Wednesday, February 29, 2012

Transcranial Direct Current Stimulation

DARPA: A Shockingly Cool Government Entity
In 2008, the "Operation Neuroscience" presentation by DARPA discussed the use of Transcranial Direct Current Stimulation to augment the brains of soldiers undergoing a form of threat detection training. The results were pretty astounding. Those receiving a 2 milliamp stimulation to the right temple showed a 2.1X improvement in threat vs. non-threat accuracy, and a 3.1x improvement in threat only recognition. Reading about such a dramatic improvement through the use of Transcranial Direct Current Stimulation (or tDCS), one may arrive at one or more of the following assumptions:

A. This is some fancy advanced new technology that isn't available to the average schmoe.
B. This is probably some complex mechanism that is out of my price range.
C. Running electrical current through my brain is probably too dangerous to play around with.

Well, if you made any of those assumptions then your incorrect. Let's start with A. 

Dr. Frankenstein and the History of tDCS
tDCS has been around for a very long time. Sometime in the mid to late 1700's, Luigi Galvani serendipitously touched a freshly skinned frogs leg muscle with a scalpel that happened to have a charge of static electricity and he observed the resulting kick. In fact because of this discovery, what we today label electrophysiology was called Galvanism through much of the nineteenth century. Galvani was pretty limited in what he could do with static; Fortunately, Volta invented a battery right about the same time.
How long do you really think it was before someone thought, "Dude, what would happen if we strapped that sucker up to someones brain?" By 1804, the illustrious Giovani Aldini began experimenting with stimulation of patients with small currents transcranially. Two important items of note about Aldini. One, he was Galvani's nephew. Two, he was Mary Shelley's inspiration for the character Dr. Frankenstein. Aldini worked with patient suffering from what was at that time called melancholy, and his researched proved highly efficacious. For one reason or another, tDCS never really took off as a treatment modality. It was replaced in the 1930's with a far more drastic electrophysiological intervention: Electroconvulsive or "Electroshock" Therapy.

Electroshock therapy really deserves a digression. The current cultural conception of what Electroshock therapy entails is primarily shaped by scary ass movies depicting it being used punitively. These movies show patients seizing, shitting, and pissing themselves as doctor and nurses stand by in amusement. In the early days of electroshock therapy? Yeah, this wasn't all that far off. I mean, the history of psychotherapy is pretty frightening overall. Compulsory sterilization persisted into the 1950's. Electroshock therapy was a replacement for a far more dangerous "shock therapy" which used insulin to put a patient into a coma. Electroconvulsive therapy as performed today uses muscle blockers so the days of people writhing around are over. It's also the gold standard for depression. No joke. Those who are unresponsive to pharmacological treatments are given the option for electroconvulsive therapy and it's the most effective known means of treating depression. Many need only a few treatment and are then able to live depression free without a constant influx of medications. I've known more than one psychiatrist who stated if they were suffering from depression that they would prefer electroconvulsive therapy to a regimen of antidepressants. Of course there are still some pretty scary stories of people permanently losing memories and whatnot.
tDCS isn't even in the same ballpark as electroconvulsive therapy in terms of voltage. Electroconvulsive therapy uses voltages up to 450 Volts. tDCS? A puny little 9 volts. tDCS uses a voltage so low that it doesn't even cause the neurons to fire. It simply makes the neurons more or less likely to fire. The point of this? Transcranial Direct Current Stimulation is a technology over 200 hundred years old, which predates the first written example of the use of the word "Biology."

The Priiiiice Issss Right!
Let's now explore assumption B, the concern that tDCS is complex and or out of ones price range. Well, a good start is to look at these 3 commercial models available:

1. CESta
Voltage - 9V
Amperage - 1 to 2.35 milliamps
Bells and whistles: "Micro-TENS stimulation," Auto-shut off, A colloidal silver making attachment which costs more, reusable electrode clamps.
Price - 350.00$ US

2. Alpha-Stim 100
Voltage - 9V
Amperage - 10 to 600 MICROamps (so 0.6 milliamps)
Bells and whistles: Cool carrying case, a bunch of disposable electrodes and supplies like conductive gel with proprietary wire connectors to stop you from buying other electrodes, a free battery, and a belt clip.
Price - 995.00 US

3. CES ultra
Voltage - 9V
Amperage - 0. to 1.5 milliamps
Bells and whistles: It's a white box with a switch on the side. They make you fill out a bogus prescription form for doctor to review before giving it to you. I wouldn't buy this one simply because if they can't take a straight photo...
Price - 349.00 US

So, yes this is some relatively expensive gear right? Pfff... Man, I could make one of these for like a couple of bucks. In fact, I have made one for a couple of bucks. In fact, I'm going to SHOW YOU how to make one for a couple of bucks. I'm sorry that my version will lack fancy glowing LED lights. No belt clip. If someone will send me 100$ I swear that I will figure out how to make it give you colloidal silver. If you want a "Micro-TENS" feature, just stick the electrodes on your muscle instead. It won't do anything, but neither will the expensive models. Micro-TENS is primarily a bunch of bogus claims using voltages lower than that which cause a muscle contraction. 

