Washington: Scientists, including one of Indian-origin, have found key structural differences in the brains of parrots that may explain the birds' unparalleled ability to imitate sounds and human speech.
These brain structures had gone unrecognised in studies published over the last 34 years, researchers said.
By examining gene expression patterns, the new study found that parrot brains are structured differently than the brains of songbirds and hummingbirds, which also exhibit vocal learning.
In addition to having defined centres in the brain that control vocal learning called "cores", parrots have what the scientists call "shells" or outer rings, which are also involved in vocal learning.
The shells are relatively bigger in species of parrots that are well known for their ability to imitate human speech, the researchers found.
"This finding opens up a huge avenue of research in parrots, in trying to understand how parrots are processing the information necessary to copy novel sounds and what are the mechanisms that underlie imitation of human speech sounds," said Mukta Chakraborty, a post-doctoral researcher in the lab of Erich Jarvis, an associate professor of neurobiology at Duke University and a Howard Hughes Medical Institute Investigator.
Parrots are one of the few animals considered "vocal learners", meaning they can imitate sounds. Researchers have been trying to figure out why some bird species are better imitators than others.
Besides differences in the sizes of particular brain regions, however, no other potential explanations have surfaced.
Until now, the budgerigar (common pet parakeet) was the only species of parrot whose brain had been probed for the mechanisms of vocal learning.
The researchers from Denmark and the Netherlands donated precious brain tissue for the study.
They characterised the brains of eight parrot species besides the budgerigar, including conures, cockatiels, lovebirds, two species of Amazon parrots, a blue and gold macaw, a kea and an African Grey parrot.
The researchers looked for specific gene markers that are known to have specialised activity in the brains of humans and song-learning birds.
They compared the resulting gene expression patterns in all the parrot brains with neural tracing experiments in budgerigars.
Even the most ancient of the parrot species they studied, the Kea of New Zealand, has a shell structure albeit rudimentary. This suggests that the populations of neurons in the shells probably arose at least 29 million years ago.
The scientists now want to find out whether the shells give parrots a greater ability to imitate human speech.
