The Chronicle

Study finds novel similarities between bird and human brains

A study on birds’ brains could lead to a greater understanding of the human brain.

A research team—led by Erich Jarvis, Howard Hughes Medical Institute Investigator of Neurobiology at the School of Medicine—concluded a 10-year study in which they mapped the brains of eight species of birds. The findings, which were published in two papers in the Journal of Comparative Neurology in July, found that the brains of all vertebrates—which includes mammals, birds and reptiles, among others—have important similarities. The new understanding could aid further research in language and speech development.

“If you really look at the behavior complexity of different bird species, they can display quite simple to very complex behaviors that you can find in any mammal—some of which are considered more unique to humans, like language,” Jarvis said. “If we are going to translate discoveries that we find from a songbird to a human, we need to know the similar cell-types in songbirds and humans.”

By using a computational analysis of the activity of 52 genes across 23 areas of the bird brain, the team—which included Chun-Chun Chen, a postdoctoral fellow in the Jarvis Lab, and Harvey Karten, a professor of neuroscience at the University of California San Diego School of Medicine—found that bird brains have a columnar organization. Previously, only mammals were thought to have this structure.

“One of the challenges we’ve had using bird brains to understand brain function overall is that it’s hard to translate discoveries in birds to other species, including mammals and humans,” Jarvis said. “One of the reasons it’s hard to make those translations is that we didn’t know about the organization of the bird brain to begin with.”

Another breakthrough in the study was the discovery that a void—known as the ventricle—that exists between two groups of cells does not act as a barrier. Instead, the two cell groups actually divide in a sheet and flow around the ventricle while multiplying.

Although it may make studies on birds easier to understand, Richard Mooney, George Barth Geller professor of neurobiology at the Duke Institute for Brain Sciences, said that mice will not disappear from neurobiology laboratories.

“I don’t think birds will replace mice,” Mooney said, “[Birds and mice] each have a great utility, but it’s much, much easier to understand what the homologies are between the mouse brain and the human brain…. But even so, bird behavior in many ways is much more like our behavior than mouse behavior.”

Jarvis and his colleagues studied how the gene expression of birds’ brains reacted to various environmental factors—such as bird songs, light, movement and a magnetic field that simulated navigational circuits.

“We’re looking at combinations of genes and the reason why we think we were able to get further than other studies in the past is because they were only doing one or two genes and we had decided that wasn’t enough evidence,” Jarvis said. “We needed many more genes.”

The discovery about the structure of birds’ brains could change evolutionary biology because it shows that the circuitry we use to perform specific tasks like detecting sound have not changed much in the past 200 million years, Karten said.

“Prior to now, the notion had been that mammals evolved their cortex as a specific novel event,” Karten said. “Now it would be much more sensible that the mammalian cortex is just one way of taking the exact same circuitry and packaging it differently.”

Understanding the sequence and process of evolution could help researchers understand developmental disabilities, he noted.

“If we understand how cells form in mammals compared to reptiles and birds, that might give us some insight into what the developmental sequences are at the molecular level,” Karten said. “And if those steps are disrupted at the molecular level, it could explain the mechanisms for mental retardation.”