How We Hear
Hair Cells are critical to hearing; they're
also the components that are generally the cause of what is normally
called sensorineural hearing loss.
An important component of how we hear is the
auditory processing done by our brain.
September 2007 - True Identity of Pivotal Hearing
Structure Is Revealed
September 2007 - Scientists
Identify Important Sound Processing Region of Brain
September 2007 -
How Your Brain Focuses on Certain Sounds
October
2007 - The acute effects of alcohol on auditory thresholds
October 2007 - Scientists discover new hearing mechanism
October 2007 - Good Hearing Dooms Young Loiterers
November 2007 - Non-nerve cells key for development of
hearing
December 2007 -
Rutgers Discovery Offer
Potential for Improved Cochlear Implants
December 2007 - New Brain Mechanism Identified For
Interpreting Speech
December 2007 -
Hearing Chemicals More Complicated Than Scientists
Thought
January 2008 - Human auditory neurons more
sensitive than those of other mammals
January 2008 - How the Auditory Cortex
Processes Sound
February 2008 - New findings contradict a
prevailing belief about the inner ear
February 2008 - Mammalian Protein Helps
Calibrate Hearing
March 2008 - How We Follow a Single Conversation
in a Noisy Room
April 2008 - Humans have more distinctive hearing
than animals
May 2008 - Study links low-frequency hearing to
shape of the cochlea
May 2008 - St. Jude finds 'dancing' hair cells
are key to humans' acute hearing
July 2008 - Sensing Tension: Molecular Motor
Enable Hearing Mechanism
July 2008 - Ultrasonic frogs can tune their ears
to different frequencies
August 2008 - Understanding Hearing, Molecule by
Molecule
August 2008 - Caltech neurobiologists discover
individuals who 'hear' movement
August 2008 - Tuning in to a new language on the
fly
August 2008 - One Reason for Difficulty
Understanding at Parties
September 2008 -
The Cocktail Party Effect
September 2008 -
Listener's Brain Predicts Speaker's Words
October 2008 - Fruit Flies May be Good Subjects
for Human Hearing Research
October 2008 -
Prosthetic Ears Improve Hearing and Speech
Recognition
December 2008 - New discovery leading towards intelligent hearing aids
December 2008 - Rats Help Understand Human
Hearing
December 2008 - UCLA Study Explores Hearing Mechanism
January 2009 - Hard to hear at holiday parties? Blame
your brain
March 2009 - Cochlear Dead Zones: What are they and what
do you do about them?
March 2009 - Proteins Linked To Congenital
Deafness Help Build, Maintain Inner Ear Stereocilia
March 2009 - It's Not Just About Hair Cells: New
Research Shows Tectorial Membrane Plays a More Active Role in Helping Us
Hear
March 2009 - Brain Auditory Regions
Reassigned for those with Hearing Loss
March 2009 - NIH Awards $1.8 Million For Binaural
Research
April 2009 - How Quiet Sounds Are Magnified By
'Flexoelectric Motors' In The Ear
April 2009 - Stanford researchers' discovery of ion
channel turns ear on its head
May 2009 - Rutgers Research May Hold Key to Hearing
Loss Remedy
May 2009 - Estrogen Controls How Brain Processes
Sound
May 2009 - Hearing Through Your Bones
May 2009 - Humans Hear Better Than Some Animals
May 2009 - Scripps Research Scientists Discover
Molecular Defect Involved in Hearing Loss
May 2009 - Beyond cochlear implants: awakening the
deafened brain
June 2009 - When an Ear Witness Decides the Case
July 2009 - Studies Demonstrate Human Preference For
Listening With Right Ear
July 2009 - Where's that sound coming from?
July 2009 - Brain Section Multitasks In Handling
Phonetics, Decision-Making
August 2009 - Researchers Identify
Brain's Speech Processing Mechanism
September 2009 - Gene discovery reveals a critical
protein's function in hearing
October 2009 - Scientists Show How Tiny Cells Deliver
Big Sound in Cochlea
October 2009 - Can Better Hearing Aids Help
You Think Better?
