Researchers see evidence of memory in the songbird brainJune 29, 2009CHAMPAIGN, Ill. - When a zebra finch hears a new song from a member of its own species, the experience changes gene expression in its brain in unexpected ways, researchers report. The sequential switching on and off of thousands of genes after a bird hears a new tune offers a new picture of memory in the songbird brain. The finding, detailed this month in the Proceedings of the National Academy of Sciences, was a surprise, said principal investigator David Clayton, a professor of cell and developmental biology at the University of Illinois. 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. The new experiments 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. In the study, each bird was kept in quiet isolation overnight before it heard a recording of a new song. The recording was then repeated 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," Clayton said. "And what we found is that 24 hours after the experience its brain is still trying to make sense of what it heard." The new study took a broad snapshot of gene activity in the brain. Using DNA microarray analysis, the researchers measured changes in levels of messenger RNAs in the auditory forebrain of finches exposed to a new song. These mRNAs are templates that allow the cell to translate individual genes into the proteins that do the work of the cells. Any surge or drop in the number of mRNAs in brain cells after a stimulus offers clues to how the brain is responding. Some genes were upregulated within 30 minutes of exposure to a new song, the researchers found, and these included a lot of transcription factors that modulate the activity of other genes. Many other genes were downregulated, including those that code for ion channel proteins, which allow ions to flow into the cell. This could be one way that the brain dampens its response to a powerful stimulus, protecting itself from too much disturbance, Clayton said. "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," Clayton said. "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." On the other hand, if the system were completely resistant to disturbance, no memory would form, he said. Twenty-four 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 said. Those genes that were originally upregulated or downregulated had returned to baseline, and a new network of genes was engaged. A major focus of this new network appears to be the regulation of energy metabolism. This suggests a lot is still going on in the brain, Clayton said. "It's like we've lifted the hood and we're seeing that these things are just chugging away," Clayton said. "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." University of Illinois at Urbana-Champaign |
|||||||||||||||||||||
| Related Gene Expression Current Events and Gene Expression News Articles Deciphering the regulatory code Embryonic development is like a well-organised building project, with the embryo's DNA serving as the blueprint from which all construction details are derived. Experimental agent reduces breast cancer metastasis to bone Researchers have reduced breast cancer metastasis to bone using an experimental agent to inhibit ROCK, a protein that was found to be over-expressed in metastatic breast cancer. Geneticists Hunt for Scleroderma Triggers At its most benign, the autoimmune disease scleroderma can discolor parts of the skin of its sufferers. At its most pernicious, it can thicken and harden their skin, their blood vessels, and their internal organs before, in many cases, killing them. Hunting for the Prozac Gene Prozac works wonders for some depressed people, but not for others. In some cases, patients derive little benefit and at worst, it can lead to bizarre hallucinations and fits of rage. Changes in brain chemicals mark shifts in infant learning When do you first leave the nest? Early in development infants of many species experience important transitions-such as learning when to leave the protective presence of their mother to start exploring the wider world. Study finds mercury levels in children with autism and those developing typically are the same In a large population-based study published online today, researchers at the UC Davis MIND Institute report that after adjusting for a number of factors, typically developing children and children with autism have similar levels of mercury in their blood streams. Mercury is a heavy metal found in other studies to adversely affect the developing nervous system. A master mechanism for regeneration? Biologists long have marveled at the ability of some animals to re-grow lost body parts. Newts, for example, can lose a leg and grow a new one identical to the original. Zebrafish can re-grow fins. Checkered history of mother and daughter cells explains cell cycle differences When mother and daughter cells are created each time a cell divides, they are not exactly alike. They have the same set of genes, but differ in the way they regulate them. Small mechanical forces have big impact on embryonic stem cells Applying a small mechanical force to embryonic stem cells could be a new way of coaxing them into a specific direction of differentiation, researchers at the University of Illinois report. Applications for force-directed cell differentiation include therapeutic cloning and regenerative medicine. The food-energy cellular connection revealed Our body's activity levels fall and rise to the beat of our internal drums-the 24-hour cycles that govern fundamental physiological functions, from sleeping and feeding patterns to the energy available to our cells. More Gene Expression Current Events and Gene Expression News Articles |
|||||||||||||||||||||
|
|||||||||||||||||||||
|
|||||||||||||||||||||