By ScienceDaily, December 27, 2012
A White-Throat Sparrow
A bird listening to
birdsong may experience some of the same emotions as a human listening to
music, suggests a new study on white-throated sparrows, published in Frontiers
of Evolutionary Neuroscience.
"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," says Sarah Earp, who led the research as an undergraduate
at Emory University.
For male birds
listening to another male's song, it was a different story: They had an
amygdala response that looks similar to that of people when they hear
discordant, unpleasant music.
The study,
co-authored by Emory neuroscientist Donna Maney, is the first to compare neural
responses of listeners in the long-standing debate over whether birdsong is
music.
"Scientists
since the time of Darwin have wondered whether birdsong and music may serve
similar purposes, or have the same evolutionary precursors," Earp notes.
"But most attempts to compare the two have focused on the qualities of the
sound themselves, such as melody and rhythm."
Earp's curiosity
was sparked while an honors student at Emory, majoring in both neuroscience and
music. She took "The Musical Brain" course developed by Paul Lennard,
director of Emory's Neuroscience and Behavioral Biology program, which brought
in guest lecturers from the fields of neuroscience and music.
"During one
class, the guest speaker was a composer and he said that he thought that
birdsong is like music, but Dr. Lennard thought it was not," Earp recalls.
"It turned into this huge debate, and each of them seemed to define music
differently. I thought it was interesting that you could take one question and
have two conflicting answers that are both right, in a way, depending on your
perspective and how you approach the question."
As a senior last
year, Earp received a grant from the Scholars Program for Interdisciplinary
Neuroscience Research (SPINR), and a position in the lab of Maney, who uses
songbirds as a model to study the neural basis of complex learned behavior.
When Earp proposed
using the lab's data to investigate the birdsong-music debate, Maney thought it
was a great idea. "Birdsong is a signal," Maney says. "And the
definition of a signal is that it elicits a response in the receiver. Previous
studies hadn't approached the question from that angle, and it's an important
one."
Earp reviewed
studies that mapped human neural responses to music through brain imaging.
She also analyzed
data from the Maney lab on white-throated sparrows. The lab maps brain
responses in the birds by measuring Egr-1, part of a major biochemical pathway
activated in cells that are responding to a stimulus.
The study used
Egr-1 as a marker to map and quantify neural responses in the mesolimbic reward
system in male and female white-throated sparrows listening to a male bird's
song. Some of the listening birds had been treated with hormones, to push them
into the breeding state, while the control group had low levels of estradiol
and testosterone.
During the
non-breeding season, both sexes of sparrows use song to establish and maintain
dominance in relationships. During the breeding season, however, a male singing
to a female is almost certainly courting her, while a male singing to another
male is challenging an interloper.
For the females in
the breeding state every region of the mesolimbic reward pathway that has been
reported to respond to music in humans, and that has a clear avian counterpart,
responded to the male birdsong. Females in the non-breeding state, however, did
not show a heightened response.
And the
testosterone-treated males listening to another male sing showed an amygdala
response, which may correlate to the amygdala response typical of humans
listening to the kind of music used in the scary 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."
A major limitation
of the study, Earp adds, is that many of the regions that respond to music in
humans are cortical, and they do not have clear 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," she says.
Earp, who played
the viola in the Emory orchestra and graduated last May, is now a medical
student at the Cleveland Clinic.
So
what music makes her brain light up? "Stravinsk's 'Firebird' suite,"
Earp says.
Story Source:
The above story is reprinted from materials provided by Emory University. The original article was written by Carol Clark.Note: Materials may be edited for content and length. For further information, please contact the source cited above.
Journal Reference:
- Sarah E. Earp, Donna L. Maney. Birdsong: Is It Music to Their Ears? Frontiers in Evolutionary Neuroscience, 2012; 4 DOI: 10.3389/fnevo.2012.00014
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