Jesse: This is actually our second episode related to transcranial direct current stimulation, but for people who didn't make it for the first episode could you kind of give us an overview of the technology? As in, what tDCS is in a nutshell.

Nathan: So tDCS is just a very fancy term for running a very small amount of electricity through your head. And why people do this strange thing is that, when you do this you send a little bit of that electricity through the brain and that can actually alter the behavior of nerve cells. Depending on whether you're sending a positive or negative current, you can make those cells more or less likely to fire. And it turns out that how likely nerve cells are to fire are to do with a whole bunch of things people who're interested in cognitive enhancement might care about. So for instance, by doing this you can improve your working memory, your short-term memory of yourself. Concentrate more, treat depression. It is actually a very flexible thing. You can do a lot of different things with this very simple technology.

Jesse: So there's these sponges that go in different places on the scalp, that have some sort of liquid on them to make them conductive.

Nathan: Yeah.

Jesse: Is there like sort of a head map of where you're putting different sponges to get these different effects?

Nathan: So what people use to position the sponges and make sure that they're positioning them in the right position is something called the 10-20 system. Where you actually either put on a headset that's calibrated to have attachment points at the right spot on your head or you measure a certain percentage of the distance from your nose to the back of your head and between your ears. And that gives you a coordinate system. So when you see a study that says - "We put an electrode at F3 and it improved cognition" - anyone can then find F3 on themselves and put an electrode there.

Jesse: Very interesting. It reminds me of almost the weird phrenology experiments from like the 1920's and 30's. The idea that different bumps on people's head can have effects on their personality.

Nathan: In a way it's very similar to that because oftentimes the reason that we say to put the electrodes on a particular spot is because we have data from MRI's and such. That spot lights up when you're doing a task. And you say okay maybe we want to improve your performance on that task, so let's see what happens if we make that spot light up more efficiently. So in a way you're looking at this anatomical thing and you're saying, "No, you're trying to tie it to cognitive performance." It works a bit better than the phrenology, I think.

Jesse: What sort of divergence is there between one person's brain and the next, as far as where some of these points might be?

Nathan: That's actually a really interesting question in the context of this thing; because it turns out that one of the biggest differences in that is whether you're left or right-handed. If you're left-handed you will have a lot of things that are normally on the left side of your brain, for right-handed people; if you're left-handed there's a chance that those will be on the right side of your brain or they'll be kind of mixed between the two hemispheres. This is not like the anatomy, this is like the functions that the different parts do. And this is actually why if you're in a brain study; lots of them just exclude left-handed people entirely. That's actually a concern for left-handed people who're doing tDCS because if you're left-handed we really don't know very well how your brain is organized.

Jesse: Wow! That seems like a major oversight at this point. There's a lot of lefties out there.

Nathan: It's kind of how neuroscience works, is that first we want to kind of figure out how the brain of a prototypical human works and then deal with all the messy human diversity. There's good sides and bad sides to that approach, I think. But that is how it is.

Jesse: Thank you for the explanation. So tell us about OpenBrain Stim and when you opened the doors on that and sort of the goals of that project.

Nathan: Okay. I started working on that project several years ago and it came after I had this unsuccessful attempt at building this other kind of brain stimulator which now seems to be complete pseudoscience, which was why it didn't work.

Jesse: *Laughs*

Nathan: I read one of the very early articles about how people had been using this thing called tDCS to improve maths performance. And I'm not actually that great at math. So I thought, "Oh that looks kind of interesting" and I looked at it and thought, "Whoa actually this is really simple. I could build one." So I built a very simple brain stimulator which was also very scary and dangerous as it turns out. I tried it out and I got interested in it. I started looking around to find out what people were doing and I saw that people were building these kind of simple stimulators and there were also these commercial stimulators. So I was wondering could you make something that someone could build, that would also have the features of one of those commercial stimulators. That was where I kind of got the idea for OpenStim; to take these DIY stimulators to the next level.

Jesse: So, that was a couple of years ago now and you've built a small online community around that?

Nathan: The community kind of happened on it's own. When I first started doing it there were maybe a couple of dozen people on the internet who were doing similar things and now that's grown to several thousands. It's pretty crazy.

Jesse: That's awesome!

Nathan: What was interesting was actually like when I first released the OpenBrain Stim, no one was all that excited about it. And it was really this year I think with a lot of the publication and popular media excitement about tDCS which is when it really started taking off.

Jesse: You recommend running any sort of tDCS system from your laptop while not plugged into the wall. Can you go into the details of some of the safety considerations?

Nathan: So the main reason why you don't want to run plugged into the wall is that there's a low but entirely unavoidable possibility that there would be some sort of power surge. And if your laptop is plugged into the wall, that surge could theoretically climb up through your laptop's cord and through the cord that's connecting the stimulator to you and into your brain. And at that point lots of bad things could happen. As long as you're not connected to that kind of main power source, your laptop battery is actually very safe or you can load a program directly on to the board's memory and then just run it off a regular 9 volt battery.

Jesse: How many amps are we talking about here, that are actually passing into the head?

Nathan: So OpenStim usually reaches it maximum depending on how much resistance your skull and skin has. The maximum will be about 2.5 milliAmps. So to put that in perspective that's about a tenth of the power that it takes to light up a single LED. And I mean that's I think where some of the confusion here comes from about the safety of tDCS - is that people think of it as a form of something like electroshock therapy, which actually uses an amount of current that is hundred times of what is used in tDCS.

