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Auditory Evoked Potentials for the Evaluation of Hearing Sensitivity in Navy Dolphins. Assessment of Hearing Sensitivity in Adult Male Elephant Seals

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Final technical rept. 15 Apr 2004-30 Sep 2006

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A custom auditory evoked potential AEP system was used to assess the feasibility of rapidly testing the hearing of bottlenose dolphins by tracking the magnitude of the envelope following response EFR. Tests were conducted in-air N4 and on submerged dolphins N3 for which behavioral audiograms had been obtained in San Diego Bay or a quiet above ground pool. For in-air AEP measurements, differences between AEP and pool behavioral thresholds increased with threshold magnitude and ranged from 0 to 18 dB. For underwater AEP measurements, differences between AEP and pool behavioral thresholds varied from - 10 to 9 dB. After benchmarking the AEP approach, AEP thresholds were obtained from 42 dolphins housed at the Navy Marine Mammal Program. Animals ranged from 4 to 47 years of age and consisted of 28 males and 14 females. Consistent with other mammalian systems, the range and sensitivity of hearing declined with age with onset typically occurring between the ages of 20 and 30. Males generally exhibited hearing loss at a younger age than female dolphins. The AEP system was subsequently applied to the northern elephant seal Mirounga angustirostris to determine how to adapt AEP approaches to larger animals with less robust auditory systems.

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  • Biology
  • Anatomy and Physiology

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