Identifying Dead Regions in the Cochlea: Psychophysical Tuning Curves and Tone Detection in Threshold-Equalizing Noise

Abstract

The 56% agreement rate between the TEN and PTC tasks indicates that at least one of these tasks was only partially reliable as a diagnostic tool. Factors unrelated to the presence of dead regions may contribute to excess masking in TEN without producing tip shifts in PTCs. Thus it may be appropriate to view tuning curve results as more reliable in cases where TEN and PTC results disagree. The current results do not provide support for the TEN task as a reliable diagnostic tool for identification of dead regions.

The relative phonetic contributions of a cochlear implant and residual acoustic hearing to bimodal speech perception

“…The 500 Hz cutoff of the simulation is on the higher end of the actual bimodal group, and the slope is shallower in comparison. Also, despite measurable thresholds in the upper frequencies for the actual bimodal group, it is possible that these regions may not actually be receiving useful input, as there may be dead regions in the cochlea of these listeners (Summers et al, 2003;Moore, 2004). These factors, combined with a compressed dynamic range and the fact that testing was unaided, likely reduced the effective acoustic frequency range of the actual bimodal listeners relative to the LP condition for the simulated listeners.…”

Factors affecting psychophysical tuning curves for normally hearing subjects

“…A dead region is defined as a region of the cochlea with no functioning inner hair cells and/or neurons (Moore, 2001). When the signal frequency falls in a dead region, the tip of the PTC is usually shifted away from the signal frequency (Florentine and Houtsma, 1983;Huss and Moore, 2003;Moore et al, 2000;Moore and Alc antara, 2001;Summers et al, 2003;Thornton and Abbas, 1980). It is commonly assumed that the frequency at the tip of the (shifted) PTC defines one boundary of the dead region.…”

Identificação de zonas mortas da cóclea por meio do teste TEN

“…Although we saw a significant difference between the MT and the AT at all frequencies, the number of inconclusive results (Figure 1) and the calibration procedure for the TEN test version we used in this study, as well as the results obtained by Summers,19 who noted divergences between the TEN test and the PTC for 8 out of 18 ears, led us to question the need for further studies to demonstrate the TEN test sensitivity in detecting dead regions in the cochlea.…”

“…PTC is a proven and internationally accepted method to study cochlear tuning curves (Halpin 20 ). Summers et al 19 used a fixed TEN level of 70, 85 or 90 dB/ERB, which for certain thresholds, would be a negative signal-to-noise ratio. We fixed the TEN level at a signal-to-noise ratio of +10 dB, so that there would be no noise filter difficulties.…”

“…Figure 1 shows that 92% of seventy-six tested ears had results indicating dead regions, which agrees with previous results that suggest a significant prevalence of dead regions in individuals with sloping sensorineural hearing loss. 3,5,6,13,14,9,19 Summers et al 19 used TEN and psychophysical tuning curves (PTC) to assess eighteen ears with moderate to severe sloping sensorineural hearing loss. Results from both tests were similar, showing dead regions in six ears and no dead regions in four ears out of ten ears.…”