Nile crocodiles may not be a very musical lot, but neuroscientists from Ruhr University Bochum in Germany stuck some of them in a functional MRI (fMRI) scanner and played them Bach’s Brandenburg Concerto No. 4 anyway.
The purpose of this peculiar experiment, detailed in a study that appeared last month in Proceedings of the Royal Society B, was to give scientists a unique chance to witness how the reptilian brain responds to sound.
The Brandenburg Concerto No. 4 has been used in previous animal studies because it has fast amplitude changes and a broad spectrum of frequencies, thus allowing researchers to investigate how the brain responds to complex sounds.
If you’re wondering why the German team turned to Nile crocodiles (Crocodylus niloticus) instead of a less threatening species of reptiles, the answer is simple. Nile crocodiles are ancient vertebrates that have remained virtually unchanged in the 200 million years since they emerged on the face of the Earth. Because of this, these animals provide an invaluable opportunity for scientists to study evolutionary-biology patterns, CNET reports.
The exotic audience to Bach’s concerto was made up of five, 1-year-old crocs that were small enough to fit in the MRI scanner. Provided by a French crocodile farm, the specimens were only 3.2-feet-long.
According to Gizmodo, such an audacious feat has never been attempted before. This is the first-ever experiment to use fMRI in a study of cold-blooded animals, which have completely different body temperatures and breathing patterns, compared to mammals or birds. In fact, the study authors deem their experiment “a technological breakthrough,” considering it was the first one to prove that fMRI can be used on reptiles.
Study senior author Felix Strockens revealed that one of the biggest challenges of the experiment — aside from the live crocodiles, that is — was finding “a temperature which allowed us to pick up a good signal and was comfortable for the animal.”
“We also had to keep this temperature stable within the scanner, which is relatively difficult since the coils used for scanning also emit heat,” Strockens told Gizmodo.
The soothing effect of classical music came in handy to the researchers, who were relieved to see that their study subjects remained calm throughout the experiment. The animals were only partly sedated, since a full anesthesia would have changed their brain activity, thus interfering with the results.
“Everything went fine and neither we nor the animals got injured,” said Strockens.
The findings revealed that crocodile brain activity is more similar to that of mammals and birds than previously expected. The fMRI showed brain activity patterns that closely resembled those previously observed in birds.
“Given that birds produce quite sophisticated ‘music’ on their own, one can assume that they have specialized brain areas to process complex sounds,” Strockens said in a statement.
“But we did not expect that crocodiles have areas which look and seem to work so similar,” he added.