R= V/I
     Lets take a look at the parameters of the stimulation that are optimal according to the research. For one thing, the maximum amperage has been arbitrarily set at 2 milliamps. According to the article "Safety criteria for transcranial direct current stimulation (tDCS) in humans" the amperage in rats which result in damage are something like 140 amps, which is over two orders of magnitude higher than a measly 2 milliamps. The circuit I'm going to show you will produce around 1.91 milliamps.
If you want to change around your amperage, feel free. Ohms law is really easy to play with. It shows that Resistance (in kiloohms) is equal to Voltage (in Volts) divided by Current (in milliamps).
     I was trying for a 2 milliamp, so 9 volts divided by 2 miliamps equals a resistance of 4.5 milliohms. The reason I ended up with 1.91 is because good ol' Radio Shack stocks 4.7 millohm resistors. They cost maybe three bucks for a 5 pack. These things are so simple to make and so cheap you could throw them in all your friends stockings for Christmas.

Safety Disclaimer AKA assumption 3
Safety? Are you kidding? The major thing to worry about is that if you let the electrode sponges dry out they feel kind of itchy. Well... that and the list of contraindications. You absolutely under no circumstances should use tDCS if you have a pacemaker or have seizures. That should be obvious though. I mean if your doctor tells you to stay away from magnets or you will die, then your an idiot if it doesn't occur to you to not send voltage through your head. Same with the epilepsy spin. I mean if a cartoon explosion makes you flap on the floor like a dying flounder, do I really need to explain why this is a bad idea? Fine. I will generalize this even further. If you have pretty much any medical abnormality you should speak with your physician prior to using tDCS. Ok, here's my "don't hold my ass responsible" type of disclaimer... Speak with your physician and do your own due diligence prior to assembling or using the device I am going to describe. I take no responsbility. It's all you buddy. No seriously. If you mess up and smoke starts coming out your ear, don't come knocking on my door man.

Making It
Parts List:

9 Volt Battery
4.7 kohm resistor
Toggle switch
9 volt battery connector
2 alligator clips
Elastic head band

1. Attach the "positive" or cathodal wire of the 9Volt battery connector to the resistor.
2. Attach the other end of the resistor to the toggle switch.
3. Attach the other end of the toggle switch to a length of wire.
4. Attach another length of wire to the other end of the 9 Volt connector.
5. Put the alligator clips on the ends of the lengths of wires
6. Cut out two little squares of sponge and soak them in some salt water.

Well, your pretty much done. You can put more effort in and make it nice and pretty. It's a good idea to solder each connection and use shrink tubing to cover connections. It's nice if you put the whole thing is a little project box with the switch on top. You can color code your wires so you know which is which etc.
Why salt water sponges you ask? Well, the salt water sponges are functioning as your electrodes. Sodium Chloride breaks apart into positive and negative ions when placed in water which makes it conductive. It works better than bare metal and I prefer them to the professional pads. If you have a big mess of hair, no problem! You can apply conductive gel, which can be easily purchased on the web.
I advise using a voltmeter to check your output amperage and voltage. Here's a pic of the first one I made.

Using the tDCS
The next step is figuring out where to place your electrodes. Fortunately here, we don't have to reinvent the wheel. Electroencephalogram electrode placement is based off of standard positions in what is called the 10-20 international system. Heres a link to a tutorial:

Another option is to buy a pre-made EEG cap. While this may be easy... it's also much pricier. For example the supplier Easycap sell the cap alone without electrodes for 125.00 US.
At some point... I intend to make this investment. Proper placement really is the most difficult step.
For now though... start by testing out your device. This is the fun way. Place one of your electrodes on your neck and the other above your eye. Try flicking it on and off a few times. See the flashes of light? Your stimulating the optic nerve. Good, your tDCS works.

Using a 10-20 EEG electrode placement guide, identify the region you want to stimulate. The DARPA research indicates that the pre-frontal cortex is a particularly effective region. The Anode was placed at F8, and the cathode was placed on the upper left arm. The participants were stimulated for 30 minutes at either 1 or 2 milliamps. The F8 is pretty much a persons temple so it's not hard to find.

Oh, and the anode in tDCS is always the positive lead wire. When you apply the anode to a region of the brain, it makes it more likely to fire. When you apply the Cathode, it make the region less likely to fire. What your doing is raising or lowering the resting voltage state of neurons relative to their threshold. Although 9 volts won't make the neurons fire, they will require less stimulation to do so. So consider a few applications for which tDCS may or may not be efficacious. Those who maintain a practice of meditation can reach states where they isolate their consciousness from sensory input. Perhaps a less practiced man could achieve similar states by apply the cathode to the appropriate region. Research has already indicated that tDCS can increase ones ability to memorize and learn. tDCS just has so much potential and I would advise anyone interested in self-improvement to invest some time looking through a few online journals. I'm sure that if you do so you'll recognize tDCS as an augment worth considering. 

Sources, Links, etc.

Michael A. Nitsche, David Liebetanz, Nicolas Lang, Andrea Antal, Frithjof Tergau, Walter Paulus (2003). Safety criteria for transcranial direct current stimulation (tDCS) in humans. Clinical Neurophysiology 114:2220–2222. 


