Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Found: A Likely New Contributor to Age-Related Hearing Loss

13.07.2015

New nerve cell connections on sensory cells in mice could be at fault

Conventional wisdom has long blamed age-related hearing loss almost entirely on the death of sensory hair cells in the inner ear, but research from neuroscientists at Johns Hopkins has provided new information about the workings of nerve cells that suggests otherwise.


Paul Fuchs, Johns Hopkins Medicine

Mature hair cells, left, lose connections to outgoing neurons (blue) and gain connections to incoming neurons (red) as they age, right.

In a paper published July 1 in The Journal of Neuroscience, the Johns Hopkins team says its studies in mice have verified an increased number of connections between certain sensory cells and nerve cells in the inner ear of aging mice. Because these connections normally tamp down hearing when an animal is exposed to loud sound, the scientists think these new connections could also be contributing to age-related hearing loss in the mice, and possibly in humans.

“The nerve cells that connect to the sensory cells of the inner ear are known to inhibit hearing, and although it’s not yet clear whether that’s their function in older mice, it’s quite likely,” says Paul Fuchs, Ph.D., the John E. Bordley Professor of Otolaryngology–Head and Neck Surgery at the Johns Hopkins University School of Medicine. “If confirmed, our findings give us new ideas for how physicians may someday treat or prevent age-related hearing loss.”

Fuchs says the new research builds on the knowledge that inside the ear lies a coiled row of sensory cells responsible for converting sound waves into electrical signals sent through nerve cells to the brain, which processes and tells animals what they “hear.” Two sets of these so-called hair cells — named for the filaments that act like antennae picking up sound waves — exist, an inner tier closest to the brain and an outer tier. The outer ones have a secondary function: to amplify the sound waves within the inner ear. Not surprisingly, Fuchs notes, a loss of outer hair cells closely correlates with a loss of hearing.

But studies over the last decade have suggested that changes over time also occur in the connections between hair cells and the nerve cells to which they are attached.

Each of those nerve cells is like a one-way street, Fuchs says, taking signals either from the ear to the brain or vice versa. The nerve cells that take signals to the ear are known to turn down the amplification provided by outer hair cells when an animal is, for example, exposed to a noisy environment for an extended period of time.

Previous research has suggested that with age, inner hair cells in mice and humans experience a decrease in outgoing nerve cell connections, while incoming nerve cell connections increase.

To find out if the new connections worked — or worked normally — Stephen Zachary, a graduate student in Fuchs’ laboratory, painstakingly recorded electrical signals from within the inner hair cells of young and old mice.

He found that the incoming nerve cells were indeed active and that their activity levels correlated with the animals’ hearing abilities: The harder of hearing an animal was, the higher the activity of its incoming nerve cells.

“These nerve cell connections seem to be reverting back to the way they worked during early development before the animals’ sense of hearing was operating,” says Fuchs. “We don’t know why the new connections form, but it might be as simple as a lack of competition for space once the outgoing nerve cells have retracted.”

If the same phenomenon is occurring in human ears, Fuchs and his team say there may be ways of preventing the incoming nerve cells from forming new connections with inner hair cells, a technique that could help maintain normal hearing through old age.

This work was supported by grants from the National Institute on Deafness and Other Communication Disorders (R01 DC001508, T32 DC000023, P30 DC005211, F31 DC014184).

Contact Information
Catherine Kolf
Senior Communications Specialist
ckolf@jhmi.edu
Phone: 443-287-2251
Mobile: 443-440-1929

Catherine Kolf | newswise
Further information:
http://www.jhmi.edu

More articles from Life Sciences:

nachricht Mass spectrometry sheds new light on thallium poisoning cold case
14.12.2018 | University of Maryland

nachricht Protein involved in nematode stress response identified
14.12.2018 | University of Illinois College of Agricultural, Consumer and Environmental Sciences

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Data use draining your battery? Tiny device to speed up memory while also saving power

The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

Im Focus: Topological material switched off and on for the first time

Key advance for future topological transistors

Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

Data use draining your battery? Tiny device to speed up memory while also saving power

14.12.2018 | Power and Electrical Engineering

Tangled magnetic fields power cosmic particle accelerators

14.12.2018 | Physics and Astronomy

In search of missing worlds, Hubble finds a fast evaporating exoplanet

14.12.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>