What a couple of days. First the New Yorker, now PBS tv! If you’re new to tDCS I’d caution you to note that Marom Bikson, one of the leading tDCS researchers in the world, is quoted below as saying ‘perhaps’, as in perhaps it improves brain function. Also, in the section where Andy McKinley is able to dramatically increase reporter Miles O’Brien’s performance of a vigilance task, ask yourself if you really have a need to improve your ‘Where’s Waldo’ score. Unfortunately, the piece doesn’t go into the use of tDCS as a tool to fight depression, which in my opinion, has come closest so far to a verifiable effect borne out by much clinical research. My point is simply that it’s early. We don’t have our tDCS ‘killer app’ yet. Stay tuned!
MILES O’BRIEN: But step aside, grande latte. There’s a new kid on the block.
MAROM BIKSON: So, current is going to come out of the device to the electrodes on your forehead and it’s going to flow through your head.
MILES O’BRIEN: Biomedical engineer Marom Bikson at the City College of New York is prepping me for a dose of transcranial direct current stimulation, or TDCS, a jump-start for my brain.
MAROM BIKSON: It can make the brain perhaps function information more effectively and therefore make you, let’s say, better at things. Or it can make the brain more likely to undergo plasticity, more malleable, more able to learn.
MILES O’BRIEN: A human brain has 100 billion nerve cells or neurons. Neurons are networkers. They make multiple connections with each other via synapses. We have about 100 trillion of them. All of this runs on electricity that we generate ourselves.
MAROM BIKSON: Now, this was the montage that we tried on you.
MILES O’BRIEN: It turns out each of our neurons is a microscopic battery with a-tenth of a volt of electricity. When we’re using them to remember things or do math or write this story, they fire electrical spikes.
MAROM BIKSON: When we’re adding electricity to the brain with TDCS, instead of a tenth of a volt, we’re producing a 1,000th-of-a-volt change, so it’s not enough to trigger a spike. It’s not enough to generate a spike, but it’s enough to modulate the spikes, to maybe get more spikes or to get less spikes.
Fantastic to have a resource in the community like Nathan who has the background and technical expertise to do a deep dive into assessing a device like the new Foc.us v2. The entire review is a must read but here I’m quoting his analysis of the safety issues.
The foc.us also includes some new safety features designed to reduce the risk of high-current-density induced injuries. The most interesting is a soft voltage limit; while the device can technically output voltages out to 60V, users can specify a lower limit to not exceed. This provides protection if the connection between electrodes and the head starts to fail (due to electrode drying or drift, for instance); rather than increase voltage to the absolute maximum in an attempt to drive the target current over the failing connection (which can result in very high current density through a small patch of skin), the device can be configured to simply allow the current to drop using this limit. Unfortunately, there’s no actual alert that the connection is failing (although this can be deduced from looking at the current monitor during operation) but this still provides a good way to avoid many of the safety issues that the high maximum operating voltage would otherwise entail.
Another important area of safety is the ability of the current regulator to maintain its specified current and voltage outputs under varying conditions. Here I tested the device under two conditions: with relatively stable impedance at varying levels (simulating a typical use case in a person sitting still) and in an “impulse” condition, where impedance changes instantly from very high to very low or vice versa. The purpose of this testing method is to measure the device’s response to temporary very sharp changes in impedance caused by disconnection and reconnection of the electrodes as might occur in the Edge device when used during athletic performance.
Here the foc.us performed perfectly; neither current nor voltage ever significantly exceeded their specified maximums under varying conditions. The response to impulses was particularly impressive, with no significant “overshoot” even at the maximum voltage output.
It is the rare human who doesn’t wish to change something about his or her brain. In my case, it’s depression, which runs on both sides of my family. I’ve been taking antidepressants for almost twenty years, and they help a lot. But every couple of years the effects wear off, and I have to either up the dose or switch to a different drug—neither process can be repeated indefinitely without the risk of liver or kidney damage. So although my symptoms are under control for now, I worry, depressively, about what will happen when I exhaust the meds. As I was researching this piece, my attention was caught by a number of randomized controlled trials showing a benefit from tDCS for depression. (The data are insufficient to allow definitive conclusions, but larger trials are in progress.) I was almost embarrassed by how excited I felt. What if it was possible to feel less sad—to escape the deterministic cycle of sadness? What if you could do the treatment yourself, at home, without the humiliation and expense of doctors’ visits? I asked Vince Clark whether any private physicians use tDCS outside of a research setting.
