Brain Stimulation And You: How Does It Work And Can It Really Juice Up Your Thinking Cap?

Apr 8, 2016 09:00 AM By Ed Cara

Medical Daily takes a look at the ins-and-outs of brain stimulation, from its useful applications in medicine to its growing but possibly unwarranted hype as a mind enhancer. Above, users try out their foc.us tDCS headsets. foc.us, CC BY 4.0

For as long as people have had access to electricity, we’ve tried to use it to cure our maladies. From grabbing onto electric eels to treat our headaches in the 1st Century to subjecting ourselves to electroshock therapy in attempts to dispel depression and schizophrenia, we’ve often come out with mixed, but not entirely fruitless, results.

Thankfully, as modern medicine has progressed, so too has our mastery of therapeutic lightning in a bottle. Nowadays, a variety of electrical stimulation techniques that more precisely target the brain have found homes within doctors’ offices. They’ve proven effective in treating Parkinson’s disease and other movement disorders, while also showing promise for conditions like anorexia, tourette syndrome, and, you guessed it, depression. Meanwhile, techniques like transcranial direct current stimulation (tDCS) are becoming increasingly commercialized as easy-to-use consumer products that can either juice up our noggins or calm our anxious minds.

With all the noteworthy buzz surrounding brain stimulation, Medical Daily decided to break down its basics and provide an honest look at its overall potential in the near future.

Restoring Balance

Brain stimulation can be broadly broken into two categories: invasive and noninvasive.

The most common type of the former is known as deep brain stimulation(DBS), where a battery-powered device, the implanted pulse generator (IPG), one or more electrode leads, and extension wires are all surgically rooted within the body. Where the leads go on the brain depends on which condition is being treated, but the basic premise remains the same: Electrical pulses sent from the pulse generator to the leads cause a disruption in nearby neural activity.

Because the symptoms of movement disorders coincide with erratic neural patterns in the targeted brain region (often the subthalamic nucleus for Parkinson’s), it’s theorized DBS acts as a sort of pacemaker, temporarily restoring a healthy rhythm of activity. DBS was first approved by the Food and Drug Administration for the treatment of essential tremors and Parkinson’s in 1997, and since then, the devices, and clinicians who use them, have gotten better at targeting specific regions.

Noninvasive stimulation, which includes the still-available but last resort electroshock therapy described above, works on a less forceful principle. With tDCS, which is quickly becoming the technique of choice due to its affordability and precision, two electrodes are placed on the head — an anode and cathode — where they send constant electrical currents to the neurons beneath them during a treatment session. Rather than shocking the brain into normalcy, though, the currents are thought to only nudge it back. The cathode hyperpolarizes the neurons underneath it, making it harder for them to fire and presumably slowing the neural activity nearby, while the anode does the opposite, making it easier for neurons to fire and likewise ramping up our local connection speed, seemingly in a repeatable and predictable pattern.

Hype Before Results

Cool as these stimulation techniques are, though, we shouldn’t overhype them.

Despite increasing sophistication and the potential for research into their broader applications to lead somewhere great, they’ll likely never be a first line treatment for many, if any, conditions. In the case of DBS, that’s not merely because of the surgical upkeep they require and severe side effects, like hallucinations, that they cause, but also because the brain is a beautiful and intricate mess. Much as we’d like to assume, our brains aren’t neatly arranged into segments that correspond perfectly to one specific physical or mental function of the body. For instance, remembering something requires different shifting parts of the brain, the specific regions depending on whether it’s a fond memory of your first kiss or tracking down the last place your keys were.

The same is true of the neural dysfunctions that cause someone to shake uncontrollably or feel persistently depressed. Even for disorders like Parkinson’s, DBS is only recommended for those who already respond well to the common Parkinson’s drug levodopa — the precursor chemical of dopamine — and are otherwise mentally healthy. Similarly, the more complicated the condition, neurologically speaking, the less likely DBS will be effective; if only because the powerful shock can’t fix everything.

