PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Listen to this: Stanford research upends understanding of how humans perceive sound

2013-11-20
(Press-News.org) Contact information: Tracie White
traciew@stanford.edu
650-723-7628
Stanford University Medical Center
Listen to this: Stanford research upends understanding of how humans perceive sound STANFORD, Calif. — A key piece of the scientific model used for the past 30 years to help explain how humans perceive sound is wrong, according to a new study by researchers at the Stanford University School of Medicine.

The long-held theory helped to explain a part of the hearing process called "adaptation," or how humans can hear everything from the drop of a pin to a jet engine blast with high acuity, without pain or damage to the ear. Its overturning could have significant impact on future research for treating hearing loss, said Anthony Ricci, PhD, the Edward C. and Amy H. Sewall Professor of Otolaryngology and senior author of the study.

"I would argue that adaptation is probably the most important step in the hearing process, and this study shows we have no idea how it works," Ricci said. "Hearing damage caused by noise and by aging can target this particular molecular process. We need to know how it works if we are going to be able to fix it."

The study will be published Nov. 20 in Neuron. The lead author is postdoctoral scholar Anthony Peng, PhD.

Deep inside the ear, specialized cells called hair cells detect vibrations caused by air pressure differences and convert them into electrochemical signals that the brain interprets as sound. Adaptation is the part of this process that enables these sensory hair cells to regulate the decibel range over which they operate. The process helps protect the ear against sounds that are too loud by adjusting the ears' sensitivity to match the noise level of the environment.

The traditional explanation for how adaptation works, based on earlier research on frogs and turtles, is that it is controlled by at least two complex cellular mechanisms both requiring calcium entry through a specific, mechanically sensitive ion channel in auditory hair cells. The new study, however, finds that calcium is not required for adaptation in mammalian auditory hair cells and posits that one of the two previously described mechanisms is absent in auditory cochlear hair cells.

Experimenting mostly on rats, the Stanford scientists used ultrafast mechanical stimulation to elicit responses from hair cells as well as high-speed, high-resolution imaging to track calcium signals quickly before they had time to diffuse. After manipulating intracellular calcium in various ways, the scientists were surprised to find that calcium was not necessary for adaptation to occur, thus challenging the 30-year-old hypothesis and opening the door to new models of mechanotransduction (the conversion of mechanical signals into electrical signals) and adaptation.

"This somewhat heretical finding suggests that at least some of the underlying molecular mechanisms for adaptation must be different in mammalian cochlear hair cells as compared to that of frog or turtle hair cells, where adaptation was first described," Ricci said.

The study was conducted to better understand how the adaptation process works by studying the machinery of the inner ear that converts sound waves into electrical signals.

"To me this is really a landmark study," said Ulrich Mueller, PhD, professor and chair of molecular and cellular neuroscience at the Scripps Research Institute in La Jolla, who was not involved with the study. "It really shifts our understanding. The hearing field has such precise models — models that everyone uses. When one of the models tumbles, it's monumental."

Humans are born with 30,000 cochlear and vestibular hair cells per ear. When a significant number of these cells are lost or damaged, hearing or balance disorders occur. Hair cell loss occurs for multiple reasons, including aging and damage to the ear from loud sounds. Damage or impairment to the process of adaptation may lead to the further loss of hair cells and, therefore, hearing. Unlike many other species, including birds, humans and other mammals are unable to spontaneously regenerate these hearing cells.

As the U.S. population has aged and noise pollution has grown more severe, health experts now estimate that one in three adults over the age of 65 has developed at least some degree of hearing disability because of the destruction of these limited number of hair cells.

"It's by understanding just how the inner machinery of the ear works that scientists hope to eventually find ways to fix the parts that break," Ricci said. "So when a key piece of the puzzle is shown to be wrong, it's of extreme importance to scientists working to cure hearing loss."

### Stanford postdoctoral scholar Thomas Effertz, PhD, is also an author of the study.

The research was funded by the National Institutes of Health (grants F32DC010975, K99DC013299, RO1DC0003896 and P30-44992) and the German Academic Exchange Service.

Information about Stanford's Department of Otolaryngology-Head & Neck Surgery, which also supported this work, is available at: http://med.stanford.edu/ohns. The study is part of the Stanford Initiative to Cure Hearing Loss, a large-scale research effort to find biological cures for deafness.

The Stanford University School of Medicine consistently ranks among the nation's top medical schools, integrating research, medical education, patient care and community service. For more news about the school, please visit http://mednews.stanford.edu. The medical school is part of Stanford Medicine, which includes Stanford Hospital & Clinics and Lucile Packard Children's Hospital. For information about all three, please visit http://stanfordmedicine.org/about/news.html.

