Simulating psychophysical tuning curves in listeners with dead regions

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.