Middle- and Long-Latency Auditory Evoked Potentials in Bottlenose Dolphins (Tursiops truncatus) Resulting from Frequent and Oddball Stimuli

Abstract: Middle- and long-latency auditory evoked potentials (AEPs) have not been extensively studied inmarine mammals. Differences in longer latency potentials resulting from infrequent “oddball” stimuli inserted within a train of repeated, or “standard,” auditory stimuli can potentially be used to detect the discrimination ability of an individual. To investigate the characteristics of evoked responses resulting from the oddball paradigm, AEPs were recorded using 100-ms pure tones as stimuli and recording AEP epochs of 500 ms from two bottlenose dolphins (Tursiops truncatus). The P50 response to a 40-kHz pure tone was attenuated when that stimulus was repeated (the standard stimulus), with an 80% probability of occurrence. When a 30-kHz oddball tone was presented (20% probability of occurrence), however, the P50 response amplitude increased, indicating dishabituation to the novel stimulus. The attenuation of the P50 response to the standard tone was observed when the standard and oddball tones were reversed (30-kHz standard; 40-kHz oddball). The results demonstrated sensory gating, either habituating to a repeated stimulus (“gating out”) and/or dishabituating to a novel stimulus (“gating in”). The presence of one or both of these responses suggests that the P50 response to oddball stimuli has the potential to indicate discrimination of a particular set of auditory stimuli.

Key Words: bottlenose dolphin, Tursiops truncatus, auditory evoked potentials, middle- and long latency responses, auditory discrimination

Document Type: research article

DOI: 10.1578/AM.33.1.2007.34

Page Numbers: 34-42

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