Abstract: Auditory steady-state responses were measured in a bottlenose dolphin (Tursiops truncatus) and used to illustrate objective techniques to determine the presence or absence of a response. Experimental measurements were conducted under water in a quiet pool. Sound stimuli were pure tones that were both amplitude and frequency modulated. Evoked responses were recorded using noninvasive surface electrodes. Two frequency-domain techniques were used to assess the presence or absence of a response. The F test compares the evoked potential power at a single frequency (the amplitude modulation frequency) to the noise power averaged over adjacent frequencies. Magnitude squared coherence (MSC) is a ratio of the signal power at a single frequency to the signal-plus-noise power and reflects the degree to which the system output is determined by the input. For the measurements here, both techniques provided identical results. Evoked potential thresholds based on the lowest detected response compared favorably to behavioral thresholds obtained in the same environment.

Key Words: hearing, evoked potentials, objective detection, bottlenose dolphin, Tursiops truncatus

Document Type: research article

DOI: 10.1578/AM.33.1.2007.43

Page Numbers: 43-54

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