What is tDCS?

Transcranial Direct Current Stimulation (tDCS) is a type of neurostimulation where you apply a very small level of direct current through one electrode (Anode) and it flows through the brain to another electrode (Cathode). 

This has a pronounced physiological reaction. The direct current creates a condition under the electrode that affects the neurons: the basement membrane of the neurons at the anode become more positive making them more likely to fire, and the basement membrane of the neurons at the cathode become more negative making them less likely to fire.

Through this simple method, tDCS has been researched to increase insight, improve learning of new things, and also help treat depression and stroke.

For the cognitive enhancement, it is necessary to be performing the task you want to learn while you are stimulating (or inhibiting) with a TDCS device the areas that will be neurologically active during the learned activity. This way the neurons are more likely to fire, and hence increasing brain plasticity.

But what is happening electrically?

(For a more detailed discussion on the Electrical Nature of tDCS go to the blog)

The exact pathways of current from the anode electrode to the cathode electrode through the brain is not entirely known. The modeled circuit of the head (including skin, periosteum, skull, brain..) can be considered a simple design of just a resistor. But in reality that is not the case at all with so many non uniform materials the current must flow through.

It is more likely a much more complex system with some current flowing along the connective tissue in the scalp, and some flowing through the brain. It is generally known that the current intensities are highest under the anode and cathode electrodes; but from a bigger picture of current density to increased positive charges at the basement membrane is a large step (is it capacitive from the skull, with charge buildup on both sides?) I imagine we will soon know more.

 

The Resistance of a Montage

I am of the opinion, like some other people in the early adopter tDCS community, that a single 9V battery is not sufficient to provide the full regulated current (particularly 2mA) for all the well known montages. So I did a small experiment to give some evidence to this.

 (she was not at the party, pilfered the pic from www.diytdcs.com, hope ok John!)

At an Easter party, on five people, I measured the resistance of the R Anode F10 to L Cathode upper arm, also known as the Darpa accelerated learning montage. The people may have been stuffed with turkey and ham and wine, but I do not think that would have affected their resistance very much.

As the method, I used the Cognitive kit at a setting of 1mA. The Cognitive kit comes with sponge electrodes and the electrodes were soaked in saline of 1/4 tsp per cup of water. The current regulation of the Cognitive kit will be +/-5%, hence by measuring the voltage between the Anode and Cathode with a simple voltmeter, and knowing the expected current, the resistance can be calculated with some confidence. Just by testing the resistance with the meter may work, but the injected current is unknown and the accuracy is questionable.

Results were as follows:

1. 6.7kohm
2. 7.4kohm
3. 6.8kohm
4. 7.8kohm
5. 6.3kohm

Actually I was surprised at the consistency of the measurements, but I am confident of the method and then of the results. If this resistance is consistent with other people, then a single 9V battery will not be about to provide 2mA with this montage.

It may not make me popular to say it, but that means DIY devices and commercial devices that use only a single 9V battery would be inadequate to provide the 2mA for this particular montage.

Of course, I did this not just for curiosity sake, the Cognitive kit is designed with 2 x 9V batteries for this very reason. As a side note, the higher end tDCS devices (which includes Human Bioelectric's future device, MindStim) may have only one 9V battery, or even a lower voltage battery, but they include a boost circuit to raise the voltage to provide the potential needed to supply the 2mA in the high resistance circumstances.

New Website, humanbioelectric.com

At Human Bioelectric we not only design and develop tDCS devices, it is also important for us to provide relevant and useful information for the early adopter tDCS community as well as those first investigating this fascinating topic.

As we develop our online presence, we will better perform both tasks. To help achieve this, we have created a new company website:

www.humanbioelectric.com

It is somewhat a work in progress, but pretty cool nonetheless.

An Indiegogo Campaign for MindStim, A Neurostimulation device using tDCS

Excited to present MindStim, A quality neurostimulation device using the technology of tDCS.     

Neurostimulation is gaining momentum as an alternative to pharmaceuticals to affect cognitive ability and to treat psychological disorders. Over the next few years there will be more neurostimulation devices produced for general commercial as well as medical use.

 TDCS is a type of neurostimulation that has grown through a large early adopter community on the one side and a growing research use on the other side. The medical use has been limited mostly to brain stimulation clinics using medical devices for off label purposes. 


In the current regulatory environment, tDCS is not regulated, but there is so much promise for tDCS for medical uses, and when you consider the research, there is more convincing evidence for tDCS success for medical uses like depression and stroke, compared to lasting cognitive changes. Hence we at Human Bioelectric want to develop a tDCS medical device. And that requires extensive production engineering, extensive 3rd party safety testing, and then the clinical trials start (hence the Indiegogo campaign), and this well before any kind of regulation for general medical use. 

Our product is MindStim (drawing of prototype below).

