I’ve been intrigued by the Thync device ever since I heard one of its scientific leaders (William Tyler) speak at a conference on brain stimulation, but between its rather expensive price point and a lack of Android compatibility I’d had a lot of trouble getting my hands on one–until John Humphrey at DIY tDCS sent me a unit to try out! Over the last few weeks I’ve been putting the thing through its paces and found some interesting things about how (and how effectively) it works.

How does it work?

The Thync device actually consists of two parts–the Thync module and an adhesive ‘strip” that both passes current through your head and physically holds the module on. The device is attached at two points–the module sits over your left forehead, while the other end of the strip attaches to either the back of your neck (for the “calm” mode) or behind your ear (for the “energy” mode). These two connections complete a circuit that allows the device to send its “vibes” through your head.





Thync headset in the “energy” configuration

An interesting consequence of this design is that Thync is very spatially non-focal. Although the company claims to target specific nerves, there is probably quite a lot of “off target” current interacting with various other systems, including current passing through the brain directly. All this means that, it’s wise to take Thync’s claims about how their device works by stimulating specific nerves with a grain of salt.



The actual current that the device is sending through the head is a current-regulated set of rapid pulses. It’s a high frequency alternating current signal that is in many ways similar to the one generated by a TENS device used to treat pain (although the pulse frequency of the Thync device is much higher, typically somewhere between 1 and 10 kilohertz depending on the “vibe” being used.)

The other difference between the Thync and other nerve stimulators is that the “vibe” signals are extremely complex. While most nerve stimulators use a single, repeating pattern the Thync vibes are not only all different from each other but also vary continuously throughout each session.





One way to deal with this complexity and figure out how the vibes actually work is to figure out what’s different between vibes with supposedly opposite effects–the “awake” and “sleep” vibes, for instance. One difference here is anatomical–the vibes that are supposed to make you calm, like the sleep vibe, use an electrode placed over the back of the neck, while the “energy” vibes place the electrode behind the ear. There’s also an interesting difference in the signals the device uses though: the calm vibes seem to be significantly “burstier” (their power varies more at high frequencies) than the energy vibes.



This property is interesting in light of Thync’s (largely hypotheticall) interpretation of how how input to sensory nerves might affect arousal level, which focuses on how these inputs might cause norepinephrine-containing neurons in the locus ceruleus to switch between constantly-firing states (associated with high arousal and energy) and intermittent firing (associated with lower arousal). It’s therefore possible that the “bursty” input from the Calm vibes is designed to encourage intermittent firing, while the more constant input from Energy vibes is intended to increase constant firing. (Keep in mind that while I think this is plausible, it’s just my interpretation and not necessarily correct)





Bursty signal (top) vs continuous signal (bottom)

Vibes also have a number of other interesting parameters however. The power and rate of nerve-stimulating pulses delivered by the vibe fluctuates throughout the session (these changes are slow enough that I suspect that they’re related mostly to comfort and reducing habituation rather than having a direct functional role) and different vibes use differently shaped waveforms, something that might be useful in tuning stimulation to affect specific subpopulations of nerve fibers (you could even, theoretically, use this property to make the Thync only activate the nerve fibers under one of the electrodes and leave the ones under the other electrode alone).



These vibes also have another property–they sometimes include what is essentially tDCS, or more specifically an AC waveform superimposed on a constant DC current. Unlike most nerve stimulators (where the flow of current one direction through the circuit is balanced by flow the other way), the Thync device uses unbalanced waveforms where the total current flowing one way is higher than the total current flowing the other–creating a DC current which can be quite strong (up to 5 milliamps at the device’s maximum power!)



An example Thync waveform with a DC offset. The positive current (arbitary units) is greater than the negative component, creating a net flow of charge.





Oddly, the tDCS doesn’t seem to have a clear functional role. In all cases, the forehead-mounted part of the device acts as the anode of the circuit–something that would make sense if, for instance, Thync was trying to replicate this protocol which showed caffeine-like effects from frontal stimulation . But the device delivers the same kind of tDCS when you turn on the “sleep” vibe, a somewhat strange design decision if the tDCS was what was supposed to keep you awake. Instead, I suspect that the use of tDCS is sort of incidental–the device uses a waveform that is optimized for something else, and just happens to have a net flow of charge.

The takeaway

One of the big takeaways here should be that the Thync’s mechanism of action is very broad. In addition to acting on the targeted cranial nerves, the fact that current is allowed to diffuse through the head means that it is potentially acting on a number of other mechanism, such as direct current stimulating and high frequency alternating current stimulation/random noise stimulation acting directly on the brain.



That is not bad per se–lots of interventions,particularly those targeted at the brain, have complex and poorly understood mechanisms of action. But the complexity of Thync’s mechanism of action also leaves a lot of unanswered questions–could it produce subtle cognitive deficits, as some forms of tDCS seem to do? Does it affect inflammatory processes in the brain? Can it alter brain plasticity? Answers to these questions seem to be critical for informed use of the device.

But does it work?

All these potential mechanisms of action are, of course, contingent on the assertion that the Thync device actually does what it says it does–makes you calmer or more energetic, depending on which vibe you’re using. So for that, it’s worth taking a look at the evidence behind the device.



The idea that pulsed electric current can influence energy and mood is actually not a new concept–its modern form, which bears some interesting similarities with the techniques used by the Thync device, was first developed by European and Soviet scientists as a way to reduce the need for chemical anesthesia during medical procedures. This technology was later adapted to forms known as “electrosleep” and “cranial electrotherapy stimulation”, which found some success in treating arousal disorders like anxiety and insomnia. More recently, sedative effects have been reported from the Cefaly nerve stimulator, an experiment that is interesting in that it is one of the only cases where the sedation could be attributed to stimulation of a particular nerve (in this case the trigeminal).

