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Sunday, May 18, 2008

How a magnet turned off my speech

Words failed me. I stuttered as Prof Vincent Walsh turned off the speech centre of my brain for a few thousandths of a second to demonstrate the power of transcranial magnetic stimulation, a popular way to interfere with the most complex known object in the universe.

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  • Sitting in the basement of a lab in Queen Square, London, where the nation's greatest concentration of brain surgeons can be found, I am told to recite a nursery rhyme as a way to see if the experiment has worked.

    How a magnet turns off Roger Highfield's speech
    Watch as Roger Highfield's speech is turned off

    For this remarkable demonstration of how to boggle a brain, the professor is wielding what looks like a giant black key against my head.

    I am reciting a nursery rhyme as he moves the coil about and delivers a high powered pulse, signified by snapping noise, a twitch on my scalp and an unpleasant, though pain free, nervy feeling in my mouth.

    Prof Walsh is shifting the coil around the left side of my head, hunting for the speech area of my brain, named Broca's area after the 19th century doctor.

    Disconcertingly for me (Prof Walsh seemed unconcerned), he had difficulty finding my Broca's and only succeeded after he called for a bigger coil to be used, as powerful magnetic pulses were delivered through my skull by his colleague, Dr Neil Muggleton.


    I was reciting Humpty Dumpty and hoping that all the Queens Square's neurologists and all the Queens neurosurgeons would not have to put my brain back together again.

    Finally he located my Broca's and the train of pulses stopped me in my tracks. I wanted to recite the rhyme but stumbled and stuttered as my speech area was disabled.

    Intriguingly, I could still sing Humpty Dumpty as he buffetted my Broca's: it turns out that singing is controlled by the right side of the brain, the opposite hemisphere to the one he stimulated.

    "That is why you can sing but not talk."

    This is also why some people with stroke can sing sentences, even though they cannot speak.

    The first practical demonstration of TMS was made 23 years ago by Prof Anthony Barker at the University of Sheffield.

    Since then, it has become a relatively simple, non-invasive, and painless way to interfere with the workings of the brain, though there is a risk of epilepsy.

    Many scientists now use it for basic research. Some have used it to induce electrical changes in the brain's temporal lobes, which have been linked with religious belief, because some sufferers of temporal lobe epilepsy seem to experience hallucinations that bear a striking resemblance to mystical experiences of holy figures.

    Many doctors believe it has a role in helping a damaged brain to heal.

    TMS offers a kinder alternative to electroconvulsive therapy, the treatment of last resort for people with severe depression who do not respond to drugs.

    Others have used it to treat severe epilepsy, and there are efforts to use it to quieten the voices heard by schizophrenics and to track nerve development in infants.

    A few even believe that it could actually enhance cognitive skills.

    Prof Allan Snyder, at the University of Sydney believes TMS can act as "a creativity-amplifying machine".

    But Prof Walsh is highly sceptical. "Brain stimulation does not release hidden talents and when it is used to improve things in patients, it comes at the cost of blocking some nerve pathways to encourage others."

    Original here

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