Health

Why brains and airports have a lot in common

Professor Ed Bullmore, University of Cambridge
Image caption Prof Ed Bullmore, University of Cambridge

Brains are beautiful. I know not everybody will instinctively think of them in that way.

But when you look a bit more deeply at the way brains are wired up, by a complex network of connections between different cells or regions, they look beautiful to me

In my research we mostly use brain scanning to map how different parts of the brain are connected to each other.

For example by mapping the bundles of nerve fibres that carry information through the brain we can find the nodes of the network with the strongest connections, or the most connections, and so find key "hubs" within the brain.

You can think of it by comparison to the global airline network. A few airports, like London Heathrow, have many more flights and more long-haul, intercontinental flights than most other airports.

These are the hubs of the airline network and it turns out that brain networks are a lot like airline networks, in the sense that a few hubs of the brain network make many more connections, and more long-distance connections, than most of the other regions of the brain.

Image copyright PASIEKA/SCIENCE PHOTO LIBRARY
Image caption Wiring in the brain.

Our understanding of brain networks and hubs has grown exponentially in the last ten years.

People might have heard of the genome - that is the whole genetic sequence of someone's DNA. Now we can also talk about the connectome - a word that has only existed for about 10 years - to capture the ambition that we might be able to map out the complete network of the brains of humans and other animals.

That's an idea that would have seemed absurdly over-ambitious just a decade ago; now it's very exciting to see that suddenly it looks as if it might be possible to map the connectome as comprehensively as we have already mapped the genome.

One very important implication of being able to map the brain networks of healthy individuals is that it puts us in a much stronger position to recognise how brain network organization might be different or abnormal in people with psychiatric disorders.

When I qualified as a doctor, around 30 years ago, it was still debatable whether schizophrenia and other serious mental illnesses were brain disorders, or somehow emerged from the mind rather than the brain.

Now that has clearly shifted and we have evidence that schizophrenia, for example, is certainly a brain disorder.

In the last 5 years, we have begun to understand what that means in terms of brain networks. So now we know that, on average, the brain networks of people with schizophrenia have less strongly connected hubs.

Going back to the global airline network analogy, the brain of someone with schizophrenia wouldn't have Heathrow or JFK. It might have as many flights but they would be mediated through lots of smaller airports rather than a few large hub airports.

What's also new is that we are just beginning to understand how human brain networks form over the course of development, particularly in adolescence, which is a high risk time for many mental health disorders.

We are understanding more about how network hubs are formed by the strengthening of their connections during adolescence in healthy young people. In future, we hope to show that the path of development that leads to schizophrenia is associated with differences in how network hubs form during the course of adolescence.

Image copyright F WALSH
Image caption The human brain is a biological masterpiece

It is also exciting to see how these network diagrams we are getting out of brain imaging can be linked to what we are learning about the genetics of schizophrenia.

In the last few years, for the first time, we have been able to identify which genes in particular put people at risk of becoming schizophrenic.

So if we can bring those two things together - the genome and the connectome - then we may be able to understand more clearly what the genetic mechanisms are that drive brain network development to go off on a somewhat different path that leads to schizophrenia.

If we can do that then we could design new treatments that may be more effective at reducing the risk that young people with a first episode of psychotic symptoms will develop a chronic and disabling form of schizophrenia.

Turning this new knowledge about the connectome into better treatment options for people with mental health disorders is a key goal for this research in the next 10 years.

Then we could say that brain networks are not only beautiful they are also medically useful.

Professor Ed Bullmore is Head of Psychiatry at the University of Cambridge and Vice-President of ImmunoPsychiatry at GSK. He has been elected as a Fellow of the Royal College of Physicians, the Royal College of Psychiatrists, and the Academy of Medical Sciences. His research focuses on mathematical analysis of neuroimaging data, applications of neuroimaging to understanding of neuropsychiatric disorders, and development of new therapeutic approaches for mental health disorders.

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