Loud noise, especially repeated loud noise, is known to cause irreversible damage to the hair cells inside the cochlea and eventually lead to deafness. In mammals this is irreversible, however both birds and fish are able to re-grow the damaged hair cells and restore hearing. New research published in BioMed Central's open access journal BMC Neuroscience shows that growth hormone is involved in this regeneration in zebrafish. Researchers from Western Kentucky University and the University of Louisville worked together to see which genes were switched on or off after acoustic trauma and found distinct patterns of gene expression. Two days after noise injury, inner ear cells were busy dividing to repair and replace the damaged hair cells. This repair was associated with an alteration in the regulation of 839 genes and many of the cellular pathways involved were the same as those involved in cancer.
A new study by researchers from the Perelman School of Medicine at the University of Pennsylvania shows that declines in hearing ability may accelerate gray mater atrophy in auditory areas of the brain and increase the listening effort necessary for older adults to successfully comprehend speech. When a sense (taste, smell, sight, hearing, touch) is altered, the brain reorganizes and adjusts. In the case of poor hearers, researchers found that the gray matter density of the auditory areas was lower in people with decreased hearing ability, suggesting a link between hearing ability and brain volume. "As hearing ability declines with age, interventions such as hearing aids should be considered not only to improve hearing but to preserve the brain, " said lead author Jonathan Peelle, PhD, research associate in the Department of Neurology.
University of Iowa scientists have discovered a new role for a protein that is mutated in Usher syndrome, one of the most common forms of deaf-blindness in humans. The findings, which were published Aug. 8 in Nature Neuroscience, may help explain why this mutation causes the most severe form of the condition. The study suggests that the protein called harmonin, which is known to be involved in sound sensing in the inner ear, may also play a role in the transmission of sound information to the brain. Hearing starts with the transmission of sound by inner hair cells in the ear. Sound waves cause movement of special structures called stereocilia on the tips of the hair cells. Harmonin is thought to mediate this movement, which then activates the cells and initiates transmission of sound information as electrical and chemical signals to the brain.
A study conducted by Hamilton Farris, PhD, Research Assistant Professor of Neuroscience and Otorhinolaryngology at LSU Health Sciences Center New Orleans, reveals new information about the way tungara frogs in the tropical rain forest hear, sort, and process sounds which is very similar to the way humans do. The knowledge could be applicable to communication disorders associated with hearing loss and attention deficits or difficulties. Dr. Michael Ryan at the University of Texas, Austin, collaborated on the study, published online in Nature Communications on August 2, 2011. "An important component of successful communication is being able to tell which sender among many is sending the signal, " explains Dr. Farris. "In auditory neuroscience it's called the 'cocktail party problem.
Motorcycle helmets, while protecting bikers' brains, may also be contributing to hearing loss. Scientists mapped the airflow and noise patterns to find out why. The distinctive roar of a Harley's engine is loud, but studies have revealed the biggest source of noise for motorcyclists is actually generated by air whooshing over the riders' helmets. Even at legal speeds, the sound can exceed safe levels. Now, scientists have identified a key source of the rushing din. Researchers from the University of Bath and Bath Spa University placed motorcycles helmets atop mannequin heads, mounted them in a wind tunnel, and turned on the fans. By placing microphones at different locations around the helmet and at the mannequin's ear, the researchers found that an area underneath the helmet and near the chin bar is a significant source of the noise that reaches riders' sensitive eardrums.