Middle-ear and inner-ear contribution to bone conduction in chinchilla: The development of Carhart's notch

Abstract

While the cochlea is considered the primary site of the auditory response to bone conduction (BC) stimulation, the paths by which vibratory energy applied to the skull (or other structures) reaches the inner ear are a matter of continued investigation. We present acoustical measurements of sound in the inner ear that separate out the components of BC stimulation that stimulate the inner ear via ossicular motion (compression of the walls of the ear canal or ossicular inertia) from the components that act directly on the cochlea (cochlear compression or inertia, and extra-cochlear ‘third-window’ pathways). The results are consistent with our earlier suggestion that the inner-ear mechanisms play a large role in bone-conduction stimulation in the chinchilla at all frequencies. However, the data also suggest the pathways that conduct vibration to the inner ear via ossicular-motion make a significant contribution to the response to BC stimulation in the 1 to 3 kHz range, such that interruption of these path leads to a 5 dB reduction in total stimulation in that frequency range. The mid-frequency reduction produced by ossicular manipulations is similar to the ‘Carhart's notch’ phenomenon observed in otology and audiology clinics in cases of human ossicular disorders. We also present data consistent with much of the ossicular-conducted sound in chinchilla depending on occlusion of the ear canal.

Identification of induced and naturally occurring conductive hearing loss in mice using bone conduction

“…A difference is that the ‘notch’ occurs in the middle of the human auditory range (2 to 4 kHz), while the BC sensitivity changes we observe in mice with conductive impairments are in the lower frequency range of hearing, 5 to 8 kHz. Since only a little is known about the contribution of the multiple stimulus pathways that contribute to BC in different animals (Tonndorf et al 1966b; Chhan et al 2013; 2016), the difference in the frequency range where conductive impairments affect BC thresholds in mice and men may reflect a difference in the frequency dependence of components of BC hearing that depend on ossicular transmission of sound or the normal middle-ear load (Stenfelt et al 2002; Stenfelt & Goode 2005; Kim et al 2011; Stenfelt 2015; Chhan et al 2016). Consistent with such interspecies variations, the largest effects of middle-ear manipulation on BC-evoked cochlear potentials in cats occurred between 250 and 1000 Hz (Tonndorf et al 1966a; Tonndorf, 1972).…”

“…Consistent with such interspecies variations, the largest effects of middle-ear manipulation on BC-evoked cochlear potentials in cats occurred between 250 and 1000 Hz (Tonndorf et al 1966a; Tonndorf, 1972). Bone-conduction experimental work in chinchillas, dogs, and rats, however, suggests that middle-ear bone conduction pathways make significant contributions to the BC response in a mid-range of frequencies (Tonndorf et al 1966b; Chhan et al, 2013, 2016). …”

“…Tonndorf and Tabor, 1962; Tonndorf et al 1966a&b; Tonndorf 1972; Steel et al, 1987; Chhan et al 2013, 2016), but in general their use has been limited to investigations of how specific anatomical manipulations affected the response to BC sound. Here, we examine the use of a new technique to quantify the sensitivity to BC in different strains of mice with the idea of developing test standards, which, when combined with well-controlled standard AC sensitivity measurements, will allow independent determinations of conductive and sensory-neural hearing function.…”

Az otoscleroticus eredetű hallócsontláncolati fixatiók klinikuma

“…Emellett a csontvezetéses görbén típusos esetben 2000 Hz-en csipkeszerű hallásküszöbemelkedés látható, ez az ún. Carhart-csipke [11,12]. A pre-és a posztoperatív eredmények leginkább a csontlég-köz értékeinek összehasonlításával jellemezhetők [13] (2. ábra).…”

Effectiveness of Bone Conduction Stimulation Applied Directly to the Otic Capsule Measured at Promontory: Assessment in Cadavers

“…BC is also believed to reflect the cochlear function DOI: 10.1159/000505607 in hearing. Unlike AC, BC is a collection of parallel mechanisms initiated by vibrations applied to the skull that lead to hearing sensation [Chhan et al, 2013[Chhan et al, , 2016Stenfelt, 2011;Stenfelt and Goode, 2005a;Stenfelt et al, 2002Stenfelt et al, , 2003Tonndorf, 1966;vonBékésy, 1960]. Two groups of multiple BC stimulus pathways to the inner ear that contribute to BC hearing have been proposed in the literature: (1) the middle ear conduction group and (2) the direct inner ear stimulation group.…”