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Speech and Language research topics

Hearing

The foundation for recognising spoken language is auditory perception. How do we perceive the sounds around us, and how do basic auditory processes deliver the information needed to recognise speech? A major challenge facing the auditory system is to deliver this information in the presence of interfering voices, such as when listening to one speaker in a noisy party. Here, we focus on the mechanisms by which the normal auditory system accomplishes this task, and on how deaf people fitted with a cochlear implant may be able to do so. We perform this research using both behavioural tests, and using brain-imaging techniques such as fMRI and EEG. more

Speech input and phonological processing

This is the biggest area of research in the Speech and Language programme, and involves a number of collaborative projects bringing together the research interests and skills of all of the scientists in the group. The aim is to identify the cognitive and neural processes involved in mapping between auditory signals and the mental lexicon. How do we represent the sounds of word in the brain, and how is speech mapped onto those lexical representations? more

Recognising continuous speech

When we hear someone speak, we get the impression that we hear a series of discrete words. But, in natural speech, there are no gaps or silences between words. Words in written text come conveniently packaged between white spaces that tell us where the words begin and end. But, a central problem facing human listeners is to discover where the words begin and end in the speech signal. So, how do people find out where the words are in continuous speech? more

The Mental Lexicon - Morphology and Semantics

What it the structure of lexical representations? Is the mental lexicon organised in terms of whole-word representations, or are representations predominantly morphemic in character. [e.g. of morphological structure] How is the meaning of words represented in the brain, and where in the brain are those representations stored more

Short-term memory

Because spoken language unfolds over time, speech comprehension and production depend critically on our ability to store information for short periods of time. We need to store the results of any analysis of the immediate input so that we can integrate that input with subsequent information. Most importantly, we have to store that information in the correct serial order. "Man bites dog" does not have the same meaning as "dog bites man". "Dog" is not the same word as "god". Understanding how we can store information in short-term memory is therefore an important part of understanding how we can perceive language. more

Reading. The Bayesian Reader model (Norris, 2006).

Let's pretend that human perception was perfect. How would a perfect, or optimally designed, system read? Might people come pretty close to behaving like an optimal system? Rather surprisingly, it seems that they do. If we make the assumption that perception works by a process of collecting noisy samples from the input (in this case, from the earliest stages of the visual system) we can construct a formal model of how people should behave when reading individual words, or when performing common laboratory tasks such as deciding whether letters form real words or nonsense words. This is the principle behind the Bayesian Reader model (Norris, 2006). This simple idea turns out to give a principled explanation of a wide range of experimental data on reading.

On example of this model's success is in explaining why common words are easier to read than rare words. This seems so obvious that it hardly needs an explanation, but there are lots of reasons why it might be so. How easy a word is to read is approximately a logarithmic function of how frequently it occurs in the language. Why should this be a logarithmic function rather than anything else? Well, it turns out that this is exactly how an optimal system has to behave. By assuming that people approximate optimal recognisers, we get the form of this function for free.

One of the big benefits of this style of modelling (see also the Shortlist B model of Norris & McQueen, 2008) is that almost everything about the model follows automatically from the assumption that people are behaving almost optimally. Currently the model is being extended to cover masked priming (Norris & Kinoshita, 2008), modelling reaction-time distributions, and understanding how the order to letters is represented during reading.

EEG (Electroencephalography) & MEG (Magnetoencephalography)

This work uses recordings of the electrical potentials produced by the brain as a way of telling us what the brain is doing. An important feature of these techniques is that they allow us to make very accurate measurements of the timing of brain processes. more

Meaning

Semantics, the science of the meaning of signs, has a foundation in brain research. At the MRC Cognition and Brain Sciences Unit, we are investigating the brain correlates of words and sentences with the aim to map different facets of semantics to specific areas of the neural substrate. more

Syntax

What are the brain mechanisms linking together words and morphemes into sentences of higher and higher complexities? Scientists at the MRC Cognition and Brain Sciences Unit use neuroimaging, especially magneto- and electroencephalography, MEG and EEG, to elucidate the neural circuits of syntax and morphological processing. more

Aphasiatherapy

Aphasia is the loss of language caused by disease of the brain. If aphasia becomes chronic over the months and years after, for example, a stroke, there had been only little hope for patients for improving their abilities again. However, a recent discovery is that post-stroke aphasia can be treated effectively by a new form of intensive language therapy that practices language in action contexts. Scientists at the MRC CBU have been developing this new method and are currently collaborating with colleagues abroad to optimise it and make it more efficient for clinical practice. This translational research is expected to have a continuous clinical impact.

The MRC-CBU as a research institution does, at this point, NOT offer therapy of aphasia.

Links to aphasia therapy websites at CBU and elsewhere:

More

http://www.aphasianow.org/

http://research.ncl.ac.uk/aphasia/