  1. Perhaps you could suggest a better way of doing this? My primary concern is of course for safety. The study conducted by Nitsche, Liebetanz, Lang, et. all as cited above seems to indicate that even without the resistor, a 9v simply doesn't provide enough juice to cause a lesion or harm. I remember as a child placing a 9v battery on my tongue. Sure! It stimulates all those sensory receptors. It's tingly right? On the other hand... I can still taste even today, so those sensory neurons weren't harmed in process and they certainly don't have the added insulation of a 1/2 inch or so of temporal bone.
    I would be interested in any suggestions you could make. For example, I've considered simply keeping the voltimeter as part of the circuit to give me a readout as to the actual volt/amp passing through the head. It's obviously going to be much lower than that provided by sampling from the anode to the cathode (which provides another cushion of safety). Perhaps I should in fact be using a smaller size resistor.

    1. I tried it and messed up but smoke didn't come out of my ears,it came out of my ass and now when I fart it smells like burnt shit and has a static discharge to it. I'm afraid to fart in the shower because I might get electrocuted. If I turn the lights off and fart I can see lightning bolts shoot out along with a blue flame. I farted at work yesterday and somebody said they smelled burnt hot-dogs. Starting to get worried. Thanksgiving is coming up and I don't want the family thinking I burnt the turkey. What should I do?

  2. Very interesting stuff. How is it working for you so far? Have you noticed any changes?

  3. The resistance of your head is about 4k, plus the 4.7k gives 8.7k so Ohm's Law says you'll get 1 mA through your head tops with your setup.

    Instead of the 4.7k, use a Semitec 2 mA Current Regulating Diode

    If you care to ramp up the current to prevent phosphenes, use a 100k audio-taper pot from Radio Shack.

  4. I forgot to mention - you need 2x2" TENS electrodes from Amazon - peel off the gel and place over 2x3" sponges soaked in salt water - 1 level tsp in a quart of water - otherwise you risk electrode burns

  5. That's awesome! I have TENS pads, although I've never had an issue with the sponges yet. Where did you get the 4k resistance number from? So my plan is to take off a bit more than a month and then I'm going to build a newer model incorporating these suggestions. I am going to do two weeks of eeg readings without and then a few weeks with in order to have some kind of non-subjective results to report. I'll also journal the subjective for fun. I was thinking of also adding something like a graph of dual-n-back with and without although since any practice will cause improvement overall, the numbers wouldn't really mean much.

  6. I set my gizmo to 2 mA across my head, then I measured the voltage at its terminals which was 8V - since I=V/R, R=8/2=4k

    BTW, in my gizmo, the voltage drop across the CRD is 1.6V, across the LED is 1.9V, so the circuit overhead is 3.5V and the net V available to drive a current through your head from a 9V battery is only 5.5V - I have to use 2 9V batteries or an A23 12V battery to get 2 mA

    What electrode placement are you using? Anodal L DLPFC for depression, or anodal R anterior temporal lobe for insight and task learning?

  7. Basic circuit of my gizmo:

  8. you've gone dark - are you OK?

  9. Sorry man! I was working. Long shifts and such. I intend to upgrade to your model this friday!

  10. I'm assembling the newer version now. :( Have the wrong led lights though.

    1. shouldn't matter - 20 mA LEDs glow at 2 mA

  11. Cassox, can you elaborate on the electrode placement for enhanced memorization? Reading through the various resources it appears some are suggesting the anodal placement on DLPC (left) while others are referring to the F8 region which is temporal (right). Any insights? Thanks, Don

  12. I'll tell you what I'm currently working on. I got a Neurosky Headset, which is a semi-ok version of an eeg. They have plenty of research and documentation saying it's great and research grade etc. I'm not entirely sure about this yet. Regardless, I'm going to get a good two weeks worth of graphing without using the tDCS. Then I'm going to graph with it as a comparison. I'll bring in optimal placement and focus on that with the next post too. Hope I can answer any questions at that time. Give me a week or two.

  13. Happy New Year! do you have any new insights regarding the electrodes placement? Don

  14. You really should be using a current limiter.

  15. Actually, I haven't been playing around with this for a while. I really am going to come back and explore this more. I really want a good method of recording eeg changes. Neurosky wasn't adequate. I'm currently looking at a Powerlab Data Aquisition system, but may have to go the EEG at home route instead. Either way, I really advise people interested in building a tDCS to take a look at Grindhouse Wetware. These guys have a much better design than the one I came up with.

  16. The "biocurrent kit" one is very basic, safe and low price. I have been experiencing it for 19 days now, for personal issues (anodal(+) left-DLPFC...), and this is kind of perfect.

  17. Actually, this does look like a far better option than my version. It's available here "" I still think the 165$ price tag is a tad excessive though. I think that the Grindhouse Wetware model is more cost effective, but perhaps not as accessible to those who don't solder etc. This is far more affordable than the rip-off models described in the blog above. Another little update - I'm going to be ordering an Olimex board for EEG analysis associated with the IR Vision project to be used for Electroretinography, so afterward I'm going to come back to this project as I'll be able to publish some objective findings.