Convergent Properties of Vestibular-Related Brain Stem Neurons in the Gerbil

• Published in: Journal of neurophysiology 2000-04, Vol.83 (4), p.1958-1971
• Main Authors: Kaufman, Galen D, Shinder, Michael E, Perachio, Adrian A
• Format: Article
• Language: English
• Subjects: Acceleration; Animals; Ear, Inner - physiology; Gerbillinae; Head Movements - physiology; Interneurons - physiology; Life Sciences (General); Oculomotor Nerve - physiology; Otolithic Membrane - physiology; Reaction Time - physiology; Reflex, Vestibulo-Ocular - physiology; Rotation; Space life sciences; Stereotaxic Techniques; Vestibular Nerve - physiology; Vestibular Nuclei - physiology; Wakefulness
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.2000.83.4.1958

Department of Otolaryngology, University of Texas Medical Branch, Galveston, Texas 77555-1063 Kaufman, Galen D., Michael E. Shinder, and Adrian A. Perachio. Convergent Properties of Vestibular-Related Brain Stem Neurons in the Gerbil. J. Neurophysiol. 83: 1958-1971, 2000. Three classes of vestibular-related neurons were found in and near the prepositus and medial vestibular nuclei of alert or decerebrate gerbils, those responding to: horizontal translational motion, horizontal head rotation, or both. Their distribution ratios were 1:2:2, respectively. Many cells responsive to translational motion exhibited spatiotemporal characteristics with both response gain and phase varying as a function of the stimulus vector angle. Rotationally sensitive neurons were distributed as Type I, II, or III responses (sensitive to ipsilateral, contralateral, or both directions, respectively) in the ratios of 4:6:1. Four tested factors shaped the response dynamics of the sampled neurons: canal-otolith convergence, oculomotor-related activity, rotational Type (I or II), and the phase of the maximum response. Type I nonconvergent cells displayed increasing gains with increasing rotational stimulus frequency (0.1-2.0 Hz, 60°/s), whereas Type II neurons with convergent inputs had response gains that markedly decreased with increasing translational stimulus frequency (0.25-2.0 Hz, ±0.1 g). Type I convergent and Type II nonconvergent neurons exhibited essentially flat gains across the stimulus frequency range. Oculomotor-related activity was noted in 30% of the cells across all functional types, appearing as burst/pause discharge patterns related to the fast phase of nystagmus during head rotation. Oculomotor-related activity was correlated with enhanced dynamic range compared with the same category that had no oculomotor-related response. Finally, responses that were in-phase with head velocity during rotation exhibited greater gains with stimulus frequency increments than neurons with out-of-phase responses. In contrast, for translational motion, neurons out of phase with head acceleration exhibited low-pass characteristics, whereas in-phase neurons did not. Data from decerebrate preparations revealed that although similar response types could be detected, the sampled cells generally had lower background discharge rates, on average one-third lower response gains, and convergent properties that differed from those found in the alert animals. On the basis of the dynamic response o