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Journal ArticleDOI

Compound action potential (AP) tuning curves.

01 Mar 1976-Journal of the Acoustical Society of America (Acoustical Society of America)-Vol. 59, Iss: 3, pp 591-597
TL;DR: With a tone‐on‐tone masking procedure the compound action potential (AP), elicited by brief tone bursts of set frequency and intensity, was decreased by a constant fraction, and the frequency–intensity pairs formed by the masker generate the AP tuning curve.
Abstract: With a tone‐on‐tone masking procedure the compound action potential (AP), elicited by brief tone bursts of set frequency and intensity, was decreased by a constant fraction. The frequency–intensity pairs formed by the masker that yield this decrease generate the AP tuning curve. It is demonstrated that such tuning curves are very similar to both psychophysical tuning curves and single VIIIth‐nerve‐fiber tuning curves. Changes in the properties of these curves are described as functions of stimulus frequency and level, mode of masking (simultaneous and forward), and parameters of the masker.Subject Classification: [43]65.40, [43]65.42, [43]65.58.
Citations
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Journal ArticleDOI
TL;DR: The emergence of sensitive drive in such regions after prolonged recovery periods in lesioned animals thus suggests that the auditory cortical frequency map undergoes reorganization in cases of partial deafness.
Abstract: We have examined the effect of restricted unilateral cochlear lesions on the orderly topographic mapping of sound frequency in the auditory cortex of adult guinea pigs. These lesions, although restricted in spatial extent, resulted in a variety of patterns of histological damage to receptor cells and nerve fibres within the cochlea. Nevertheless, all lesions resulted in permanent losses of sensitivity of the cochlear neural output across a limited frequency range. Thirty-five to 81 days after such damage to the organ of Corti, the area of contralateral auditory cortex in which the lesioned frequency range would normally have been represented was partly occupied by an expanded representation of sound frequencies adjacent to the frequency range damaged by the lesion. The thresholds at their new characteristic frequencies (CFs) of clusters of cortical neurones in these regions were close to normal thresholds at those frequencies (mean difference across all animals was 3.8 dB). In a second series of experiments, the responses of neurone clusters were examined within hours of making similar cochlear lesions. It was found that shifts in CF toward frequencies spared by the lesions could occur, but thresholds were greatly elevated compared to normal (mean difference was 31.7 dB in five animals). The emergence of sensitive drive in such regions after prolonged recovery periods in lesioned animals thus suggests that the auditory cortical frequency map undergoes reorganization in cases of partial deafness. Some features of this reorganization are similar to changes reported in somatosensory cortex after peripheral nerve injury, and this form of plasticity may therefore be a feature of all adult sensory systems.

615 citations

Journal ArticleDOI
08 May 2008-Neuron
TL;DR: This work studies a mouse model without alteration to outer hair cell and organ of Corti mechanics or to mechanoelectric transduction, but with diminished prestin function, demonstrating that prestin-based electromotility is required for cochlear amplification.

352 citations


Cites background or methods from "Compound action potential (AP) tuni..."

  • ...The integrated intensity of prestin bands was measured in arbitrary units using Kodak ID Image Analysis software as described before (Cheatham et al., 2005)....

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  • ...In addition, a simultaneous, tone-on-tone masking paradigm (Dallos and Cheatham, 1976) was used to acquire CAP tuning curves....

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  • ...Included are compound action potential (CAP) threshold functions (Dallos et al., 1978; Johnstone et al., 1979) and CAP simultaneous masking tuning curves (Dallos and Cheatham, 1976)....

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  • ...Samples were washed with PBS, incubated with 2 antibodies, mounted on glass slides with Fluoromount-G (Southern Biotechnology Associates, Inc., Birmingham, AL), and observed with a Leica confocal system with a standard configuration DMRXE7 microscope....

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  • ...As a consequence, the average WT tuning curve appears to be more shallowly tuned than those published previously (Dallos and Cheatham, 1976; Cheatham et al., 2004, 2007)....

