Tag Archives: Singing

Scientists find neurons in the human brain that only respond to singing

Credit: Pixabay.

Music and the human brain seem to be deeply intertwined, a bond that may have first appeared when the first australopithecine ancestor got up on her hind legs 4.4 million years ago and walked. This bipedal rhythm may have made our lineage particularly sensitive to musicality, so much so that we now know that the human brain has dedicated neural circuitry for processing and interpreting musical information.

In 2015, neuroscientists at MIT identified a population of neurons in the auditory cortex that responds specifically to music. In a new study that appeared today in the journal Current Biology, the same team of researchers led by Sam Norman-Haignere have identified specific neurons in the brain that light up only when we hear singing, but not other types of music.

“The work provides evidence for relatively fine-grained segregation of function within the auditory cortex, in a way that aligns with an intuitive distinction within music,” said Norman-Haignere, a former MIT postdoc who is now an assistant professor of neuroscience at the University of Rochester Medical Center.

The singing brain

For their original 2015 work, the scientists used functional magnetic resonance imaging (fMRI) to scan the brains of participants as they listened to a collection of 165 sounds. These included everyday sounds like a dog barking or traffic in a busy city, as well as different types of speech and music.

After analyzing the brain patterns using a novel interpretation technique for fMRI data, the researchers identified a neural population that responded differently to both music and speech.

However, fMRI –which detects the changes in blood oxygenation and flow that occur in response to neural activity while a person lies down inside a machine equipped with very powerful magnets — has its limitations. A much more precise method for recording electrical activity in the brain is electrocorticography (ECoG), which directly measures patterns of activity using electrodes implanted inside the skull. The obvious drawback is that this is highly invasive. Let’s just say there aren’t too many keen volunteers that would gladly have their skulls drilled for science — unless you already don’t have much to lose.

Electrocorticography is becoming relatively widely used to monitor patients with epilepsy who are about to undergo surgery to treat their seizures. This allows doctors to pinpoint the exact location in the brain where a patient’s seizures are originating, which can be different from person to person.

Some of these patients agreed to participate, and MIT researchers were able to gather data from them over several years. Many of the 15 participants involved in the study didn’t have electrodes fitted in their auditory cortex, but some did — and the insight they provided proved valuable. Using a novel statistical approach, the researchers were able to identify neural populations that were responsible for the electrical activity recorded by each electrode.

“When we applied this method to this data set, this neural response pattern popped out that only responded to singing,” Norman-Haignere says. “This was a finding we really didn’t expect, so it very much justifies the whole point of the approach, which is to reveal potentially novel things you might not think to look for.”

“There’s one population of neurons that responds to singing, and then very nearby is another population of neurons that responds broadly to lots of music. At the scale of fMRI, they’re so close that you can’t disentangle them, but with intracranial recordings, we get additional resolution, and that’s what we believe allowed us to pick them apart,” he added.

When ECoG data was combined with fMRI, the researchers were able to determine even more precisely the locations of the neural populations that responded specifically to signing, but not other kinds of music.

“The intracranial recordings in this study replicated our prior findings with fMRI and revealed a novel component of the auditory response that responded nearly exclusively to song,” Norman-Haignere told ZME Science.

These song-specific hotspots were found at the top of the temporal lobe, near regions that are selective for language and music. This suggests that song-specific populations of neurons likely respond to perceived pitch, so they might tell the difference between spoken words and musical vocalization, before sending this information to other parts of the brain for further processing.

These findings enrich our understanding of how the human brain responds to music. For instance, previous research showed music impacts brain function and human behavior, including reducing stress, pain and symptoms of depression, as well as improving cognitive and motor skills, spatial-temporal learning, and neurogenesis, which is the brain’s ability to produce neurons. 

But many mysteries still remain, which is why the MIT researchers plan to study infants’ neural response to music, in hopes of learning more about how brain regions tuned to music develop. 

“At present, we know very little about song-selective neural populations, in part because we just discovered them and in part because this type of data takes a long time to collect. Those are great questions that future research will hopefully shed some light on,” Norman-Haignere told ZME Science.

Singing mouse.

The brains of singing mice might hold the secret of how we engage in conversation

Singing mice from the cloud forests of Costa Rica could help us better understand how our brains handle speech.

Singing mouse.

Image credits NYU School of Medicine.

The male Alston’s singing mouse (Scotinomys teguina) is quite the skillful bard. These tiny mammals can produce songs from a repertoire of almost one hundred audible noises and a host of sounds we can’t even perceive. There’s also surprising structure to their musical interactions — much like humans engaged in conversation, the mice challenge their competitors by singing in turn, a new paper explains.

