The Uses of TDCS

The dramatic potential benefits of tdcs is just beginning to trickle through our society. Imagine having a tool that has such widespread uses as alleviating depression to helping people learn a language faster, or helping with pain to improving math skills; and this tool is easy to build and still shows little side effects after substantial research. This is transcranial direct current stimulation (tdcs).

As tdcs spreads into the mainstream, people will come up with weird and wonderful uses. I decided to outline some major categories how people may use the technology of tdcs for clinical as well as cognitive enhancement purposes.

1.       From the medical establishment, clinical uses are the most prevalent of course: depression, bipolar (especially with depression), pain, speech disorders, stroke etc. Although some montage prescriptions may be frequent treatments (two or more times per week), the particular montage prescription with a particular condition will most likely have been researched in a small clinical study, so you would think risk is low. On the other hand as people begin to experiment themselves and they may be mixing tdcs treatments with other medications, chance an adverse reaction is greater.

2.     Some people will use tdcs to receive a mental boost on a frequent basis, nearly daily to keep sharp, and keep motivation and mood up. Obviously the chances of side effect are great here. Long term steady use has not been thoroughly studied, and it begs the question, if you use it all the time to maintain some level of personality and performance, what happens when you stop?

3.     Some people are using only for a particular grand task or project: learning a new skill, learning a new language, working on an important project at work. For this situation the person would receive a treatment more frequently (couple times a week or more) when doing the skill or work, and it should improve this skill during the other times. For example someone receiving treatments while studying for the SATs a couple times per week for a few months while studying, could see a better score when they take the SAT without receiving treatment, of course. Personally, this is what I do. Particularly if I have a large writing project to do, I will give myself treatments at early in the day, or the night before, while writing and/or studying about the topic. I feel my writing is more focused and more productive. Since this is generally a shorter period of time, the risk is lower.

I discuss adverse reaction. As more people do tdcs, adverse reactions will happen. someone that is unstable who probably shouldn’t have done it, might hurt somebody, hurt themselves, end up in an ER, and then tdcs will be the culprit. It happens when certain vitamins become popular, and think of the adverse reactions with drug trials…
And lastly, of course, if ever in doubt about a medical condition, consult your doctor before receiving treatments. Also to minimize risk and any side effects, you can start with lower levels of stimulation (1mA or less), and stimulate less frequently (once a week or less). If no side effects or adverse effects are noticed, then you can increase frequency or current amplitude. 

A little less Simple DIY TDCS circuit using CRDs

There has been some important points brought up about the benefits (easy to build, robustness) and drawbacks (turn on transients and lack of accuracy) of the Simple DIY TDCS circuit using CRDs. Considering the lack of accuracy, this is a characteristic of the diode not the circuit.

For the E-102, the the datasheet only gives a range of 0.88mA - 1.32mA. But I have seen that there is a higher probability of finding them near 1mA (for example if you test 100 of them most will be between 0.9mA - 1.1mA), with some outliers at the full range. And physiologically, it is still not clear whether 0.9mA will be much different than 1.0mA will be much different than 1.1mA.

Regarding the transients at turn on, that is a circuit issue. So to remedy, it is easy to add an LC filter at the output (see picture below for new schematic). The LC filter acts to dampen any transients. Bench testing shows the ramp up to be 500ms, which is plenty to dampen any turn on pulses, but unfortunately not enough to prevent any flash that occurs with certain montages. At mouser.com, the L can be 22R105C and the C can be UKL1E100KDDANA.

The above explanation is for informational purposes only, and I take no responsibility for the use or intended use of this information. TDCS is currently not FDA regulated, and there is no intention here in providing a TDCS device. Also I suggest you read, read, and read more about TDCS, particularly any safety considerations before undertaking any project like DIY TDCS and contact your health provider if you have any particular questions about your particular condition.

UPDATE

I always attach the electrodes and attach all connections before I turn on at the Battery. Make a switch at the battery and the switch at the battery should be turned on last after the electrodes are attached. If you turn the battery on first, not only will you be putting on hot electrodes but there will be a transient probably higher than 1mA.

For a simple, more foolproof circuit see the Simple DIY TDCS Circuit using CRD's below.

Will tDCS ever be a bottom up, widespread success?

tDCS has been known for a number of years now, and for any intrepid explorer, with a little knowledge of circuit theory, but most importantly a little bravery, a DIY tDCS is easily within reach. Simple designs can be found on this blog here, and also at Brent's Speakwisdom blog. But it appears the number of intrepid explorers is not that really big when it comes to the general population. Hence some people have decided to buy a device.

