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Shedding new light on human brain networks

Pioneering work visualizing human brain networks may help predict recovery time of stroke patients, and understand why certain people are more vulnerable to mental illness. The new research was presented today at the annual British Science Festival by Dr Marco Catani of the Neuroanatomy and Tractography Laboratory at the Institute of Psychiatry, King’s College London.

In the past, MRI scans of the brain have proven particularly useful at identifying areas of the brain that become activated when people perform certain tasks. For example, specific areas of grey matter in the left hemisphere of the brain are known to be responsible for our language functions, including Broca’s area for speech production (top left hand side of the image) and Wernicke’s area for auditory comprehension (bottom right).

Dr Catani and his team at the IoP are pioneering a new MRI method, Diffusion Tensor Imaging (DTI) Tractography, in order to reveal what conventional MRI cannot: the intricate bundle of white matter pathways between these areas which are responsible for our most complex cognitive functions and behaviour. Identifying the white matter pathways that connect these areas, their location and the development of the millions of neurons that make up the fibres of the brain is key to better understanding cognitive functions and disorders.

Through DTI Tractography, Dr Catani’s team have discovered a new component of the language pathway, called the arcuate fasciculus, in the human brain. This pathway connects the Broca’s and Wernicke’s areas to a third area that they dubbed the Geschwind's territory whose functions are still unknown. Any damage, or disconnections to this pathway has important consequences for individuals’ cognitive abilities.

This connection is present on the left hemisphere in all people. However, they found that in 60% of the population the connective pathway only develops in the left hemisphere of the brain, compared to the remaining 40% which displayed either only mild development on the right (20%) or complete symmetry between both sides (20%). They also found significant gender differences, with only 40% of women displaying extreme left-lateralization, where the connective pathway only develops on the left, compared to a much higher proportion of men (85%).

Dr Catani says: ‘We know that individuals’ brains are wired up in very different ways and develop under the influence of genetic and environmental factors. Our research has shown that the anatomy of the brain for these specific language pathways is very different between men and women. We found that  men were much more likely than women to develop a connective pathway only on the left side of the brain.

‘This has important consequences. For example, it could help explain why women recover their language function better and more rapidly after strokes, as they are more likely to be able to rely on pathways on both sides of the brain. Similarly, and we are just developing tests to explore this further, these findings may go some way to explaining why boys are statistically much more likely to develop autism.

‘We have also recently reported in Biological Psychiatry that auditory hallucinations, or hearing voices, in schizophrenia is linked to damage to both sides of the language pathways. This suggests that patients with schizophrenia and auditory hallucinations may respond better to a bilateral stimulation of language pathways than stimulation only on one side.’

‘We hope this method will be used in the future to better predict how individuals will recover their brain function after strokes, helping clinicians to make better, more accurate prognoses and tailor care of their patients. We also hope that further research will lead to a more in-depth understanding of the vulnerability of the brain to disorders such as schizophrenia and autism.’

Following his press conference, Dr Marco Catani joined a panel of experts to present his work at a lecture entitled ‘How the Brain Recovers’ at the British Science Festival

For more information, please contact Seil Collins, Press Officer, Institute of Psychiatry, email or tel: 0207 848 5377

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