Early “electrotherapy” protocol, somewhat reminiscent of what the Thync does.



Source:https://www.alleviahealth.com/wp-content/uploads/2014/06/Zaghi-et-al.-2009.pdf



This means that the claim that the Thync device can induce calmness or help sleep is quite plausible. However, because of the variations in protocols used by these devices, it’s important to look at efficacy of the Thync device specifically, something that Thync did in two blinded studies.

The first of these studies , looking at the immediate subjective and physiological effect of Thync’s calm vibes, found a number of changes indicating that it decreased physiological arousal. Most importantly for users, the researchers reported that the Thync reduced reported anxiety on the Profile of Mood States. The second study found that using Calm vibes before bed resulted in a significant increase in sleep quality, as well as an improvement of several other aspects of mental health likely due to the better sleep.

While these results suggest that the Thync calm vibes can reduce physiological arousal, for a consumer device it’s important to take into account the practical significance of an effect, not just the statistical significance. The reduction in stress seen on the POMS, while statistically better than the placebo, is still quite modest–a reduction of 0.37 points on a 36 point scale. In practical terms that’s a very small effect–for instance it’s slightly smaller than the baseline difference between relaxed men and relaxed women.

While the effects on sleep quality are more dramatic (including an increase of about 20 minutes in the nightly time asleep that likely drove several other improvements in mental health ) I’m not convinced that using the Calm vibes for an immediate effect (the way they’re advertised) would produce any real noticeable effect. As for the Energy or Fitness vibes, Thync has produced no research no them whatsoever.

Impressions

There are a lot of things about Thync that made me go “wow”–the technology, the vision of affective and cognitive enhancement through electrical signalling, and the prospects for what technology like this could tell us about how the brain works.

What didn’t particularly wow me was Thync as a consumer product. While it definitely has a sci-fi coolness to it, there’s a question here that’s important to address: Is the Thync more effective in any way than breathing exercises, listening to music, taking a walk, meditation, or any of the dozens of other methods for modulating arousal that don’t require sticking a $200 machine to your face? Given the modest effects of the calm vibes and the unknown effectiveness of the energy vibes, I’m not sure it is.

Another aspect of the “is it worth it” calculation is risk, and I think this is one of the biggest ways that Thync’s entry as a consumer device is premature. There is of yet no universally-accepted standard for showing that a device like this is safe–for instance,should there be screening just for obvious problems like skin burns, or also for more subtle ones like depressive symptoms?–and our incomplete understanding of how the Thync actually affects the brain makes it even harder to tell what adverse effects we should look for. That’s not to say that the Thync device is dangerous (so far there have been no reports of serious adverse effects), but the lack of good safety standards and a solid mechanism of action means that adverse effects we simply haven’t detected yet are a very real possibility.



None of these are intractable problems of course. Thync could always do more research, or publish research that they’ve already done, and they have an opportunity to play a major role in the project of figuring out how we should think about the safety and effectiveness requirements for these devices. But for now, the Thync device reminds me a lot of what Dr. Tyler said about neurostimulation technology at NYC neuromodulation–that much of it was a “neat lab trick looking for a way out”. So far, I don’t think they’ve found it.

Other observations

In addition to its nerve-stimulating effects, the Thync app makes heavy use of psychological suggestion. Notice the number of times that the voiceover says something like “when I use this vibe, I feel <x>”–this is a classic technique that’s used (by hypnotists, for example) to actually induce specific sensations. That’s not to say that the Thync relies entirely on this kind of suggestion ( the placebo-controlled studies show that there is some effect directly attributable to stimulation), but the suggestion might be just as powerful (or even more so) than the effects of the stimulation.

Thync has two “generations” of Calm vibes: the first uses higher frequency stimulation, while the newer generation uses a lower frequency. This is likely due to research showing that the low frequency stimulation was more effective.





Unlike, say, tDCS, you’re supposed to be able to feel a sensation from Thync–in the target range it feels like tingling, and if the power is turned up too high you get a dull burning sensation. One implication of this is that placebo stimulation can feel different from real stimulation and studies need to be very careful to make sure their blinding is actually effective.





It’s entirely possible to use the Thync with custom or third-party electrodes so long as they can snap into the two snap connectors on the bottom of the Thync module. The Thync won’t detect it as a calm or energy strip, but you can use any vibe with the custom electrodes.





The actual effect of the Thync vibes on POMS scores is surprisingly small compared to the glowing anecdotal reviews that people give of them. This is mostly likely because people are reporting placebo effects, but it could also be related to flaws in the experimental design. One interesting thing is that the subjects who got a placebo were also quite relaxed, suggesting that they might have been at their individual “floor” of anxiety before the treatment or that the placebo might have actually had some active effect.

Recordings

To download recordings of the Thync vibes,click here



I’ve made recordings of the complete Thync vibes for anyone who’s interested in taking a look at them. Because of the frequencies that the Thync device operates at, audio recording and analysis software is well suited to recording and analyzing the vibes; in this case I used an external USB microphone input to capture the voltage drop across a resistor. The values in this file represent the current output by the Thync device at 2% power. Due to the limitations of the audio card, high-amplitude vibes had to be recorded with a different resistor than low-amplitude vibes–this means that for files prefaced with “100” the scale is -4.35 mA to 4.35 mA, while for files prefaced with “33” it is -13.18 ma to 13.18 mA. For files prefaced with “473” the scale is -0.92 mA to 0.92 mA. In all these recordings, the Thync output closest to its USB port is connected to the “terminal” input of the microphone TRS connector, the other output is connected to the sleeve.

Thync recording configuration.