Zapping your own brain to treat depression? Surely it's too good to be true

How neurostimulation fooled us all – and why the field needs to take a hard look at its methods in future.

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It’s 200 years since Mary Shelley imagined a mad scientist who hit a cadaver with a jolt of electricity. Now one is doing it for real. György Buzsáki, a professor of neuroscience at New York University, wanted to investigate burgeoning claims about transcranial direct current stimulation (tDCS).

No one is claiming that tDCS can bring a corpse to life – at least not yet – but there are many adherents who believe that the technique, which involves passing small currents between electrodes attached to the head, can improve mental focus, assist learning, ramp up performance in mathematical tasks, improve sleep, reduce pain and even alleviate depression.

In many ways, this is nothing new. The Romans were known to use electric eels to ward off headaches. The first claim for transcranial electricity as an antidepressant was made in 1801, and studies in the 1960s also claimed some success in combating mental illness. But in the past decade, the practice has entered the scientific mainstream – and been applied to all manner of ills.

A study published in April by an international team of researchers concluded that tDCS had “significant” pain-relieving effects for MS patients. A 2013 review of experiments on 200 patients said the effect on major depression “remains unclear” but merits further investigation. Other studies suggest tDCS is a “promising tool to facilitate stroke recovery” and shows “potential for providing tinnitus relief”.

A wave of positive news stories has encouraged people without specific health problems to give tDCS a try. It is possible to cobble together your own apparatus using a battery, some wires, electrodes and sponges, but ready-to-wear tDCS kits are becoming affordable, too. This month, a UK-based company called foc.us will begin shipping units it describes as “a Swiss army knife of brain stimulation technologies”, designed to help users wake up, concentrate and (particularly) achieve better video-game scores.

The new focus module even has a “double-blind sham” setting, so you can test for yourself whether the current really is making a difference. It deploys the same techniques used in scientific studies in order to disguise whether or not it is putting out a charge.

The big question is: what does the current actually do? It comes from a small (typically nine-volt) battery, hooked up to a pair of electrodes that are little more than sponges soaked in saline to ensure good electrical contact. The current travels from electrodes, which are held by a band on the sides of the forehead, into the skin. After that, though, all bets are off – at least according to Buzsáki’s research.

Buzsáki set up the system on a cadaver and measured how much of the current penetrated the skull and made it into the brain. Not much, so it would seem. He is still writing up his results for peer review, but presented an outline at the annual meeting of the Cognitive Neuroscience Society in New York early last month. In his talk, he explained that so little electrical charge gets through the skull and into the brain that stimulating neurons to fire would require applying roughly twice the current that most commercial devices supply.

Buzsáki has tried the higher level – 4 milliamps will begin to activate neurons – and it is “alarming”, he says. Once he got up to 5 milliamps, he started to feel dizzy.

Buzsáki’s critics have two responses. First, they suggest that living tissue has fundamentally different electrical characteristics, and so experiments on dead tissue tell us nothing. Buzsáki disagrees: if anything, more current will make it into the inactive tissue of a cadaver’s brain than into the brain of a live person, he says.

Second, critics argue that there need not be enough current to make neurons fire, just enough to bring them closer to the threshold for firing. That may be valid, Buzsáki says, but does not provide enough justification for the claimed effects.

Buzsáki’s results do not spell the end of tDCS, but the field will need to take a hard look at its methods to avoid what is known in neuroscience as a “dead salmon moment”.

In 2010, Dartmouth College’s Craig Bennett performed a functional magnetic resonance imaging scan on a long-dead fish. Employing statistical manipulations of the fMRI data widely used in neuroscience research, Bennett could generate signs of brain activity where none was possible. Buzsáki’s cadaver and Bennett’s salmon now join Mary Shelley’s Frankenstein as a warning to overreaching scientists everywhere. 

Michael Brooks holds a PhD in quantum physics. He writes a weekly science column for the New Statesman, and his most recent book is At the Edge of Uncertainty: 11 Discoveries Taking Science by Surprise.

This article appears in the 12 May 2016 issue of the New Statesman, The anti-Trump