Jesse: Right, it's not exactly like putting a lightening rod on your forehead.

Nathan: Exactly.

Jesse: So what are some of these subjective benefits that you've received personally from tDCS?

Nathan: The coolest one that I like to talk about is - I was trying to do a protocol that is supposed to improve your working memory by making your prefrontal cortex more active. And unfortunately when I was trying to do this I had the polarity reversed, so I was actually making my prefrontal cortex less active. And before I knew this what I was doing was I was working on this programming problem, I had not been able to figure it out for like a week. I turned the stimulator on - it's actually shutting down my prefrontal cortex and then all of a sudden the computer feels like it's programming itself. And I kind of like fly through this problem, I get it, it's a close state essentially. So what i think is happening actually is that the prefrontal cortex is good at kind of helping you learn to do new things but if you have something that you're already good at doing it interferes. So if you can shut it down when you're doing something you already know how to do, that's already established, it let's the more efficient part of the brain take over. It's my hypothesis.

Jesse: What's the level of sort of community involvement at this point online - not necessarily with the building of the devices but with the comparisons of subjective effects of applying current to different areas on the scalp?

Nathan: I think that there's a lot of work that happens specially on our [subreddit](http://www.reddit.com/r/tDCS). It's hard to say how useful it is because it is usually like forum posts, people talking about their particular subjective experiences. One thing that I'd like to setup if I ever have time to or see someone else setup is actually a kind of a systematic way of tracking the effects that are associated with particular places where current is delivered. Because I think that is actually something that would really benefit the community.

Jesse: What are your goals for developing the online community over let's say the next year or two?

Nathan: I think that one of the most important things of this DIY tDCS community and the community of people who are using commercial devices to do their own therapies and experiments on themselves - is defining some sort of standard for safety of devices in use. Because what we're having right now is just an explosion of available devices and it's very difficult to compare the devices figure out how safe they actually are. So one thing that I think really should happen, needs to happen and will eventually happen is crowd-sourcing a set of standards that you can apply safety standards and efficacy standards, that you can apply to any device. And you can then say to everyone that this device is pretty unsafe because it doesn't meet these parts. I think that is going to be the incredibly important in terms of the ability of people to trust tDCS devices and also not to get hurt while using them.

Jesse: How many retail devices are available out there? I know there's the one - Focus - that's the only one that I've heard about. But are there many others?

Nathan: There are three or four devices right now that are definitely marketed to the users of tDCS. There's the Focus, there's the Transcranial Technology's Stimulator; there's one that's just called The Brain Stimulator. Those are the main ones. The other thing that people use is the device called The Iontophoresis Machine which delivers current in the same way as a tDCS device does but it wasn't built for that, it was built for delivering medication to parts of skin, but it works. So people use that too.

Jesse: How long is a tDCS session normally?

Nathan: So in research you can do anything. Typically you'll see like 5 to 20 minutes. For people who're doing it to themselves as a DIY thing to improve performance attempts to skew towards the upper end of that. So maybe like 20 to 35 minutes, I think would be the typical range. The idea is that the longer you do the tDCS on yourself for, the longer the effect lasts after you turn the stimulator off.

Jesse: And what is sort of the timeline to drop back to the baseline levels of potentiation within the brain?

Nathan: So that's actually a really interesting question because the question is how do you measure that. And it turns out that we can only directly measure the excitability, which is how likely neurons are to fire. We can even almost directly measure that in couple of parts of the brain - like the parts that controls motor activity. So when you do that what you typically see is that you have most of the benefits or most of the effects of tDCS is gone within about 2 hours after the stimulator is turned off. But on the other hand you have trials now where they're using it to treat depression. And what you'll have is that people will go in and they will get tDCS for 20 minutes every 2 days or so and then over a long period of time their depression symptoms improve. So what that suggests to me is that maybe in other parts of the brain that effect can last much longer or maybe there are effects that are not what you're measuring just with that simple test. For example changes in gene expression, changes in myelination of neurons that occur over a longer timescale.

Jesse: Has there been any instances where somebody has hurt themselves using tDCS?

Nathan: Kind of. The worst thing that seems to have happened with the current generation of tDCS devices is that you can get burns on your skin. And that usually happens if you're using electrodes that are too small. So for example the Focus has very very small electrodes that go on your forehead, so when they started marketing it we started seeing a whole bunch of reports of burns from it. And that's because you're forcing current through a small area. But the damage from that seems to be confined to the skin. There is no evidence that it actually hurts the brain. There was some concern a while ago that if you send current through your brain stem you could actually interfere with neural systems that generate breathing. There was a single case reported in like the 70's that showed that but people tried to replicate it and they couldn't. So generally in terms of your brain this is actually thought to be very safe.

Jesse: So if somebody hasn't really been involved, hasn't really known anything about tDCS prior to hearing this interview and they hear this and they get all excited - what's the best place for them to start?

Nathan: Okay so I mentioned the tDCS [subreddit](http://www.reddit.com/r/tdcs) a while ago and that's this website that has a lot of people discussing tDCS. But we also have a wiki site that has a list of frequently asked questions and like things that people getting started will want to know. You want to know about safety and kind of what devices actually seem to work well. So I would really advice them to check that out and if they have questions to actually post on their too. Because there's a lot of people who are very experienced and who would be much more happier to help you out than have you fry your brain doing something wrong.