Featured Research

from universities, journals, and other organizations

Brain wiring quiets the voice inside your head

Date:
September 3, 2013
Source:
Duke University
Summary:
Researchers have developed the first diagram of the brain circuitry that enables a complex interplay between the motor system and the auditory system to occur. The research could lend insight into schizophrenia and mood disorders that arise when this circuitry goes awry and individuals hear voices other people do not hear.

A mouse brain's motor cortex shows a subset of neurons, labeled in orange, that have long axons extending to the auditory cortex. These neurons convey movement-related signals that can alter hearing. Blue dots in the background show brain cells that do not send axons to the auditory cortex.
Credit: Richard Mooney Lab, Duke University

During a normal conversation, your brain is constantly adjusting the volume to soften the sound of your own voice and boost the voices of others in the room. This ability to distinguish between the sounds generated from your own movements and those coming from the outside world is important not only for catching up on water cooler gossip, but also for learning how to speak or play a musical instrument.

Related Articles


Now, researchers have developed the first diagram of the brain circuitry that enables this complex interplay between the motor system and the auditory system to occur.

The research, which appears Sept. 4 in The Journal of Neuroscience, could lend insight into schizophrenia and mood disorders that arise when this circuitry goes awry and individuals hear voices other people do not hear.

"Our finding is important because it provides the blueprint for understanding how the brain communicates with itself, and how that communication can break down to cause disease," said Richard Mooney, Ph.D., senior author of the study and professor of neurobiology at Duke University School of Medicine. "Normally, motor regions would warn auditory regions that they are making a command to speak, so be prepared for a sound. But in psychosis, you can no longer distinguish between the activity in your motor system and somebody else's, and you think the sounds coming from within your own brain are external."

Researchers have long surmised that the neuronal circuitry conveying movement -- to voice an opinion or hit a piano key -- also feeds into the wiring that senses sound. But the nature of the nerve cells that provided that input, and how they functionally interacted to help the brain anticipate the impending sound, was not known.

In this study, Mooney used a technology created by Fan Wang, Ph.D., associate professor of cell biology at Duke, to trace all of the inputs into the auditory cortex -- the sound-interpreting region of the brain. Though the researchers found that a number of different areas of the brain fed into the auditory cortex, they were most interested in one region called the secondary motor cortex, or M2, because it is responsible for sending motor signals directly into the brain stem and the spinal cord.

"That suggests these neurons are providing a copy of the motor command directly to the auditory system," said David M. Schneider, Ph.D., co-lead author of the study and a postdoctoral fellow in Mooney's lab. "In other words,they send a signal that says €˜move,€™ but they also send a signal to the auditory system saying 'I am going to move.'"

Having discovered this connection, the researchers then explored what type of influence this interaction was having on auditory processing or hearing. They took slices of brain tissue from mice and specifically manipulated the neurons that led from the M2 region to the auditory cortex. The researchers found that stimulating those neurons actually dampened the activity of the auditory cortex.

"It jibed nicely with our expectations," said Anders Nelson, co-lead author of the study and a graduate student in Mooney's lab. "It is the brain's way of muting or suppressing the sounds that come from our own actions."

Finally, the researchers tested this circuitry in live animals, artificially turning on the motor neurons in anesthetized mice and then looking to see how the auditory cortex responded. Mice usually sing to each other through a kind of song called ultrasonic vocalizations, which are too high-pitched for a human to hear. The researchers played back these ultrasonic vocalizations to the mice after they had activated the motor cortex and found that the neurons became much less responsive to the sounds.

"It appears that the functional role that these neurons play on hearing is they make sounds we generate seem quieter," said Mooney. "The question we now want to know is if this is the mechanism that is being used when an animal is actually moving. That is the missing link, and the subject of our ongoing experiments."

Once the researchers have pinned down the basics of the circuitry, they could begin to investigate whether altering this circuitry could induce auditory hallucinations or perhaps even take them away in models of schizophrenia.

The research was supported by grants from the National Institutes of Health (NS077986, DA028302, and NS079929).


Story Source:

The above story is based on materials provided by Duke University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Anders Nelson, David M. Schneider, Jun Takatoh, Katsuyasu Sakurai, Fan Wang, Richard Mooney. A Circuit for Motor Cortical Modulation of Auditory Cortical Activity. The Journal of Neuroscience, 2013 DOI: 10.1523/JNEUROSCI.2275-13.2013

Cite This Page:

Duke University. "Brain wiring quiets the voice inside your head." ScienceDaily. ScienceDaily, 3 September 2013. <www.sciencedaily.com/releases/2013/09/130903194055.htm>.
Duke University. (2013, September 3). Brain wiring quiets the voice inside your head. ScienceDaily. Retrieved March 1, 2015 from www.sciencedaily.com/releases/2013/09/130903194055.htm
Duke University. "Brain wiring quiets the voice inside your head." ScienceDaily. www.sciencedaily.com/releases/2013/09/130903194055.htm (accessed March 1, 2015).

Share This


More From ScienceDaily



More Health & Medicine News

Sunday, March 1, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Could a $34 Smartphone Device Improve HIV Diagnosis in Africa?

Could a $34 Smartphone Device Improve HIV Diagnosis in Africa?

Reuters - Innovations Video Online (Feb. 27, 2015) A dongle that plugs into a Smartphone mimics a lab-based blood test for HIV and syphilis and can detect the diseases in 15 minutes, say researchers. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Doctor Says Head Transplants Possible Within Two Years

Doctor Says Head Transplants Possible Within Two Years

Buzz60 (Feb. 27, 2015) An Italian doctor is saying he could stick someone&apos;s head onto someone else&apos;s body. Patrick Jones (@Patrick_E_Jones) reports. Video provided by Buzz60
Powered by NewsLook.com
How Your Dentist Could Help Screen You For Diabetes

How Your Dentist Could Help Screen You For Diabetes

Newsy (Feb. 27, 2015) A new study from researchers at New York University suggests dentists could soon use blood samples taken from patients&apos; mouths to test for diabetes. Video provided by Newsy
Powered by NewsLook.com
The Best Tips to Makeover Your Health

The Best Tips to Makeover Your Health

Buzz60 (Feb. 27, 2015) If you&apos;re looking to boost your health this season, there are a few quick and easy steps to prompt you for success. Krystin Goodwin (@Krystingoodwin) has the best tips to give your health a makeover this spring! Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins