Abstract
Previous studies in dolphins suggests that, like humans, dolphins display an “oddball” response in the auditory cortex when one auditory stimulus has a low probability of occurrence relative to others in a stimulus train. However, the previous dolphin studies used stimuli and sequences that were not biologically relevant to the animal. Additionally, human experiments showed that the magnitude of the auditory cortical response scales with attention when the subjects must respond to a “target” sound. The present study compared auditory cortical responses in four dolphins (two juvenile and two geriatric) to three whistle-like stimuli. We contrasted auditory cortical responses when the stimuli were presented in a randomized sequence to those in a predictable sequence where an oddball was present based on fixed probabilities. Two different conditions were tested: (1) when the dolphins were passively listening to the stimuli and (2) when the dolphins were trained to listen to the stimuli and produce a whistle response to one of the three stimuli designated as the target. This paper will discuss the differences in auditory cortical responses between the two sequences and conditions, as well as notable differences between the juvenile and geriatric subjects. [Work funded by ONR.]