Overview
Transcranial stimulation is a noninvasive procedure that stimulates neurons via magnetic, direct current, or alternating current. This first experiment leverages direct current stimulation.
I began researching transcranial stimulation when my sister suffered a traumatic brain injury after she was hit by a truck. I perused journal articles that published evidence that electrical stimulation can produce a number of effects, such as reducing headaches and improving motor control. I built a stimulation device to investigate and to customize the approach. I mention this anecdote to describe my initial reason for interest in this project; however, I would be very cautious about actually implementing it on my sister, and would not do so without consulting her doctors. I play mad scientist, but not M.D.
1 Arduino (UNO works; I chose the RedBoard from Sparkfun because it has a USB mini-B port)
1 Breadboard
1 Arduino and Breadboard Holde
1 6-Channel, 256-Position Digital Potentiometer (Analog Devices, AD5206BN10)
1 resistor, 10-50 ohms (I use one 12 ohm and one 5.1 ohm in series)
Materials
For the Board
For the Electrodes
I tried several electrodes, such as sponges and commercially available gel adhesive varieties. I found that these had the lowest electrical resistivity.
Steel foil
Styrofoam
Electrical tape
oscilloscpe probes
Assembly and Software
OpenStim is an open source system for Transcranial Direct Current Stimulation. I assembled the hardware according to their open source schematic and installed the software according to their instructions.
OpenStim has 2 dependencies: Processing (provides a runtime environment for the OpenStim software), and Arduino Programming Software (serves as the IDE). I installed both dependencies on a laptop.
The precompiled binaries for the OpenStim software are only available for Windows, so for the first pass I set up this device using a Windows machine. I develop on a Linux machine however, so after seeing that it worked in Windows I downloaded the source code and compiled it on Linux.
Next I installed OpenStim Firmware on the Arduino. This entails connecting the Arduino board to a laptop using a USB cable and uploading the firware using the Arduino IDE. It compiled on the Arduino board.
I then installed OpenStim software on the laptop. The software provides an interface that is used to calibrate the device, since the resistor in the circuit and the type of electrodes will provide different resistance from system to system. Calibrating the device ensures that dangerous levels of current are not delivered while using the device to stimulate the brain. The Arduino can only supply 5V, and the software is programmed not to deliver more than 1mA of current.
After calibrating the system and declaring it error free, I used the OpenStim software to view the program that describes the montage (the amount of current delivered for a given time interval). I set the current to 1.6mA and the time duration to 5 minutes to match the procedure taken in a study by Chi and Snyder on improved insight using TDCS.
Data Collection and Analysis
I investigated journal articles to identify several montages that I wished to try.
I replicated their work and kept detailed notes about my own results. Below is one of the tables of data I collect and a few plots I've put together.
This was an interesting mix of electronics, software, and neurology. This photo was taken the first time I tried it. I had finally constructed and tested a set of electrodes I considered satisfactory.