At www.alltdcs.com, you can find the currently available devices that will provide the necessary regulated current to implement a tDCS treatment. It is somewhat confusing as some "off label" devices are much more expensive and have been designed and tested for a different function. And then there are less expensive units that have started to be released with novel ways to try to circumvent the lack of FDA regulation on tDCS medical devices.

Since devices are somewhat easy to make, and easy to purchase, it makes me wonder why more of the population is not clambering for tDCS. Again on speakwisdom, there has been a discussion about the likelihood of a counter top tDCS device. Is it likely? Who would benefit? Will it ever happen?

The typical route for a medical device is years of solid successful research by the research community; then the FDA gets involved and undertakes longer, larger, clinical studies to show efficacy, and ensures public safety. After all that, and many, many years later, if there is a FDA regulation, then the testing to achieve regulation is often prohibitive except for large companies. Only much later, can companies piggy back on the work of early adopters and the price becomes cheaper. Think of the ease and cost of TENS units.

This is the likely path of tDCS. But tDCS may be different: because of its ease in implementing a working DC regulator, and the demand that may grow faster than the FDA can react (with creative, inexpensive devices and kits for sale), there may be a bottom up movement that has no precedent (the closest may be the vitamin and supplement industry). It would be great to see a different path happening for tDCS but first, a large chunk of the population has to be practising first.

I doubt that will happen. Not so much because of the lack of money to be made from large companies (companies always find a way to make a lot of money), but from the "don't try this at home" syndrome. It is difficult to read any media about tDCS and not see the experts say, "don't try this at home", "it is dangerous", "it is your brain you are experimenting with". It may take years, perhaps a lifetime, before it is generally accepted that a small electrical current, which really doesn't do much to skin and muscle, can have a dramatic and exciting affect on the brain and nervous system. Can that little itch, and slight burn if you like it at 2mA, really cause a change in mental capabilities of a person? Amazingly yes.

What is the cause of the "don't try this at home". First I don't think the research community is intentionally dragging their feet, but they are partly to blame for the slow acceptance. They are consistently publishing positive results, and follow along the status quo of research, more clinical studies, FDA regulation, etc. By the nature of their business, researchers need to be conservative to get more funding.

I think the biggest culprit in "don't do this at home" is the cultural fear of electricity generally, and particularly the cultural fear of providing electric current through the brain. I am not sure how to make the general population more comfortable with electricity and it's amazing potential (the Biocurrent kit was intentionally designed for simplicity and ease) but a widespread tDCS use that is not just prescribed by the doctor will only occur if this fear is washed away in truths and honesty about tDCS.

And if you "do try this at home", be knowledgeable and be safe.

The Biocurrent kit is currently available!

The Biocurrent kit is a safe, easy-to-use, apparatus that supplies regulated current through sponge electrodes. By using a unique method of regulation (CRDs), the Biocurrent kit provides regulated current at 1.0mA, 1.5mA, and 2.0mA in a simple to use plug in kit. No soldering is required, all the items necessary to produce biological current are included in the kit (Battery pack, Regulator boxes, cables, sponge electrodes, and elastic band to fix to the body).

For increased safety the cable connectors are specifically chosen to only fit one way and because of inline resistor, current is limited in case of short or failure.

Go to The Biocurrent kit site to find out more and to purchase your device.

The Biocurrent kit

The 2mA regulation box

Simple DIY TDCS circuit using CRDs

There are a lot of good circuits online for motivated people to try to build their own tDCS circuit.  For these schematics, the direct current output levels are controlled either with resistors in series (perhaps varied with a potentiometer), or current regulated mostly using a three pin regulator like the LM334 and feedback resistor to set the current level. The discussion whether regulated current or line resistor is better is not the topic here, personally I think regulated current is miles better, safer, more rugged. I would like to discuss and present a simpler, safe, tDCS circuit that is even easier to build than the three pin LM334 with resistor.

Current regulating diodes (CRD) have been discussed previously on reddit/tDCS and other tDCS websites, but the schematic has not been described. CRDs (or they are also called Current Limiting Diodes) basically are the current equivalent to the zener diode. With a zener diode, once you reach its rated voltage, it turns on. For the CRD, once the bias voltage is applied (and bias current allowed to flow), that device will continue to regulate (maintain) that current regardless of changes in input voltage or output load. This is perfect for tDCS. As the battery voltage drops, the current remains the same (to a certain point of course), also if the head electrodes shift, or dry a little and the head resistance increases, the current remains the same.

