A headset with four electrodes to zap the brain with a surge of electricity offers to improve computer gamers' response time so they can eliminate more zombies and raid more tombs.

The $US249 ($273) device, which is available on the internet, passes a current to the prefrontal cortex using a stimulation technique that is also used to treat depression.

Headset for gamers

But a Sydney world leader in the use of the procedure has warned of the unknown side effects of using the headset and its long-term impact on brain function.

The company website says: ''Overclock your brain using transcranial Direct Current Stimulation to increase the plasticity of your brain. Make your synapses fire faster.''

The company says the headset is not a medical device and is not regulated by the US Food and Drug Administration. It also says the device meets all regulated safety standards but warns against its use by epilepsy sufferers or anyone with implants.

Professor Colleen Loo, from the University of NSW school of psychiatry and clinical and research psychiatrist with the Black Dog Institute said the effect on the brain was dependent on where and how the electrodes were positioned. ''It's a bit like having an accelerator and brake in a car,'' she said. ''Neither is bad and both are very useful but applying them judiciously at the right time and in the right context is absolutely essential. I think stimulation of yourself with do-it-yourself kits is potentially quite dangerous.

''Even with a single session, I am concerned about people doing some mischief to themselves … if you did this while playing a game and then you went out and drove a car and had an accident, did it affect your reaction time, your co-ordination?''