You're a scientist who wants to better understand how the reptilian brain responds to sound. What do you do?

You slide crocodiles into an MRI scanner and play Bach for them, of course. (Everyone knows crocodiles don't like Beethoven.)

Enlarge Image Michel Gunther

In an attempt to study evolutionary-neurobiology patterns, an international team of researchers turned to the crocodile, an ancient species of vertebrates that's barely changed over millions of years and thus constitutes a link between dinosaurs and modern birds.

They wanted to gauge how crocodiles respond to complex rather than simple sounds, so they put small, year-old Nile crocs into a MRI scanner used for animal research. (Their five subjects came from a French crocodile farm.) Then they monitored the reptiles' brain activity as they listened to Bach's Brandenburg Concerto No. 4, which has fast amplitude changes and a broad spectrum of frequencies.

They were surprised to discover brain activity patterns strongly resembling those identified in mammals and birds in similar studies.

"Given that birds produce quite sophisticated 'music' on their own, one can assume that they have specialized brain areas to process complex sounds. But we did not expect that crocodiles have areas which look and seem to work so similar," German neuroscientist Felix Ströckens says.

Ströckens is one of the researchers who just published a study titled "Functional MRI in the Nile crocodile: a new avenue for evolutionary neurobiology" in the journal Proceedings of the Royal Society B: Biological Sciences.

While scientists have studied crocodile brains anatomically, functional studies like this one are rare, and scanning the crocs presented some practical challenges. The researchers couldn't deeply anesthetize the creatures, for example, since that would have interfered with their brain activity. And even smaller crocodiles, in this case 3.2 feet or a meter long, can exert quite a force with their tails and jaws.

"Fortunately, they stayed very calm," Ströcken reports. Yeah, classical music tends to have a soothing effect.

The researchers also had to tweak the scanner to accommodate the crocodiles' physiology. They call their experiment a technical breakthrough that proved functional MRI can be used in reptiles, which have vastly different body temperatures and breathing patterns than mammals or birds.

"This will allow future studies to investigate many species which have not been investigated yet with this non-invasive method," Ströcken says.

The other bonus? There are some really cultured crocodiles running around now.

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