Three auditory brainstem response (ABR) methods tested and compared in two anuran species

Area of Science:

• Auditory Neuroscience
• Animal Bioacoustics
• Comparative Physiology

Background:

• Hearing sensitivity is crucial for animal communication and survival.
• Auditory brainstem response (ABR) measurements are a common, non-invasive method to assess hearing sensitivity.
• Existing ABR methods vary in stimulation techniques, potentially affecting audiogram results.

Purpose of the Study:

• To compare the effectiveness of three auditory brainstem response (ABR) measurement methods in assessing hearing sensitivity in frogs.
• To determine which ABR method yields the most accurate and sensitive audiograms across a range of frequencies.
• To identify potential biases and limitations of different ABR stimulation techniques.

Main Methods:

• Three ABR methods were applied to the same individual frogs: tone burst ABR (tABR), long-duration tone ABR (ltABR), and masked ABR (mABR).
• Hearing sensitivity was measured across frequencies from 100 to 3500 Hz.
• Audiograms were compared between subjective (visual inspection) and objective (signal-to-noise ratio) threshold definitions.

Main Results:

• All methods revealed two main hearing sensitivity peaks between 400-600 Hz and 1500-1600 Hz.
• The masked ABR (mABR) method produced the most sensitive audiograms.
• Long-duration tone ABR (ltABR) showed decreased sensitivity above 1000 Hz due to neural limitations; tone burst ABR (tABR) was less specific at low frequencies with shorter durations.

Conclusions:

• The masked ABR (mABR) method is recommended for obtaining the most sensitive audiograms in frogs.
• Tone burst ABR (tABR) can be effective with longer durations (e.g., 25 ms).
• Long-duration tone ABR (ltABR) is not suitable for assessing hearing thresholds above 1000 Hz due to potential biases.