Songbirds Can Sing Like Humans With Complex Vocal Cords

Songbirds sing much like humans do. In fact, a recent study revealed the vocal muscles of Bengalese finches can change function to help produce different parameters of sound, similar to how trained opera singers are able to bellow different notes.

"Our research suggests that producing really complex song relies on the ability of the songbirds' brains to direct complicated changes in combinations of muscles," Samuel Sober, a biologist at Emory University and lead author of the study, explained in a news release. "In terms of vocal control, the bird brain appears as complicated and wonderful as the human brain."

While pitch is important to songbird vocalization, there is no single muscle devoted to controlling it. Rather than contracting one muscle to change pitch, songbirds have to activate a lot of different muscles in concert. These changes differ based on type of vocalizations. For instance, depending on what syllable the bird is singing, a specific muscle will contract to either increase or decrease pitch.

Similar vocal mechanisms have been shown in studies of the human "voice box," or larynx, which houses the vocal cords and an array of muscles that help control pitch. However, instead of a larynx, songbirds have a vocal organ called the syrinx, which holds their vocal cords deeper in their bodies. Furthermore, a songbird has two sets of vocal cords, while humans only have one. This gives songbirds an advantage, enabling them to produce two different sounds simultaneously, in harmony with itself.

"Lots of studies look at brain activity and how it relates to behaviors, but muscles are what translate the brain's output into behavior," Sober added in the university's release. "We wanted to understand the physics and biomechanics of what a songbird's muscles are doing while singing."

To do this, researchers created a new technique involving electromyography (EMG), which allowed them to measure how a songbird's neural activity triggers the production of a particular sound through the flexing of certain vocal muscles. 

"It tells us how complicated the neural computations are to control this really beautiful behavior," Sober said, adding that songbirds have a network of brain regions that non-songbirds do not.

Their study was recently published in the Journal of Neuroscience.

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