Making sense of the world through a cochlear implant

13 March 2007

Scientists at University College London and Imperial College London have shown how the brain makes sense of speech in a noisy environment, such as a pub or in a crowd. The research suggests that various regions of the brain work together to make sense of what it hears, but when the speech is completely incomprehensible, the brain appears to give up trying.

The study was intended to simulate the everyday experience of people who rely on cochlear implants, a surgically-implanted electronic device that can help provide a sense of sound to a person who is profoundly deaf or who has severe hearing problems.

Using MRI scans of the brain, the researchers, funded by the Wellcome Trust and the Medical Research Council, identified the importance of one particular region, the angular gyrus, in decoding distorted sentences. The findings are published in the current issue of the 'Journal of Neuroscience'.

In an ordinary setting, where background noise is minimal and a person's speech is clear, it is mainly the left and right temporal lobes that are involved in interpreting speech. However, the researchers have found that when hearing is impaired by background noise, other regions of the brain are engaged, such as the angular gyrus, the area of the brain also responsible for verbal working memory – but only when the sentence is predictable.

"In a noisy environment, when we hear speech that appears to be predictable, it seems that more regions of the brain are engaged," explains Dr Jonas Obleser, who did the research while based at the Institute of Cognitive Neuroscience (ICN), UCL. "We believe this is because the brain stores the sentence in short-term memory. Here it juggles the different interpretations of what it has heard until the result fits in with the context of the conversation."

The researchers hope that by understanding how the brain interprets distorted speech, they will be able to improve the experience of people with cochlear implants, which can distort speech and have a high level of background noise.

"The idea behind the study was to simulate the experience of having a cochlear implant, where speech can sound like a very distorted, harsh whisper," says Professor Sophie Scott, a Wellcome Trust Senior Research Fellow at the ICN. "Further down the line, we hope to study variation in the hearing of people with implants – why is it that some people do better at understanding speech than others? We hope that this will help inform speech and hearing therapy in the future."

Contact

Craig Brierley
Media Officer
Wellcome Trust
T +44 (0)20 7611 7329
E c.brierley@wellcome.ac.uk

Notes for editors

1. The Wellcome Trust is the largest independent charity in the UK and the second largest medical research charity in the world. It funds innovative biomedical research, in the UK and internationally, spending around £500 million each year to support the brightest scientists with the best ideas. The Wellcome Trust supports public debate about biomedical research and its impact on health and wellbeing.

2. The Medical Research Council is dedicated to improving human health through excellent science. It invests on behalf of the UK taxpayer. Its work ranges from molecular level science to public health research, carried out in universities, hospitals and a network of its own units and institutes. The MRC liaises with the Health Departments, the National Health Service and industry to take account of the public’s needs. The results have led to some of the most significant discoveries in medical science and benefited the health and wealth of millions of people in the UK and around the world.

3. University College London
Founded in 1826, UCL was the first English university established after Oxford and Cambridge, the first to admit students regardless of race, class, religion or gender, and the first to provide systematic teaching of law, architecture and medicine. In the Government's most recent Research Assessment Exercise, 59 UCL departments achieved top ratings of 5* and 5, indicating research quality of international excellence.

UCL is the fourth-ranked UK university in the 2006 league table of the top 500 world universities produced by the Shanghai Jiao Tong University. UCL alumni include Mahatma Gandhi (laws 1889, Indian political and spiritual leader); Jonathan Dimbleby (philosophy 1969, writer and television presenter); Junichiro Koizumi (economics 1969, Prime Minister of Japan); Lord Woolf (laws 1954 - Lord Chief Justice of England and Wales), Alexander Graham Bell (phonetics 1860s - inventor of the telephone), and members of the band Coldplay.

4. Imperial College London
Rated as the world's ninth best university in the 2006 Times Higher Education Supplement University Rankings, Imperial College London is a science-based institution with a reputation for excellence in teaching and research that attracts 11 500 students and 6000 staff of the highest international quality.

Innovative research at the College explores the interface between science, medicine, engineering and management and delivers practical solutions that improve quality of life and the environment - underpinned by a dynamic enterprise culture.

With 62 Fellows of the Royal Society among its current academic staff and distinguished past members of the College including 14 Nobel Laureates and two Fields Medallists, Imperial's contribution to society has been immense. Inventions and innovations include the discovery of penicillin, the development of holography and the foundations of fibre optics. This commitment to the application of its research for the benefit of all continues today, with current focuses including interdisciplinary collaborations to tackle climate change and mathematical modelling to predict and control the spread of infectious diseases.

The College's 100 years of living science will be celebrated throughout 2007 with a range of events to mark the centenary of the signing of Imperial's founding charter on 8 July 1907.