Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2008 May 17

Logarithmic Spirals
Image Credit: M101 - NASA, ESA, CFHT, NOAO; Typhoon Rammasun - MODIS, NASA
Comparison: Lawrence Anderson-Huang (Ritter Astrophysical Obs., Univ. Toledo)

Explanation: Uncomfortably close Typhoon Rammasun (right) and 25 million light-year distant galaxy M101 don't seem to have much in common. For starters, Rammasun was only a thousand kilometers or so across while M101 (aka the Pinwheel Galaxy) spans about 170,000 light-years, making them vastly dissimilar in scale, not to mention the different physical environments that control their formation and development. But they do look amazingly alike: each with arms exhibiting the shape of a simple and beautiful mathematical curve known as a logarithmic spiral, a spiral whose separation grows in a geometric way with increasing distance from the center. Also known as the equiangular spiral, growth spiral, and Bernoulli's spiral or spira mirabilis, this curve's rich properties have fascinated mathematicians since its discovery by 17th century philosopher Descartes. Intriguingly, this abstract shape is much more abundant in nature than suggested by the striking visual comparison above. For example, logarithmic spirals can also describe the tracks of subatomic particles in a bubble chamber, the arrangement of sunflower seeds and, of course, cauliflower.

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DIY brain therapy could halt migraines

A British team is to test a home "brain stimulation" method to short-circuit migraines before they become disabling.

Migraine is the most common neurological condition in the developed world. It affects over 15% of the UK population and is a more than just a headache; it can cause intense throbbing, visual disturbance and nausea and attacks can be so severe that sufferers have to take time off work.

Recently, a team at Ohio State University showed that zapping the brain with a magnetic field, using transcranial magnetic stimulation, TMS, can abort attacks as they start to develop, when sufferers see an "aura" , a disturbing pattern of zig zags, stars or flashes.

But the coil has to be applied to precisely the right part of the brain to be effective and now a simpler method to achieve the same effect, using two electrodes, is to be tested on migraine sufferers around the country by Prof Vince Walsh of the UCL Institute of Cognitive Neuroscience, Queen Square.

"We need to get brain stimulation into the home - you can't nip off to see your neurologist when you know you're going to have a migraine".

He will be discussing the method at the end of the month at a major conference of 300 researchers from around the world in London. The meeting is organised by the UCL institute with Magstim, the British company that pioneered TMS and is now developing stimulators that are easily portable and simple to use.

These new brain stimulators, called DC machines, introduce very weak electrical currents. But like TMS, DC also has the same effect of changing the "excitability" of brain cells, either damping down their reactivity or boosting it, which can change the way that the brain responds.

Although the prototype electrical stimulator costs around £5000, the hope is that the costs will fall as more are used. The device is much easier to use than TMS since it does not have to be precisely positioned over the correct brain region, which is currently done with a brain scanner.

The electrical version simply requires two electrodes, colour coded pink and yellow, to be put on head. Then a current passes between them, through the brain.

The method promises to have long lasting results for up to 90 minutes.

"This is a huge advantage of DC because TMS effects only last for a few minutes," says Prof Walsh, who expects the results of his trial next year.

The same techniques can help people cope with the aftermath of a stroke too. Both magnetic and electrical stimulation can sensitise the brain immediately before physiotherapy, so they can help a stroke patient to regain the ability to move a paralysed limb.

Recent trials suggest that the method is capable of improving speech and the ability to make arm and hand movements by making the brain more plastic, so areas spared by the stroke are coopted to take over from those that have been damaged.

"Patients can be helped to learn to grip cutlery, turn water taps, pout things - simple everyday abilities they may have lost after a stroke," he says. "The method helps the brain find new solutions. There is a wholly convincing study of the benefits with stroke in a trial at the National Institutes of Health in America," adds Prof Walsh.

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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.

DIY brain therapy could halt migraines 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. 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."

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