AP Biology class blog for discussing current research in Biology

Tag: Sound

Hearing Loss Clue Uncovered

In the United States, approximately forty-eight million (twenty percent) of men and women suffer some degree of hearing loss, as it is the third most common physical condition after arthritis and heart disease. While it is most often associated with the population sixty-five and
older, hearing loss effects all ages, as thirty school children per out one-thousand are afflicted in some varying degree. An individual is able to hear sound involving the ear’s main structures. In age-related hearing loss, one or more of these structures is damaged: the external ear canal, the middle ear, and the inner ear. External ear canal impairment is related exclusively to conducive hearing loss. The middle ear, which is separated from the ear canal by the eardrum may be caused by sensorineural hearing loss. Lastly, the inner ear, which contains the cochlea, the main sensory organ of hearing. When the vibrations from the middle ear enter the cochlea it causes the fluid to move and the sensory hair cells pick up this movement. In response to the movement of the fluid the hair cells send an electrical signal up the auditory nerve to the brain where it’s recognized as sound.


Now, how do these different internal departments of the human ear gradually induce hearing loss? While we get older, some may develop presbycusis, which causes the tiny hair-like cells in the cochlea to deteriorate over time. Clarity of sound decreases, as the hairs are unable to vibrate as effectively in response to sound. Recently, otolaryngologists have discovered new evidence that human hearing loss relates to a certain genetic mutations. A study at the University of Melbourne revealed “a novel genetic mutation was first identified in 2010 as causing hearing loss in humans… now discovered that this mutation induces malfunction of an inhibitor of an enzyme commonly found in our body that destroys proteins – known scientifically as SERPINB6. Individuals who lacked both copies of this “good gene” were shown to have lost their hearing by twenty years of age.


Although this discovery is changing the way scientists previously viewed hearing loss, the answer to why this mutation, SERPINB6, is a catalysts for such loss, is inconclusive. However, this mutative gene has created a revelation for many: it is now not unusual to show gradual signs of hearing loss under the age of sixty years.


To better understand the effects of the mutant gene, mice were used in order to imitate the condition from youth to adulthood. At only three weeks of age, mice with SERPINB6 had begun to lose hearing – three weeks is equivalent to pubescent or teenage years in humans. And as we could have predicted, the mice continued to show a decrease in hearing ability, much the same as humans. Researchers examined the mice’s inner ear, which revealed the cells responsible for interpreting sound (sensory hair cells) had died.


Fortunately, this new discovery of a mutant gene in human sensory cells has created new attention to better understand the case of those who are effected by the condition. 



Why do you enjoy music?

Have you ever wondered why that new song you enjoyed hearing that new song on the radio? This recent study shows that there are four regions of our brain responsible for pleasure while listening to music. The main region is called the nucleus accumbensand is located in the “reward center” of the brain. This region is responsible for making predictions and when the prediction your brain makes is correct it releases feel-good chemicals. Along with guessing correctly pleasant surprises also cause this region to release those same chemicals. The other three regions look for patterns, compare the sounds to other sounds you have heard before, and link emotional ties within the song. This study took the brain activity of 19 people who were listening to music in an MRI machine. They were then asked whether they would like to buy the song they were listening to and there was a direct correlation between how much a person was willing to spend on a song and how much the nucleus accumbens was stimulated. This can lead to further investigation on how the brain deciphers complex sounds such as speech.

Photo taken by Ferrari + caballos + fuerza = cerebro Humano 
Link URL:

Wait, you don’t hear that ringing, too?

Defined as “the perception of sound in one or both ears or in the head when no external sound is present” by the American Tinnitus Foundation, tinnitus affects 50 million people in the US and forty percent of veterans.  It can be caused by everything physical trauma or long-term exposure to loud noises (i.e. combat veterans or teenagers with iPods) to hormonal imbalance or aspirin use. Currently, there are many treatments available, although the success rate of these treatments varies. The main reason for this is that the best way of treating tinnitus would involve delivering medication to the inner ear, the site of the problem. Currently, doctors have no way of putting medication in the inner ear, but this could change  in a few years thanks to the the beginning of a new project by the US Department of Defense, who has commissioned Draper Laboratory to work out a

concept for a small delivery device inserted near the membrane-covered window—no more than three millimeters in diameter—separating the middle ear from inner ear. Once at the membrane the device … would release a drug into the cochlea… The plan is to embed wireless communications into the capsule so that a patient or doctor can control the dosage. After the capsule finishes delivering its supply of drugs, it would dissolve. 


Courtesy of:
These may be setting up my generation for a tinnitus epidemic many years from now.


The project is only in its beginning stages, so it will be years before patients can actually reap any benefits from this technology. However, I take comfort in knowing that should I develop tinnitus, I could possibly have access to better treatment than is available today. This is especially relevant to my generation; everywhere you look, there are teenagers blasting their iPods, unknowingly (or not caring) causing permanent damage. Despite the warnings received from adult, many teens will not listen, and will continue to cause damage with loud noise. Should this treatment be developed, the tinnitus that will be inevitable developed by a large portion of my generation will treated, and possibly cured.