New Stuff! Enobio 32: EEG Cap now in 32 channels. Neurosurfer: Combine 2D & 3D (inculding Oculus Rift support) Neurofeedback games. Starstim Home Research Kit: Allows physicians to facilitate telemedicine tDCS sessions. Starstim tCS: Starstim without EEG. NUBE: Cloud data management for your tDCS and EEG studies. (Neuroelectrics has been distributing Starstim devices at the university research level for some years. We should assume they’ve collected a lot of fascinating data.)
Neurosurfer Software in action:
This paper proposes combining tDCS with fNIRS (functional near infrared spectroscopy) for the purpose of monitoring effects of tDCS especially in the context of enhancing cognition, i.e. immediate and direct feedback that tDCS is ‘working’.
Using fNIRS to Monitor the Relationship of Cognitive Workload and Brain Dynamics fNIRS provides an attractive method for continuous monitoring of brain dynamics in both seated or mobile participants. fNIRS is safe, highly portable, user-friendly and relatively inexpensive, with rapid application times and near-zero run-time costs. The most commonly used form of fNIRS uses infrared light, introduced at the scalp, to measure changes in blood oxygenation as oxy-hemoglobin converts to deoxy-hemoglobin during neural activity, i.e., the cerebral hemodynamic response. fNIRS uses specific wavelengths of light to provide measures of cerebral oxygenated and deoxygenated hemoglobin that are correlated with the fMRI BOLD signal. Below we briefly review fNIRS studies of cognitive workload.
Furthermore, from the article, it may be misinterpreted that I starting using tDCS to treat my vision, but this is not true. I have always been interested in self-improvement, and wanted to try new things to become a better person and live my life in the right way. A few months before stumbling upon tDCS, I had started to spend more time in meditation and exercising regularly, as well as taking nutritional supplements and becoming vegetarian. So tDCS seemed like one more thing to try to see if it made a difference for me, and I did not expect that it would affect my vision at all. However, after using it one evening, I noticed that I was able to see better in low light. It was a strange feeling at first, but after trying it for several nights in a row, it was very evident that I could perceive things that I simply couldn’t see before, such as the upper floors of tall buildings, and traffic from more than a few meters away. While my visual acuity remains the same, my contrast perception and ability to notice small objects have noticeably improved.
I’ve copied the entire post from the Foc.us blog. This is a significant development. tACS, transcanial alternating current stimulation, has been discussed in the DIY community as a hopeful, eventual, capability that would evolve out of a microprocessor-based DIY project. That means software and a level of complexity that most DIYers aren’t prepared to take on. But not only tACS, tRNS – transcranial random noise stimulation, tPCS – transcranial pulsed current stimulation (something I know nothing about), and a Sham setting… well, Foc.us has definitely set the bar here. This is a $199 device! (Plus headset, sponges and shipping $298) [CORRECTED]. Windows-only software at present though Mac ‘coming soon’). This will have a serious impact on any of the DIY commercial tDCS devices.
That said, this is an announcement from the manufacturer. I expect the Reddit tDCS crowd will be exploring these claims over the next few months. This is exciting news and opens the door to some serious citizen science.
The latest firmware update for the foc.us v2 developer edition is now available for download. It’s quite a big release in terms of new features so here’s a quick run down of whats new.
New modes – tACS, tRNS, tPCS
In addition to tDCS (constant current) you can now create different energy waveforms – shaped like waves, pulses or noise.
tACS – transcranial alternating current stimulation
tACS mode allows you to create a sine wave current where you can set the maximum current, current offset and frequency. It is even possible for the polarity of the electrodes to switch – flipping a cathode to an anode (and vice versa) up to 300 times per second.
tPCS mode enables you to create pulses of current. You can control the frequency, offset and also the duty cycle of the waveform. Full explanation of tPCS settings can be found here.
tRNS – trancranial random noise stimulation
tRNS mode can create random waveforms where either the frequency, the current or both take random values between the min and max values set. tRNS settings are here.
Sham – Off, On or Double Blind
Sham mode is used by researchers to check for placebo effect in studies. If you set to On, the current will begin, but then turn off (after a user configurable duration). But if you want to test yourself, knowing sham was on would defeat the purpose. But if you set sham to “double blind” then you may or may not receive a sham session.
During a neuromodulation session the resistances involved vary and so the voltage changes to maintain the target current. It is now possible to set a limit on the voltage you want to use in all modes. If you find you are sensitive to the voltage you can use this setting to find a comfortable setup.
