Bats and dolphins are both characterized by a sonar system that helps them navigate their way and detect objects. Now, scientists have found that the brains of these two animals are also remarkably similar.

Researchers mapped the sensory and motor system of the brain of the dolphin by studying the brains of a pantropical and common dolphin and found at least two areas that are associated with hearing.

Most mammals only have one area linked to hearing and this makes the brain of the dolphin similar to those of bats. Experts think this has something to do with these two creatures' use of echolocation that allows them to see and navigate their environments.

The researchers, whose study was reported in the journal Proceedings of the Royal Society B on Wednesday, said that their findings came as a surprise given that bats and dolphins are far apart on the evolutionary tree.

Study researcher Gregory Berns, a neuroscientist from the Emory University, said that the two animals had diverged for millions of years, but their brains possibly evolved similar mechanisms so they can use sound not just for hearing but also for creating mental images.

"For decades, we've thought of the dolphin brain as having one primary auditory region," said study researcher Lori Marino, a neuroscientist who specializes in the brains of cetaceans. "This research shows that the dolphin brain is even more complex than we realized."

The researchers hypothesized that the cetaceans have more than one neural area linked with sound because they use sound for different purposes. Marino said that dolphins are the animal kingdom's most sophisticated users of biological sonar having the ability to produce different types of sound simultaneously and effectively using echolocation to hunt for food and communicate with other dolphins.

"The present findings are the first to demonstrate that a putative auditory afferent system from the thalamus to the temporal lobe exists in cetaceans," the researchers wrote. "These results compellingly point to the possibility of a future revision of our knowledge of how cetaceans process auditory and, perhaps, other forms of sensory information."

The study marks the first time that scientists use a technique known as diffusion tensor imaging (DTI) on a dolphin's brain and on a specimen that is already over a decade old. The researchers said that the success of their study opens up the potentials of using the tool to study different brains of animals that are archived in museums around the world.

Photo: Gregory "Slobirdr" Smith | Flickr

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