Hearing Speech Requires Quiet

Hearing Speech Requires Quiet—In More Ways than One

A very interesting paper by:

Kim Krieger, Research Writer, University of Connecticut

Perceiving speech requires quieting certain types of brain cells, report a team of researchers from UConn Health and University of Rochester in an upcoming issue of the Journal of Neurophysiology. Their research reveals a previously unknown population of brain cells, and opens up a new way of understanding how the brain hears, according to an article on the UConn Today website.

Your brain is never silent. Brain cells, known as neurons, constantly chatter. When a neuron gets excited, it fires up and chatters louder. Following the analogy further, a neuron at maximum excitement could be said to shout. When a friend says your name, your ears signal cells in the middle of the brain. Those cells are attuned to something called the amplitude modulation frequency. That’s the frequency at which the amplitude, or volume, of the sound changes over time.

Amplitude modulation is very important to human speech. It carries a lot of the meaning. If the amplitude modulation patterns are muffled, speech becomes much harder to understand. Researchers have known there are groups of neurons keenly attuned to specific frequency ranges of amplitude modulation; such a group of neurons might focus on sounds with amplitude modulation frequencies around 32 Hertz (Hz), or 64 Hz, or 128 Hz, or some other frequencies within the range of human hearing. But many previous studies of the brain had shown that populations of neurons exposed to specific amplitude modulated sounds would get excited in seemingly disorganised patterns. The responses could seem like a raucous jumble, not the organized and predictable patterns you would expect if the theory, of specific neurons attuned to specific amplitude modulation frequencies, was the whole story.

UConn Health neuroscientists Duck O. Kim and Shigeyuki Kuwada passionately wanted to figure out the real story. Kuwada had made many contributions to science’s understanding of binaural (two-eared) hearing, beginning in the 1970s. Binaural hearing is essential to how we localise where a sound is coming from. Kuwada (or Shig, as his colleagues called him) and Kim, both professors in the School of Medicine, began collaborating in 2005 on how neural processing of amplitude modulation influences the way we recognise speech. They had a lot of experience studying individual neurons in the brain, and, together with Laurel Carney at the University of Rochester, they came up with an ambitious plan: they would systematically probe how every single neuron in a specific part of the brain reacted to a certain sound when that sound was amplitude modulated, and when it was not. They studied isolated single-neuron responses of 105 neurons in the inferior colliculus (a part of the brainstem) and 30 neurons in the medial geniculate body (a part of the thalamus) of rabbits. The study took them two hours a day, every day, over a period of years to get the data they needed.

While they were writing up their results, Shig became ill with cancer. But still he persisted in the research. And after years of painstaking measurement, all three of the researchers were amazed at the results of their analysis: there was a hitherto unknown population of neurons that did the exact opposite of what the conventional wisdom predicted. Instead of getting excited when they heard certain amplitude modulated frequencies, they quieted down. The more the sound was amplitude modulated in a specific modulation frequency, the quieter they got.

It was particularly intriguing because the visual system of the brain has long been understood to operate in a similar way. One population of visual neurons (called the “ON” neurons) gets excited by certain visual stimuli while, at the same time, another population of neurons (called the “OFF” neurons) gets suppressed.

Last year, when Shig was dying, Kim made him a promise.

“In the final days of Shig, I indicated to him and his family that I will put my full effort toward having our joint research results published. I feel relieved now that it is accomplished,” Kim says. The new findings could be particularly helpful for people who have lost their ability to hear and understand spoken words. If they can be offered therapy with an implant that stimulates brain cells directly, it could try to match the natural behavior of the hearing brain.

“It should not excite every neuron; it should try to match how the brain responds to sounds, with some neurons excited and others suppressed,” Kim says.

The research was funding by the National Institutes of Health.

Original Paper: Kim DO, Carney LH, Kuwada S. Amplitude modulation transfer functions reveal opposing populations within both the inferior colliculus and medial geniculate body. Journal of Neurophysiology. 2020. DOI: https://doi.org/10.1152/jn.00279.2020.

