Posts tagged ear
Articles and news from the latest research reports.
Deep inside a mouse’s ear, a swirling galaxy of cells
Is this a churning galaxy in some faraway corner of the universe? A neon rose plucked by a 1990s raver? Or just a dollop of fluorescent paint swirling down the drain? Nope - it’s the cochlea of a mouse that has been stained with antibodies to reveal cells with different functions.
The image, created by Karen Avraham and Shaked Shivatzki of Tel Aviv University in Israel, was the winning entry in the GenArt 2012 human genetics image competition.
Overlaid on the twisting cochlea is a cascade of green letters that make up the DNA sequence of connexin 26. Mutations in this gene are the most common cause for deafness, says Avraham. The image is an artistic representation of deep sequencing, a technique for detecting variances in DNA.
Avraham says deep sequencing is revolutionising the hunt for genetic mutations because of its speed and low cost. Where sequencing a genome once cost millions of dollars and took years, it now takes weeks and costs about $1000.
"By finding the mutations responsible for human disease, scientists can diagnose disorders in a way that was impossible before," she says.
Scientists are growing ears, bone and skin in the lab, and doctors are planning more face transplants and other extreme plastic surgeries. Around the country, the most advanced medical tools that exist are now being deployed to help America’s newest veterans and wounded troops.
Top Image: A research engineer at the Laboratory for Tissue Engineering and Organ Fabrication at Massachusetts General Hospital, displays a titanium frame designed for the reconstruction of a human ear, left, and a three dimensional plastic ear model, right, at the lab, in Boston.
Bottom Image: A chart provided by the Laboratory for Tissue Engineering and Organ Fabrication at Massachusetts General Hospital, depicts the progression, from left to right, of implanted tissue engineered for ear development and construction, at the lab in Boston.
(Source: spokesman.com)
Decoding the secrets of balance
July 25, 2012
(Medical Xpress) — New understanding of how the brain processes information from inner ear offers hope for sufferers of vertigo.
If you have ever looked over the edge of a cliff and felt dizzy, you understand the challenges faced by people who suffer from symptoms of vestibular dysfunction such as vertigo and dizziness. There are over 70 million of them in North America. For people with vestibular loss, performing basic daily living activities that we take for granted (e.g. dressing, eating, getting in and out of bed, getting around inside as well as outside the home) becomes difficult since even small head movements are accompanied by dizziness and the risk of falling.
We’ve known for a while that a sensory system in the inner ear (the vestibular system) is responsible for helping us keep our balance by giving us a stable visual field as we move around. And while researchers have already developed a basic understanding of how the brain constructs our perceptions of ourselves in motion, until now no one has understood the crucial step by which the neurons in the brain select the information needed to keep us in balance.
The way that the brain takes in and decodes information sent by neurons in the inner ear is complex. The peripheral vestibular sensory neurons in the inner ear take in the time varying acceleration and velocity stimuli caused by our movement in the outside world (such as those experienced while riding in a car that moves from a stationary position to 50 km per hour). These neurons transmit detailed information about these stimuli to the brain (i.e. information that allows one to reconstruct how these stimuli vary over time) in the form of nerve impulses.
Scientists had previously believed that the brain decoded this information linearly and therefore actually attempted to reconstruct the time course of velocity and acceleration stimuli. But by combining electrophysiological and computational approaches, Kathleen Cullen and Maurice Chacron, two professors in McGill University’s Department of Physiology, have been able to show for the first time that the neurons in the vestibular nuclei in the brain instead decode incoming information nonlinearly as they respond preferentially to unexpected, sudden changes in stimuli.
It is known that representations of the outside world change at each stage in this sensory pathway. For example, in the visual system neurons located closer to the periphery of the sensory system (e.g. ganglion cells in the retina) tend to respond to a wide range of sensory stimuli (a “dense” code), whereas central neurons (e.g. in the primary visual cortex at the back of the head tend to respond much more selectively (a “sparse” code). Chacron and Cullen have discovered that the selective transmission of vestibular information they were able to document for the first time occurs as early as the first synapse in the brain. “We were able to show that the brain has developed this very sophisticated computational strategy to represent sudden changes in movement in order to generate quick accurate responses and maintain balance,” explained Prof. Cullen. “I keep describing it as elegant, because that’s really how it strikes me.”
