High-pass filtering distorts auditory brainstem responses: Evidence from click and tone stimuli

Alexandra R. Tabachnick (atabach@udel.edu)University of Delaware

Joseph C. Toscano (joseph.toscano@villanova.edu)Villanova University

Introduction DiscussionResults• The click-evoked transient ABR is frequently

measured by clinicians to help diagnose problems in auditory processing.

• Many researchers are currently interested in studying the ABR to complex stimuli like speech and music1.

• Despite previous work, it remains unclear how ABR components may track fine-grained changes in frequency.

• Filtering is a critical step in data processing. However, excessive high-pass filtering can severely distort cortical and subcortical responses2,3, which may explain inconsistency in previous work.

• The present study includes two experiments testing the effect of high-pass filtering on 1) the click-evoked transient ABR and 2) the tone-evoked transient ABR, in order to identify appropriate filtering protocol and to test frequency-mapping of the ABR.

ABRs were recorded with an active electrode at the vertex (Cz), the reference electrode on the left mastoid (M1), and ground electrode anterior to Fz.

Experiment 1: Clicks • ABRs were collected to 1000 µs clicks. • Participants heard 6000 clicks, at ~6.1/second. • Wave I (2-4 ms) and Wave V (6-10 ms) were

selected for analysis. • Artifact rejection information was collected after

only low-pass filtering (DC-3000 Hz), then used when applying each of 5 high-pass filter settings (0.1 Hz-100 Hz).

• All were Butterworth filters with a 24 dB/octave roll-off and low-pass of 3000 Hz.

Experiment 2: Tones • ABRs were collected to 20ms 2-1-2 tones in

notched noise across a six-step frequency continuum (250 Hz-8000 Hz).

• Participants heard 17,400 tones total, at ~6.7/second.

• Wave V (6-10 ms) and Wave VI (10-13 ms) were selected for analysis.

• The same artifact rejection and filtering procedures were used as in Experiment 1.

• Excessive high-pass filtering (>10 Hz) diminishes the amplitude of ABR components, consistent with previous findings.

• With appropriate filters, we found that the amplitude of Wave VI tracks stimulus frequency log-linearly.

• Tonotopic organization is preserved and easily detectable early in processing, indicating that ABR-audiometry may be possible.

• 250 Hz seems to follow a different pattern — need to study more fine-grained steps in low-frequency range.

• ABR researchers should consider high-pass filter settings when interpreting findings.

3aPPb15.

Experiment 1: Clicks Experiment 2: Tones

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References & Acknowledgments

Acknowledgements

We would like to thank Brandon Henken for assistance with stimulus creation, Emma Folk for help with participant recruitment, and Nicole Johnson for assistance with data collection.

References

1. Skoe, E., & Kraus, N. (2010). Auditory brain stem response to complex sounds: a tutorial. Ear and Hearing, 31(3), 302–24.

2. Stapells, D. R., & Picton, T. W. (1981). Technical aspects of brainstem evoked potential audiometry using tones. Ear and Hearing, 2(1), 20-9.

3. Tanner, D., Morgan-Short, K., & Luck, S. J. (2015). How inappropriate high-pass filters can produce artifactual effects and incorrect conclusions in ERP studies of language and cognitions. Psychophysiology, 52(8), 997-1009.

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Wave VI: Other Measurements

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