November 2009 - Birds' selective fall hearing may
hold lessons for humans
November 2009 - Hearing Loss and the Perception of
Speech
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September 2007
While the visual regions of the brain have been
intensively mapped, many important regions for auditory processing remain
"uncharted territory." Now, researchers at the Hebrew University of
Jerusalem and elsewhere have identified a region responsible for a key
auditory process-perceiving "sound space," the location of sounds, even
when the listener is not concentrating on those sounds. The findings
settle a controversy in earlier studies that failed to establish the
auditory region, called the planum temporale, as responsible for
perception of auditory space by default.
Full Story
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September 2007
On September 19, a research report by Helsinki
University of Technology, Laboratory of Computational Engineering
scientists appeared in the online, open-access journal PLoS ONE (Public
Library of Science), showing that selective attention increases both gain
and feature selectivity of the human auditory cortex. The ability to
select task-relevant sounds for awareness, while ignoring irrelevant ones,
constitutes one of the most fundamental of human faculties, but the
underlying neural mechanisms have remained elusive. While most of the
literature explains the neural basis of selective attention by means of an
increase in neural gain, a number of papers propose enhancement in neural
selectivity as an alternative or a complementary mechanism.
Full
Story
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October 2007
There is very little knowledge about
alcohol-induced hearing loss. Alcohol consumption and tolerance to loud
noise is a well observed phenomenon as seen in the Western world where
parties get noisier by the hour as the evening matures. This leads to
increase in the referrals to the "hearing aid clinic" and the diagnosis of
"cocktail party deafness" which may not necessarily be only due to
presbyacusis or noise-induced hearing loss.
Full Story
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October 2007
The mosquito is no longer just a blood-sucking
pest -- it is also the name of an ultra-sonic teenage deterrent system
that is being introduced to the Regina market. Using a high-frequency
tone, the device annoys youths and deters them from loitering and being in
its general vicinity within minutes of activation. It has been used in the
United Kingdom since 2005 and is now being implemented in Canadian
markets, such as Vancouver, and it might make its debut in Saskatchewan
very soon. "It is currently being used at convenience stores, schools,
pubs, and malls," Michael Gibson of Moving Sound Technologies said Friday
from Vancouver. "Store owners are using the devices to get kids that are
hanging out in front of stores and (hurting business) to leave the
storefront." Gibson said his company has installed these devices in four
locations of a large convenience store chain in Vancouver and Victoria
that had unwanted traffic. He said store patrons simply weren't going into
the store because they didn't want to encounter unwanted people hanging
around outside.
Full Story
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November 2007
New research indicates that non-nerve cells play a
critical role in stimulating auditory nerve firing in the absence of
sound, in preparation for the development of hearing. "It was known that
this 'spontaneous' activity helps auditory nerves make proper connections
with other nerve cells in the brain, which enables the accurate encoding
of sound; however, the trigger that initiates this activity was not
known," senior author Dr. Dwight E. Bergles told Reuters Health. "We
discovered that non-nerve cells in the developing inner ear stimulate
electrical activity in nerves that carry sound information from the ear to
the brain." Dr. Bergles, from the Johns Hopkins School of Medicine in
Baltimore, said the discovery that non-nerve cells were involved in the
initial stimulatory activity was particularly surprising since it had been
thought that these cells were merely bystanders.
Full Story
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December 2007
While neurotrophins have historically been prized
for the survival value they impart to nerve cells, the researchers found
that in the cochlea they do a great deal more. Their presence in relative
proportions transforms the spiral ganglion neurons into either fast-firing
transmitters to carry high-pitched sound messages to the brain, or
slow-firing carriers for the transmission of lower pitched signals. The
neurotrophins accomplish this at the molecular level by tightly regulating
a newly defined and complex series of signaling proteins. Davis explained
that one end of the cochlea is home to the slower-firing neurons
characterized by a preponderance of NT-3, while the other cochlear end is
rich in BDNF, making those neurons faster-firing. Both neurotrophins are
present in gradients throughout the range, but at any specific locale
their amounts vary relative to each other - lots of BDNF and a little NT-3
in the high frequency transmitters, for example, and the reverse as you
move toward the other end.
