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Local cochlear damage reduces local nonlinearity and decreases generator-type cochlear emissions while increasing reflector-type emissions
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Image of FIG. 1.
FIG. 1.

Simultaneous measurement of DP and DPOAE and locally damaged cochlea. (A) DPAOE was measured in the ear canal pressure responses close to the eardrum with a sensitive microphone with two-tone stimuli to the ear canal in a closed-field sound configuration (sound system coupled to the ear canal opening with bone wax). Simultaneously, the intracochlear DP was measured in ST pressure responses in turn one with a micro-pressure-sensor. (B) Sensor positioned close to the basilar membrane. (C) Sensor indenting the cochlear partition. BM: basilar membrane; IHC: inner hair cells; OHC: outer hair cells; ST: scala tympani; SV: scala vestibuli; TM: tectorial membrane.

Image of FIG. 2.
FIG. 2.

Gerbil DPOAE includes multiple types. (A) Amplitude and (B) phase of DPOAE obtained from one animal (wg97, SPL, and 1.25, frequency ). Phases were normalized to ear canal and phases. Dashed and solid lines represent responses with of 1.05 and 1.25, respectively. The fine structure in the amplitude and different phase slopes indicate that the DPOAE is a combination of multiple types.

Image of FIG. 3.
FIG. 3.

CAP thresholds before and after local damage. Solid and dashed lines indicate healthy and locally damaged conditions (wg95 and wg122).

Image of FIG. 4.
FIG. 4.

Cochlear mechanics before and after local damage. Single-tone intracochlear pressure responses measured at the same location, close to the BM pre- and post-damage in two animals (wg95 and wg122). [(A) and (C)] Pre-damage gain relative to stimulus pressure in the ear canal; [(B) and (D)] Post-damage gain. Stimulus SPLs are labeled. [(E) and (F)] Single-tone pressure phase referenced to EC. Solid and dashed lines represent the cochlear conditions, healthy or locally damaged, respectively.

Image of FIG. 5.
FIG. 5.

with in the cochlea (DP) and ear canal (DPOAE) pre- and post-damage. (A) DP amplitude, measured at a distance from the BM; (B) DPOAE amplitude; (C) DP phase; and (D) DPOAE phase. All phases are referenced to EC and phases. Solid and dashed lines represent cochlear condition, healthy or locally damaged. Gray line in panel (C) shows phase. There was no change in the low frequency region below 6 kHz (wg95, SPL).

Image of FIG. 6.
FIG. 6.

with in the cochlea (DP) and ear canal (DPOAE) pre- and post-damage. Same format as Fig. 5 (wg95, SPL).

Image of FIG. 7.
FIG. 7.

DP and DPOAE of animal wg122. DP was measured at from the BM pre- and post-damage ( SPL, frequency step was 0.5 kHz). Same format as Fig. 5.

Image of FIG. 8.
FIG. 8.

CAP threshold shifts and changes in DPOAE level upon local damage. Thick and thin lines show changes in DPOAE and CAP thresholds upon damage. [(A)–(D)] , plotted vs ; [(E)–(H)] plotted vs frequency. Data were from locally damaged experiments wg95, wg96, wg122, and wg131. Gray bands show the damaged region based on the sensor location ( region) and verified with CAP changes in animals wg95 and wg122.

Image of FIG. 9.
FIG. 9.

Using DPOAE to gauge the cochlear condition (five animals). The darker gray bands display average DPOAE and the lighter gray bands the average CAP thresholds across eight animals with normal CAP thresholds. The width of the bands indicates the standard deviation. The lines show DPOAE and CAP results from individual animals. The thicker lines show DPOAE levels, with the solid line pre-damage and the dotted line post-damage. The thinner lines show the corresponding CAP thresholds curves, solid pre-damage, and dotted post-damage. The DPOAE shown is at frequency with , .

Image of FIG. 10.
FIG. 10.

DPOAE pre- and post-damage phases. Data from experiments wg91, wg92, wg93, wg95, wg122, and wg131. The 20 kHz region was damaged either by locally indenting the BM or by the invasive intracochlear measurement. Solid and dashed lines represent the phase under healthy and locally damaged conditions, respectively. The DPOAE shown is at frequency with or 90 dB and . The gray line shows an example of two times forward phase with BF .


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Local cochlear damage reduces local nonlinearity and decreases generator-type cochlear emissions while increasing reflector-type emissions