Posts tagged hearing impairment
Articles and news from the latest research reports.
New study finds blind people have the potential to use their ‘inner bat’ to locate objects
New research from the University of Southampton has shown that blind and visually impaired people have the potential to use echolocation, similar to that used by bats and dolphins, to determine the location of an object.
The study, which is published in the journal Hearing Research, examined how hearing, and particularly the hearing of echoes, could help blind people with spatial awareness and navigation. The study also examined the possible effects of hearing impairment and how to optimise echolocation ability in order to help improve the independence and quality of life of people with visual impairments.
Researchers from the University of Southampton’s Institute of Sound and Vibration Research (ISVR) and University of Cyprus conducted a series of experiments with sighted and blind human listeners, using a ‘virtual auditory space’ technique, to investigate the effects of the distance and orientation of a reflective object on ability to identify the right-versus-left position of the object. They used sounds with different bandwidths and durations (from 10–400 milliseconds) as well as various audio manipulations to investigate which aspects of the sounds were important. The virtual auditory space, which was created in ISVR’s anechoic chamber, allowed researchers to remove positional clues unrelated to echoes, such as footsteps and the placement of an object, and to manipulate the sounds in ways that wouldn’t be possible otherwise (e.g. get rid of the emission and present the echo only).
Dr Daniel Rowan, Lecturer in Audiology in ISVR and lead author of the study, says: “We wanted to determine unambiguously whether blind people, and perhaps even sighted people, can use echoes from an object to determine roughly where the object is located. We also wanted to figure out what factors facilitate and restrict people’s abilities to use echoes for this purpose in order to know how to enhance ability in the real world.”
The results showed that both sighted and blind people with good hearing, even if completely inexperienced with echolocation, showed the potential to use echoes to tell where objects are. The researchers also found that hearing high-frequency sounds (above 2 kHz) is required for good performance, and so common forms of hearing impairment will probably cause major problems.
Dr Daniel Rowan adds: “Some people are better at this than others, and being blind doesn’t automatically confer good echolocation ability, though we don’t yet know why. Nevertheless, ability probably gets even better with extensive experience and feedback.
“We also found that our ability to use echoes to locate an object gets rapidly worse with increasing distance from the object, especially when the object is not directly facing us. While our experiments purposely removed any influence of head movement, doing so might help extend ability to farther distances. Furthermore, some echo-producing sounds are better for determining where an object is than others, and the best sounds for locating an object probably aren’t the same as for detecting the object or determining what, and how far away, the object is.”
The knowledge gained from this study will help researchers to develop training programmes and assistive devices for blind people and sighted people in low-vision situations. The team is also extending their research to investigate finding of objects in three-dimensional space and why some blind people seem to be able to outperform others, including sighted people.
Scientists prevent development of deafness in animals engineered to have Usher syndrome
Hearing impairment is the most common sensory disorder, with congenital hearing impairment present in approximately 1 in 1,000 newborns, and yet there is no physiological cure for children who are born deaf. Most cases of congenital deafness are due to a mutation in a gene that is required for normal development of the sensory hair cells in the inner ear that are responsible for detecting sound. To cure deafness caused by such mutations, the expression of the gene must be corrected, a feat that has been elusive until recently.
Rosalind Franklin University of Medicine and Science (RFUMS) Assistant Professor Michelle Hastings and her team, along with investigators at Louisiana State University Health Sciences Center in New Orleans, Louisiana and Isis Pharmaceuticals in Carlsbad, CA, have now found a way to target gene expression in the ear and rescue hearing and balance in mice that have a mutation that causes deafness in humans. The results of the study are reported in the paper, Rescue of hearing and vestibular function in a mouse model of human deafness, which was published February 4, 2013 in the journal Nature Medicine.
Dr. Hastings collaborated with research leaders across the country, including RFUMS colleagues Francine Jodelka and Anthony Hinrich, who were co-first authors on the study, as well as Dr. Dominik Duelli and Kate McCaffrey; co-first author Dr. Jennifer Lentz at Louisiana State University Health Sciences Center New Orleans, and Dr. Lentz’s research team, including Drs. Hamilton Farris and Nicolas Bazan and Matthew Spalitta; and Dr. Frank Rigo at Isis Pharmaceuticals. The collaboration led to the development of a novel therapeutic approach to treat deafness and balance impairment by injecting mice with a single dose of a small, synthetic RNA-like molecule, called an antisense oligonucleotide (ASO). The ASO was designed to specifically recognize and fix a mutation in a gene called USH1C, that causes Usher syndrome in humans. The ASO blocks the effect of the mutation, allowing the gene product to function properly, thereby preventing deafness.
Usher syndrome is the leading genetic cause of combined deafness and blindness in humans. Treatment of these Usher mice with the ASO early in life rescues hearing and cures all balance problems. “The effectiveness of the ASO is striking,” states Hastings. “A single dose of the drug to newborn mice corrects balance problems and allows these otherwise deaf mice to hear at levels similar to non-Usher mice for a large portion of their life,” she says.
Validating ASO efficacy in the Usher mice is an important step in the process of developing the strategy for human therapy. Dr. Lentz, who has been studying Usher syndrome for almost 10 years and engineered the mice to model the human disease, states, “Successfully treating a human genetic disease in this animal model brings the possibility of treating patients much closer.”
The results of the study demonstrate the therapeutic potential of this type of ASO in the treatment of deafness and provide evidence that congenital deafness can be effectively overcome by treatment early in development to correct gene expression.
"The discovery of an ASO-type drug that can effectively rescue hearing opens the door to developing similar approaches to target and cure other causes of hearing loss," says Dr. Hastings who has been awarded a grant from the National Institute of Health to further develop the ASOs for the treatment of deafness with Drs. Lentz, Rigo and Duelli.
(Source: eurekalert.org)