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Role of the temporal window in dolphin auditory brainstem response onset
James J Finneran1, Jason Mulsow2, Madelyn G Strahan2
1United States Navy Marine Mammal Program, Naval Information Warfare Center Pacific Code 56710, 53560 Hull Street, San Diego, California 92152, USA.
The Journal of the Acoustical Society of America
|December 2, 2020
Summary
Auditory brainstem responses (ABRs) in dolphins show amplitude increases with sound envelope risetime and duration. These findings relate ABR amplitude to the initial sound pressure envelope integral within the dolphin
Area of Science:
- Marine Biology
- Bioacoustics
- Auditory Neuroscience
Background:
- Auditory brainstem responses (ABRs) provide insights into auditory system function.
- Understanding sound processing in cetaceans is crucial for marine mammal conservation.
- The relationship between sound envelope characteristics and ABRs in dolphins requires further investigation.
Purpose of the Study:
- To investigate the impact of sound onset envelope properties on auditory brainstem response (ABR) peak amplitude in bottlenose dolphins.
- To determine how variations in stimulus risetime, plateau duration, and pressure influence ABR amplitude.
- To explore the temporal integration window of the dolphin auditory system.
Main Methods:
- Auditory brainstem responses (ABRs) were recorded in six bottlenose dolphins using linear-enveloped, broadband noisebursts.
- Stimulus parameters manipulated included onset envelope pressure rate-of-change, plateau pressure, risetime, and plateau duration.
- Two experimental conditions varied: (1) constant rate-of-change with varied risetime/plateau pressure, and (2) constant plateau pressure/risetime with varied duration.
Main Results:
- When stimulus onset envelope pressure rate-of-change was constant, ABR amplitudes increased exponentially with risetime, with time constants of 55 µs (P1) and 64 µs (N5).
- Maximal ABR amplitudes were achieved with risetimes between 275–320 µs under constant rate-of-change conditions.
- With constant plateau pressure and risetime, ABR amplitudes showed a linear increase with stimulus sound exposure level up to durations of approximately 250 µs.
Conclusions:
- Dolphin ABR amplitude is significantly influenced by the integral of sound pressure envelope over the initial ~250 µs of a stimulus.
- This temporal integration window aligns with the known critical interval for hearing in dolphins.
- The study elucidates the relationship between acoustic temporal processing and neural encoding in the dolphin auditory system.
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