While tDCS also has this drawback, there’s an even deeper problem with it: We’re not entirely sure it works at all, at least in healthy people. In 2015, a review of 59 studies found no “reliable effect of tDCS on executive function, language, [or] memory,” as well as other measures of cognitive function in healthy subjects. Though some studies did find a brain boost, others effectively canceled them out. The study’s lead author and graduate student in neuroscience at the University of Melbourne, Jared Horvath, has also published research showing a similar lack of reliably measured physical changes in healthy subjects given tDCS.

It isn’t necessarily that tDCS doesn’t influence patients; certainly the number of people who report not being able to form words after a session or slightly burnt skin suggest something real is happening. But Horvath argues that researchers don’t yet have a firm grasp on the best way to study its effects, or how to channel the technique into something consistently beneficial.

A 2014 paper by Horvath and his colleagues detailed some of these flaws. For one, scientists can often spot the group of test subjects that receives tDCS versus a placebo, which might subtly influence their findings. People also have widely different reactions to tDCS, not only when compared to other people, but also after each individual session. And finally, there’s the distinct possibility that any treatment effects may disappear as soon as a user moves or thinks too much. Even having hair that’s too thick can interfere with the electrodes’ ability to reach the brain, a factor that’s obviously hard to take into account. Most of these problems can be seen when studying other forms of noninvasive brain stimulation too.

“I hope my work helps elucidate that research and medical progress is a tricky business,” Horvath told Medical Daily. “Scientists and researchers are as human as anyone else and we will chase our ideas and passions wherever they lead us; but, just because we're exploring something does not mean that thing will prove effective.”

Our shoddy homework is especially concerning when looking at the rise of consumer tDCS devices such as the Thync, which is only inspired by the DIY tDCS device kits readily available (Thync claims to use a novel form of neurostimulation). Unlike more reserved scientists, the companies behind these devices have touted them as mini-miracle workers, capable of restoring our mood, memory, and sleep to peak levels of awesome.

Despite exaggerated health claims, there’s no real check on their accuracy from expected places like the government, which hasn’t yet figured out how to regulate them. As Anna Wexler, a PhD candidate at MIT who is currently studying the subject, wrote in a 2015 paper and accompanying Slate article, the question of regulation is definitely a thorny one.

“Should they be considered medical devices, subject to stringent regulation from the Food and Drug Administration? Or are they ‘wearable technology’ like the Fitbit, subject to more lenient consumer regulation from the Consumer Product Safety Commission?” she wrote. The latter would require companies to pass a high bar of evidence before their products can reach the public, while the former would lead to a gold rush of Thync-like caps, all probably more effective at relieving our wallets of money than our brains of stress.

Regardless of what ends up happening, Wexler recommends we stay on our guard when evaluating these home-use devices. “Consumers should always take health claims — whether they are coming from electrical stimulation devices, dietary supplements, or even food — with a grain of salt,” she told Medical Daily.

None of this is to say that tDCS and its ilk are a bust, only that we’re nowhere near the home stretch of their development. While their effects on the Average Joe are still muddy, there is more support for their use in alleviating conditions like fibromyalgia, depression, and maybe even Parkinson's — though Horvath offers a word of caution even there.

Citing an upcoming review from top tDCS researchers in Europe, he told Medical Daily that the experts couldn’t recommend tDCS as an absolutely effective treatment for any medical condition. For a few conditions, they determined tDCS was probably or possibly effective, but for the majority looked at, they declined to offer any stamp of approval. “It appears the clinical research is as variable, unpredictable, and heterogeneous,” as the research on healthy volunteers, he said.

Brain stimulation, particularly DBS, has and will continue to have an important role in medicine; that's undeniable. But if you ever decide to attach some electrodes to your noggin, it’s best to keep this familiar saying in your mind too: If it sounds too good to be true, it probably is.

http://www.medicaldaily.com/brain-stimulation-how-does-it-work-parkinsons-disease-381118