I found these article in The Scientist

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Mind controls: Running electricity through the skull

11:09 11 April 2011 by Robson

Magazine issue 2807.

It sounds too good to be true: changing the brain's activity simply by placing

electrodes on the surface of the scalp. But that's the idea behind transcranial

direct current stimulation (tDCS). No scalpel required.

With this technique, the electrodes are simply damp sponges about 4 square

centimetres in area, and they are used to deliver a current of just a couple of

milliamps. " There may be some mild tinglings under the electrodes, but that's

about it, " says Leonardo Cohen at the National Institutes of Health in Bethesda,

land.

tDCS should not be confused with electroconvulsive therapy, where a much larger

shock of 600 milliamps is applied to the whole brain. ECT is designed to trigger

seizures and must be done under a general anaesthetic. It has side effects such

as memory loss and confusion and so is only given to people with very serious

depression.

So how does tDCS work? Neurons underneath the positively charged electrode are

stimulated to fire more frequently in response to normal incoming signals. The

negative electrode has the opposite effect, quietening the underlying cells. If

one region needs to be boosted without muting another, the negative electrode

can be placed over a thicker part of the skull, such as the area above the eye,

to minimise impact.

As tDCS has only been used for about a decade its full potential is still

unknown. Perhaps the most widely tested medical use has been to treat brain

damage arising from a stroke. In a study on 10 people, five consecutive days of

treatment led to improvements in language a week later (Stroke, vol 41, p 1229).

The technique is also being investigated as a treatment for depression, chronic

pain and migraine.

Because tDCS seems so safe it is being studied as a potential cognitive

enhancer. For example, Cohen has shown it can help people learn a task involving

precise hand movements: people who had tDCS during the training period performed

better than their peers three months down the line (Proceedings of the National

Academy of Sciences, vol 106, p 1590). Another group has shown it can boost

mathematical skills (Current Biology, vol 20, p 2016).

VERDICT Equipment is simple and cheap, and the technique looks safe. Perhaps has

the most potential for cognitive enhancement.

Mind controls: Electrodes sitting on the brain's surface

11:09 11 April 2011 by Clare

Magazine issue 2807. Subscribe and save

Pushing electrodes deep into the brain allows precision targeting but requires

risky surgery. Placing electrodes on the surface of the scalp carries

little-to-no health risk, but it cannot be focused on an area of less than 4

square centimetres. Could we get the best of both worlds through epidural

cortical stimulation?

With this technique, rather than placing the electrodes inside the brain, they

are put on its surface. So while surgery is needed, it is a safer procedure: a

hole is drilled in the skull and a tape with several electrodes on it is slid

over the brain's surface membrane, the dura mater. " Dura is Latin for 'tough', "

says Mark , a neuropsychiatrist at the Medical University of South

Carolina. " It's pretty safe. "

Epidural cortical stimulation is being investigated as a treatment for several

conditions, including intractable pain and epilepsy. 's team has recently

tested it in five people with severe depression who hadn't responded to drugs or

other forms of brain stimulation. Three improved significantly and remained

better a year later (Biological Psychiatry, vol 67, p 101).

VERDICT Could become a safer alternative to deep brain stimulation for

conditions where the brain region involved is near the surface.

Mind controls: A traffic cop on the nerve superhighway

11:09 11 April 2011 by Clare

Magazine issue 2807. Subscribe and save

Imagine if there were a major highway into the brain that could be safely

accessed from elsewhere in the body. That's what vagus nerve stimulation is

tapping into.

The vagus nerve is a bundle of neurons connecting the brain to many of the major

organs, with nerves running both from the organ to the brain and vice versa. It

does a multitude of jobs, including helping to control heart rate, breathing and

appetite.

It is possible to wrap electrodes around the nerve in the lower neck and connect

these to a small power source implanted in the chest, programmed to turn on and

off at regular intervals. Trial and error has shown that altering the frequency

and timing of stimulation can affect the brain in different ways.

A stimulator made by US firm Cyberonics is approved in that country for treating

severe forms of epilepsy and depression. However, exactly how it works and which

parts of the brain it targets is still unclear.

As the Cyberonics device is commercially available and fairly easy to implant,

it is being investigated for many different uses. Some people who have had a

device implanted have lost weight as a side effect, possibly because stimulation

is mimicking the normal messages from our gut to our brain that signal when we

are full. Research on pigs published last year showed that vagus nerve

stimulation stopped the animals overeating and even made them select healthy

food options (Appetite, vol 55, p 245).

If the effects extend to people who are obese, vagus nerve stimulation would

look a good option next to stomach stapling, as the operation to do this carries

a 0.5 per cent risk of death.

VERDICT Looks fairly safe but how it works is still unclear.