Stimulating the brain with a magnet may be a good treatment for stroke victims, say scientists.
The technique is non-invasive
A University College London team says it has found a way to produce beneficial effects that last more than an hour, after 40 seconds stimulation.
The technique, transcranial magnetic stimulation, had previously shown promise, but with short-lived results.
The scientists, whose findings are in the journal Neuron, hope they could aid the recovery of stroke victims.
Transcranial magnetic stimulation (TMS) uses an electromagnet applied to the scalp to cause a very temporary disruption in the firing of neurons in the brain at the site of stimulation.
It is possible to pinpoint very specific areas.
The repetitive magnetic pulses, lasting for seconds, produce the neurological effects.
But generally, these rarely last longer than 30 minutes.
UCL had already used TMS on people with partial damage to their spinal cord to improve muscle and limb movement and increase the ability to feel sensations.
Professor John Rothwell and colleagues at the Institute of Neurology have refined TMS to be more powerful and produce longer-lasting effects.
They carried out their tests on healthy volunteers, aiming the pulses at the part of the brain that controls movement, the motor cortex.
They found the excitatory effect of TMS builds up rapidly, within about a second, while the inhibitory effect builds up over several seconds.
This means that by adjusting the length of stimulation they were able to choose between stimulating the brain or suppressing it.
Professor Rothwell said: "We can turn up or turn down the brain at will."
They believe one of the shortcomings of previous stimulation approaches was that they produced a mix of both excitation and inhibition.
Furthermore, the effects appeared to last much longer - more than 60 minutes - and did not cause any side effects, he said.
Professor Rothwell said: "Now that we have improved the technique, we can use it to explore whether stimulation of damaged areas in stroke patients' brains can help speed up their recovery."
They plan to give patients TMS therapy before they have physiotherapy to put the brain into a better state to respond to the physiotherapy.
A spokeswoman from The Stroke Association said: "This is an interesting piece of research that may have positive implications on the treatment of stroke."
It might be useful in epilepsy. Professor John Duncan, consultant neurologist and medical director of the National Society for Epilepsy said: "There are suggestions that TMS may result in the brain being less likely to generate epileptic seizures."