Comparison of maximum length sequence and randomized stimulation and averaging methods on the bottlenose dolphin...

Area of Science:

• Marine Mammal Auditory Neuroscience
• Bioacoustics
• Neurophysiology

Background:

• Auditory brainstem responses (ABRs) are crucial for assessing hearing in marine mammals.
• High stimulation rates are necessary for efficient ABR testing in cetaceans.
• Understanding the impact of temporal variability in stimulation is key for accurate ABR interpretation.

Purpose of the Study:

• To compare auditory brainstem responses (ABRs) in bottlenose dolphins using maximum length sequences (MLS) and iterative randomized stimulation and averaging (I-RSA).
• To evaluate the effect of different temporal variabilities in interstimulus intervals at high stimulation rates on ABR measures.
• To determine if the increased jitter in MLS significantly affects dolphin ABRs.

Main Methods:

• ABRs were recorded in six bottlenose dolphins (Tursiops truncatus) using click stimuli.
• Experiment 1 varied click rate (25–1250 Hz) with constant click level, comparing MLS (factor of 6 interval variation) and I-RSA (±0.5 ms interval variation).
• Experiment 2 varied stimulus rates (100–1000 Hz) and click levels (105–135 dB re: 1 μPa).

Main Results:

• Both MLS and I-RSA showed decreased ABR peak amplitudes and increased latencies/interwave intervals with higher rates in Experiment 1.
• In Experiment 2, lower click levels resulted in increased peak latency and decreased amplitude, with reduced effect at higher rates.
• The greater temporal jitter inherent in MLS did not substantially alter dolphin ABRs compared to I-RSA.

Conclusions:

• Both MLS and I-RSA are viable methods for high-rate ABR testing in bottlenose dolphins.
• The specific temporal variability of MLS does not introduce significant confounding factors for dolphin ABR assessment.
• These findings support the use of high-rate ABR techniques for efficient auditory evaluation in cetaceans.