Gene activity in songbirds' brains changes when they hear new song
Washington, June 27 (ANI): University of Illinois researchers have found that gene expression in the brain of the zebra finch changes when it hears a new song from a member of its own species.
Writing about this finding in the Proceedings of the National Academy of Sciences, the researchers say that it offers a new picture of memory in the songbird brain.
Lead researcher David Clayton, a professor of cell and developmental biology at the university, says that he and his colleagues had not expected to see so many genes involved, and thought that any changes in gene activity after a bird heard a new song would quickly dissipate.
He revealed that his team's work uncovered three distinct profiles of gene expression in the brain. One is typical of a bird sitting alone in silence. A second profile appears quickly just after a bird hears a recorded song - but only if the song is new to the bird. A third profile then emerges 24 hours later, after the song has become familiar.
"I can tell you whether the bird has heard a particular song before or not just by looking at the molecular assay," Clayton said.
During the study, the researchers kept each bird in quiet isolation overnight before it heard a recording of a new song. They then repeated the recording every 10 seconds for up to three hours.
"The most important thing in its whole life is the sound of another bird of its species singing. And what we found is that 24 hours after the experience its brain is still trying to make sense of what it heard," Clayton said.
He said that the team used DNA microarray analysis to measure changes in levels of messenger RNAs (mRNAs) in the auditory forebrain of finches exposed to a new song, as any surge or drop in the number of mRNAs in brain cells after a stimulus offers clues to how the brain is responding.
The researcher said that some genes were upregulated within 30 minutes of exposure to a new song, and those genes included a lot of transcription factors that modulate the activity of other genes.
He further said that many other genes were downregulated, including those that code for ion channel proteins, which allow ions to flow into the cell.
According to him, this could be one way that the brain dampens its response to a powerful stimulus, protecting itself from too much disturbance.
"Whenever something unexpected and different comes along, such as the song of a new bird in the neighborhood, it's going to deform the listening bird's neural network. And so the system has to basically absorb some of that, make some changes and not be overwhelmed by it. If you push the system around too much, cells die," Clayton said.
On the other hand, he said, no memory would form if the system were completely resistant to disturbance.
The research team observed that 24 hours after the initial stimulus, the pattern of activated genes was entirely different from that of the initial response, regardless of whether the bird heard the song again on day two or not.
Clayton says that the genes that were originally upregulated or downregulated had returned to baseline, and a new network of genes was engaged.
He adds that a major focus of this new network appears to be the regulation of energy metabolism, and this suggests a lot is still going on in the brain.
"It's like we've lifted the hood and we're seeing that these things are just chugging away. The bird had this one day of experience and a day later the brain is in a different state.
It's still in high gear. It's still processing stuff. It's still reverberating and echoing," Clayton said. (ANI)