Virtual ears and the cocktail party effect

Nov 17, 2008
Virtual ears and the cocktail party effect
The 'cocktail party effect' describes how our brains develop the ability to focus on particular sounds among a background of noise.

(PhysOrg.com) -- Oxford University research has helped understanding of the so-called ‘cocktail party effect’ – how our brains develop the ability to pinpoint and focus on particular sounds among a background of noise.

The study, published in the Journal of Neuroscience, has implications for the emergence of hearing abilities in children and for restoring hearing after fitting hearing aids and cochlear implants.

Humans begin to develop their hearing at a very early stage. Even a 28 week old foetus will respond to sound, and newborn infants can distinguish different types of speech sound. Our hearing continues to develop throughout childhood, including the ability to distinguish between sounds coming from different directions and to understand speech in difficult acoustic environments, such as a busy room with many echoes.

Nerve cells in the superior colliculus, one of the brain regions responsible for processing sound, mature during infancy, gradually developing a preference for specific sound directions. Which of these nerve cells are active therefore signals where sounds are located, forming an auditory map of the environment.

Researchers led by Professor Andrew King, a Wellcome Trust Principal Research Fellow at the University of Oxford, have developed a method that enables the changes in the selectivity of the nerve cells for different directions of space to be to separated out from the development of the auditory map.

The technique, used on ferrets, involves using ‘virtual ears’ which can enable an infant ferret to hear sounds as if it were an adult.

The researchers in the Department of Physiology, Anatomy and Genetics placed tiny microphones inside the opening of the ears of adult ferrets to capture the sound as modulated by an adult head. This sound, when played back over headphones to an infant ferret, appears to be coming from outside the ferret's head, but mimics what an adult would hear.

By measuring the responses of nerve cells in the brain, the researchers were able to see how the infant brain differs from the adult and to show that the development of the selectivity of the nerve cells for sound location and their assembly into the auditory map are influenced by independent factors.

‘Our research showed that the region of space to which the nerve cells respond is determined by the shape of the ferret's ears and their distance apart, both of which change with age,’ says Professor King. ‘On the other hand, the gradual development of the auditory map is influenced by the experience of the sounds that are heard.’

Professor King believes that this has implications for a child’s ability to learn how to hear after a hearing aid or cochlear implant has been fitted. Other work from this group has shown that even the adult brain is remarkably able to adapt.

‘We have shown that the neural circuits of our hearing apparatus can adjust to a loss of hearing in one ear,’ says Professor King. ‘Clearly, the adult brain is still plastic and able to adapt, so fitting hearing aids and cochlear implants in adults is worthwhile.’

Provided by Oxford University

Explore further: Unprecedented germ diversity found in remote Amazonian tribe

Related Stories

Mice sing like songbirds to woo mates

Apr 01, 2015

Male mice sing surprisingly complex songs to seduce females, sort of like songbirds, according to a new Duke study appearing April 1 in the Frontiers of Behavioral Neuroscience.

Researchers reveal how hearing evolved

Feb 06, 2015

Lungfish and salamanders can hear, despite not having an outer ear or tympanic middle ear. These early terrestrial vertebrates were probably also able to hear 300 million years ago, as shown in a new study ...

After merger, chimpanzees learned new grunt for 'apple'

Feb 05, 2015

Chimpanzees have special grunts for particular types of foods, and their fellow chimps know exactly what those calls mean. Now, by studying what happened after two separate groups of adult chimpanzees moved in together at ...

QuadStick controller says Go for quadriplegic gamers

Feb 06, 2014

Children and adults sidelined by serious illness and immobility from life as healthy people know it b may find relief from anxiety and depression with a "pill" in the form of online games, a drug-free mood ...

Recommended for you

Bacteria play only a minor role stomach ulcers in cattle

Apr 17, 2015

Scientists at the University of Veterinary Medicine Vienna investigated whether stomach ulcers in cattle are related to the presence of certain bacteria. For their study, they analysed bacteria present in ...

New research reveals how our skeleton is a lot like our brain

Apr 17, 2015

Researchers from Monash University and St Vincent's Institute of Medical Research in Melbourne have used mathematical modelling combined with advanced imaging technology to calculate, for the first time, the number and connectivity ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.