Wave, Pulse and Noise programs
These are pretty advanced settings so there are also three new programs with default values you can try.
These new settings give you even greater control over your neuro-stimulation options. And with double blind you check if its working for you.
Okay, I think we’re on the edge of a shift in thinking. Here’s prof. Bikson referring to 2mA as ‘baby aspirin’ and pointing out that ‘the dose hasn’t increased in 15 years’. Combine this with the revelation (previous post to the blog) that the Thync device is using up to 10mA (pulsed current) and that much of the experiments that went on with the Thync device were conducted by Bikson and you can’t help but conclude that researchers are ready to up the dosage. But that was one of my very first questions and I asked it far and wide, ‘Why 2mA?’.
“There’s already technology available today that can, with limited discomfort or no discomfort, deliver much higher intensities than people are using. And there’s no theoretical—not even real—reason to think that this might be hazardous,” Bikson says. “We’re at baby aspirin levels right now. [Researchers] are going really slow with this stuff.”
So why not ramp up the experiments? Researchers have to be especially cautious because of how new the science of tDCS is—and perhaps to avoid the horrors that have been observed to coincide with ECT.
“Part of the reason why people are on the fence is because the effects are small, [but] of course they’re small. The dose has not increased in 15 years,” Bikson says.
But Bikson says that might be keeping them from making real headway—and from having the sort of impact on test subjects that would get the medical community engaged with this stuff.
If Tyler is right, it could explain why tDCS results have been so hard to replicate. Researchers position tDCS electrodes based on the assumption that they affect the areas of the brain directly below. But sometimes they may be accidentally stimulating the cranial nerves instead, leading to inconsistent results. Based on his new hypothesis, Tyler changed where he placed the electrodes, targeting these nerves specifically.
Early experiments showed enough of an effect to suggest the hypothesis was right, Tyler says. But the effects weren’t huge. The next step was to amplify the effect by increasing current levels without causing pain or skin damage. Researchers at Thync, which was founded in 2011, did this in part by using pulses of electricity, rather than steady current, and operating at frequencies that don’t stimulate pain receptors.
I experienced the difference that these measures make when I tried out a conventional tDCS device side-by-side with Thync’s technology. At three or four milliamps of electrical current, conventional tDCS was quite painful. That’s why most experiments are done at around one milliamp. In contrast, I couldn’t even feel the pulses from Thync’s device at 10 milliamps.
Very well-written and detailed article on the upcoming Thync device. Links to full article below.
I set the vibe level to 60, and felt a slight pressure on my forehead as the vibe commenced. It wasn’t painful but I did note an almost immediate change as the calming electrical signals began to enter my brain. This wasn’t a placebo and it wasn’t suggestion: it was real.
“Think about a stressful situation,” Sumon advised. “Then focus on it a bit later to see how you react to it.”
Naturally, I thought about the hike back to my car and the exodus from Boston before rush hour commenced. Already the apprehension that previously seemed to be looming was a mere thought, nothing more. Just a few moments after starting the demo I felt a steady flow of relaxation coursing through my body. It was a bit like tubing down a lazy river at a water park; pleasant and entertaining, yet not too intense. I continued to take notes on my reactions as Sumon worked on his computer. It was like a comfortable visit with a colleague I’d known for a while.
“You may feel some euphoria,” Sumon stated. I agreed; the experience was like the buzz of a couple of beers, minus the “belly glow” that goes with it.
I raised the intensity level to 62, then 64 and finally 68. I noticed when I increased the threshold I felt a slight twist of pressure in my temple as the sensor responded, but it wasn’t uncomfortable or distracting. However, 68 represented a euphoric flow a bit higher than I seemed to need, so I dialed back down to 62.
I reflected on my upcoming drive home and felt nothing other than confidence. The car would be fine where I had parked it and the drive would be okay too. Even if things got sticky, I had the radio to listen to and no particular demands on my schedule for the evening. There were far worse things than sitting in Boston traffic, I reflected absently.
The fMRI scan revealed increased activity in the left hemisphere of Padgett’s brain, which is where mathematical skills are thought to originate. Another area in Padgett’s brain that lit up was the left parietal cortex, a region responsible for integrating information coming from different senses. Brogaard’s team also used a transcranial magnetic stimulation (TMS) as a way to pinpoint the exact location of Padgett’s synesthesia. The TMS involves directing a magnetic pulse at a desired part of the brain, which either activates or inhibits a specific region. The results of the TMS experiment showed that when zapping Padgett’s parietal cortex, his synesthesia could be turned on and off.