Simulating psychophysical tuning curves in listeners with dead regions

Abstract

Objective: This study investigates the relation between diagnosis of dead regions based on the off-frequency psychophysical tuning curve (PTC) tip and the frequency and level of the probe tone. Design: A previously developed functional model of auditory processing was used to simulate the complete loss of inner hair cells (IHC), dysfunction of outer hair cells (OHC), complete loss of IHCs in combination with OHC dysfunction, and IHC insensitivity. The model predictions were verified through comparison with experimental data. Study sample: This study compares PTC data of five normal-hearing listeners and six hearing-impaired listeners with model-simulated PTC data. Results: It was shown that OHC activity and IHC insensitivity may significantly alter the shift of PTC tips with increasing probe level. Conclusions: Model results suggest that OHC activity and IHC insensitivity can change the outcome of dead region diagnosis using PTCs. Supplementary to PTC dead region diagnostic information, model results may provide additional information regarding the edge frequency of a dead region and OHC function.

Key Words::

• Dead regions
• psychophysical tuning curve
• inner hair cells
• outer hair cells
• functional model
• modeling

Acknowledgements

We would like to thank Ray Meddis for his help in understanding the DRNL filterbank. Particularly, we value his advice on approaches in the model to simulate OHC dysfunction. Furthermore, we would sincerely like to thank Torsten Dau for his extensive support in the preparation of this manuscript. Torsten Dau provided financial support to the research project, gave constructive comments on the structure of the manuscript, and provided a critical review on an early version of the manuscript. We would like to thank Dr. Smurzynski and two anonymous reviewers for their significant contribution to improve the quality of this manuscript. This work was financially supported by the Heinsius-Houbolt Fund.

Declaration of interest: xxx

Notes

Notes

1. High level presentations are problematic in some listeners with loudness recruitment. This is even more problematic for the TEN test, because the TEN is a broadband noise that ranges between 0.354 kHz and 6.5 kHz. However, the total loudness perception of the TEN can be reduced by limiting the frequency range of the noise by filtering (Markessis et al, 2006).

2. The numbering of listeners (e.g. Lxx) refers to the original numbering of ears (e.g. HIxx) (Warnaar & Dreschler, 2012).

3. The geometric mean frequency of the masker refers to a frequency that is equal to the root-mean-square of the lower-, and upper cutoff frequencies.

4. This frequency-intensity domain was selected based on the range of probes presented to HI listeners.

5. The masking level of a broadband noise that exceeds one DRNL channel (or auditory filter of a listener) can be calculated from: effective masking level = log(bandwidth noise) − log(ERB).