The cost of cognition: The blessing and curse of human brain complexity

By Shane Huntington

Neuroscientist Prof Seth Grant explains how genetics gave rise to the modern human brain, and how the very complexity that characterises our brains makes them vulnerable to neurological diseases that reveal themselves in mental illness.

SHANE HUNTINGTON

I'm Dr Shane Huntington. Thanks for joining us. Our ability to comprehend the environment around us, to adapt rapidly the changing conditions and to imaginatively express ourselves through art are all outstanding outcomes of an evolutionary process that has generated human brains of stunning complexity. But what is it that enables our grey matter to achieve such feats? Are these features solely the territory of human beings or do we share similar traits with other life forms? As with any mechanism, be it electrochemical or mechanical, added complexity leads to potential problems that are correspondingly complex to resolve. Diseases that affect the way we think and use our bodies are many and stem from a variety of causes but almost always situated in the brain. Today on Up Close we're joined by neuroscientist Professor Seth Grant to explore how the evolution of synapses has given vertebrates like us the ability to think and learn whilst also making us susceptible to mental illness and diseases of the brain. Seth Grant is Professor Molecular Neuroscience in the Centre for Neuroregeneration at the University of Edinburgh. He is in Melbourne to speak at the 2014 Melbourne Brain Symposium, an event jointly organised by the Melbourne Neuroscience Institute and the Florey Institute of Neuroscience and Mental Health. He is also delivering the annual Kenneth Myer Public Lecture as a guest of the Florey Institute. Welcome to Up Close, Seth.

SETH GRANT

Yes, thank you, Shane.

SHANE HUNTINGTON

I think we'll start with just the role that synapses actually play in the brain. Can you give us a description of where they fit in?

SETH GRANT

Well most people will realise of course that all organs in the body are made from cells and there's very large numbers of them but the nerve cells in the brain are very unusual compared to other cells in other parts of the body because they have specialised junctions between them which are called synapses. Now not only do they have junctions between them but the nerve cells in the brain have very long extensions or fibres which have names like axons and dendrites. Those long axons and dendrites have on them about 10,000 synapses per cell which means then that every nerve cell in the brain can contact as many as 10,000 other nerve cells. Just contrast that with a liver cell for example. A liver cell may only touch another 10 or 20 cells so nerve cells and the synapses are what make the brain different to all other organs.

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The cost of cognition: The blessing and curse of human brain complexity