This project also holds a personal significance for me.  As someone who wants to eventually enter the armed forces, I am relieved to know that such a common issue among veterans is coming a step closer to being eradicated. Despite the technology used today to prevent noise damage,  I know of Iraq and Afghanistan war veterans who are experiencing tinnitus, and even hearing loss. I’m glad that research is being conducted on a condition that, while it may not sound terribly crippling, can actually have a huge effect on one’s quality of life.

So, readers, do any of you have or know someone with tinnitus  If so, how did you or the person you know develop it? And, if you have it, would you consider one day utilizing this kind of treatment?

Post, discuss, talk with your friends. Discussion breeds awareness, which is key to arriving at a cure.

Sorry, What Did You Say?

Credit: Cyclone

Are you able to zone out in a noisy room and just focus on one thing? I know that I am able to do this when I am really into a book and I block every other sound out when I am reading. Are you able to focus on only one voice in a room of many?

A recent study has shown that the brain has the ability to focus so intensely that it can make a single voice seem like the only sound in a room full of other noises. Nima Mesgarani and Edward Chang of the University of California, San Francisco, studied what happens in the brains of people who are trying to follow one of two talkers. Scientists call this scenario “cocktail party problem.” In the study, electrodes were placed under the skulls of three people for an epilepsy treatment. The electrodes picked up high gamma waves from nerve cells. The pattern and strength of the high gamma waves reflect which sounds the people were paying attention to. The scientists gave the test subjects a signal word and told them to focus on that speaker once that word was spoken. Throughout this experiment, the researchers recorded brain activity and sorted that activity into patterns that reflect voices and words. They found that before the signal word was uttered, the patterns in the brain showed up as a mishmash, but once that word was heard, the subjects’ attention focused on that one voice and their brain activity shifted to a pattern similar to that seen when the listener heard only a solo speaker.

Micheyl said, “scientists already knew that attention influences perception, but the new results demonstrate that this is a literal, direct reflection of auditory attention at the neural level.” These results help explain how people are able to pick out a single speaker from a multitude of incoming sounds. Scientists hope that with these results and a deeper understanding of the brain’s power to focus, it will be possible to better treat people who can’t sort out sound signals effectively, something that can decline with age.

The next time you are in class and feel like you can’t listen to your teacher because the rest of the students in your class are making a lot of noise, try to focus on only your teacher’s voice. Your brain has the power to do this, so if you put your mind to it, you will be able to see that it isn’t so hard to listen to one person amidst a group of jumbled noises!

Eek! I hate that sound!

Do you get goose bumps when you hear nails dragged across a chalkboard? Do you have to cover your ears and wonder why this sounds makes you so uncomfortable? If you have, fear no more!

A recent study was conducted by scientists to discover why certain noises make people cringe. The study consisted of 104 people who listened to six different chalkboard squeaks. After listening to the squeaks, the people had to rate their discomfort level. The researchers then measured changes in the listeners’ vital signs and skin conductivity, indicators of stress, while replaying the two most annoying squeaks. The sounds contained frequencies that ranged up to 12,000 hertz (Hz) and beyond. The scientists thought that maybe filtering out the highest frequencies would make the fingernail-scraping sound less chilling. Yet, they found that cutting out the lowest or highest frequencies did not change the listeners’ level of discomfort. They did, however, find that removing all tones between 2,000 and 4,000 Hz made the experience a little less painful. The researchers are not completely positive why this sound range makes the experience worse, but they believe that maybe the ear canal naturally resonates with those frequencies more than others. The sensitivity to this sound range can very well be why people with noisy jobs tend to lose hearing in this frequency range first.

Ouch! That hurts!

Scientists concluded from this study that sound waves alone are not the only factor that makes for this distressing experience. Knowing that a screech comes from a chalkboard, instead of something pleasant, adds to the listener’s irritation. The fact that the brain associates hearing squeaks on a chalkboard with an unfavorable experience triggers the listener to react negatively when such sounds are heard. Scientist Randolph Blake at Vanderbilt University believes that vision is another factor that adds to the painfulness of the experience. He said, “I’m convinced that watching somebody scrape their nails on a chalkboard will make the experience even more unpleasant.” Thus, our reactions to certain sounds are part psychological and part physical.

These findings help illuminate why people react badly when they hear unpleasant sounds. Although the study has not found a solution to making these experiences somewhat more enjoyable, these findings have helped scientists determine which sound frequencies people are more sensitive to, which could help researchers learn more about our the complexity of our hearing and its sensitivity. What other types of sounds give you the chills? Do you think that researchers and scientists can find a way to make unpleasant noises more enjoyable? What do you think their ideas and methods would be? As for now, try to stay away from fingernails dragging across a chalkboard, because although you may know why your body does not like hearing it, you sure don’t want to have to go through the pain!

Powered by WordPress & Theme by Anders Norén

Skip to toolbar