By Caroline Catherman
Very few animals learn to speak in a way that comes close to the human method.
The repertoire of growls, barks and howls of most animals is innate, genetically predetermined at birth. Humans, on the other hand, adopt any language that exists in their early environments.
But songbirds learn to sing the same way humans learn to speak. Their songs feature who they are and what they want, which is usually to mate, nurture, or defend their territory. Birds and humans share so many similarities that information from the study of how they develop the ability to “speak” allowed researchers to try to determine why certain human speech, cognitive and social impairments occur. produce, taking into account the well-established link between speech, brain function and social interaction.
Stephanie White, researcher and laboratory director at the University of California, Los Angeles, has studied birds for over 20 years. She says birds provide the opportunity to study how human speech works because in many cases studies of human brain regions are limited to dissecting dead brains.
“Behavior does not translate into a dish,” she added.
Voice learning in birds
Songbirds, parrots, hummingbirds, and a few other animals learn to communicate in any song pattern or in the language their parents “speak”. Just as almost any human could learn English, Swahili, or Khoisan, almost any songbird could theoretically attempt to imitate a white-crowned sparrow’s song, a chaffinch song, or a songbird song. robin, said David Rosenfield, director of Houston Methodist’s Speech and Language Center. It’s all done through a rare ability called vlocal learning.
Birds hear a sound in the environment, remember it, and then produce it from memory. But a bird is only able to do this for a small window early in life, when some areas of the brain are still flexible.
If songbirds are not exposed to their melodies for a brief period as babies, their “critical period,” they will never be able to sing like normal wild birds. And that means they won’t be able to communicate effectively. Even if they are exposed to bird songs later in life, they can only produce rough approximations of normal bird songs, according to ethnologist Peter Marler. famous 1970 study white-crowned sparrows. The study exposed the birds to songs at different times and compared the resulting tunes that each bird sang.
“The bottom line is that if the bird doesn’t hear what it’s supposed to produce, it won’t learn it,” Rosenfield said.
Voice learning in humans
Human voice learning works in a similar sequence and, as with birds, scientists’ attempts to understand language disorders from stuttering developmental disorders like autism focus on the first experiences.
In humans, this critical window for acquiring language proficiency covers the first years of life and ends between the age of five and the onset of puberty, as in Elissa L. Newport 1990 see again in Cognitive sciences.
Then, just as babies give babbling that slowly turns into words and then into sentences, birds will make scrambled sounds that are rough approximations of bird songs and, with practice, turn them into full bird messages.
The famous of Marler 1970 study hypothesized that birds, like babies, keep a memory of the sound of their guardian’s language, compare it to the sounds they make, and adjust their sounds accordingly to match the pattern during language development.
Historical applications of bird research to humans
After realizing the similarities between how humans and birds learn to speak, scientists began testing bird brains for shared brain areas and genes.
Numerous studies, such as this report 2015 by Andreas R. Pfenning of the Department of Neurobiology at Howard Hughes Medical Institute and several co-investigators, confirmed that the brain of songbirds share unique ways of speaking that are found in few species other than humans. The area of a bird’s brain called HVC is crucial for learning and song production, similar to certain areas of the human prefrontal cortex related to speech. This region of the brain helps control Zone X in birds, a group of about 2,000 genes dedicated to the production of learned vocalizations. Zone X is similar to the basal ganglia, one of the regions of the human brain that connects to the human prefrontal cortex and plans and controls the joint.
In 2001, the FOXP2 gene became the first gene identified to affect the development of human speech, due to its relationship to many other areas of the brain and hundreds of other genes. Subsequent research found that it was also crucial for birds: when baby birds were given a serum that altered how their FOXP2 genes worked, they couldn’t learn to sing a normal song.
Since then, research into shared genes in birds and humans has advanced.
“Not just for FOXP2, but for many genes there is greater similarity in the gene expression profile of these regions. [in humans] and bird brains as not, ”White said.
Current translational research on birdsong
Today, translational research is focused on experimentally manipulating certain genes and areas of the brain in songbirds to see what happens. The results of these studies are helping scientists develop hypotheses about the role these same genes and areas of the brain play in human vocal learning.
A study published in Science Advances in February 2021, for example, injected birds with a serum that primarily prevented FOXP1, a gene closely related to FOXP2, from controlling other genes in HVC.
The chicks who had heard the adults sing before the injection were able to learn to sing normally, completing the vocal learning process smoothly. But birds that hadn’t heard an adult sing before the injection failed to sing the notes that would allow them to communicate with other birds. They sang songs that sounded like birds that hadn’t been exposed to an adult teacher at all.
Prior to this study, researchers knew that FOXP1 would play a role in vocal learning, said Therese Koch, co-lead author of the study. They now know more about the how and why.
“Previously, it was not possible to disentangle the role of FOXP1 in… understanding an example so that you could copy it, versus the actual learning process to make that copy,” Koch said.
This study has important implications for humans. Mutations in the FOXP1 gene can lead to intellectual disabilities, developmental delays, and autism-like behaviors in a disorder known as FOX-P1 syndrome. The gene is also linked to autism spectrum disorders: studies have shown that some people on the autism spectrum may have too much FOXP1 expression.
Now, Koch has said that she and her co-researchers at the University of Texas Southwestern Medical Center could dig deeper into why exactly this gene might prevent birds from learning from guardians, in order to understand why this gene is linked to all these human troubles.
“Is it the social fact… that the bird doesn’t care about other birds after the FOXP1 overthrow, that it just doesn’t care?” Koch asked. “Or is it just that he can’t form those memories properly, because potentially the neurons where we knocked down FOXP1 are involved in storing the memory of a tutor song to guide further learning?” We don’t know any of this at the moment, but all of these questions would be interesting to consider in the future. “
The future of songbird research
In California, White hopes to take this research even further in his UCLA Integrative Biology and Physiology Laboratory. Because scientists have identified genes and neural networks involved in critical period vocal learning in birds, they could in theory target these areas in drugs that will treat communication problems in humans, he said. she declared. She added that researchers in her lab have tried to identify areas of the brain to target drugs in their resident zebra finches, but have found nothing so far.
“The current model for drug development are rodents and non-human primates,” she said. “[But] there is a gaping hole in the ability to deal with speech delay problems and children who are not verbal.
Currently, there are no FDA approved drugs on the market for stuttering. A drug prescribed to children with the autism spectrum, risperidone, may solve problems such as repetitive behavior, but not the social communication aspect of autism. White says songbirds may be the animal model’s solution, but it will take a “big shift in NIH thinking” to get the research to this point.
Other experts suggest being cautious about applying songbird models to treat human communication disorders. Michael Lombardo, who heads the Laboratory for Autism and Neurodevelopmental Disorders at the Istituto Italiano di Tecnologia in Italy, recently published a study linking gene expression in songbirds and humans to linguistic outcome subgroups early. But he said in an interview that there was not yet enough evidence to link the development of songbirds to language processing in autism spectrum disorders, for example.
“Everything about songbirds is a much more simplified and specific process than what human language represents,” he said. “The evidence developed in songbird research may have no real value in helping to treat language problems in children with autism. But I guess we have to wait and see what the research shows. “
Caroline Catherman is a health, environment and science journalist at Medill. You can follow her on Twitter at @CECatherman.