Science behind ‘Polly want a cracker’ could guide future treatment design for speech disorders

By recording for the first time the brain activity of parakeets as they made sounds, a research team at NYU Grossman School of Medicine found that their brains generate patterns seen before only in humans as they speak.

Published online March 19 in the journal Nature, the study mapped the activity of a group of nerve cells in the bird’s brain called the central nucleus of the anterior arcopallium (AAC), which is known to strongly influence the muscles in its vocal organ. Different groups of AAC cells were found to produce sounds akin to consonants and vowels.

When parakeets sing, certain cells become active at specific pitches, like pressing the keys on a piano, with the newfound pattern resembling the organization behind human speech. Based on their findings, the researchers suggest that humans and parakeets — unlike any other animal studied so far — share a similiar connection between higher brain activity and sound production.

“An important way to develop new treatments for speech disorders is to find animal models that can offer new insights into speech-related brain processes,” said senior study author Michael Long, PhD, the Thomas and Suzanne Murphy Professor in the Department of Neuroscience, and faculty in the Institute for Translational Neuroscience, at NYU Langone Health. “The brain processes uncovered in parakeets may help to explain the mechanisms behind communication disorders affecting millions of Americans.” These include apraxia (trouble planning speech movements) and aphasia (difficulty producing language), which can result from trauma caused by a stroke.

Mystery of Humans and Parakeets

“Incredibly flexible” spoken language is produced through delicate patterns in the human brain, the researchers say. To determine whether the patterns are unique to humans, the research team performed the first brain recordings in AAC of the budgerigar, a type of small parrot that can mimic hundreds of human words.

Part of the study’s results were focused on the contrast between the budgerigar’s brain and that of the zebra finch, a songbird species known to produce complex vocalizations. While both species can imitate sounds using dedicated brain regions as well as specialized vocal organs, only parrots can produce human words.

The zebra finch requires more than 100,000 practice trials to learn a rigid song, with experiments confirming that its brain establishes a fixed pattern of activity through a painstaking process of trial and error. In contrast, parakeets — like humans — can quickly adapt their vocal behavior. Using their internal “vocal keyboard,” they learn to flexibly reuse and creatively recombine motor commands to achieve different sounds, the study found.

Moving forward, the research team plans to study the higher brain functions that decide “which piano keys get pressed” via incoming signals to the AAC. Uncovering these processes may shed light on higher cognitive abilities in humans as well as on strategies that enrich the artificial intelligence models behind chatbots (large language models).

“Our results confirm that AAC neurons systematically represent vocal pitch and exert precise control over it, with this system showing unprecedented commonalities with human brain activity,” says lead author Zetian Yang, a postdoctoral scholar in Dr. Long’s lab. “This work therefore establishes this parakeet as a critical new model for investigating speech motor control.”

This research was supported by funding from the Simons Collaboration on the Global Brain.