By James Randerson | guardian.co.uk

A magnetic field can stimulate the brain and promote the growth of new nerve cells, scientists have found, raising the possibility of treating conditions linked to neuron death such as Alzheimer's disease, and perhaps one day of enhancing humans' memory capacity. Experiments on mice used a technique, transcranial magnetic stimulation, or TMS, which has become a standard tool for investigating the brain. Avoiding the use of surgery to open the skull, rapidly changing magnetic fields induce weak electrical signals in brain neurons. TMS has been used experimentally to treat disorders such as depression, Parkinson's and schizophrenia; it is also useful for temporarily shutting down some brain regions while enhancing others in experiments to find how the brain works. Fortunato Battaglia and a team at City University in New York gave mice up to five short bursts of TMS a day for five days, then looked at their brains. New Scientist magazine reports today that they found large increases in the proliferation of stem cells in part of the hippocampus - a brain region known to act in memory formation and mood regulation. They also saw changes in a part of the brain for controlling movement. This is the first time TMS has been shown to stimulate new neurons. "There is a lot of potential for this technique," said Professor Battaglia, who presented his results in Boston this month. "The effect on the stem cells is the most exciting finding ... This opens applications for patients with neurodegenerative diseases, especially Alzheimer's, and patients recovering from stroke." The team also saw evidence of long-term potentiation - changes to the nerve cells making them more sensitive and more likely to fire if stimulated by neurons next to them. In all areas of the brain tested, TMS modified chemical receptors on the surface of nerve cells so they remained active for longer. Alzheimer's disease is associated with neuron loss in the hippocampus, so stimulating growth could repair the damage. Even if TMS cannot stimulate growth of neurons in humans, its ability to strengthen existing neural pathways could be beneficial to Alzheimer's patients. The next step is to demonstrate TMS improves memory in mice, and to find how to get the best effect. Prof Battaglia said it would be premature to test people. "You could go to humans, but it would be some sort of fishing expedition. Working in animals allows us to optimise the technique," he said, though he hopes eventually the technique can improve memory. "Theoretically that could also be an application." Exercise and antidepressants promote neuron growth, but it has been impossible to target specific brain areas. Article from: http://www.guardian.co.uk/medicine/story/0,,2086758,00.html

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