Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2014 May 23;8:110. doi: 10.3389/fnins.2014.00110

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

Copyright © 2014 Gold and Bajo.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

PMC Copyright notice

Unilateral conductive hearing loss yields conflicting reports of tinnitus generation in adult human and non-human normal-hearing subjects. (A) Chronic (>7 days) insertion of an earplug into one ear produced subjective reports of tinnitus in 10/18 human listeners, evaluated on a tinnitus similarity likeness scale; the group average tinnitus likeness indicated the development of a low-pass sensation peaking between 8 and 12 kHz. Inset is the attenuation function for earplug insertion, indicating a sloping attenuation of high-frequency stimuli up to ~30 dB SPL for stimuli >3–4 kHz. Modified with permission from Schaette et al. (2012). (B) Using GPIAS as a surrogate reporter of tinnitus presence in adult normal-hearing rats, unilateral earplug insertion also revealed tinnitus-like symptoms, as a reduction in startle-suppression efficacy for gaps inserted into carrier noise (60 dB SPL) narrow-bandpassed at 12, 16, 20, and 24 kHz. No such reduction developed for a 6 kHz narrowband carrier. Gray bars = baseline startle suppression ratio; black bars = plug startle suppression ratio; asterisk = significant difference within frequency band compared to baseline (p < 0.05). Modified with permission from Lobarinas et al. (2013a). (C) Conversely, testing of the effects of unilateral plugging on an operant sound detection task for stimuli presented at 10 kHz (upper) and lower (20 kHz) in adult rats showed there to be no effect upon detection functions for either stimulus bandwidth; by contrast, animals that underwent acoustic overexposure (narrowband noise centered at 16 kHz, 105 dB SPL, 1 h) displayed marked reduction in detection functions at 20 kHz, interpreted as the presence of tinnitus whose spectral content matched that frequency band. Control = open circles; normal-hearing with plug = filled squares; acoustic trauma without plug = open squares. Modified with permission from Bauer and Brozoski (2001). (D) A similar evaluation of the effects of unilateral earplug in adult rats found no difference between GPIAS functions in the same subjects prior to and following earplug insertion. Background noise was centered at 10 kHz, at which plug insertion produced a mean attenuation of 22 dB SPL. Modified with permission from Turner et al. (2006).