# Initial Stages of Olfactory Information Processing

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA, SAN DIEGO · 2020 · $316,199

## Abstract

PROJECT SUMMARY/ABSTRACT
The long-term goal of this project is to reveal the mechanisms by which complex odors are encoded, with a
special focus on the initial stages of olfactory information processing. The research design takes advantage of
the anatomical simplicity and powerful genetic toolkit of Drosophila melanogaster, which allows systematic
molecular genetic analysis of olfactory circuits as well as in-depth physiological and behavioral analysis of
olfactory function. The results may have major implications for the control of insect vectors of disease.
The project focuses on ephaptic interactions, a novel, non-synaptic form of olfactory circuit communication,
which take place between any two grouped olfactory receptor neurons (ORNs) housed in the same insect
sensory hair (sensillum). Despite its ubiquity, how ephaptic communication regulates olfactory function and
behavior is poorly understood. We recently provided the first description of the importance of ephaptic
inhibition in insect olfaction. In the current study, we will first focus on defining the importance of ephaptic
excitation. A systematic, functional survey will be performed to define the strength of ephaptic excitation
between grouped ORNs (Aim 1). The respective electrotonic properties of grouped ORNs will also be
determined (Aim 2). The strength of ephaptic interactions will be quantified between a pair of ORNs from both
directions with a view to testing the hypothesis that ephaptic interactions are asymmetric across sensillum
types. Furthermore, the ultrastructure of grouped ORNs will be described using serial block-face electron
microscopy (SBEM) and 3D reconstruction imaging technologies (Aim 3). This Aim is designed to identify the
biophysical factors that underlie asymmetric ephaptic interactions in a sensillum. Morphological features of an
identified ORN, such as dendritic caliber, number of dendritic branches, as well as soma size, will be analyzed
and compared between neighboring ORNs. The hypothesis that the physically larger ORN in a pair exerts
stronger ephaptic interactions upon its neighbor will be tested. This Aim could also lead to critical technical
breakthroughs to broaden the application of SBEM in illuminating the 3D ultrastructure of any identified cell in
diverse tissues. Lastly, the functional importance of ephaptic interactions in odor-guided behavior will be
determined (Aim 4). Specifically, we will extend our behavioral assay and define the role of ephaptic inhibition
on courtship behavior in sensillum which houses ORNs responsive to pheromone cues. We will also perform
the first test of the functional importance of ephaptic excitation between another ORN pair that mediates
behavioral responses to food odors.
The proposed research will determine the functional importance and biophysical principles of a novel form of
olfactory circuit interaction mechanism. These findings have the potential to revolutionize our understanding of
olfactory information ...

## Key facts

- **NIH application ID:** 9928408
- **Project number:** 5R01DC015519-05
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN DIEGO
- **Principal Investigator:** Chih-Ying Su
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $316,199
- **Award type:** 5
- **Project period:** 2016-06-06 → 2021-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9928408

## Citation

> US National Institutes of Health, RePORTER application 9928408, Initial Stages of Olfactory Information Processing (5R01DC015519-05). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/9928408. Licensed CC0.

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