# Optical and biophysical characterization of the vestibular periphery

> **NIH NIH R21** · UNIVERSITY OF ILLINOIS AT CHICAGO · 2020 · $239,850

## Abstract

Project Summary
 Prior research demonstrates that afferent responses from semicircular canal cristae and otolith organ
maculae deviate from the coherent mechanical stimulation imparted by their overlying accessory structures. This
implicates further processing by hair cells (HCs), primary afferents, and the HC - afferent synapse. Processing
is complicated by the parallel modes of synaptic transmission between HCs and afferents, and the convergence
of multiple HCs onto a single afferent. In the vestibular periphery progress towards describing variations in
afferent discharge in terms of the time course of underlying voltage- and ion-sensitive conductances has been
impeded by two major anatomical features of the vestibular epithelia: 1) access to HCs and afferents in their
native bi-ionic (endolymph - perilymph) environment is mechanically impeded, so there are few in situ recordings
to serve as controls for pathophysiology in recordings made from isolated cells or epithelial explants; and 2)
analysis of integration at the level of a ramifying afferent is complicated by multiple HC convergence onto each,
and the impossibility of using a single patch-electrode to space-clamp a distributed afferent arbor. To overcome
the inaccessibility problem associated with obtaining physiological data for vestibular HCs in their native
environment, we will measure voltages using slow, potentiometric (Nernstian) dyes, whose equilibrium partition
(concentration) is voltage-dependent. These dyes will be superfused across the vestibular and auditory epithelia
in a turtle half-head preparation. The voltage-dependent fluorescence of slow redistributive dyes will be
measured using multiphoton microscopy (MPM), and calibrated using microelectrode recordings from HCs,
afferents and supporting cells via the readily accessible perilymphatic space of the auditory papilla. The
type I HC/calyceal afferent synapse is relatively compact electrically, but HC convergence onto a single afferent
over distances of 10s to 100s of microns makes it difficult to address the passive and active properties of an
afferent arbor. As a consequence, it remains problematic to characterize afferent integration using conventional
electrophysiological techniques. We will examine afferent convergence by patch recording single afferents using
electrodes filled with electrochromic voltage-sensitive dyes (VSDs). Steady-state depolarizations and
hyperpolarizations of the afferent via the patch electrode will be used to optically characterize the passive cable
properties of the ramifying afferent using lattice light sheet microscopy (LLSM). Pulses of current injected through
the patch electrode, or electrical stimulation of the nerve - phase-locked to image acquisition on the LLSM - will
be used to image and average orthodromic and antidromic AP propagation in the parent axon and throughout
the afferent arbor. We propose novel approaches to make highly significant measures that are currently
unavailable....

## Key facts

- **NIH application ID:** 9894783
- **Project number:** 5R21DC017292-02
- **Recipient organization:** UNIVERSITY OF ILLINOIS AT CHICAGO
- **Principal Investigator:** JONATHAN JAMES ART
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $239,850
- **Award type:** 5
- **Project period:** 2019-04-01 → 2023-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9894783

## Citation

> US National Institutes of Health, RePORTER application 9894783, Optical and biophysical characterization of the vestibular periphery (5R21DC017292-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9894783. Licensed CC0.

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