Navigation Links
Sound Separated into Sound Frequencies

It has long remained a mystery how even in loud environments - like a factory with rattling machines, or a party with music and a cacophony of people// talking - we can hear the voice of our conversational partner. This showed that the brain chooses what to hear.

Neurophysiologists still do not fully understand how we do this. But they do know that the cochlea is mapped out in certain areas of the brain, and like the retina, this mapping is point-for-point. Thus, in interpreting our environment it is important for the brain to separate sound into its constituent frequencies. That means that particular sound frequencies best activate certain groups of neurons in the auditory cortex. Scientists have used electrophysiological and anatomical studies to determine which areas of the brain are responsible for certain frequencies - but mainly in animals, like those of the macaque monkey.

These kinds of studies are only rarely conducted on humans; therefore, much of our knowledge comes from the work with animals. Neurologists primarily use functional magnetic resonance imaging (fMRI) to see "through" the human brain - including the auditory cortex. Looking at hearing, they saw a pattern of activity comparable to that of monkeys. "But the comparisons were indirect," says Christopher Petkov, who led research at the Max Planck Institute. Until now, there had not been any fMRI conducted on the auditory cortex of monkeys, for comparison. "We have now closed that gap," he explains. Scientists have compared the results that various methods produce on the auditory cortex of macaques and these can now be linked to the human imaging using the same technique. They can also now investigate more thoroughly to what extent a monkey’s neuronal auditory centres resemble - and differ from - humans’. This will help advance research into how the primate brain separates sound mixtures in our typically noisy listening environment.

In the new fMRI study, scientist s went beyond identifying individual auditory cortex fields (ACFs); earlier studies had predicted those findings. The researchers also created frequency maps for most of these fields. At first, they mapped several ACFs, then a total of eleven, organised like a mosaic on the surface of the brain. They observed a periodic pattern: a topographic preference for certain frequencies, that either increases or decreases as one progresses across a field. In certain neighbouring fields, the frequency develops in the exact opposite way revealing many mirror reversals of the mosaic pattern. Each sound frequency can thus be found in each ACF. Petkov explains that "in the context of such similar organization for so many fields, certainly different fields have different tasks, but we are only beginning to understand what those differences are."

The researchers have, however, divided the ACFs into two groups already, using hints from electrophysiological work in these primates. Each ACF is responsible for a different sound signal. Three of these fields, which together create a kind of "core" for the auditory cortex, react to individual frequencies in simple sounds like tones. The other eight - including newly described ones - respond better to sounds that are a mixture of different frequencies, like many of the sounds in our environment. These ACFs enclose the three core fields like a belt, and seem to be eight in number.

The pitch pattern in each individual ACF was not as differentiated as, for example, on a piano keyboard. The organisation of the topography could be best observed when sounds lay four octaves apart from one another. Petkov explains that "this is due to the conditions necessary for the imaging technique." In order to see clear signals at all with fMRI, the scientists presented tones that were louder than the soft test tones that are commonly used in electrophysiological studies. "Larger and larger areas of the auditory cortex become active w hen we do this, but our challenge was to preserve the broad topography by not presenting sounds too loudly," Petkov explains. This was an interesting observation for the Max Planck researchers because noise affects the auditory cortex, leading to hearing loss, which also probably disrupts such organised patterns of the brain. Now that many of these fields can be functionally identified, studies can focus on how the responses of these fields are changed by hearing loss and how to restore the functionality of these regions.

Source: Eurekalert
'"/>




Related medicine news :

1. Cure For Deafness Leads Scientist To Find How Fishes Can Hear And Hum Sounds At Same Time
2. Have You Ever Wondered How We Perceive Different Sounds?
3. Bird Flu Alert Sounded In Tamil Nadu
4. Sound Of Sneezing Could Speak About Ones Personality Traits
5. Sound Technology Aids in the Monitoring Of Osteoarthritis
6. UN Sounds Alarm Over Rising Cocaine Consumption In Europe
7. Listening to the Sound of Skin Cancer
8. Limit Consumption of Sound salmon
9. India Sounds Bird Flu Alert in Border States
10. Northeast States Sound Bird Flu Alert
11. Conjoined Twins Separated by Saudi Doctors
Post Your Comments:
*Name:
*Comment:
*Email:


(Date:6/25/2016)... ... ... First Choice Emergency Room , the largest network of independent freestanding ... of its new Mesquite-Samuell Farm facility. , “We are pleased to announce Dr. ... James M. Muzzarelli, Executive Medical Director of First Choice Emergency Room. , Dr. ...
(Date:6/25/2016)... ... June 25, 2016 , ... ... non-athletes recover from injury. Recently, he has implemented orthobiologic procedures as a method ... —Johnson is one of the first doctors to perform the treatment. Orthobiologics are ...
(Date:6/25/2016)... ... June 25, 2016 , ... Conventional wisdom preaches the benefits of ... of the latter, setting the bar too high can result in disappointment, perhaps even ... progress toward their goal. , Research from PsychTests.com reveals that behind ...
(Date:6/24/2016)... ... 2016 , ... Those who have experienced traumatic events may suffer from a ... such as drug or alcohol abuse, as a coping mechanism. To avoid this pain ... following a traumatic event. , Trauma sufferers tend to feel a range of emotions, ...
(Date:6/24/2016)... CA (PRWEB) , ... June 24, 2016 , ... Marcy was in a crisis. Her ... would lash out at his family verbally and physically. , “When something upset him, he ... he would use it. He would throw rocks at my other children and say he ...
Breaking Medicine News(10 mins):
(Date:6/26/2016)... 2016 Story Highlights: ... within the health care industry is causing providers to ... , Deloitte offers a suite of solutions for health ... efficient cost optimization: labor resource analysis, revenue cycle optimization ... better outcomes and better economics ...
(Date:6/24/2016)... Calif. , June 24, 2016  Global ... a biopharmaceutical company developing novel therapeutics for the ... needs, today announced the closing of its previously ... common stock, at the public offering price of ... the offering were offered by GBT. GBT estimates ...
(Date:6/24/2016)... DUBLIN , June 24, 2016 ... addition of the "Structural Electronics 2015-2025: Applications, ... In-Mold Electronics, Smart ... Integrated Photovoltaics Structural electronics involves ... as load-bearing, protective structures, replacing dumb structures such ...
Breaking Medicine Technology: