Summary: A new mouse study uncovers a brain circuit that may support the rapid back-and-forth timing of human conversation. The discovery could clarify mechanisms behind speech disorders and suggest directions for future therapies.
Source: UT Austin.
Researchers from New York University School of Medicine and The University of Texas at Austin studied the singing behavior of Alston’s singing mice from the cloud forests of Costa Rica and identified a brain circuit that appears to enable high-speed vocal turn-taking. Published in the journal Science, the findings illuminate how distinct cortical circuits coordinate rapid vocal exchanges and may help scientists better understand and treat a range of speech disorders.
When two male Alston’s singing mice encounter one another—typically a resident defending its territory and an outsider or “recruit”—they perform alternating vocalizations that resemble a duet. The recruit starts singing only after the resident finishes, and it abruptly stops if the resident resumes. This tight alternation, known as vocal turn-taking, mirrors the millisecond-level timing humans use in conversational speech.
“The recruit signals his presence and intent to compete; the resident signals that he’s already established,” said Steven Phelps, study co-author and professor of integrative biology and director of the Center for Brain, Behavior and Evolution at UT Austin. “Those exchanges are driven by precise, rapid coordination of vocal production.”
Unlike standard laboratory mice, which rarely show these structured vocal exchanges, Alston’s singing mice provide a natural mammalian model to study sub-second vocal coordination. That makes them valuable for neuroscience research into how brains time and control communicative interactions.
Using behavioral observation and neural perturbation experiments, the team found that motor cortical circuits separate the generation of sounds from the rapid control of when to start and stop singing. In other words, the brain areas that command the muscles to produce notes are distinct from circuits in motor cortex that gate the very fast onsets and offsets required for conversational exchange.
“Our work directly demonstrates that a region of motor cortex is essential for vocal interaction in both these mice and in humans,” said Michael Long, senior author and an associate professor of neuroscience at NYU School of Medicine. The study shows how motor cortical activity can influence the precise pacing of vocalizations on a moment-by-moment basis, enabling coordinated turn-taking.
“By separating production circuits from timing control, evolution has given singing mice neural tools for tight vocal control similar to that seen in insect chirps, bird duets, and human conversation,” added Arkarup Banerjee, co-first author and postdoctoral scholar in Long’s lab. Banerjee noted that despite many examples of vocal exchanges across species, suitable mammalian models for studying the neural basis of rapid conversational timing were previously lacking.
The authors propose a hierarchical framework for vocal control in these animals: lower-level circuits execute the motor patterns that produce sound while higher-level motor cortical circuits modulate pacing and rapid turn-taking. This systems-level view helps explain how sensory cues are transformed into precisely timed motor responses during natural social interactions.
Looking ahead, the researchers are applying insights from the singing mouse model to human studies of speech circuits. By identifying neural activity patterns that enable two brains to coordinate vocal exchanges, scientists can search for the processes that fail in conditions such as autism or after stroke. That knowledge could guide development of targeted therapies to restore or improve communication in affected individuals.
“To design better treatments for people whose rapid conversational reply generation has been disrupted—by developmental disorders, neurodegenerative disease, or injury—we first need to understand how the brain coordinates dozens of muscles and sensory feedback at subsecond timescales,” Long said.
Previous work by Phelps and colleagues has shown that male singing mice use their calls not only to attract mates and deter rivals of their own species, but also to repel males of closely related, smaller species. Together, these behavioral and neural findings emphasize the ecological relevance and evolutionary importance of precise vocal timing.
Study authors include Daniel E. Okobi Jr., Arkarup Banerjee, Andrew M. M. Matheson, Steven M. Phelps, and Michael A. Long, representing the NYU Neuroscience Institute, the Department of Otolaryngology at NYU School of Medicine, and the Center for Brain, Behavior and Evolution at UT Austin.
Funding: This research was supported by the New York Stem Cell Foundation, the Simons Foundation Society of Fellows, and the Simons Collaboration on the Global Brain.
Source: Marc Airhart – UT Austin
Publisher: Organized by NeuroscienceNews.com.
Image Source: Image credited to Bret Pasch.
Original Research: Abstract for “Motor cortical control of vocal interaction in neotropical singing mice” by Daniel E. Okobi Jr., Arkarup Banerjee, Andrew M. M. Matheson, Steven M. Phelps, and Michael A. Long in Science. Published March 1, 2019.
doi: 10.1126/science.aau9480
UT Austin. “In Singing Mice, Researchers Find Clues to Our Own Rapid Conversations.” NeuroscienceNews. March 1, 2019.
Abstract
Motor cortical control of vocal interaction in neotropical singing mice
Acoustic communication often demands rapid motor adjustments in response to sensory input, yet the sensorimotor processes underlying such behaviors remain poorly understood. This study examines vocal exchanges in Alston’s singing mouse (Scotinomys teguina) and shows that males modify singing behavior during social interactions on subsecond timescales, resembling both classical sensorimotor tasks and elements of conversational speech. The authors identify an orofacial motor cortical region and, through perturbation experiments, demonstrate hierarchical control of vocal production: the motor cortex modulates the pacing of singing on a moment-by-moment basis, enabling precise vocal interactions. These results provide a systems-level framework for understanding the sensorimotor transformations that support natural social vocal behavior.