Electric current

POPULAR BRAIN STIMULATION DOESN’T BOOST IQ

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Despite its popularity, using a weak electric current to boost brainpower doesn’t live up to the hype. A new study shows that the most common form of the treatment actually has a statistically significant detrimental effect on IQ scores.

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, study senior author and assistant professor of psychiatry, cell biology and physiology, biomedical engineering, and neurology at the UNC School of Medicine.

“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.”

TWO TYPES OF BRAIN STIMULATION

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.”

‘EXPLOSION’ OF STUDIES

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. He also says some of the studies that have made waves were poorly designed. Some studies were not properly double-blinded or properly placebo controlled. Other studies were very small—fewer than 10 people.

A recent meta-analysis of a large number of tDCS papers showed that tDCS is far from a magic pill for cognitive enhancement or brain-related health conditions.

“Aside from stimulating the motor cortex, which has very exciting implications for stroke rehabilitation, I think the jury is still out on tDCS,” says Frohlich, who is a member of the UNC Neuroscience Center.

PUTTING ON THE ELECTRODES

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.

All participants then retook the IQ tests. Frohlich expected that most, if not all, IQ scores would improve, but that the participants who received tDCS would not improve their scores any more than would the people who did not undergo tDCS

SCORES THAT SANK

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.

When Frohlich and colleagues analyzed the test scores, they saw that the scores for three of the four kinds of cognitive tests were very similar between the two groups of participants. But the scores for perceptual reasoning were much lower among people who underwent tDCS.

Perceptual reasoning tests fluid intelligence, which is defined as the ability to think logically and apply innovative problem solving to new problems.

Within the category of perceptual reasoning, the researchers saw the biggest differences in the subcategory of matrix reasoning—when participants viewed two groups of symbols and had to find the one symbol missing from the other group.

“This is one of the classical assays of fluid intelligence,” Frohlich says, “where you have to identify hidden rules and apply logic to find a missing element.”

NO ‘MAGIC PILL’

Frohlich emphasizes, “Our findings do not preclude the possibility that other tDCS paradigms may be less harmful or even beneficial. However it is time to make sure that everybody uses gold standard, placebo-controlled, double-blind study designs. Also, our study demonstrates the importance of more research on how stimulation interacts with brain activity.”

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”

Frohlich adds, “I think our study demonstrates that we need to think of smarter ways to engage the brain to really target the specific brain dynamics involved in what we want to improve, such as cognition for people with depression or schizophrenia. I think tACS is an option, as well as more sophisticated modalities we’ve yet to develop.”

‘Determination’ can be induced by electrical brain stimulation.

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Applying an electric current to a particular part of the brain makes people feel a sense of determination, say researchers

The men were having a routine procedure to locate regions in their brains that caused epileptic seizures when they felt their heart rates rise, a sense of foreboding, and an overwhelming desire to persevere against a looming hardship.

The remarkable findings could help researchers develop treatments fordepression and other disorders where people are debilitated by a lack of motivation.

One patient said the feeling was like driving a car into a raging storm. When his brain was stimulated, he sensed a shaking in his chest and a surge in his pulse. In six trials, he felt the same sensations time and again.

Comparing the feelings to a frantic drive towards a storm, the patient said: “You’re only halfway there and you have no other way to turn around and go back, you have to keep going forward.”

When asked by doctors to elaborate on whether the feeling was good or bad, he said: “It was more of a positive thing, like push harder, push harder, push harder to try and get through this.”

A second patient had similar feelings when his brain was stimulated in the same region, called the anterior midcingulate cortex (aMCC). He felt worried that something terrible was about to happen, but knew he had to fight and not give up, according to a case study in the journal Neuron.

Both men were having an exploratory procedure to find the focal point in their brains that caused them to suffer epileptic fits. In the procedure, doctors sink fine electrodes deep into different parts of the brain and stimulate them with tiny electrical currents until the patient senses the “aura” that precedes a seizure. Often, seizures can be treated by removing tissue from this part of the brain.

“In the very first patient this was something very unexpected, and we didn’t report it,” said Josef Parvizi at Stanford University in California. But then I was doing functional mapping on the second patient and he suddenly experienced a very similar thing.”

“Its extraordinary that two individuals with very different past experiences respond in a similar way to one or two seconds of very low intensity electricity delivered to the same area of their brain. These patients are normal individuals, they have their IQ, they have their jobs. We are not reporting these findings in sick brains,” Parvizi said.

The men were stimulated with between two and eight milliamps of electrical current, but in tests the doctors administered sham stimulation too. In the sham tests, they told the patients they were about to stimulate the brain, but had switched off the electical supply. In these cases, the men reported no changes to their feelings. The sensation was only induced in a small area of the brain, and vanished when doctors implanted electrodes just five millimetres away.

Parvizi said a crucial follow-up experiment will be to test whether stimulation of the brain region really makes people more determined, or simply creates the sensation of perseverance. If future studies replicate the findings, stimulation of the brain region – perhaps without the need for brain-penetrating electrodes – could be used to help people with severe depression.

The anterior midcingulate cortex seems to be important in helping us select responses and make decisions in light of the feedback we get. Brent Vogt, a neurobiologist at Boston University, said patients with chronic pain and obsessive-compulsive disorder have already been treated by destroying part of the aMCC. “Why not stimulate it? If this would enhance relieving depression, for example, let’s go,” he said.