The brains of these mice can help us understand the brain mechanisms that underpin our own ability to converse with one another. We tend to take this ability pretty much for granted, but it’s nowhere near widespread in nature, the paper notes. Standard laboratory mice, for example, produce ultrasonic sounds without evident timing of exchanges.

I talk, then you talk, and that’s our, communication hack

“Our work directly demonstrates that a brain region called the motor cortex is needed for both these mice and for humans to vocally interact,” says senior study author Michael Long, PhD, an associate professor of neuroscience at the New York University (NYU) School of Medicine.

Evolution has separated the duties of sound production and control circuits (i.e. those that handle the timing of replies) in the brains of singing mice, the team reports. This is similar to what is seen in crickets, some species of birds, and “possibly human discussion”, adds study co-first author Arkarup Banerjee, a post-doctoral researcher in Long’s lab.

The findings are based on electromyography measurements which the team performed on singing mice, meant to determine the relationship between different brain centers and muscular contractions. The readings were performed on two mice which coordinated their responses.

It’s an exciting find, the team adds, as we simply don’t have suitable mammalian models for the study of back-and-forth communication in the wild. A lot of animals engage in vocalization, sure, but their communication is more similar to a chatroom where everybody is talking at the same time than a balanced conversation. Up to now, they explain, the most reliable animal model neuroscientists could use to study vocal exchanges was the marmoset (family Callitrichidae), but it, too, came with significant limitations: their conversational turns are very slow compared to human speech, and unlikely to result from the fast muscle response to sensory cues, the team notes.

And no hard feelings, marmosets, but that just doesn’t cut it:

“We need to understand how our brains generate verbal replies instantly using nearly a hundred muscles if we are to design new treatments for the many Americans for whom this process has failed, often because of diseases such as autism or traumatic events, like stroke,” says Long.

The team found that the brains of singing mice come equipped with specialized areas that control how their muscles create specific notes. Separate circuits in the motor cortex enable the fast starts and stops that form a conversation between vocal partners. The former areas allow these mice to create the actual sounds, while the latter control their timing to prevent a cacophony.

Mice’s songs also change in social situations as individuals “bend and break the songs” to converse. They also report finding a functional “hotspot” in the side of the front of the motor cortex — the orofacial motor cortex or OMC — that regulates song timing.

In the future, the team plans to apply the mouse model to guide similar exploration of human speech circuits. They hope that understanding how two brains engage in conversations can help us identify what goes wrong in the context of disorders that interfere with communication, and even finding cures.

The paper ” Motor cortical control of vocal interaction in neotropical singing mice” has been published in the journal Science.

The oceans are filled with song, and here’s a part of it

The oceans might be a much livelier place than we’d think, new research has found. Just like birds sing on three branches on land, the waters are filled with the song of fish. Most of the sounds come from soloist fish, which repeat the same calls over and over again. But when calls from different species overlap, they form a beautiful chorus.

Just wait till this one starts singing.
Image credits David Iliff.

While it may seem pretty silent to us underwater, fish actually rely on sound heavily for reproduction, feeding, or settling territorial disputes. Nocturnal predatory fish use calls to help them stay together in the dark waters and diurnal fish employ several calls to warn trespassers they’re in occupied territory.

Robert McCauley and his colleagues from the Curing University in Perth, Australia, went to the coastal waters off Port Headland in Western Australia for an 18-month long performance. During this time they recorded and identified seven distinct fish choruses, some singing at dawn and others at dusk.

The low, bass-like “foghorn” call is made by the Black Jewfish (Protonibea diacanthus), while the grunting one which resembles “the buzzer in Operation board game,” as researcher Miles Parsons puts, it belongs to a species of Terapontid. The quieter ba-ba-ba sound is made by batfish.

The sounds were recorded with two sea-noise loggers. One of these was placed near the shore of Port Headland and the second one was placed 21.5 km (13.36 miles) away, in offshore waters. This method allowed the team listen in on the area’s fish over a large area and a long period of time, so they could monitor the state of local ecosystems .

“This is a method that allows us to understand what’s happening at Port Headland 24/7 for a year and a half,” says Simpson.

“I don’t know any scuba diver that can stay down there that long!”

The researchers mapped which chorus was seen at which points in time throughout the year, and it’s way more lively there than I would have imagined.

Days on which choirs were detected on the inshore and offshore recordings taken between March-2011 and September-2012.
Image credits Miles J. G, Parsons et al., Bioacustics, 2016.

“We are only just beginning to appreciate the complexity involved and still have only a crude idea of what is going on in the undersea acoustic environment,” says lead researcher McCauley.

“I’ve been listening to fish squawks, burble and pops for nearly 30 years now, and they still amaze me with their variety,” he concludes.

The full paper “Fish choruses off Port Hedland, Western Australia” has been published in the journal Bioacoustics.