Brain Linked to Hearing Problems at Cocktail Parties

March 2010

Editor: We know that hearing loss is a major cause of difficulty understanding speech in the presence of background noise. Less well known is that how the brain processes sound contributes to the difficulty more often than was previously thought. Here's a press release on the research being done at the University College London.

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Do you struggle to hear properly at parties and at other group gatherings? If so, you are not alone and your brain--rather than your ear--could be to blame for this inability to 'zoom in' on the person you want to hear. New research undertaken by Deafness Research UK scientists at the University College London (UCL) Ear Institute is leading to a greater understanding of the role of the brain in auditory processing. The brain appears to play a greater role than was previously understood and unraveling its secrets offers new hope for the deaf and hard of hearing, and in particular, the 'cocktail party' problem.

Current research centers on how we as humans manage to hear speech in noisy backgrounds. The so-called 'cocktail party' problem is nothing to do with drinks, but is rather the term coined to describe the brain's ability to focus our listening attention on a single speaker amid a mixture of conversations, background noises and other distractions. Little is known about the cocktail party problem, and further research will benefit deaf and hard of hearing people; particularly those with cochlear implants and hearing aids, as these devices struggle in noisy environments.

The UCL Ear Institute laboratory is one of the leading international research groups investigating binaural hearing--the ability to process sounds using both ears.

This ability enables most of us to talk in a noisy place, blocking out other sounds to hear our friend/s, but, at the same time, to respond immediately if someone calls our name. The ability can be critical, and early research in the 1950s focused on the problems faced by air traffic controllers, when multiple messages were received from pilots over a single loudspeaker. If you consider today's busy hospital emergency room, with several people shouting vital instructions at once, you can appreciate the significance of the 'cocktail party' effect.

Vivienne Michael, chief executive of Deafness Research UK, said: "Scientists are particularly interested in how the central auditory system is able to cope with noisy environments; a major challenge for hearing research over the next decade will be to improve the performance of cochlear implant devices. 'Bionic hearing' provides a remarkable chance for the deaf to hear, sometimes for the very first time.

"The work of the Ear Institute is essential for those with hearing problems and we continue to fund some of its most vital and groundbreaking research. We are only just beginning to appreciate the role the brain and this research gives us hope for improving not just the performance of implants and hearing aids, but the lives of people with hearing disabilities everywhere."

The UCL team is using a variety of techniques to investigate the cocktail party problem, including in vivo and in vitro brain recordings, psychophysics and computer modeling and human neurophysiology, using EEG and functional MRI. Many people struggle to hear in the cocktail party environment, particularly those with only one functional ear, who (research shows) are more disturbed by interfering noise and further work is needed to help those with implants.

Given the apparent importance of two ears for isolating specific sounds in noisy places, it is believed the auditory system performs a cross-correlation between the signals coming from both ears and that the brain is capable of analyzing the pattern to determine the signal from the desired sound source. The brain has been described as akin to a radio, selecting which channel we should pay attention to from the many it is capable of receiving. The brain also may have its own mechanism for selection, depending on the importance of the sound stimulus.

For example, it may be more important to respond to the shouted 'watch-out' warning if someone is about to spill a drink on your new cocktail dress, rather than concentrate on your conversation or more seriously, to respond to the horn of a car in a busy, noisy street. While bionic ears are transforming life for profoundly deaf people, so far, no implant or technology can completely replicate the capabilities of the human brain and auditory system.