Researchers create “wiring maps” for key songbird brain regions

Just like humans, songbirds learn how to speak to their parents. The male imitates his father’s songs and then sings to attract his partner. Although the circuits that produce human speech are more complex, the songbird’s brains provide a viable model to better understand how humans learn to speak and what goes wrong with communication disorders like autism.

Dr. Todd Roberts, associate professor of neuroscience, investigator for Peter O’Donnell Jr., and the Peter O’Donnell Jr. Brain Institute, Southwest UT, is dedicated to studying songbird research. His latest research is published in Elifethe first “wiring diagram” of interconnected circuits in key areas of the songbird’s brain is reported, providing important insights into how sound learning occurs in songbirds, which could help researchers develop better human voice models.

Dr. Roberts is with Massimo Trusel, a professor at Neurscience, who is with Massimo Trusel, Neurosel of Neuroscience of Neurscience. “This study breaks new grounds by providing a specific functional mapping of the first cell type in core sensory and electric pathways that are crucial to core sensory and vocal learning.”

PhD. Roberts and Trusel and colleagues work with Zebra Finch, which is often a pet in the United States and is also the model species with the most vocal learning. For decades, researchers have known that avian brain regions called “HVC” are crucial to Birdsong. Damage to this area greatly impairs Songbirds’ ability to sing and removes it, thus preventing the song from being produced. Earlier anatomical studies have shown that HVC acts like a hub, which receives electrical input from four brain regions and sends electrical output to three other brain regions. However, it is not clear how these input and output circuits transmit information through this hub.

To elucidate this process, UTSW researchers used a technique called optogenetic circuit mapping, in which they insert genes into targeted neurons so that their activity can be controlled by light. By stimulating a single population of neurons to input the input into the HVC, and then measuring the electrical activity of the output neurons, they can see which neurons communicate with each other.

Their findings show that there is an unexpectedly high degree of specificity in how input circuits of input circuit lines and output circuits transmit information through this hub. They map connectivity to an input pathway, a brain region called the nucleus, suggesting that it communicates with all three groups of output neurons in the HVC. Another input pathway, from a brain region called the Uvaeformis nucleus, communicates with one output pathway only in HVC. The mirror image of this connectivity is shown by a third input, which comes from an area called the medial giant cell nucleus, which communicates strongly with two output pathways overlooked by the Uvi Turnich nucleus. The fourth input pathway, from an area called The Nucleus Avalanche, communicates strongly with one output pathway and is even less common with the other two.

Surprisingly, the researchers also found that two of these input pathways communicate directly with each other, revealing previously unknown links in this well-studied circuit. Researchers plan to investigate this newfound connection in future research. They also plan to study how perturbations in various parts of the system affect singing behavior in the zebra finch and use this detailed circuit diagram to build a computational model of how these brain regions play a role in learning and generating vocalization.

Other UTSW researchers who contributed to the study include Ziran Zhao, BS, graduate researcher; Ethan Marks, BS, research technician; and former graduate student Dr. Danyal Alam, Roberts Laboratory.

Dr. Roberts is a Thomas O. Hicks scholar in UTSW medical research.

This study was supported by the National Institutes of Health (UF1NS115821 and R01NS108424).