# Neural basis of precedence-type sound localization processes

> **NIH DC R21** · UTAH STATE HIGHER EDUCATION SYSTEM--UNIVERSITY OF UTAH · 2026 · $189,530

## Abstract

Project Summary
This research project aims to study the neural basis of the precedence-type sound localization processes,
including the Franssen effect. This central computation is key to understanding the normal function of auditory
perception and is a priority area in NIH's hearing research. The precedence phenomena play a critical role in
speech-in-noise, dichotic, and temporal processing, in addition to source location and echo identification.
Illusions such as these are distortions in perception that provide insights into the workings of the auditory system.
The basic precedence effect consists of two ‘identical’ tone bursts are presented with various timing relations
from separate loudspeakers situated on either side; the listener perceives a single ‘fused’ sound as coming from
the speaker that broadcasted the leading sound. The Franssen effect is an illusion where the listener incorrectly
perceives the sound as coming from a loudspeaker that broadcasts a leading short-duration sound pulse with a
fast amplitude rise and slow decay. This happens despite most of the sound originating from a contralaterally
placed lagging loudspeaker producing long-duration sound with a slow onset. The proposed research takes
advantage of the natural preference of a species of gray treefrogs (Hyla versicolor) for slow-rise, long-duration
(SR-LD) sound pulses that represent those used to elicit FE illusions. In choice tests, H. versicolor females
strongly prefer SR-LD sound pulses over the fast-rise, short-duration (FR-SD) pulses of their sister species Hyla
chrysoscelis and approach the transducer broadcasting the former. In aim 1, we plan to conduct behavioral
experiments that take advantage of this natural preference. We hypothesize that subjects will erroneously
approach a loudspeaker broadcasting FR-SD pulses when they precede SR-LD pulses form an orthogonally
placed loudspeaker. In aim 2, we propose to make extracellular recordings from single neurons in the anuran
inferior 

## Key facts

- **NIH application ID:** 11306642
- **Project number:** 5R21DC022648-02
- **Recipient organization:** UTAH STATE HIGHER EDUCATION SYSTEM--UNIVERSITY OF UTAH
- **Principal Investigator:** Rishi Kiran Alluri
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** DC
- **Fiscal year:** 2026
- **Award amount:** $189,530
- **Award type:** 5
- **Project period:** 2025-04-01T00:00:00 → 2028-03-31T00:00:00

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/11306642

## Citation

> US National Institutes of Health, RePORTER application 11306642, Neural basis of precedence-type sound localization processes (5R21DC022648-02). Retrieved via AI Analytics 2026-07-14 from https://api.ai-analytics.org/grant/nih/11306642. Licensed CC0.

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