Why Scientists Played Bach’s Classics For Crocodiles In MRI Scanners

Studying animals, be it living or a long-extinct species requires a whole lot of testing and experiments. Scientists have been conducting a range of works to better understand modern-day animals and their evolutionary history, but just recently something weird happened – a group of researchers took a small number of Nile crocodiles (Crocodylus niloticus) under MRI scanners and played classical music by Johann Sebastian Bach.

Though playing music to a cold-blooded reptile may sound both very strange and dangerous, the international group conduct this daring task in a bid to better understand reptilian brains and how they respond to various complex sounds.

Today, ancient fossils help us understand evolution mammals and birds, but when it comes to focusing specifically on their brains, there is not enough evidence to study. Meaning, we cannot determine how the brains functioned back then and have changed over millions of years. However, crocodiles, which count among the most ancient species of vertebrates, might offer some answers. The animals serve as a crucial link between the age of dinosaurs and modern-day birds and have hardly changed over last 200 million years.

"Analyses of crocodile brains thus provide deep insights into the evolution of the nervous system in mammals and may help us understand at which point certain brain structures and behaviors associated therewith were formed," Felix Ströckens, the lead researcher behind the work, said in a statement.

That said, the group took five small, young crocs into a functional MRI or fMRI scanner – used commonly for clinical diagnostic and research – and played the classical music to see how their brains responded. The task was not easy and required a whole lot of modifications.

"We had to overcome a number of technical obstacles," research team member Mehdi Behroozi said in the statement. "For example, we had to adjust the scanner to the crocodile's physiology, which differs massively from that of mammals in several aspects."

On analyzing the neural activity as the classical music – with fast amplitude changes and broad frequencies – was played, the researchers noted additional areas of the animal’s brain activated from complex sound, something that did not happen with simple sounds. More importantly, these patterns of neural activity closely matched with those observed in mammals and birds that were a part of other similar studies.

As a result, the group believes the neural mechanisms for processing sensory stimuli could have formed at an early evolutionary stage and tracked back in all vertebrates.

"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," Ströckens told CNET.

In addition, the latest work also demonstrates a technical breakthrough and proves the non-invasive MRI scanning technology can offer a reliable way to study cold-blooded reptiles, something that has never been done in the past. It could also help scientists study animal species that have not been studied in depth.

The study, titled “Functional MRI in the Nile crocodile: a new avenue for evolutionary neurobiology,” was published April 25 in the journal Proceedings of the Royal Society B: Biological Sciences.