This kind of selectivity in response is important for everyday life, since it enhances the brain’s perception of sudden changes in body posture. So that if you step off an unseen curb, within milliseconds, your brain has both received the essential information and performed the sophisticated computation needed to help you readjust your position. This discovery is expected to apply to other sensory systems and eventually to the development of better treatments for patients who suffer from vertigo, dizziness, and disorientation during their daily activities. It should also lead to treatments that will help alleviate the symptoms that accompany motion and/or space sickness produced in more challenging environments.
Provided by McGill University
Source: medicalxpress.com
Noise Exposure Can Cause Long-Lasting Changes To Sensory Pathways; Touch-Sensing Nerve Cells May Lead To Future Tinnitus Treatments
Article Date: 03 Feb 2012 - 0:00 PST
We all know that it can take a little while for our hearing to bounce back after listening to our iPods too loud or attending a raucous concert. But new research at the University of Michigan Health System suggests over-exposure to noise can actually cause more lasting changes to our auditory circuitry - changes that may lead to tinnitus, commonly known as ringing in the ears.
U-M researchers previously demonstrated that after hearing damage, touch-sensing “somatosensory” nerves in the face and neck can become overactive, seeming to overcompensate for the loss of auditory input in a way the brain interprets - or “hears” - as noise that isn’t really there.
The new study, which appears in The Journal of Neuroscience, found that somatosensory neurons maintain a high level of activity following exposure to loud noise, even after hearing itself returns to normal.
The findings were made in guinea pigs, but mark an important step toward potential relief for people plagued by tinnitus, says lead investigator Susan E. Shore, Ph.D., of U-M’s Kresge Hearing Research Institute and a professor of otolaryngology and molecular and integrative physiology at the U-M Medical School.
“The animals that developed tinnitus after a temporary loss in their hearing after loud noise exposure were the ones who had sustained increases in activity in these neural pathways,” Shore says. “In the future it may be possible to treat tinnitus patients by dampening the hyperactivity by reprogramming these auditory-touch circuits in the brain.”
In normal hearing, a part of the brain called the dorsal cochlear nucleus is the first stop for signals arriving from the ear via the auditory nerve. But it’s also a hub where “multitasking” neurons process other sensory signals, such as touch, together with hearing information.
During hearing loss, the other sensory signals entering the dorsal cochlear nucleus are amplified, Shore’s earlier research found. This overcompensation by the somatosensory neurons, which carry information about touch, vibration, skin temperature and pain, is believed to fuel tinnitus in many cases.
Tinnitus affects up to 50 million people in the United States and millions more worldwide, according to the American Tinnitus Association. It can range from intermittent and mildly annoying to chronic, severe and debilitating. There is no cure.
It especially affects baby boomers, who, as they reach an age at which hearing tends to diminish, increasingly find that tinnitus moves in. The condition most commonly occurs with hearing loss, but can also follow head and neck trauma, such as after an auto accident, or dental work. Tinnitus is the number one disability afflicting members of the armed forces.
The involvement of touch sensing (or “somatosensory”) nerves in the head and neck explains why many tinnitus sufferers can change the volume and pitch of the sound by clenching their jaw, or moving their head and neck, Shore explains.
While the new study builds on previous discoveries by Shore and her team, many aspects are new.
“This is the first research to show that, in the animals that developed tinnitus after hearing returned to normal, increased excitation from the somatosensory nerves in the head and neck continued. This dovetails with our previous research, which suggests this somatosensory excitation is a major component of tinnitus,” says Shore, who serves on the scientific advisory committee of the American Tinnitus Association.
“The better we understand the underlying causes of tinnitus, the better we’ll be able to develop new treatments,” she adds.
Source: Medical News Today