title: Structures that contribute to middle-ear admittance in chinchilla.
abstract: We describe measurements of middle-ear input admittance in chinchillas (Chinchilla lanigera) before and after various manipulations that define the contributions of different middle-ear components to function. The chinchilla's middle-ear air spaces have a large effect on the low-frequency compliance of the middle ear, and removing the influences of these spaces reveals a highly admittant tympanic membrane and ossicular chain. Measurements of the admittance of the air spaces reveal that the high-degree of segmentation of these spaces has only a small effect on the admittance. Draining the cochlea further increases the middle-ear admittance at low frequencies and removes a low-frequency (less than 300 Hz) level dependence in the admittance. Spontaneous or sound-driven contractions of the middle-ear muscles in deeply anesthetized animals were associated with significant changes in middle-ear admittance.
authors.affiliation: Eaton-Peabody of Auditory Physiology, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, MA, USA. John_Rosowski@meei.harvard.edu
authors.forename: John J
authors.initials: JJ
authors.lastname: Rosowski
authors.forename: Michael E
authors.initials: ME
authors.lastname: Ravicz
authors.forename: Jocelyn E
authors.initials: JE
authors.lastname: Songer
mesh_terms: D000158:Acoustic Impedance Tests; D000161:Acoustic Stimulation / Q000379:methods; D000162:Acoustics; D000818:Animals; D002682:Chinchilla / Q000033:anatomy & histology* / Q000502:physiology; D003051:Cochlea / Q000502:physiology; D004307:Dose-Response Relationship, Radiation; D004429:Ear Ossicles / Q000502:physiology; D004432:Ear, Middle / Q000033:anatomy & histology* / Q000502:physiology*; D013057:Spectrum Analysis; D014432:Tympanic Membrane / Q000502:physiology