Full Story
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September 2008
Researchers study animal behavior to help humans
better cut through the chatter.
The next time you attend a cocktail party, notice
how quickly everyone instinctively raises their voice as the room begins
to fill with many speakers, each focused on different conversational
partners. Thanks to the so-called "cocktail party effect," most of us are
able to filter out the background chatter and pick out that particular
voice of greatest interest. This ability to selectively respond even as
infants to auditory stimuli embedded in noise is not unique to humans.
Many animals, such as penguins, fish and frogs, share with us this
remarkable skill.
Full Story
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September 2008
Scientists at the University of Rochester in New
York have shown for the first time that our brains automatically consider
many possible words and their meanings before we've even heard the final
sound of the word. Previous theories have proposed that listeners can only
keep pace with the rapid rate of spoken language - up to five syllables
per second - by anticipating a small subset of all words known by the
listener, much like Google search anticipates words and phrases as you
type. This subset consists of all words that begin with the same sounds,
such as "candle," "candy," and "cantaloupe," and makes the task of
understanding the specific word more efficient than waiting until all the
sounds of the word have been presented. But until now, researchers had no
way to know if the brain also considers the meanings of these possible
words. The new findings are the first time that scientists, using an MRI
scanner, have been able to actually see this split-second brain activity.
The study was a team effort among former Rochester graduate student
Kathleen Pirog Revill, now a postdoctoral researcher at Georgia Tech, and
three faculty members in the Department of Brain and Cognitive Sciences at
the University of Rochester.
Full Story
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October 2008
Prosthetic ears appear to improve hearing and
speech recognition in noisy environments, according to a report in the
September/October issue of Archives of Facial Plastic Surgery, one of the
JAMA/Archives journals. Some patients require prosthetic ears because
their pinna (outer ear) was removed during surgery for cancer or damaged
by trauma, according to background information in the article. "Their
external auditory canal is usually intact, and the remainder of their
auditory system should function normally," the authors write. "In these
patients, the physician must strive not only to correct the aesthetic
defect caused by the missing pinna but also to correct the hearing loss
caused by its absence." William E. Walsh, MD, CMI, of Northwestern
University Feinberg School of Medicine, Chicago, and colleagues analyzed
eight different silicone rubber prostheses in a two-part study. In the
first part, the researchers used a life-sized plastic foam head with a
12-millimeter hole drilled through at the location of the external
auditory canal. A microphone was placed at the entrance of the ear canal
to measure sound pressure levels both with and without the prosthesis
while the head was rotated 360° in 30° increments.
Full Story
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January 2009
It's almost New Year's Eve, a time for plunging
into boisterous crowds bathed in loud music. And for some of us, that
means turning to an old friend and hearing things like this: "Did you know
(BOOM-da-da-BOOM) went over (Bob! You look wonder-) so she said
(clink-clink) and then I (Here, have another one) what would you do?" Huh?
Too noisy to hear! But wait - how come these younger people understood
what she said? What's wrong with your ears? Actually, part of the problem
may be your brain. In fact, it may lie in your brain's dimmer switch for
controlling the input from your ears. That bit of brain circuitry appears
to falter with age, and scientists are getting some clues about why.
Full
Story
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March 2009
I've heard a lot about "cochlear dead regions,"
but I'd like to hear exactly how you define them?
Sure, here goes. They are regions in the cochlea
where the inner hair cells and/or the neurons are effectively not
functioning at all. As you probably know, the inner hair cells are laid
out in a row along the length of the basilar membrane. Each inner hair
cell normally responds to the vibration of the basilar membrane in the
region where it is located. Each region or place is tuned and responds
most strongly to one specific frequency, which is called the
characteristic frequency (CF). The CF is low toward the apex of the
cochlea and high toward the base. This is sometimes called tonotopic
organization, or frequency-to-place mapping. When the inner hair cells
and/or neurons are not functioning at a given place along the basilar
membrane, then no information about the basilar membrane at that place is
transmitted to the brain. It is as if there is an infinite hearing loss at
that place. This is what I call a dead region. Often, when the inner hair
cells are badly damaged or nonfunctioning, the neurons connecting to them
degenerate.
