Directional preference of otolith-related neurons in vestibular nucleus

Abstract

Background: Due to the paired structure of two labyrinths at both sides of ear, their communication is conducted through the interconnected commissural pathway. The close interconnection produces the neural responding property in vestibular nucleus, and the mechanical movement of the hair cells mainly specifies the property. However, the mechanism to initiate the responding property was evident based on the structure, but few direct experimental data were provided to understand the responding property based on the structure.Experimental Approach: The directional preference was investigated, which was one of critical neural responding property to illustrate the functional structure. Also, a chemically induced unilateral labyrinthectomy (UL) was performed to emphasize the preference. For the model evaluation, static and dynamic behavioral tests were applied, and the results demonstrated a practical model construction. Following the evaluation, an extracellular neural activity was conducted for the neuronal responses to the horizontal head rotation and the linear head movement.Results: Seventy seven neuronal activities were recorded from thirty SD rats (270-450 g, male), and total population was divided into three groups; left UL (20), sham (35), right UL (22). Based on the directional preference, two sub-groups were again classified as contra- and ipsi-preferred neurons. There was no significance between those sub-groups (contra-: 15/35, 43%; ipsi-: 20/35, 57%) in sham model. However, more ipsi-preferred neurons (19/22, 86%) were observed after right UL while left UL caused more contra-preferred neurons (13/20, 65%). In particular, the convergent neurons mainly led this biased difference in the population (ipsi-: 100% after right UL & contra-: 89% after left UL).Conclusion: The directional preference was evenly maintained under a normal vestibular function, and its unilateral loss biased the directional preference of the neurons, depending on the side of lesion. Moreover, the dominance of the directional preference was mainly led by the convergent neurons which had the neural information related with head rotation and linear translation.