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Journal ArticleDOI
TL;DR: Although Tectb−/− mice have a low-frequency hearing loss, basilar-membrane and neural tuning are both significantly enhanced in the high-frequency regions of the cochlea, with little loss in sensitivity.
Abstract: Frequency tuning in the cochlea is determined by the passive mechanical properties of the basilar membrane and active feedback from the outer hair cells, sensory-effector cells that detect and amplify sound-induced basilar membrane motions. The sensory hair bundles of the outer hair cells are imbedded in the tectorial membrane, a sheet of extracellular matrix that overlies the cochlea's sensory epithelium. The tectorial membrane contains radially organized collagen fibrils that are imbedded in an unusual striated-sheet matrix formed by two glycoproteins, alpha-tectorin (Tecta) and beta-tectorin (Tectb). In Tectb(-/-) mice the structure of the striated-sheet matrix is disrupted. Although these mice have a low-frequency hearing loss, basilar-membrane and neural tuning are both significantly enhanced in the high-frequency regions of the cochlea, with little loss in sensitivity. These findings can be attributed to a reduction in the acting mass of the tectorial membrane and reveal a new function for this structure in controlling interactions along the cochlea.

179 citations

Journal ArticleDOI
TL;DR: Data support the idea that forward transduction is not degraded in OHCs lacking prestin, and frequency selectivity in CAP tuning curves recorded in homozygotes is demonstrated.
Abstract: Gross-potential recordings in mice lacking the Prestin gene indicate that compound action potential (CAP) thresholds are shifted by ∼45 dB at 5 kHz and by ∼60 dB at 33 kHz. However, in order to conclude that outer hair cell (OHC) electromotility is associated with the cochlear amplifier, frequency selectivity must be evaluated and the integrity of the OHC's forward transducer ascertained. The present report demonstrates no frequency selectivity in CAP tuning curves recorded in homozygotes. In addition, CAP input–output functions indicate that responses in knockout mice approach those in controls at high levels where the amplifier has little influence. Although the cochlear microphonic in knockout mice remains ∼12 dB below that in wild-type mice even at the highest levels, this deficit is thought to reflect hair cell losses in mice lacking prestin. A change in OHC forward transduction is not implied because knockout mice display non-linear responses similar to those in controls. For example, homozygotes exhibit a bipolar summating potential (SP) with positive responses at high frequencies; negative responses at low frequencies. Measurement of intermodulation distortion also shows that the cubic difference tone, 2f1–f2, is ∼20 dB down from the primaries in both homozygotes and their controls. Because OHCs are the sole generators of the negative SP and because 2f1–f2 is also thought to originate in OHC transduction, these data support the idea that forward transduction is not degraded in OHCs lacking prestin. Finally, application of AM1-43, which initially enters hair cells through their transducer channels, produces fluorescence in wild-type and knockout mice indicating transducer channel activity in both inner and outer hair cells.

155 citations


Cites background or methods from "Compound action potential (AP) tuni..."

  • ...In addition to threshold determinations, tone-on-tone masking curves (Dallos & Cheatham, 1976a) were also obtained to generate CAP tuning curves....

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  • ...Although IHCs probably make some contribution to the CM, evidence suggests that this response is dominated by OHC receptor currents (Dallos & Wang, 1974; Dallos & Cheatham, 1976b; Patuzzi et al. 1989a)....

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Journal ArticleDOI
14 Dec 1989-Nature
TL;DR: It is suggested that frequency selectivity in the organ of Corti is amplified by the tuned motility of the cell body of outer hair cells, which shows a sharply tuned motile behaviour when the stimulus frequency is varied between 200 and 10,000 Hz.
Abstract: The inner ear is capable of highly selective frequency discrimination. This is achieved not only by the travelling wave of the basilar membrane in the cochlear partition, but also by the active participation of nonlinear and vulnerable elements that enhance frequency selectivity. It has been shown that isolated mammalian outer hair cells respond with a change in length when subjected to sound stimulation at a fixed frequency. Here we investigate the motile behaviour of isolated cells when the stimulus frequency is varied between 200 and 10,000 Hz. By varying the frequency and the intensity of the tone, it is possible to obtain 'tuning curves' for the motile response. We demonstrate that the cell body of solitary hair cells, free from contact with the basilar membrane, shows a sharply tuned motile behaviour. We suggest that frequency selectivity in the organ of Corti is amplified by the tuned motility of the cell body of outer hair cells.

154 citations