Source: UConn Today, Journal of Neurophysiology

Image: UConn Today, Duck Kim

Researchers Find Two Biomarkers Involved in Speech in Noise

Researchers Find Two Biomarkers Involved in Speech in Noise

Taken from The Hearing Review.com

A pair of biomarkers of brain function—one that represents “listening effort,” and another that measures ability to process rapid changes in frequencies—may help to explain why a person with normal hearing may struggle to follow conversations in noisy environments, according to a new study led by Massachusetts Eye and Ear researchers and summarized on the hospital’s website. Published online last week in the scientific journal eLife, the study could inform the design of next-generation clinical testing for hidden hearing loss, a condition that cannot currently be measured using standard hearing exams.

“Between the increased use of personal listening devices or the simple fact that the world is a much noisier place than it used to be, patients are reporting as early as middle age that they are struggling to follow conversations in the workplace and in social settings, where other people are also speaking in the background,” said senior study author Daniel B. Polley, PhD, director of the Lauer Tinnitus Research Center at Mass. Eye and Ear and Associate Professor of Otolaryngology Head-Neck Surgery at Harvard Medical School. “Current clinical testing can’t pick up what’s going wrong with this very common problem.”

Daniel B. Polley, PhD

“Our study was driven by a desire to develop new types of tests,” added lead study author Aravindakshan Parthasarathy, PhD, an investigator in the Eaton-Peabody Laboratories at Mass. Eye and Ear. “Our work shows that measuring cognitive effort in addition to the initial stages of neural processing in the brain may explain how patients are able to separate one speaker from a crowd.”

Hearing loss affects an estimated 48 million Americans and can be caused by noise, aging, and other factors. Hearing loss typically arises from damage to the sensory cells of the inner ear (the cochlea), which convert sounds into electrical signals, and/or the auditory nerve fibers that transmit those signals to the brain. It is traditionally diagnosed by elevation in the faintest sound level required to hear a brief tone, as revealed on an audiogram, the gold standard test of hearing sensitivity.

Aravindakshan Parthasarathy, PhD

Hidden hearing loss, on the other hand, refers to listening difficulties that go undetected by conventional audiograms and are thought to arise from abnormal connectivity and communication of nerve cells in the brain and ear, not in the sensory cells that initially convert sound waves into electrochemical signals. Conventional hearing tests were not designed to detect these neural changes that interfere with our ability to process sounds at louder, more conversational levels.

In the eLife report, the study authors first reviewed more than 100,000 patient records over a 16-year period, finding that approximately 1 in 10 of these patients who visited the audiology clinic at Mass. Eye and Ear presented with complaints of hearing difficulty, yet auditory testing revealed that they had normal audiograms.

Motivated to develop objective biomarkers that might explain these “hidden” hearing complaints, the study authors developed two sets of tests. The first measured electrical EEG signals from the surface of the ear canal to capture how well the earliest stages of sound processing in the brain were encoding subtle but rapid fluctuations in sound waves. The second test used specialized glasses to measure changes in pupil diameter as subjects focused their attention on one speaker while others babbled in the background. Previous research shows changes in pupil size can reflect the amount of cognitive effort expended on a task.

They then recruited 23 young or middle-aged subjects with clinically normal hearing to undergo the tests. As expected, their ability to follow a conversation with others talking in the background varied widely despite having a clean bill of hearing health. By combining their measures of ear canal EEG with changes in pupil diameter, they could identify which subjects struggled to follow speech in noise and which subjects could ace the test. The authors are encouraged by these results, considering that conventional audiograms could not account for any of these performance differences.

“Speech is one of the most complex sounds that we need to make sense of,” Polley said. “If our ability to converse in social settings is part of our hearing health, then the tests that are used have to go beyond the very first stages of hearing and more directly measure auditory processing in the brain.”

In addition to Drs Polley and Parthasarathy, co-authors on the eLife report include Kenneth E. Hancock of Mass. Eye and Ear/Harvard Medical School, Kara Bennett of Bennett Statistical Consulting, Inc, and Victor DeGruttola of the Harvard T. H. Chan School of Public Health. This study was supported by the National Institutes of Health (NIDCD P50-DC015857).

