Visuo-Vestibular Information Processing by Unipolar Brush Cells in the Rabbit Flocculus

TL;DR

This study explores how unipolar brush cells in rabbits process visuo-vestibular information, revealing their roles in transforming velocity to acceleration signals.

Contribution

The study identifies diverse modulation profiles of UBCs in visuo-vestibular processing and suggests their involvement in signal transformation.

Findings

UBCs in anesthetized rabbits showed varied modulation profiles related to head velocity or acceleration.

In awake rabbits, UBCs also carried eye position signals and exhibited long response latencies.

The findings suggest UBCs may transform velocity-related signals to acceleration-related signals.

Abstract

The unipolar brush cell (UBC) is a glutamatergic granular layer interneuron that is predominantly located in the vestibulocerebellum and parts of the vermis. In rat and rabbit, we previously found using juxtacellular labeling combined with spontaneous activity recording that cells with highly regular spontaneous activity belong to the UBC category. Making use of this signature, we recorded from floccular UBCs in both anesthetized and awake rabbits while delivering visuo-vestibular stimulation by using sigmoidal rotation of the whole animal. In the anesthetized rabbit, the activity of the presumed UBC units displayed a wide variety of modulation profiles that could be related to aspects of head velocity or acceleration. These modulation profiles could also be found in the awake rabbit where, in addition, they could also carry an eye position signal. Furthermore, units in the awake rabbit could demonstrate rather long response latencies of up to 0.5 s. We suggest that the UBCs recorded in this study mostly belong to the type I UBC category (calretinin-positive) and that they can play diverse roles in floccular visuo-vestibular information processing, such as transformation of velocity-related signals to acceleration-related signals.

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