Auditory Steady-State Responses to Asses High-Frequency Temporal Processing in CI Users

Background: Temporal processing in CI users has an individually-variable frequency limit. The lower this limit, the more voice pitch perception is impeded. Psychophysical tasks assessing temporal processing, like amplitude modulation detection thresholds (AMDTs) are very time consuming. However, the amplitude of auditory-steady-state-responses (ASSRs), correlates well with AMDTs [Luke et al., Hearing Research, 324, 37-45(2015)], providing a fast objective assessment of temporal processing in CI users.

Objective: In this study ASSRs are measured to investigate temporal processing in the frequency range of voice pitch.

Methods: ASSRs are measured in post-lingually deaf CI users using a 64-channel EEG set-up. Stimuli are amplitude modulated pulse trains (900 pps) with modulation frequencies between 100-300 Hz. The CI-stimulation artifacts are removed from the EEG with linear interpolation.

Results: Above 100-150 Hz, ASSR amplitudes in CI users drop sharply and very few significant responses are found. This contrasts with measurements in normal hearing subjects, where ASSRs are present up to at least 450 Hz. A similar drop in temporal processing ability above 100 Hz was found using AMDTs [De Ruiter et al., Ear and Hearing, 36(5), 557-566(2015)].

Conclusions: Results indicate that ASSRs have the potential to reliably predict the frequency limit of temporal processing in CI users in a fast and objective way. Future work will compare high-frequency AMDT and ASSR measurements in the same subject.

Acknowledgments: Funded by Research foundation Flanders (FWO-TBM LUISTER (T002216N) & FWO-SB PhD-fellowship to Jana Van Canneyt) and jointly by Cochlear Ltd. and Flanders Innovation & Entrepreneurship (formerly IWT), project 50432.