Why brain stimulation isn't what it's cracked up to be

Why brain stimulation isn’t what it’s cracked up to be
About half of studies of some types of brain stimulation cannot be reproduced. So, how do we know if these work? Credit: www.shutterstock.com

Interest in electrical brain stimulation has skyrocketed in recent years, both in the popular media and scientific literature.

Scientists and clinicians are using the non-invasive and cheap technique to treat various neurological and psychiatric disorders, including depression, epilepsy and addiction. The US military is researching whether it improves learning and attention. And those who train elite athletes can see its potential to enhance performance.

But our research shows the evidence to back electrical brain stimulation varies in quality, and the results are commonly not reproduced in other studies. Our survey also unearthed the lengths to which some go to to present their findings in the best light.

What is electrical brain stimulation?

The type of electrical brain stimulation we studied is transcranial direct-current stimulation. This is when a small electric current is applied to the brain for 20 to 30 minutes. Electrodes are placed on the patient's head, and some of the current passes through the skull to the brain.

It is thought this alters brain function mainly by inducing persistent changes in the excitability of neurones.

This isn't to be confused with electroconvulsive therapy, which uses currents hundreds of times larger. This induces a seizure.

What we did

We used an online survey to ask researchers if they could reproduce published findings related to electrical brain stimulation. We invited all researchers who served as corresponding authors on a published scientific paper on electrical brain stimulation in humans to do so.

In all, 976 researchers from all over the world were invited to answer the question of whether they could reproduce published electrical brain stimulation effects.

We also asked whether researchers used, but didn't report, questionable in their own research – such as fiddling with statistics to make them look more favourable and selectively reporting results. And we asked if they thought other researchers used these questionable techniques, and whether they should be reported in publications.

To check what researchers actually do, we audited a random selection of 100 publications featuring research on electrical brain stimulation. We looked to see if they admitted to the dodgy practices in their publications.

What we found

For the two most popular types of electrical brain stimulation (anodal and cathodal stimulation), only 45 to 50% of researchers routinely reproduced published findings.

Some researchers were aware of others who handpicked which experimental conditions (36%) and which results (41%) to publish. They also knew researchers who manipulated results by excluding data based on a gut feeling (20%) and fiddling with the statistics (43%).

As expected, fewer researchers admitted to personally using these types of shady research practices. Still, 25% admitted to adjusting statistical analysis to optimise results – namely p-hacking, when researchers manipulate the statistics to make results appear more statistically significant than they might otherwise be.

Our research also revealed the difference between whether these questionable types of practices should be reported in research papers, and whether they are. Although 92% of respondents said all researchers should admit to the questionable practices in their publications, we found only two such admissions (2%) in our audit of published studies.

So, what do we make of this?

Meta-analyses, which are studies that pool results from several other studies, indicate electrical brain stimulation is effective in major depression. But it isn't in fibromyalgia (where people experience widespread pain without a known cause), food craving and overeating, Parkinson's disease, and speech problems after a stroke.

Unfortunately, a general finding is that electrical brain stimulation studies are often of low quality and that, when present, therapeutic effects are often small. So, before you decide to strap electrodes to your head, speak to an informed health professional.

Poor reproducibility and bad science are not unique to electrical brain stimulation research. Nor are these problems new. But public funds are being wasted on poorly conducted research that cannot be reproduced, which means the results are questionable. Such poor research is tarnishing the genuine efforts of researchers to improve human brain function.

The main reason researchers engage in questionable researcher practices is the continual pressure to publish scientific papers to gain funding or to progress scientific careers. If results are statistically significant, researchers are more likely to be published. So, researchers may consciously, or unconsciously, resort to questionable or fraudulent research practices.

What can we do about it?

Awareness of bad science is on the rise – and recommendations and guidelines are emerging to deal with this. But there needs to be more education and true incentives for scientists to conduct better, reproducible science.

If not, some scientists will continue to do as they have always done. Incentives to improve the culture of research include promoting researchers who do more open science, and funding projects that adhere to open science practices as well as those that attempt to replicate studies.

The responsibility to improve the quality of our science lies with research institutions and universities, funding agencies, scientific publishers and individual researchers.

Our goal of clinically useful stimulation techniques is a worthy one. But our progress is limited by findings of often variable and small effects currently reported, as well as the poor quality of some of the studies that claim any effects at all.

Explore further

Researchers show brain stimulation restores memory during lapses

Provided by The Conversation

This article was originally published on The Conversation. Read the original article.The Conversation

Citation: Why brain stimulation isn't what it's cracked up to be (2017, April 28) retrieved 20 June 2019 from https://medicalxpress.com/news/2017-04-brain-isnt.html
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User comments

Apr 29, 2017
This comment has been removed by a moderator.

Apr 30, 2017
Do you have one iota of actual evidence that this article or the peer-reviewed scientific study report it describes have anything but science to them? Any interest conflicts whatsoever?

Of course you don't. You're just another irresponsible Internet troll. The study was funded by the Australian national government , which exercised no control over the study.

You are defending quacks and bad scientists who the study exposes.

This article

Jun 12, 2017
I am just seeing this now, and I don't even recall what I wrote here. Was it something so horrible that it prompted such rude and incoherent feedback, and had to be removed? I tend to doubt it.

Jun 13, 2017
I am just seeing this now, and I don't even recall what I wrote here. Was it something so horrible that it prompted such rude and incoherent feedback, and had to be removed? I tend to doubt it.

Obviously you posted that the article and the study were unscientific and were plagued by interest conflicts, defending quacks and bad scientists who contradict the study. Even though you had not one iota of actual evidence for that. And you posted something that horrible, rude and incoherent even though you had so little interest that for months you ignored the responses to your baseless slander.

Sure you tend to doubt it. You tend to post irresponsible, baseless attacks on legit science then wander away without even remembering it. You're a troll: you post designed to disrupt, not to discuss.

Jun 13, 2017
Well first off, I tend to agree with this article, and I work in the functional brain imaging field so I have some insight. Apparently my alerts do not work for this site so I had no idea it was removed or that anyone replied.
It seems you did not even read the article, FYI it is about a study that questions the validity of other electrical brain stimulation studies.

So if I did post a link that is apparently not allowed, it would have been in support of this finding, and to further the conversation. By contrast all I see from you is unsubstantiated accusations, rude remarks, and out right name calling. Your response makes it quite clear who the actual troll is here.

Good day sir.

Jun 13, 2017
It seems you did not even read the article, FYI it is about a study that questions the validity of other electrical brain stimulation studies.

So if I did post a link that is apparently not allowed

I did read the article, and nothing I've posted "seems" otherwise. You're the one who can't even remember what you posted, which was removed by site moderators (so rare, only the worst are removed), and are now posting speculation derived only from your high opinion of yourself.

Meanwhile, I pointed out when you posted exactly what I just repeated to you: you posted accusations of unscientific behavior, defended quacks and bad scientists, all without evidence.

And you're attempting to recover with some vague argument from authority and propter hoc fallacies.

All of this reflects poorly on your own high opinion of yourself.


Jun 13, 2017
All I see is a sad little person lashing out to strangers on the internet about things of which you know nothing.I am sure your mother would be proud.


Jun 13, 2017
All I know is - I use my 10's unit to stimulate opposite quarters of my head...

Jun 13, 2017
All I see

Of course that's all you see. Otherwise you'd have to see yourself, unable to even remember some trolling you'll deny anyway, invoking fallacies and now bringing my mother into it. I know all I need to know about you from a few posts. I also know you couldn't resist posting again after you'd indicated you were done. You're a troll, pal - own it.

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