EEG study of attention on an auditory target detection task in dolphins and humans

How do dolphins attend to echos and ignore background noise? Is the process similar to how humans attend to conversations in a crowded room? Studies of human selective attention have highlighted endogenous brain processes modulating the magnitude of early responses to sounds in auditory evoked potentials (AEPs), yet these rely on task-specific instructions difficult to employ in animal studies. We trained an adult male dolphin (Tursiops truncatus) to attend to a stream of rapidly presented tones, and provide a whistle response to a “target” tone while withholding responses to “background” tones in an amplitude discrimination task. The background sounds were designed to function as a tonal mismatch negativity paradigm with two frequencies: a standard tone presented 80% of the time, and a deviant presented 20% of the time. Depending on condition, the target could be the same frequency as the standard or the deviant. We observed an enhanced AEP response to a deviant of the same frequency as the target, while the AEP response to the standard-target condition was reduced. This was not predicted by previous human experiments, and we are currently following up with a pilot a human task modeled after the dolphin implicit target detection task.