Male mice of the Alston's singing mouse species (Scotinomys teguina) harness the power of music to outperform competitors and woo females – consider these mice the Marvin Gayes of the animal kingdom.
Individuals are able to produce songs with an incredible range of nearly 100 audible notes and challenge each other by singing in turns, much like a duet or a rap battle. (Or, indeed, a human conversation.) Now, researchers at the New York University (NYU) School of Medicine have studied the brain activity of these mice to determine exactly how it is they are able to participate in such complex conversational behavior. The results have been published in the journal Science.
But there is more to this research than an excuse to watch adorable fluffies sing. From S. teguina's elaborate mating ritual, scientists have been able to identify a brain circuit they believe allows us humans to engage in rapid back-and-forth conversation. Knowing this, they say, can help us fashion new treatments for people who have lost the ability to converse, either from disease or traumatic events (for example, a stroke) or from a neurodevelopmental condition like autism.
"Our work directly demonstrates that a brain region called the motor cortex is needed for both these mice and for humans to vocally interact," senior study author Michael Long, an associate professor of neuroscience at the NYU School of Medicine, said in a statement.
"We need to understand how our brains generate verbal replies instantly using nearly 100 muscles if we are to design new treatments for the many Americans for whom this process has failed."
In previous research, scientists have looked to marmosets to explain back-and-forth communication. Like humans, these monkeys engage in conversation. The problem is that they do so at a much slower pace – an inconvenient fact that makes them an imperfect animal model to study. The songs of S. teguina, however, may prove to be a good alternative solution.
These mice are technically more evolutionarily distant from us than primates but they communicate at a much more rapid pace. During these musical "conversations", mice politely wait for their opponent to stop, making sure never to overlap. Yet, they are able to start their turn within a fraction of a second after the other has finished.
While their songs tend to progress in predictable patterns, the scientists observed changes in social situations that forced the mice to “bend and break” the tunes – like a conversation. By comparing song patterns and readings taken by electromyography, they located a functional “hotspot”, found in the brain's orofacial motor cortex (OMC), that regulated song timing.
The team then used a process called focal cooling to slow the neurons and, therefore, the pace of vocalizations without affecting the pitch, tone, or duration of the different notes. This cooling encouraged the mice to extend their songs and add in extra notes. Next, they injected a nerve-blocking drug into the OMC to see how it affected a mouse's performance. Drugged up, the mice often failed to respond to a recording of a "competitive" male mouse. And if they did, they took much longer to do so.
Long compares this section of the OMC to a "conductor" that enables the animals to take turns when they sing.
Next, he plans to genetically engineer mice to display some of the mutations associated with autism to find out how that affects speech. By understanding it in a simpler system (i.e. a mouse), he hopes to find out how it works in humans.
[H/T: New York Times]
