Representation of binaural masking level difference in the inferior colliculus of the barn owl (tyto alba)
type: CreativeWork
description: Auditory detection and localization is important for animals and humans and crucial for barn owls. In natural environments, the spatial separation of signal and interfering noise improves detectability of the signal. In psychoacoustics experiments this is achieved by changing the spatial attributes of the sound, for example by shifting the phase of the tone or the noise in one ear. The improvement resulting from this shift was called “Binaural Masking Level Difference“ (BMLD). I recorded the activity of neurons in the central and external nuclei of the inferior colliculus (ICC and ICX, respectively) of the barn owl. These neurons are sensitive to a variation of the interaural delay. I tested three masking configurations: 1) the noise N and the tone S were set at the best interaural delays (BD), resulting in the NBDSBD configuration; 2) the noise was set at the best interaural delay but the tone was set at the best interaural delay with 180° phase shift, or the worst interaural delay (WD), resulting in the NBDSWD configuration, 3) the noise was set at the best interaural delay with 180° phase shift and the tone was set at the best delay (NWDSBD configuration). The noise level was held constant while the tone level was varied. The detection threshold was determined using the index of discrimination according to signal detection theory. BMLD is restricted to frequencies that allows conservation of time by phase locking (<3 kHz in mammals). In the owl phase locking is observed up to 9 kHz. Therefore, I expected BMLDs at higher frequencies than 3 kHz. In the first part of the study, I show exactly this. Due to distinct neural stations in the owl inferior colliculus, it was possible to address the hierarchy of detection and localization at the neuronal level. The ICC neurons are narrowly tuned to frequency and had lower detection thresholds than the ICX neurons. Since ICC neurons responded maximally to more than one ITD in their ITD function, they could not signal a speci…
abstract: Auditory detection and localization is important for animals and humans and crucial for barn owls. In natural environments, the spatial separation of signal and interfering noise improves detectability of the signal. In psychoacoustics experiments this is achieved by changing the spatial attributes of the sound, for example by shifting the phase of the tone or the noise in one ear. The improvement resulting from this shift was called “Binaural Masking Level Difference“ (BMLD). I recorded the activity of neurons in the central and external nuclei of the inferior colliculus (ICC and ICX, respectively) of the barn owl. These neurons are sensitive to a variation of the interaural delay. I tested three masking configurations: 1) the noise N and the tone S were set at the best interaural delays (BD), resulting in the NBDSBD configuration; 2) the noise was set at the best interaural delay but the tone was set at the best interaural delay with 180° phase shift, or the worst interaural delay (WD), resulting in the NBDSWD configuration, 3) the noise was set at the best interaural delay with 180° phase shift and the tone was set at the best delay (NWDSBD configuration). The noise level was held constant while the tone level was varied. The detection threshold was determined using the index of discrimination according to signal detection theory. BMLD is restricted to frequencies that allows conservation of time by phase locking (<3 kHz in mammals). In the owl phase locking is observed up to 9 kHz. Therefore, I expected BMLDs at higher frequencies than 3 kHz. In the first part of the study, I show exactly this. Due to distinct neural stations in the owl inferior colliculus, it was possible to address the hierarchy of detection and localization at the neuronal level. The ICC neurons are narrowly tuned to frequency and had lower detection thresholds than the ICX neurons. Since ICC neurons responded maximally to more than one ITD in their ITD function, they could not signal a speci…
author: Asadollahi, Ali
language: eng
keywords: info:eu-repo/classification/ddc/590, Tiere (Zoologie), Hearing, owl, BMLD, Binaural hearing, localization, detection
date published: 2006
date modified: 2026-07-30T19:43:28Z
provider: RWTH Aachen University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Publikationsserver der RWTH Aachen University