Courtesy Christopher Olson
Ed note: Do not give your bird alcohol — birds can get alcohol poisoning and die easily.
Ever notice how the conversational buzz at a cocktail party gets a little more … rambling after two or three hours that are heavy on the champagne and light on the cheese and crackers? Turns out that happens at bird parties, too.
Researchers at the Oregon Health and Science University’s department of behavioral neuroscience have long puzzled over the way that alcohol affects the human brain, and why one too many mimosas seems to stump a wedding toast as the inebriated slur their words. Neuroscientists have noted that moderate amounts of alcohol seem to selectively inhibit some of the brain’s functions but have relatively little impact on others (speech may be tricky, but breathing and standing are attainable in most cases, for example).
To further analyze the phenomenon, scientists examined a group of zebra finches as they drank a juice mixture with 6 percent alcohol mixed delivered through their water bottles. (And no, the birds didn’t toast one another with champagne —researchers used ethanol to achieve the desired alcohol content. To their surprise though, the birds seemed quite wiling to drink the juice mixture; many other species naturally avoid alcohol.)
The birds reached blood alcohol levels of .05 to .08 percent, and while their general behavior and frequencies of song did not change, certain aspects of their singing did. Though the birds continued to perch, fly, and eat normally, their songs showed decreased amplitude and increased entropy—meaning the birds got a bit quieter, and the structure of their songs got a little looser, not unlike a tipsy person slurring their words. The untrained ear can detect only a subtle difference when the recordings were played back in slow motion, but the change was found to be statistically significant. More importantly for the researchers, those changes were found to occur when the finches’ blood ethanol contents reached a level considered "risky” in humans.
But why get a cage full of zebra finches drunk in the first place?
Scientists were curious about the areas of the brain associated specifically with vocal learning, and discovering why alcohol causes humans to lose their grasp of something they’ve used most of their lives: speech. According to lead study author Dr. Christopher Olson, knowing the ways that alcohol changes speech in birds can help us figure out why that change occurs in humans, because the two species’ brains are remarkably similar.
"Although there were some intriguing behavioral similarities in terms of vocal learning, for a long time we thought that the mammalian and avian brains were very different — mammals have a layered cortex while birds have a telencephalon and superficially they appear to be very different structures,” Olson said. "Recently though, there are a couple breakthroughs that have made us realize bird brains and mammal brains have some important similarities.”
Despite their aesthetic differences, human and avian brains have similar circuitry for motor function and learning. Both creatures also have a genetic transcription factor called FOXP2, which is vital to vocal learning. Birds also process alcohol in a similar manner to humans — slowly.
"The slow metabolism of alcohol is actually a human trait that may be contributing to some of the problems associated with alcohol — if we were able to rapidly metabolize alcohol in our livers we wouldn’t have alcohol persisting in the brain where it acts to alter behaviors and has cognitive problems,” Olson said. "It was actually an important step in the development of the zebra finch as a model — to show that they held alcohol in their bodies and brains for a decent amount of time.”
In fact, a few of the finches had to be removed from the data as outliers because even a small amount of alcohol resulted in drastic impacts on their behavior, not unlike humans who are known as "lightweights.” There were also some birds who voluntarily consumed more of the alcohol-laced juice than others — a tendency Olson believes could have a genetic link, as do so many other drinking behaviors.
"There are doubtless a number of other genes that have some influence on individual alcohol intakes, and the fact that we see individual variation in the finch suggests to me a great deal of genetic variation to work with experimentally,” Olson said.
But why use finches? Olson said the OHSU is one of the first to use this particular type of songbird in a chemical substance study, and they’re a great fit for laboratory research. The zebra finches are easy to acquire, mate irrespective of natural light patterns or seasons and their songs are very distinctive, making their vocalizations easy to analyze.
The finches’ day of partying for science is just the latest in a long line of contributions birds have made to our understanding of how the human brain learns and functions. Neuroscientists first pinpointed some of the gender differences between male and female brains by studying brain structures associated with singing in songbirds (which are smaller or absent in female birds compared to males). Seasonal songbirds also tipped scientists off to the notion that neurons could be born anew in adult brains when they began singing in springtime. The return of their songs was accompanied by physical changes in song-related areas of the brain, refuting the old adage that the brain cannot grow after the body is finished growing.
If you’re noticing a pattern here (song), it’s because Olson said bird song is similar in nature to other learned motor behavior that humans use routinely, such as learning how to type, drive, or play a musical instrument — all of these things take time and demand the learner process what’s going on in their environment as well as within their own bodies.
"It is thought to be a very reliable indicator of learning ability- as opposed to measuring the running ability of a mouse in maze as a measure of the mouse’s cognitive might, where you don’t know exactly what is driving the mouse’s behavior because it is a bit artificial,” Olson said.
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