Above is a schematic for a simple tDCS circuit that will supply 1mA. The CRD (E-102) maintains a 1mA regulated current to the head (between the Anode and Cathode). The E-102 can be purchased at www.mouser.com. Two 9V batteries are better than one, particularly if you have a less than perfect electrode-head interface, and it will last much longer without the need to change the battery; also the CRD has a 1V-2V drop so the full battery voltage is not present at the Anode. In using the CRD, you have a two pin regulator instead of a three pin regulator and a resistor for the LM334, which means simpler construction.

The 2k ohm resistor in series is for current limiting. If there is a fault condition (although I feel the CRD is more rugged than the IC LM334), and the 18V is at the anode, the absolute maximum current that the circuit can provide is 9mA. This current limiting resistor is used instead of a fuse. A 5mA fuse will blow after a surge of dangerous current, the resistor will not have that surge; the fuse is $20 and the resistor is $0.20. Also for most simple regulator circuits, if you accidently short the Anode and Cathode (if you let the electrodes drop on the table and they come together), the fuse blow and have to be replaced. This will not happen with the resistor. Yet 9mA is high, but not immediately dangerous, and if it happens when the electrodes are on the head, it will be felt and taken off (yanked off) immediately.

This circuit is not good if you want numerous current levels at say 0.1 mA increments. The LM334 with adjustable feedback resistor and microcontroller control is best for that. If you want to have multiple levels then there are other value CRDs available (1.5mA, 2.0mA) and these can be switched in or out.

The above explanation is for informational purposes only, and I take no responsibility for the use or intended use of this information. tDCS is currently not FDA regulated, and there is no intention here in providing a tDCS device. Also I suggest you read, read, and read more about tDCS, particularly any safety considerations before undertaking any project like DIY tDCS.

Important features of a tDCS device or kit

I have been investigating different tDCS devices, thinking a lot about what makes a device or kit good for tDCS use, and I came up with some points for people to consider when they are deciding to build or purchase a device or kit. Any comments or additions would be welcome.

1.      Current regulation

The idea is to maintain the level of current that you want. As the battery drains and battery voltage drops, a circuit with current regulation will make sure the output current does not change. If the electrode resistance is not optimal (maybe not enough water or saline, or head band not tight enough), then the current regulator will make sure the output current does not change (as long as the resistance isn’t too high)

There are DIY devices and designs with resistance only designs (and no current regulators) with an external potentiometer to vary the resistance to get the right current. These will work, but any fast changes of battery or electrode resistance will not have an automatic response by the circuit as happens with current regulation.

2.      Multiple, selectable, output current levels approximately in the range 1.0mA to 2.0mA

All the research shows the benefits of tDCS in the 1.0mA to 2.0mA range, with a slight warning that side effects and undesirable symptoms may start to happen greater than 2mA.

Microcontroller based systems will have control over smaller iterations of current (commonly 0.1mA) or the current levels may be switched in.

3.      Quality of electrodes

The rubber electrodes that are commonly used in TENs are one type that appears to be working and sponge electrodes with a steel plate behind and rubber encasing. I much prefer the sponge electrodes, there is less change of hot spots (as long as you keep them wet). Note that the electrodes may be at least $10 each, so if a device does not include electrodes, know that you will be adding at least $20 to the overall prices.

4.      Maximum output voltage on the electrode.

This is a safety concern that comes straight from Ohms law. If the maximum voltage at the electrode is 18V (2 x 9V battery) and if there is a fault in the current regulation/board/resistor chain, and saying there is a good connection of the electrodes on the head of R = 5kW, then even in fault condition, the maximum current would be 3.6mA (not pleasant sounding to me but not immediately dangerous). If the device is designed for other uses, it can provide higher voltages at the electrodes to reach the higher currents. Hence if there is 50V at the electrode, with our same R = 5kW, then the maximum current would be 10mA, a more dangerous level for the brain.

5.      Current limiting and fuse protection

There are two scenarios that need to be considered. Firstly, if there is a fault in the regulation/board/resistor chain you can have the maximum voltage of the unit at the electrodes (this is when you want a battery maximum of 18V at the electrodes rather than a switched upregulation). Secondly, if the user makes a very large mistake and puts the electrodes over an open wound or a way for the resistance to be much lower, and if the current regulation is working, the level should still be limited to current regulation. But if both scenarios happen at once, then the current can be dangerously high, and hence special microcontroller current limiting, or hardware current limiting through a resistor is recommended. Also a fuse is often added for the slow response.

6.      Turns off when resistance too high (or only turns on when resistance is within a certain range) or when resistance is too low

Higher end devices will have the capability to automatically turn off the output current when the electrode resistance is too high (for example if the electrodes slide off the headband). They will also turn off when the resistance is too low, if the electrodes are touching on a table or a person mistakenly places on an open wound, the resistance can be too low and the device will protect both itself and the user and turn off the output current.