EMBARGOED FOR RELEASE UNTIL: Wednesday, Nov. 20, 2013, at 9 a.m. Pacific time to coincide with publication in Neuron Print media contact: Tracie White at (650) 723-7628 (traciew@stanford.edu) Broadcast media contact: M.A. Malone at (650) 723-6912 (mamalone@stanford.edu)


ELSE PRESS RELEASES FROM THIS DATE:

Size, connectivity of brain region linked to anxiety level in young children, Stanford study shows

2013-11-20
Size, connectivity of brain region linked to anxiety level in young children, Stanford study shows STANFORD, Calif. — Prolonged stress and anxiety during childhood is a risk factor for developing anxiety disorders and depression later in life. ...

Mental stress + heart disease: Stronger presence in women under 50

2013-11-20
Mental stress + heart disease: Stronger presence in women under 50 Patients with recent heart attack tested with public speaking task Researchers have found that women younger than 50 with a recent heart attack are more likely to experience restricted blood flow ...

Top hospitals reduce readmissions by preventing complications across all diagnoses

2013-11-20
Top hospitals reduce readmissions by preventing complications across all diagnoses Checking back into the hospital within 30 days of discharge is not only bad news for patients, but also for hospitals, which now face financial penalties for high readmissions. The key ...

Financial decision makers need weather and climate information to manage risks

2013-11-20
Financial decision makers need weather and climate information to manage risks Maximizing returns on financial investments depends on accurately understanding and effectively accounting for weather and climate risks, according to a new study by the American ...

USC Viterbi engineers cut time to 3D-print heterogeneous objects from hours to minutes

2013-11-20
USC Viterbi engineers cut time to 3D-print heterogeneous objects from hours to minutes New 3D printing process speeds up fabrication of multiple-material objects Researchers at the USC Viterbi School of Engineering have developed a faster 3D printing process and ...

Focusing on faces

2013-11-20
Focusing on faces Researchers find neurons in amygdala of autistic individuals have reduced sensitivity to eye region of others' faces Difficulties in social interaction are considered to be one of the behavioral hallmarks of autism spectrum ...

Spanish scientists identify a new ancestral enzyme that facilitates DNA repair

2013-11-20
Spanish scientists identify a new ancestral enzyme that facilitates DNA repair PrimPol allows cells to make copies of their DNA even when it is damaged, and prevents breaks in the chromosomes Every day, the human body produces new cells to regenerate ...

Scientists create perfect solution to iron out kinks in surfaces

2013-11-20
Scientists create perfect solution to iron out kinks in surfaces A new technique that allows curved surfaces to appear flat to electromagnetic waves has been developed by scientists at Queen Mary University of London. The discovery could hail ...

Novel material stores unusually large amounts of hydrogen

2013-11-20
Novel material stores unusually large amounts of hydrogen X-ray study reveals the formation of iridium trihydride at high pressure This news release is available in German. An international team of researchers has synthesized a new material ...

Services fail to treat prisoners with schizophrenia -- increasing risk of violent reoffending

2013-11-20
Services fail to treat prisoners with schizophrenia -- increasing risk of violent reoffending New research from Queen Mary University of London shows released prisoners with schizophrenia are three times more likely to be violent than other prisoners, ...

LAST 30 PRESS RELEASES:

Quantum battery device lasts much longer than previous demonstrations

Gamma knife stereotactic radiosurgery for brain metastases from ovarian cancer

Meet the “plastivore” caterpillars that grow fat from eating plastic

Study identifies postoperative delirium as preventable “acute brain failure” with major health and financial implications

Climate change linked to decline in nutritional quality of food

Abdominal fat linked to reduced strength and mobility in adults

Mount Sinai implements Own the Bone® program for fragility fracture patients

Is Earth inside a huge void? 'Sound of the Big Bang' hints at possible solution to Hubble tension

When stem cells feel the squeeze, they start building bone

Revealing Myanmar earthquake as a unique event comprising multiple sub-events, including boomerang-like reverse rupture propagation and supershear rupture

AI helps radiologists spot more lesions in mammograms

Efficient elastic tissues may hold the secrets to Olympic success

Does exercise really improve mental health?

Behind the ballistics of the “explosive” squirting cucumber

Researchers find compound that inhibits cutaneous HPVs

City of Hope Research Spotlight, April/May 2025

The gut microbiota in elderly patients with acute hepatitis E infection

The Three Gorges region of the Yangtze River hits record high temperatures in 2024

Experts urge evidence-based regulations of 7-OH, not restriction, as new science emerges showing safe use

Genes for surviving plague in prairie dogs

New research shows AI chatbots should not replace your therapist

Pusan National University researchers reveal middle-class families hit hardest by South Korea's cost-of-living crisis

Understanding how heat stress reshapes fat metabolism in chickens

Chan Zuckerberg Initiative, Innovative Genomics Institute announce new Center for Pediatric CRISPR Cures

Innovative liquid biopsy test uses RNA to detect early-stage cancer

New quantum record: Transmon qubit coherence reaches millisecond threshold

How Germany’s 2021 floods could have been even worse

Study traces evolutionary origins of important enzyme complex

Tiny antibody has big impact on deadly viruses

Scientists find new way to control electricity at tiniest scale

[Press-News.org] Listen to this: Stanford research upends understanding of how humans perceive sound