Research Roundup updates HR readers on some of the latest research and clinical findings related to hearing health care. Where appropriate, sources and original citations are provided, and readers are encouraged to refer to the primary literature for more detailed information. Additionally, related articles can be found and keywords can be searched in the HR Online Archives.
Hearing in Noise: A Winner-Take-All Algorithm in the Brain?
It was originally believed that directional information was the major acoustic cue used by the auditory system when listening to one listener in the presence of many other talkers (ie, what is commonly referred to as the “cocktail party effect”). However, even though localization of different sound sources with two ears improves performance, it can be achieved monaurally—for example, in telephone conversations, where no directional information is available. Obviously, other mechanisms are in play.
Scientists led by Holger Schulze at the Leibniz-Institute for Neurobiology in Magdeburg, and the Universities of Ulm, Newcastle, and Erlangen have now found a neuronal mechanism in the auditory system that is able to solve the task based on the analysis of the temporal fine structure of the acoustic scene. The research, published in the March 5 edition of PLoS ONE, shows that different speakers have different temporal fine structure in their voiced speech and that such signals are represented in different areas of the auditory cortex according to this different time structure.
By means of a so-called winner-take-all algorithm, one of these representations gains control over all other representations. This means that only the voice of the speaker to whom you wish to listen is still represented in the auditory cortex and can thus be followed over time. This predominance of the representation of one speaker’s voice over the representations of all other speakers is achieved by long-range inhibitory interactions that are first described by Schulze and colleagues using functional neurophysiological, pharmacological, and anatomical methods.
The findings provide a deeper understanding of how the parcellation of sensory input into perceptually distinct objects is realized in the brain, and may ultimately help to improve the auditory experience of hearing aid wearers in noise.
The original article is available at www.plosone.org.
Cochlear Implants Improve Quality of Life for Recipients
A study from researchers in Berlin published in the March edition of Otolaryngology–Head and Neck Surgery evaluated the quality of life of 56 cochlear implant recipients using the Nijmegen Cochlear Implant Questionnaire (NCIQ), a self-administered assessment that asks responders about sound perception, speech, self-esteem, and social interaction. Responders reported significant improvements in all areas—with especially large gains observed in the areas of sound perception and social interaction.
Why Don’t Directional Microphones Work Better? by Ryan J. Mills, MA, and Doug Martin, PhD. September 2007 HR Archives.
The study also gauged participants using the Medical Outcome Study Short Form 36 (SF36). While the results provided by this tool are not specific to hearing loss or cochlear implants, they nonetheless indicated significant improvements in the areas of social functioning and mental health. Source: American Academy for the Advancement of Science.
Hirschfelder A, Gräbel S, Olze H. The impact of cochlear implantation on quality of life: the role of audiologic performance and variables. Otolaryngol Head Neck Surg. 2008;138(3):357-62.
Common Cold Linked to Ear Infections
A new 5-year NIH-funded study at the University of Texas Medical Branch at Galveston confirms the suspected close link between the two most common diseases of young children: colds and ear infections.
The study, which appears in the March 15 issue of Clinical Infectious Diseases, confirms the suspected close link between viral colds and ear infections. It also identifies the viruses associated with higher rates of ear infections.
Dr Tasnee Chonmaitree, a pediatric infectious disease specialist, and her colleagues followed 294 children ages 6 months to 3 years for up to 1 year each. Researchers documented about 1,300 cold episodes and a 61% rate of ear infection complication including asymptomatic fluid in the middle ear, which can cause hearing problems. Researchers also identified the types of cold viruses—adenovirus, respiratory syncytial virus, and coronavirus—that most often resulted in ear infection.
“Because we now know that the common cold is the precursor to an ear infection, it is important for parents to make extra efforts to prevent their children from catching colds,” Chonmaitree said. “It’s important to avoid exposure to sick children or adults, to avoid day care attendance, if possible, and, if that’s not an option, to choose a smaller group day care.”
Chonmaitree also recommended the use of influenza vaccine, the only vaccine available to prevent respiratory viral infection, which is now available for children older than 6 months. Source: American Academy for the Advancement of Science.
Chonmaitree T, Revai K, Grady JJ, et al. Viral upper respiratory tract infection and otitis media complication in young children. Clinical Infectious Diseases. 2008;46:815–823.