Breakthrough in understanding dementia

Brussels, 11 Sep 2006

New and more detailed techniques to investigate the human mind have pinpointed specific areas affected and types of disorder present in the human mind. The research, by Professor Matthew Lambon-Ralph, Professor of Cognitive Neuroscience at the University of Manchester, was delivered to delegates at the science festival, organised by the British Association for the Advancement of Science in Norwich, UK. The research won Professor Lambon-Ralph the Charles Darwin Award for agricultural, biological and medical sciences.

Professor Lambon-Ralph examined the break-down of semantic memory in people with dementia or specific types of stroke or brain injury, where semantic memory was impaired. He eventually found that the areas responsible are the temporal poles, located near the ears.

'Conceptual knowledge or semantic memory refers to our store of meanings for words, objects, people and so on. It is the way our brain gives meaning to all the sensory experience in our lives. It is also at the heart of communication and language,' explained Prof Lambon-Ralph.

'We have used multiple, intersecting methods to answer the question of how the brain comes to store meanings and concepts. These include the study of patients with a particular type of dementia, brain imaging methods and transcranial magnetic stimulation (TMS) - a technique that uses a magnetic coil to 'tire-out' a small area of the brain,' he said.

This technique allowed the professor to give subjects, albeit temporarily, some mild symptoms of dementia. The work links specific parts of the brain to how people interpret or remember concepts. In those with dementia, people lose their grip on concepts. 'Concepts are not deleted as whole entities but, instead, they gradually degrade,' says Prof Lambon-Ralph. 'This means that similar concepts become increasingly difficult for the patients to tell apart and they begin to confuse one concept with another.'

This gave rise to the lecture's title, 'The case of the four-legged duck: investigations of concepts and meaning', as people suffering dementia may find that what to us are simple concepts rapidly and effortlessly slip away.

'Patients show this pattern, irrespective of which type of input is probed - thus they show poor understanding of spoken words, written words, pictures, smells, sounds and touch. This indicates that our meanings are stored in abstract form and serve all the different forms of verbal and sensory input. The same problems are exhibited when the patients try to express this knowledge - they substitute a related name (for example 'duck' becomes 'chicken' or 'cat') and sometimes produce striking drawings in which concepts seem to merge together, mixing up information about birds and animals to produce four-legged ducks,' says Lambon-Ralph.

In normal subjects, Lambon-Ralph was able to reduce the effectiveness of the temporal pole, and then test them. They found the same types of degeneration - not to the same extent as in people suffering dementia, but still identifiable. 'We have used computer/mathematical models to mimic the functioning of this area and its brain connections, and thus show how concepts are formed. It does this by bringing together information from all the different senses and distilling this into a unified store,' he said.

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