 MindStim

MindStim is a full-featured, hand-held, quality tDCS device designed for safety and ease of use. This is what we have packed inside:

• Clear current display
• Very easy to use switch arrangement to select L (1.0mA, 1.5mA, 2.0mA)
• 20 minute timer
• two levels of overcurrent protection
• Current turns off with poor electrode connection (falls off head etc.)
• Low battery indicator and reverse polarity battery protection

Indiegogo Campaign

To help provide the funding to develop MindStim into a medical tDCS device, we are having an Indiegogo campaign near the beginning of May. For now our gifts will be:

• ePamphlet on tDCS (all the important information on tDCS use, montages, research, w/ pictures, drawings, keeping it clear and simple)
• Cognitive kit (Cognitive Enhancement Device), our 1st generation tDCS device: simple, safe, reliable, easy to use)
• MindStim (Cognitive Enhancement Device), our CED version, with the full features, and quality design and manufacture (but not tested as a medical device yet).

In the next few weeks, I will be releasing useful material about tDCS, updates on the MindStim development, and information on the Indiegogo campaign. Find out what's going on by leaving your email in the "follow by email" section. 

Producing a medical device is long and expensive, but tDCS has so much promise and may be able to help so many people. Please support when the campaign starts.

Some numbers on tDCS research

For medical science to prove that a particular intervention works for a particular condition (depression) or to make a neurophysiological change (improving memory) there has to be numerous studies showing statistical success. It is best when different research methods are used, and repeated over and over again to show consistency. And normally the studies start out small and then larger ones are funded.

For tDCS, the research is very broad, from depression to memory, from pain to Parkinson's; it is so broad it makes me a little skeptical and I wondered how much research has been done on various medical conditions and non medical interventions.

Just recently, in pubmed, I did a simple search of tDCS + (topic) and recorded the number of papers that come up from the search. The results are shown below. I understand that this is only an indication of what is being researched (not all are directly related and all are certainly not positive), but I thought it was interesting nonetheless.

Hits on Pubmed

tDCS and Learning                         322
tDCS and Stroke                             288
tDCS and Memory                          214
tDCS and Depression                     208
tDCS and Pain                                162
tDCS and Safety                             108
tDCS and Cognitive Enhancement  55
tDCS and Bipolar                           31
tDCS and Parkinson's                     25
tDCS and Alzheimer's                    13

Cognitive enhancement montage location: L A DLPFC, R C Supra orbital

Interest in TDCS for cognitive enhancement and for clinical purposes "at home" is growing due to the broad success in the research, the non invasive nature of the therapy, and the ease of making a device or purchasing a clinical device. Because of the grey area of regulation, the manufacturers of devices that can perform the regulated direct current necessary for tDCS do not shout very loud what to do with their devices. The responsibility where to put the electrodes is generally up to the consumer. Hence this blog entry helps clarify, maybe just a little, how to locate a common montage used for cognitive enhancement (as well as depression): Left Anodal dorsolateral prefrontal cortex (DLPFC) and Right Cathodal supra orbital position.

The L DLPFC and R Supraorbital position is also defined as F3/Fp2 on the 10/20 EEG head mapping system, and on the 10/20 system it looks something like this.

Now if you are looking at this picture, and looking in the mirror it is not exactly clear where these points lie (at least to me)

Even though measuring from cranial landmarks is one way to find these points, I always question measuring on the head, or body, because of the size differences between people. Hence to make it easier to locate the points, below are numerous pictures.

Left Anode Dorsolateral Prefrontal Cortex (DLPFC)
The left is obviously the left side of the head, and the anode is the more positive of the two leads (green wire on the Cognitive kit); current goes from electronics to anode through the head to cathode back to the electronics. For the position of the DLPFC, check out the cranium below:

And on me pointing and with a sponge electrode(see there is an advantage to having little hair, better tDCS montage location and better electrode connection).

Right Cathodal Supraorbital

The more negative electrode goes with the Cathode, often, but not always, the black wire or connector. This position is easier to find. The Supraorbital position is above (superior) to the supraorbital ridge, the brow ridge. Start with your eyes straight forward, move up (superiorly) until just over the supraorbital ridge, there you are. Some pictures below:

 

Putting it all together:

(for the one above, the L DLPFC electrodes should be under the red band, but there was definitely enough sponge surface area for current flow).

Next will be the primary motor cortex (M1)

Cognitive kit on its way

The Cognitive kit is a simple to use, safe, very straightforward way to implement tDCS cognitive enhancement sessions. With the Cognitive kit, everything is included to perform safe and easy sessions, with flexibility of any montage. Unlike all other devices, the Cognitive kit includes the more expensive Amrex sponge electrodes in the price of the kit, no expensive adapters, no extras, all included. And it is designed to be small enough to fit in your pocket for more flexibility for the user.

We are a small company, with limited resources so we are growing the company with multiple small builds, each new one larger than the last. Hence it will take a few months to catch up with demand, we apologize.

But this build of the Cognitive kit is on its way (see populated PCBs below). The release date is October 20, but we may be able to release earlier.

See www.cognitivekit.com for more information and email support@cognitivekit.com to find out about early release and release information.