December 31, 2012
Is An Appreciation Of Music Something Only Humans Have?
Brett Smith for redOrbit.com - Your Universe Online
Many birds use song to communicate everything from threats to mating intentions, but are these vocalizations considered music?
Emory University neuroscientist Sarah Earp, also a classically trained viola player, decided to tackle this question, along with her colleague Donna Maney, by comparing neural responses of birds while they listened to male bird songs.
“We found that the same neural reward system is activated in female birds in the breeding state that are listening to male birdsong, and in people listening to music that they like,” said Earp, who recently published the study´s findings in Frontiers of Evolutionary Neuroscience.
Conversely, the two researchers found that male birds listening to another male´s song had the same neurological responses as people who hear music that sounds discordant.
The researchers decided to compare the chemical pathway that is known to respond to music in humans, and that has a clear avian analog.
To perform the analysis, Earp and Maney analyzed the neurological responses of white-throated sparrows. In particular, the team focused on measuring Egr-1, a biochemical messenger that is activated in responding to a stimulus. This marker was used to map and quantify neural responses and chemical ℠rewards´ in male and female birds while they were listening to a male bird´s song.
Before the listening sessions, some of the birds had been treated with hormones designed to push them into the breeding state. The researchers also maintained a control group that had lower levels of the sexual hormones estradiol and testosterone.
The experimental group of birds was regulated because the type of bird songs that are sung depend on if the birds are in the mood to mate. During the non-mating season, both male and female sparrows establish and maintain dominance through their songs. During the breeding season, a males use their songs to court a female or to ward off another male who is seen as an interloper.
For the females in the breeding state, every region of their chemical pathway was shown to respond to the male birdsong. Testosterone-treated male birds on the other hand, showed a chemical response reminiscent of humans listening to music that is typically used in the tense scenes of horror movies.
“The neural response to birdsong appears to depend on social context, which can be the case with humans as well,” Earp says. “Both birdsong and music elicit responses not only in brain regions associated directly with reward, but also in interconnected regions that are thought to regulate emotion. That suggests that they both may activate evolutionarily ancient mechanisms that are necessary for reproduction and survival.”
The researchers noted that one of the study´s limitations is the fact that many of the regions that respond to music in humans do not have distinct counterparts in birds.
“Perhaps techniques will someday be developed to image neural responses in baleen whales, whose songs are both musical and learned, and whose brain anatomy is more easily compared with humans,” Earp said.
The question of whether birdsong can be considered music has been debated for years. Meanwhile, birds themselves have had quite an impact on popular music–from “Rockin´ Robin” to Hatebeak, a death metal band fronted by a singing parrot.