Back to Search
Start Over
Effect of infrasound on cochlear damage from exposure to a 4kHz octave band of noise
- Source :
-
Hearing Research . Mar2007, Vol. 225 Issue 1/2, p128-138. 11p. - Publication Year :
- 2007
-
Abstract
- Abstract: Infrasound (i.e., <20Hz for humans; <100Hz for chinchillas) is not audible, but exposure to high-levels of infrasound will produce large movements of cochlear fluids. We speculated that high-level infrasound might bias the basilar membrane and perhaps be able to minimize noise-induced hearing loss. Chinchillas were simultaneously exposed to a 30Hz tone at 100dB SPL and a 4kHz OBN at either 108dB SPL for 1.75h or 86dB SPL for 24h. For each animal, the tympanic membrane (TM) in one ear was perforated (∼1mm2) prior to exposure to attenuate infrasound transmission to that cochlea by about 50dB SPL. Controls included animals that were exposed to the infrasound only or the 4kHz OBN only. ABR threshold shifts (TSs) and DPOAE level shifts (LSs) were determined pre- and post-TM-perforation and immediately post-exposure, just before cochlear fixation. The cochleae were dehydrated, embedded in plastic, and dissected into flat preparations of the organ of Corti (OC). Each dissected segment was evaluated for losses of inner hair cells (IHCs) and outer hair cells (OHCs). For each chinchilla, the magnitude and pattern of functional and hair cell losses were compared between their right and left cochleae. The TM perforation produced no ABR TS across frequency but did produce a 10–21dB DPOAE LS from 0.6 to 2kHz. The infrasound exposure alone resulted in a 10–20dB ABR TS at and below 2kHz, no DPOAE LS and no IHC or OHC losses. Exposure to the 4kHz OBN alone at 108dB produced a 10–50dB ABR TS for 0.5–12kHz, a 10–60dB DPOAE LS for 0.6–16kHz and severe OHC loss in the middle of the first turn. When infrasound was present during exposure to the 4kHz OBN at 108dB, the functional losses and OHC losses extended much further toward the apical and basal tips of the OC than in cochleae exposed to the 4kHz OBN alone. Exposure to only the 4kHz OBN at 86dB produces a 10–40dB ABR TS for 3–12kHz and 10–30dB DPOAE LS for 3–8kHz but little or no OHC loss in the middle of the first turn. No differences were found in the functional and hair-cell losses from exposure to the 4kHz OBN at 86dB in the presence or absence of infrasound. We hypothesize that exposure to infrasound and an intense 4kHz OBN increases cochlear damage because the large fluid movements from infrasound cause more intermixing of cochlear fluids through the damaged reticular lamina. Simultaneous infrasound and a moderate 4kHz OBN did not increase cochlear damage because the reticular lamina rarely breaks down during this moderate level exposure. [Copyright &y& Elsevier]
- Subjects :
- *COCHLEAR implants
*ELECTROCOCHLEOGRAPHY
*BASILAR membrane
*DEAFNESS
Subjects
Details
- Language :
- English
- ISSN :
- 03785955
- Volume :
- 225
- Issue :
- 1/2
- Database :
- Academic Search Index
- Journal :
- Hearing Research
- Publication Type :
- Academic Journal
- Accession number :
- 24141156
- Full Text :
- https://doi.org/10.1016/j.heares.2007.01.016