A growing number of people who suffer from chronic pain, epilepsy and drug cravings are applying mild electric currents to parts of their skulls in the hopes that it will provide a low-cost, effective replacement cure to medication.

Others are using it in the hopes of improved cognitive function. It also promises to treat a multitude of neurological and psychiatric symptoms.

Known as transcranial direct current stimulation (tDCS), it is a non-invasive, painless brain stimulation treatment where a constant, low intensity current passes through the skull for the modulation of neuronal activity.

“There are a variety of different devices, however the simplest and most common approach is to place two saline soaked sponges on the scalp and run a weak electrical current through them,” said Dr. Michael D. Fox of Beth Israel Deaconess Medical Center in Boston. “It can be done at home with a couple of sponges and a 9 volt battery, which is why DIY tDCS exists.”

Commercial tDCS equipment is available on the market, and a do-it-yourself community has appeared on Reddit, providing unconventional tips for the use of tDCS. It is not approved by the U.S. FDA, and scientists have differing views on its efficacy.

MRI algorithm developed to investigate efficacy of tDCS

In response to the ambiguity surrounding the understanding or views of tDCS, a team led by Danny JJ Wang, a professor of neurology at the USC Mark and Mary Stevens Neuroimaging and Informatics Institute, pioneered the development of an MRI algorithm whereby the magnetic fields induced by tDCS currents may be visualized in living humans.

"Although this therapy is taking off at the grassroots level and in academia, evidence that tDCS does what is being promised is not conclusive," said Wang, the study's senior author. "Scientists don't yet understand the mechanisms at work, which prevents the FDA from regulating the therapy. Our study is the first step to experimentally map the tDCS currents in the brain and to provide solid data so researchers can develop science-based treatment."

"You cannot characterise what you cannot see, so this is a pivotal step in the development of tDCS technology," added study co-author, Maron Bikson, a professor of biomedical engineering at The City College of New York.

A technique with a history and many advocates

According to Mayank Jog, study lead author and a graduate student conducting research at the David Geffen School of Medicine at UCLA, tDCS was introduced only in 2000, but has its roots in antiquity, when people would use the electric shocks delivered by certain fish as a cure for headaches.

"Since then, this noninvasive, easy-to-use, low-cost technology has been shown to improve cognition as well as treat clinical symptoms," Jog said. Studies show people need only two weeks to show improvements with prolonged effects. Jog says the technique fosters hope, but a better grasp on what is happening is needed.

Besides a paper that recommended its use in stroke rehabilitation within South Asia, the technique does not seem to have caught on much in Asia.

Efficacy of tDCS is still debatable

The most common side effect of tDCS is a slight scalp tingling, but in rare cases, it caused burns where the electrodes were applied. There is also doubt as to whether the 1 to 2 milliamp (mA) zap involved actually travels to the brain. Wang is quick to set things straight: the purpose of tDCS is not to cause neurons to fire, but to alter the likelihood of them firing.

Although the study represents a step in the right direction, one does this at one’s risk. “I do think it’s important for… [people] to have a sense of the kinds of things that are known or not known about stimulation,” said Dr. Roy H. Hamilton of the University of Pennsylvania in Philadelphia who was not involved in the study. “And possible effects that stimulation might have that they may or may not be considering.” MIMS

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