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From technologies which allow the brain to directly control computers to using electricity to enhance brain function, the way technology can "intervene" in the brain is being reviewed.

The Nuffield Council on Bioethics has launched a public consultation on the ethics of the technology.

Applications range from medicine to warfare and even human enhancement.

Some techniques such as deep brain stimulation (DBS) are already used by thousands of patients.

Prof Thomas Baldwin, from the University of York, is leading the study. He said there had a long history of altering the brain from trepanning - drilling holes in the skull - thousands of years of ago to surgical lobotomies.

He said: "It became apparent there were a number of side effects which were seriously harmful.

"People have become much more cautious about intervening in the brain."

The consultation wants to get the public's view on newer developments.

Common

One of the most widely used techniques is DBS for Parkinson's patients. Electrodes are inserted into specific regions of the brain and are hooked up to a battery in the chest. Bursts of electricity help control the tremors associated with the condition.

DBS is also being considered for a range of other conditions from depression to Tourette's syndrome.

Dr Alena Buyx, the assistant director of the Nuffield Council on Bioethics, warned that while there were medical benefits, the therapy had "quite significant side effects" and could result in changes to speech and even personality, which raised ethical questions.

She even cited a case of patient caught stealing who used the defence of "my brain electrode made me do it".

It has also been suggested that a different type of brain stimulation, achieved by wearing a special cap,can improve people's ability to do maths.

Dr Buyx said this had triggered debates about human enhancement and whether the technology should ever be used in schools.

Brain to computer

The consultation will also ask for views about "brain computer interfaces" in which brain signals are measured and converted into instructions such as a thought-controlled wheelchair.

There is also research into using the technology to help patients with locked-in syndrome.

The same techniques have been used to control primitive computer games. However, it is thought that eventually they could be used by the military. In the same way that drone aircraft are controlled remotely, the idea would be that a soldier's brain could control machines engaged in warfare thousands of miles away.

Prof Baldwin said: "Intervening in the brain has always raised both hopes and fears in equal measure.

"Hopes of curing terrible diseases, and fears about the consequences of trying to enhance human capability beyond what is normally possible.

"These challenge us to think carefully about fundamental questions to do with the brain: what makes us human, what makes us an individual, and how and why do we think and behave in the way we do."

The public consultation will take place until 23 April 2012 and the council's recommendations will be made next year.