000502:physiology*; D009132:Muscles / Q000294:innervation; D009474:Neurons / Q000502:physiology; D011893:Rana esculenta; D012584:Sciatic Nerve / Q000502:physiology*; D014726:Vestibular Nuclei / Q000502:physiology*