Original Paper: Parthasarathy A, Hancock KE, Bennett K, DeGruttola V, Polly DB. Bottom-up and top-down neural signatures of disordered multi-talker speech perception in adults with normal hearing. eLife. 2020;9:e51419.

Source: Mass. Eye and Ear, eLife

Devon Ear syringing centre

August 27, 2019/in Devon Ear syringing centre /by admin

Devon Ear syringing centre

We talked ear health very seriously here at our Devon Ear syringing centre. Bellow is some information regarding going away and hitting the beach or pool.

The Honiton hearing centre is a leading ear wax removal centre.

As many people set out for holiday in coastal towns during the hot summer days, more attention should be paid to ear health. With people taking a dip at every opportunity the risk of an outer ear infection can increase significantly. An early diagnosis of external otitis can prevent any serious infection. Here are the causes and treatments of outer ear infections.

Don’t neglect your ear care

Outer ear infection is common in the summer, when more people cool off in the sea or in a pool. The outer ear remaining wet, contact with dirty pool water, seawater or foreign bodies, allergy, other skin conditions and chronic diseases like diabetes are the main factors that increase the risk of an outer ear infection.

Stephen Neal the Bath audiologist specialist based at the Keynsham hearing centre is available for all types of ear wax removal.

Devon Ear syringing centre

This is why patients who have previously had an outer ear infection suffer from the same disease again if attention is not paid. Outer ear infection is often caused by bacteria and fungi, while viruses and parasites can rarely be a factor. The chronic condition of the outer ear infection, which often occurs in the form of acute infections, is called “swimmer’s ear,” which is very difficult to treat.

Ways to avoid outer ear infection

The main principle for avoiding outer ear infection is to remove risk factors. The ways of avoiding can be listed as follows:

Treat and keep your chronic diseases under control.

Do not keep water in ear and do not use ear sticks during shower.

Do not swim in dirty and low chlorine pools and in dirty parts of the sea.

Use silicone stopper when swimming in order to prevent water from getting into outer ear.

Remove the water escaping to the ear after swimming with head movements.

You can use a few drops of vinegar to ensure the optimal PH level in the outer ear after swimming.

Outer ear infection includes clinical cases including serious life-threatening infections. For this reason, diagnosis should be made at the earliest stage of complaints and treatment should be started quickly.

Smelly earwax in your ear

The outer ear is a canal shaped, extending from earlap to eardrum, with one end opening outward and the other closed by eardrum. The outer ear is a structure that is susceptible to infections due to being a canal with one end open, poor ventilation and its humid environment. It is possible to list the three main symptoms of outer ear infection as pain, discharge and hearing loss. The pain can be severe and increase when you touch your ear. The discharge is yellow-green and usually smells bad. Hearing loss results from outer ear edema and discharges from outer ear due to infection. The disease can be easily diagnosed by a simple ear examination in the patient with the aforementioned complaints. In diagnosis, it is important to distinguish that the discharge is not from middle ear, but from outer ear. Therefore, a specialist examination is recommended.

After the examination, the specialist doctor will determine the best method of treatment. The outer ear should be thoroughly cleaned during treatment. Local antibiotic drops, cortisone drops and painkillers are used. Since ear

drops cannot reach the canal in patients with highly edematous and closed outer ear canal, suppositories should be placed in outer ear for a few days to ensure that the drops reach the canal.

More severe in diabetic patients

Systemic antibiotic use and rarely hospitalisation may be required for advanced outer ear infections in people with risk factors, such as diabetes. During treatment, ears should be protected from water and water sports should be suspended. Materials such as hearing aids, headphones and stoppers should not be used during this period as they make the treatment harder.

Ear syringing Devon

If you do end up having any hearing or ear issues please see your GP as soon as you can. However if you have or think you have ear wax and need this removed please book in for an appointment at the Bath Ear syringing centre.