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Giving yourself small electric shocks to boost your brainpower has become an increasingly popular pastime.

However, researchers have warned the trend, known as Transcranial Direct Current Stimulation, doesn't work.

In fact, they say that the most common form of the treatment actually has a statistically significant detrimental effect on IQ scores.

Experimental results showing transcranial direct current stimulation can boost brain activity has led some to attempt to build their own devices at home, but new research suggests they can harm cognitive performance

HOW DOES tDCS WORK?

Transcranial Direct Current Stimulation uses gentle pulses of electricity to increase the activity of neurons in the brain.

The pulses boosts the natural tiny electrical current that transmit signals within neurons.

Electrodes are attached to different parts of head depending on the area of the brain to be stimulated and the desired effect.

A low intensity current passes between the two electrodes, with the area of the brain close to the cathode being inhibited and the area close to the anode being excited.

Published in the journal Behavioural Brain Research, the study adds to the increasing amount of literature showing that transcranial direct current stimulation—tDCS—has mixed results when it comes to cognitive enhancement.

'It would be wonderful if we could use tDCS to enhance cognition because then we could potentially use it to treat cognitive impairment in psychiatric illnesses,' says Flavio Frohlich at the University of North Carolina at Chapel Hill

'So, this study is bad news. 

'Yet, the finding makes sense. It means that some of the most sophisticated things the brain can do, in terms of cognition, can't necessarily be altered with just a constant electric current.'

Frohlich, though, says that using less common alternating current stimulation—so-called tACS—could be a better approach, one that he has been investigating. Earlier this year, Frohlich's lab found that tACS significantly boosted creativity, likely because he used it to target the brain's natural electrical alpha oscillations, which have been implicated in creative thought.

With tDCS, scientists don't target these brain waves, which represent neuronal patterns of communication throughout regions of the brain. Instead, they use tDCS to target brain structures, such particular regions of the cortex.

'All of our brain structures look more or less the same, but the reason why we're all so different is that the electrical brain activities in our brains are very different,' Frohlich says. 'We have to better understand this and target specific brain activity patterns.'

Using a weak electrical current to boost the brain's natural abilities has been around for decades, but the current boom within the science community started in 2000, when German scientists published a paper showing that tDCS could change the excitability of neurons in the motor cortex—the brain region that controls voluntary body movement.

Since then, there's been an explosion of tDCS studies to try to make neurons more active or less active and therefore change outcomes for a variety of brain functions, such as working memory and cognitive acuity, and for illnesses, such as depression and schizophrenia.

But Frohlich says that scientists still don't know exactly what the direct current does to neural activity.  

In the new, Frohlich's team—including graduate student Kristin Sellers, the paper's first author—recruited 40 healthy adults, each of whom took the standard WAIS-IV intelligence test—the most common and well-validated test of IQ, which includes tests for verbal comprehension, perceptional reasoning, working memory, and processing speed.

A week later, Frohlich's team divided the participants into two groups. 

Electrodes were placed on each side of each participant's scalp, under which sat the frontal cortex.

A third electrode, which sent electricity back to the device that that produced the electric current, was placed on top of the scalp.

Duke University collaborator and coauthor Angel Peterchev created imaging simulations to ensure Frohlich's team targeted the same parts of the cortex that previous tDCS studies had targeted.

Then the placebo group received sham stimulation—a brief electrical current, which led participants to think they had been receiving the full tDCS. 

The other participants received the standard tDCS for twenty minutes—a weak electrical current of 2 millioamperes.

Brain stimulation devices have been used by researchers to study a range of brain functions but they do not believe the technology is understood well enough to be available for use by the general public

All participants then retook the IQ tests.  

Frohlich's team did find that all scores improved—most likely because of the 'practice effect' of previously taking the test. 

Surprisingly, the participants who did not receive tDCS saw their IQ scores increase by ten points, whereas participants who received tDCS saw their IQ scores increase by just shy of six points, on average. 

Frohlich stresses that the scientific community should be careful not to create simplistic storylines about tDCS being a 'magic pill' for many brain-related conditions.

'There could be dangerous consequences, especially if tDCS is used daily,' he says.

'Ours was an acute study. We don't know what the long-term effects are. 

'There is so much more we need to understand before tDCS is ready for home use without medical supervision' 

In a recent article for the Journal of Law and Biosciences, Dr Cohen Kadosh's colleague Dr Hannah Maslen argued: 'Recently, it has become very easy for individuals to purchase devices which directly modulate brain function.

'For example, transcranial direct current stimulators are increasingly being produced and marketed online as devices for cognitive enhancement. 

'Despite posing risks in a similar way to medical devices, devices that do not make any therapeutic claims do not have to meet anything more than basic product safety standards. 

'We present the case for extending existing medical device legislation to cover CEDs.'

Dr Nick Davis, an expert in brain stimulation at Swansea University added that the science underpinning the affects of such techniques were still too poorly understood to be available to the public.