How the Caged Bird Corrects Its Song

Zachary Sheldon, C’19, intended to pursue a career in clinical medicine until a little bird told him he might be better suited for neuroscience research. Last year Sheldon began studying zebra finches under the supervision of Marc Schmidt, a professor of biology and co-director of the Biological Basis for Behavior program. The project combines Sheldon’s interest in neuroscience with the coding skills he acquired minoring in computer science.

For his research project in Schmidt’s lab, Sheldon, a 2017-2018 College House Research Fellow, will disrupt neural signals that flow through what he believes is a critical piece of the zebra finch’s song production anatomy. His experiments will expand upon newly-developing research into the function of sensory feedback in a field that, until now, has focused on an auditory system. Understanding the mechanisms of sensory feedback in birds will give researchers insight into parallels in the human basal ganglia and disorders like Parkinson’s, Huntington’s, and Tourette syndrome, which could result from a malfunction in the feedback loop between the senses and the brain.

More polychromatic than their name implies, male zebra finches have white bellies, brown speckled wings, hazard-orange beaks, and yellow sideburns (though they do have black and white stripes at the top of their tails). What researchers refer to as a song actually sounds more like a dog going to town on his favorite squeak toy. Aviary research software records the finch’s song over several days and likely spares the researcher his sanity.

“The zebra finch song varies between individuals,” says Sheldon. “They have a specific song that they will sing over and over throughout their life.” The predictability of the finch’s song makes it an ideal, tractable model for sensory feedback research.

Sheldon has been busy with experiment preparation over the past year. He has prepped bird-friendly recording booths and programmed recording software to automate feedback disruption experiments and data collection. In addition, he auditioned birds to determine which sing frequently and produce a particular syllable that is ideal for his experiment.

The chosen birds will receive an implant on the Vagus nerve—a 3-D-printed nanoclip that wraps the nerve, allowing stimulation at a designated syllable in the bird’s song. Current experiments performed by Kristen Miller, C’18, involve cutting the Vagus nerve. Miller determined the Vagus nerve damage significantly degraded the bird’s song. Stimulating the nerve will provide deeper insight into how the bird uses its senses to correct an error in its song.

Sheldon suggests imagining you are an opera singer: You can hear when you hit the right note, but to hold that note for a long time you must tune into the changes happening in your body. “By the time you get to the end of that note maybe there is a lot of carbon dioxide building up in your lungs so you have to change the way you are singing it in order to maintain that same note,” says Sheldon. The stimulation will occur on the Vagus nerve to pinpoint if this the line of communication that signals to the zebra finch that changes are happening in its lungs and vocal musculature, and that it must alter its song to correct them.

“These birds use their song to attract a mate so it’s very important that they sing their correct song accurately,” says Sheldon. “They need this sensory feedback, we have hypothesized, in order to maintain that correct song output and accomplish the goal of mating.”

Sheldon hopes his research on auditory feedback and sensory impact will contribute to the valuable insights neuroscientists have discovered about songbird error detection and correction. He says, “If we understand the overall role that sensory feedback plays in this sensorimotor circuit, potentially we can translate that in to understanding how sensory feedback is integrated into the circuitry of the human brain.”

Sheldon’s research experience has changed the way he looks at birds. “When you are walking on the street in Philadelphia you see little finches hopping around and you don't think much of it,” he says. “Then when you study it in depth you can see how incredibly complex and impressive it is just for them to be able to sing a song to attract a mate.”

Songbirds have a powerful calling. Sheldon thinks they may have lured him to continue studying their tiny brains in a future doctorate program.