Full Story
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May 2009
"The Air Force is interested in reducing hearing
loss, by building better hearing protection devices for people that work
in very noisy environments, which means under airplanes," Wismer said.
"The Air Force wants to know all the pathways by which sound can reach the
ear and cause damage to hearing, because even if you block the air
pathways, noise can still reach the eardrum through these bones." The fact
that sound travels through the skull has been recognized for ages.
Beethoven, for example, found a way to hear music through his jaw after he
became deaf, by biting a rod attached to his piano. Bone-conducted hearing
also explains why we sound strange to ourselves on a recording: we're used
to hearing our voice through bone-conducted sound-waves; when it comes
exclusively through our ear canal, our voice seems distorted. Despite
extensive study, however, the phenomenon is not well understood.
Full Story
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May 2009
In the savage world of nature, the ability to hear
- and hear well - is a survival trait. Many animals rely on their keen
sense of hearing to detect danger lurking in the savannah brush. Some
animals have hearing mechanisms like humans. Others hear with their entire
bodies. And although many animals have very sophisticated acute hearing
for survival reasons, a recent study demonstrated humans actually can
distinguish between pitch better than other animals.
Full Story
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June 2009
Spoken clearly, the sounds "dah" and "bah" are
easy to distinguish. Yet if you play a film clip in which the soundtrack
says "dah" while the image on the screen shows a mouth saying "bah,"
people will swear they heard "bah." If you ask people to count the number
of times that a light flashes, and you flash the light seven times
together with a sequence of eight beeping tones, people will say the light
flashed eight times. When confronted with conflicting pieces of
information, the brain decides which sense to trust. In the first
scenario, those clearly percussing lips could never be articulating a "d,"
and so vision claimed the upper hand. But on matters that demand a
temporal analysis, and making sense of similar sounds in a sequence, the
brain reflexively counts on hearing. Click click click. You can listen to
a series of clicks at 20 beats per second and know they are separate
clicks rather than a single continuous tone. Run a series of images
together at 20 frames per second and - welcome to the movies.
Full Story
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July 2009
In a series of three studies looking at ear
preference in communication between humans, Dr. Luca Tommasi and Daniele
Marzoli from the University "Gabriele d'Annunzio" have shown that a
natural side bias, depending on hemispheric asymmetry in the brain,
manifests itself in everyday human behavior. Their findings were just
published online in the Springer Science journal Naturwissenschaften. One
of the best known asymmetries in humans is the right ear dominance for
listening to verbal stimuli, which is believed to reflect the brain's left
hemisphere superiority for processing verbal information. However, until
now, the majority of studies looking at ear preference in human
communication have been controlled laboratory studies and there is very
little published observational evidence of spontaneous ear dominance in
everyday human behavior. Tommasi and Marzoli's three studies specifically
observed ear preference during social interactions in noisy nightclub
environments.
Full Story
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July 2009
Where's that sound coming from? Thanks to
stereophonic hearing and fast-operating brain circuitry, most people with
properly functioning ears can detect almost instantaneously where sounds
originate. But how? Gaining an understanding of how the brain accomplishes
this task is the aim of Michael Burger, Ph.D., assistant professor of
neuroscience at Lehigh University in Bethlehem, Penn.
Full Story
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November 2009
A general strategy underlying hearing aid design
is the selective amplification of portions of the input sound spectrum to
compensate for a loss of hearing sensitivity. Major advances in
engineering and fitting procedures have resulted in more successful
hearing aid use in recent years (Kochkin, 2005). Nevertheless, the
effortless understanding of speech enjoyed by people with normal hearing
is not realized by many individuals with sensorineural hearing loss-even
with amplification-because the effects of the loss are not limited to a
reduction in sensitivity.
Full Story