Response of vestibular neurons to head rotations in vertical planes. I. Response to vestibular stimulation

Abstract

1. We have studied, in decerebrate cats, the responses of neurons in the lateral and descending vestibular nuclei to whole-body rotations in vertical planes that activated vertical semicircular canal and utricular receptors. Some neurons were identified as vestibulospinal by antidromic stimulation with floating electrodes placed in C4. 2. The direction of tilt that caused maximal excitation (response vector orientation) of each neuron was determined. Neuron dynamics were then studied with sinusoidal stimuli closely aligned with the response vector orientation, in the range 0.02-1 Hz. A few cells, for which we could not identify a response vector, probably had spatial-temporal convergence. 3. On the basis of dynamics, neurons were classified as receiving their input primarily from vertical semicircular canals, primarily from the otolith organs, or from canal+otolith convergence. 4. Response vector orientations of canal-driven neurons were often near +45 degrees or -45 degrees with respect to the transverse (roll) plane, suggesting these neurons received excitatory input from the ipsilateral anterior or posterior canal, respectively. Some neurons had canal-related dynamics but vector orientations near roll, presumably because they received convergent input from the ipsilateral anterior and posterior canals. Few neurons had their vectors near pitch. 5. In the lateral vestibular nucleus, neurons with otolith organ input (pure otolith or otolith+canal) tended to have vector orientations closer to roll than to pitch. In the descending nucleus the responses were evenly divided between the roll and pitch quadrants. 6. We conclude that most of our neurons have dynamics and response vector orientations that make them good candidates to participate in vestibulospinal reflexes acting on the limbs, but not those acting on the neck.

Responses of caudal vestibular nucleus neurons of conscious cats to rotations in vertical planes, before and after a bilateral vestibular neurectomy

“…Some vestibular nucleus neurons, which we refer to as spatiotemporal convergence (STC) units, respond as though they receive vestibular inputs from receptors with differing spatial and frequency components (such as graviceptive and velocity responses with different spatial orientations) (Baker et al 1984;Kasper et al 1988;Schor and Angelaki 1992). The response vector orientations for such cells vary as a function of tilt frequency; furthermore, the gains of responses to CW and CCW wobble rotations are usually significantly different (Kasper et al 1988;Schor and Angelaki 1992). To determine if STC neurons are present in the CVN, the ratio of the gain of the responses to CW and CCW wobble stimulation was determined for the highest frequency rotations employed for a unit (usually 0.5 Hz), where the STC response is expected to be most evident.…”

“…Although a variety of studies have considered the responses of vestibular nucleus neurons to rotations and translations of the head (e.g., Chubb et al 1984;Kasper et al 1988;Gdowski and McCrea 1999;Dickman and Angelaki 2002;Zhou et al 2006), virtually all of these experiments have focused on units in the rostral or middle portions of the nuclear complex. With the exception of a small GABAergic cell population that comprises the parasolitary nucleus (Barmack and Yakhnitsa 2000), the caudal vestibular nuclei (CVN) have not been extensively studied, particularly in conscious animals.…”

Response Linearity of Alert Monkey Non-Eye Movement Vestibular Nucleus Neurons During Sinusoidal Yaw Rotation

“…The majority of such studies have concentrated on frequency-response characteristics, including the development of transfer functions to describe the dynamics of the responses in terms of linear systems theory (Angelaki et al 2001;Buettner et al 1978;Dickman and Angelaki 2004;Fuchs and Kimm 1975;Milsum 1970, 1971;Ramachandran and Lisberger 2008;Shinoda and Yoshida 1974). In some seminal literature, investigators varied frequency while holding the amplitude of excursion constant, which varied peak velocity with frequency (Boyle and Pompiano 1981;Buettner et al 1978;Chubb et al 1984;Dickman and Angelaki 2004;Fuchs and Kimm 1975;Kasper et al 1988;Shinoda and Yoshida 1974). Conclusions about the frequency response characteristics of neurons from experiments designed as such rely on the linearity of the system over the range of stimulus velocities that were applied; the findings in this study should influence the interpretation of those results.…”

Bilateral Otolith Contribution to Spatial Coding in the Vestibular System

“…The functional properties of central vestibular neurons in coding head movements have been extensively studied in monkeys [99,108], cats [24,31,32,74,122,123,157] and rats [4,27,[84][85][86]. In response to vestibular stimulation, neurons in the vestibular nuclei show more complicated response patterns than those in the peripheral afferents [13,27,74,84,157].…”