Spatial distribution of semicircular canal nerve evoked monosynaptic response components in frog vestibular nuclei

• Published in: Brain research Vol. 880; no. 1; pp. 70 - 83
• Main Authors: Straka, Hans, Biesdorf, Stefan, Dieringer, Norbert
• Format: Journal Article
• Language: English
• Published: London Elsevier B.V 13-10-2000; Amsterdam Elsevier; New York, NY
• Subjects: Animals; Biological and medical sciences; Brain - physiology; Brain Stem - physiology; Ear and associated structures. Auditory pathways and centers. Hearing. Vocal organ. Phonation. Sound production. Echolocation; Electric Stimulation; Evoked Potentials - physiology; Field potential; Fundamental and applied biological sciences. Psychology; In Vitro Techniques; Organotopic organization; Rana; Rana temporaria; Reaction Time; semicircular canals; Semicircular Canals - innervation; Synapses - physiology; Synaptic Transmission - physiology; Topographical mapping; Vertebrates: nervous system and sense organs; Vestibular Nerve - physiology; Vestibular nerve afferent fiber; Vestibular Nuclei - physiology; Field potential; Organotopic organization; Topographical mapping; Vestibular nerve afferent fiber; Motor systems and sensorimotor integration; Vestibular nerve; Vertebrata; Frog; Semicircular canal; Distribution; Amphibia; Electrophysiology; Afferent projection; Salientia; Vestibular system; Inner ear
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(00)02768-2

Most second-order vestibular neurons receive a canal-specific monosynaptic excitation, although the central projections of semicircular canal afferents overlap extensively. This remarkable canal specificity prompted us to study the spatial organization of evoked field potentials following selective stimulation of individual canal nerves. Electrically evoked responses in the vestibular nuclei were mapped systematically in vitro. Constructed activation maps were superimposed on a cytoarchitectonically defined anatomical map. The spatial activation maps for pre- and postsynaptic response components evoked by stimulation of a given canal nerve were similar. Activation maps for monosynaptic inputs from different canals tended to show a differential distribution of their peak amplitudes, although the overlap was considerable. Anterior vertical canal signals peaked in the superior vestibular nucleus, posterior vertical canal signals peaked in the descending and in the dorsal part of the lateral vestibular nucleus, whereas horizontal canal signals peaked in the descending and in the ventral part of the lateral vestibular nucleus. A similar, differential but overlapping, spatial organization of the canal inputs was described also for other vertebrates, suggesting a crude but rather conservative topographical organization of semicircular canal nerve projections within the vestibular nuclei. Differences in the precision of topological representations between vestibular and other sensory modalities are discussed.