Neural Interruption by Unilateral Labyrinthectomy Biases the Directional Preference of Otolith-Related Vestibular Neurons

Abstract

Background: The directional preference of otolith-related vestibular neurons elucidates the neuroanatomical link of labyrinths, but few direct experimental data have been provided. Methods: The directional preference of otolith-related vestibular neurons was measured in the vestibular nucleus using chemically induced unilateral labyrinthectomy (UL). For the model evaluation, static and dynamic behavioral tests as well as a histological test were performed. Extracellular neural activity was recorded for the neuronal responses to the horizontal head rotation and the linear head translation. Results: Seventy-seven neuronal activities were recorded, and the total population was divided into three groups: left UL (20), sham (35), and right UL (22). Based on directional preference, two sub-groups were again classified as contra- and ipsi-preferred neurons. There was no significance in the number of those sub-groups (contra-, 15/35, 43%; ipsi-, 20/35, 57%) in the sham (p = 0.155). However, more ipsi-preferred neurons (19/22, 86%) were observed after right UL (p = 6.056 × 10−5), while left UL caused more contra-preferred neurons (13/20, 65%) (p = 0.058). In particular, the convergent neurons mainly led this biased difference (ipsi-, 100% after right UL and contra-, 89% after left UL) (p < 0.002). Conclusions: The directional preference of the neurons depended on the side of the lesion, and its dominance was mainly led by the convergent neurons.