So much research has been done lately on cognitive enhancement and other therapeutic practices with a small direct current through the brain.
http://www.nature.com/news/2011/110413/full/472156a.html
Studies done by the airforce has shown that subjects learn how to fly in their flight simulator in half the time. Numerous studies also show that a stimulation of the dorsal lateral prefrontal cortex can boost working memory capacity by 20% in n-back tests and digit span tests.
Oh and my favorite one, a stimulation of the left anterior temporal lobe can temporarily give one savant like abilities, essentially allowing them to be freed from perceiving the world from their preconceptions about things, and letting them see things exactly the way they are.
http://www.youtube.com/watch?v=NYAfmyMZe5g
1. Stimulation of the DLPFC for increased working memory capacity.
http://www.biomedcentral.com/content/pdf/1471-2202-12-2.pdf
2. Left PFC for depression treatment as well as attention/working memory capacity.
http://www.ncbi.nlm.nih.gov/pubmed/22215866
3. Facilitated insight via L/R temporal lobes cathode/anode
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0016655
While this may bring up horrific memories of the notorious electroconvulsive therapy where the subject foams at the mouth while he's tied down, tDCS is found to be very safe using only 1-2mA of current, as opposed to 800-1200mA with ECT.
So as a brain geek, and an aspiring neural engineer, I set out to build my own device.
The basic principle of the transcranial direct current stimulator is that the anode side of the electrode stimulates neurons while the cathode side inhibits it. Based on where these electrodes are placed, a range of functions can be induced.
Basic Components of the Brain Zapper.
A tDCS device fundamentally consists of a current regulator and a 9V battery. The 9V battery is critical as it offers a layer of safety in case of any electrical issues, the current would be limited by ohms law to about 4-5mA, about 2x higher than the normal stimulating levels. This is far below the two orders of magnitude of higher current that is determined to be the bottom limit of brain lesion formation.
http://www.ncbi.nlm.nih.gov/pubmed/19403329
In addition, an ammeter can add additional levels of safety with real time monitoring and an ohmmeter is critical to gauge contact quality of electrodes with the scalp for proper current flow. An ideal resistance should be under 4000kOhms for comfort. Too high of a resistance would lead to excess power being dissipated on the skin. It will burn, and even possibly produce skin lesions. With properly placed and prepared sponge electrodes, a resistance as low as 1500kOhms was had.
Materials
2×9V batteries
Breadboard
3×LM324 opamps(4x opamps each)
LM334 current regulator
LM317T voltage regulator
9×LEDs(7green+2red)
Lots of Resistors
Project Box
Banana plugs+Banana Jacks
Foam
Sponge
Aluminum Sheet
The Bare Bones
For the current regulator, an LM334z is perfect for the low currents needed for this. A variable resistor can be used to adjust the current. Then a 9 volt battery will be used to power it up. An ammeter will be needed to be hooked up series with it to gauge the current.
Adding an ammeter and an electrode contact quality meter
Thanks to some help I gotten in Highly Technical, I was able to build these meters with comparators. A comparator is basically a switch that is controlled by one voltage being greater than a second voltage. So with this, I can switch a series of LED indicators for my meter.
Here is the schematic for my two meters.
Adding a 5 position selector for off + 4 fixed current settings: 0.5mA, 1mA, 1.5mA, 2mA
I also wanted a switch for my current regulator so I wouldn't have to fumble with a potentiometer to get the right current every time I wanted to use it. I was able to find a 2 pole 5 position rotary switch off ebay for about $3. You ideally only need a 1 pole, but a 2 pole can be useful to power off the meters when the current regulator is powered off. This will be very useful to save power and extend battery life.
Here's a quick chicken scratch drawing of the schematic.
Adding a voltage regulator to level the battery voltage for consistent function of the comparators
A 9V battery, as seen in this graph, has a voltage that starts at nearly 9V fresh, and quickly drops off to ~7V. This would affect the consistent function of the comparators.
The LM317T is a voltage adjustable voltage regulator with a 1.25V overhead.
I chose the LM317T to operate at 6V, which can be accomplished with a potentiometer in the following circuit.
Electrodes:
35cm² is by far the most common size used for electrodes seen in studies and is in fact almost universally used. An electrode can be fabricated by placing a conducting plate into a sponge pocket, according to the Video and Instructions link by Harvard Medical School below.
They used conductive rubber in their electrodes, but I didn't have much of an idea where to get those so I used aluminum instead for its relatively low corrosive properties and high conductivity.
Aluminum sheet from Home Depot
A 1cm thick sponge was to 3cm×5cm. A small and sharp pair of scissors made cutting out the pocket to be much easier. Also be sure to round out the edges of your aluminum cutout so it slides into the pocket easily.
I found an old belt to be handy to strap the electrodes around my head. Make sure you only use non-conductive straps as a wet strap can disperse current.
Completed Project:
A project box was picked up from a local Michaels for $7. I found a set of banana jacks on ebay for $3. With a drill and two hours, I was properly proud of my work.
Important Resources for Electrode Placement and a Compilation of Studies of Various Electrode Configurations.
Video and instructions for electrode placement
Compilation of tDCS studies
Compilation of abstracts