Investigating Atlantic bottlenose dolphin mismatch negativity response to pure tone stimuli

Abstract

Marine mammals rely heavily on acoustic cues to survive but are susceptible to hearing impairment due to anthropogenic noise. The quality of life and well-being of marine mammals under professional care is based on enrichment through training and communication conspecifics and zoo staff. Mismatch Negativity (MMN) is an electrophysiological exam that records synchronized firing of neurons from the auditory cortex and frontal lobe, allowing for assessment of echoic memory and sound differentiation capability. The objective of this study is to conduct MMN exams, with acoustic stimuli, on the Atlantic Bottlenose Dolphin (Tursiops truncatus Montagu) to study echoic memory and develop auditory cognition assessments for marine mammals in captivity. Three male Atlantic Bottlenose dolphins were tested in water at the Indianapolis Zoo. The oddball paradigm in this study included a frequency difference between two pure-tone stimuli (standard 2000 Hz, deviant 500 Hz). The results suggest that a similar MMN waveform morphology and latency (between 100 and 300 ms) are seen in dolphins when compared to humans. Average P1, N1, P2, and MMN values were determined for each dolphin. Developing MMN tests for animals under professional care will allow for application to marine mammals in natural habitats, which are exposed to high levels of anthropogenic noise.