EEG Mindwave Report by Hannah Davis, 11 April 2012.

Introduction:

The Mindwave is an EEG sensor, reading electrical activity along the scalp. It runs on one AAA battery (for about 10 hours of use) and reads neuroscience bands of 0.5 to 50 Hz. It's uni-directional (only reading the signals) and has 96% the accuracy of research-grade EEGs (although this is according to NeuroSky themselves).

Key Concepts:

Hz = cycles per second

EEG = Electro-encephalography

Information below from Wikipedia.org

Brainwaves:

Delta waves (up to 4 Hz) are found in the deepest levels of sleep.

Theta waves (4-8 Hz) are found in the transition from sleep.

Alpha waves (8-13 Hz) are predominantly found with wakeful relaxation (while eyes are closed). Alpha waves are reduced with open eyes, drowsiness, and sleep. They can apparently be controlled (http://en.wikipedia.org/wiki/Neurofeedback)

Beta waves (14-30 Hz) are increased with open eyes and found in normal waking consciousness. Low amplitude Beta waves signify active, busy concentration, or anxious thinking. Beta waves are increased when movement has to be resisted or when it's voluntarily suppressed. A reduction of Beta waves occurs with changes in movement.

Gamma waves (25-100 Hz, though 40 Hz is typical) are debated, but their rhythmic signal is stronger in meditators.

Information below from http://en.wikipedia.org/wiki/Electroencephalography

Key points about electroencephalography:

"The electrode measures electrical activity on the skin of the scalp. More specifically, it measures voltage fluctuations resulting from ionic current flows within the neurons of the brain. Neurons are electrically charged (or "polarized") by pumping ions across their membranes. Neurons are constantly exchanging ions to maintain resting potential and to propagate action potentials. Ions of similar charge repel each other, and when many ions are pushed out of many neurons at the same time, they can push their neighbors, who push their neighbors, and so on, in a wave. When the wave of ions reaches the electrodes on the scalp, they can push or pull electrons on the metal on the electrodes. Since metal conducts the push and pull of electrons easily, the difference in push or pull voltages can be measured. Recording these voltages over time gives us the EEG.

The electrical potential generated by single neuron is far too small to be picked up by EEG or MEG. EEG activity reflects the sum of the synchronous activity of thousands or millions of neurons that have similar spatial orientation. If the cells do not have similar spatial orientation, their ions do not line up and create waves to be detected. Pyramidal neurons of the cortex are thought to produce the most EEG signal because they are well-aligned and fire together. Because voltage fields fall off with the square of distance, activity from deep sources is more difficult to detect than currents near the skull."

Sources:

The Mindwave costs about $100. In my case, I borrowed it from Peter Darche, but it seems available from ThinkGeek and the Neurosky website.

Applications:

The Mindwave can be used with: Arduino, Flash, Android, iPhone, Unity, XNA, .NET, Max/MSP, PureData and more!

See below for a link about hacking the USB dongle.

Projects that have used the Mindwave:

I Am Thinking in a Room Different From the One You Are Hearing In Now: http://www.thismusicisfalse.com/?portfolio=2011-i-am-thinking-in-a-room-different-from-the-one-you-are-hearing-in-now-homage-to-alvin-lucier

Control a Slot Car Race With Your Mind: http://arduino.cc/blog/2011/10/07/control-a-slot-car-race-with-your-mind/

Projects using the Mindflex (cousin of the Mindwave):

Use the Force: http://itp.nyu.edu/shows/winter2009/use-the-force-luke-vs-wampa/

Characteristics/Description:

Essentially, when positive ions flow into the negatively charged neuron, stored energy is released, making small waves. As hundreds and thousands of neurons fire, the little waves combine to create bigger waves, which are the brainwaves themselves. The Mindwave measures these larger brainwaves.

The Mindwave works by using electrodes (one reference sensor on the earlobe, and the main sensor on the forehead in a position known as FP1, at the frontal lobe) to measure electrical activity on the skin of the scalp. Mindwave's sensor collects neural signals and inputs them into the ThinkGear chip -- a technology created by Neurosky (that is programmable). The chip processes the signal into a usable data stream. Electric noise and muscle movement are digitally filtered, while raw brain signals are amplified. Finally, the signals are analyzed by emotional state algorithms (attention/meditation) that come from both NeuroSky and research institutions.

The Mindwave filters muscle movement, pulse, and noise from other electrical devices. The earlobe sensor experiences roughly the same ambient noise but with minimal neural activity. Ambient electrical noise levels from the earlobe sensor are subtracted from the main sensor to find the neural activity.

The Mindwave can measure multiple states simultaneously. Gel is not needed.

Information above from Neurosky website.

Code Sample:

I used Eric Blue's brain-grapher Processing sketch, which worked well and laid the information out in an understandable, visual way. The code can be found on Github here: https://github.com/ericblue/Processing-Brain-Grapher.

Eric’s processing sketch obtains data using Neurosky’s ThinkGear Socket Protocol, of which more information is available here: http://developer.neurosky.com/docs/doku.php?id=thinkgear_connector_tgc A more thorough guide is available as a pdf here: http://developer.neurosky.com/docs/lib/exe/fetch.php?media=thinkgear_socket_protocol.pdf

The ThinkGear Socket Protocol is a JSON-based protocol that transmits data from the Mindwave from the serial port to an open network socket. Using the ThinkGear Connector applications can connect over TCP and ask for data in JSON or binary format. According to Eric’s github account, the default IP and port are used. The data is streamed as follows:

	{
	"eSense":
		{"attention":91,"meditation":41},
	 "eegPower":
	 	{"delta":1105014,"theta":211310,
	 	"lowAlpha":7730,"highAlpha":68568,
	 	"lowBeta":12949,"highBeta":47455,
	 	"lowGamma":55770,"highGamma":28247},
	 "poorSignalLevel":0
	 }

Application Notes:

The Mindwave defines waves into the following ranges:

  • Delta: 1-3Hz
  • Theta: 4-7Hz
  • Alpha1: 8-9Hz
  • Alpha2: 10-12Hz
  • Beta1: 13-17Hz
  • Beta2: 18-30Hz
  • Gamma1: 31-40Hz
  • Gamma2: 41-50Hz

The Mindwave also includes two categories called "Attention" and "Meditation." Where the other waves are varied, seem random, and are hard to control, the Attention/Meditation categories are able to be moved by concentrating. Not much information is revealed about the algorithms generating these categories, but according to the NeuroSky website:

Attention (more emphasis on beta wave, according to NeuroSky): Indicates the intensity of a user’s level of mental “focus” or “attention”, such as that which occurs during intense concentration and directed (but stable) mental activity. Distractions, wandering thoughts, lack of focus, or anxiety may lower the Attention meter levels.

Meditation (more emphasis on alpha wave): Indicates the level of a user’s mental “calmness” or “relaxation”. Meditation is related to reduced activity by the active mental processes in the brain, and it has long been an observed effect that closing one’s eyes turns off the mental activities which process images from the eyes, so closing the eyes is often an effective method for increasing the Meditation meter level. Distractions, wandering thoughts, anxiety, agitation, and sensory stimuli may lower the Meditation meter levels.

Other Thoughts:

  • Even if alpha supposedly correlates with meditation and beta supposedly correlates with attention, I was unable to see a connection
  • The sensor sometimes does not work/seem to connect while wearing makeup!
  • Having the meditation/attention algorithms released seems like the most interesting thing here, as those are the most reliable channels. It would be awesome to see if NeuroSky would release some more information on these in the future.
  • Connection is a big issue. Pay attention to whether it is yellow or green, and discount results from when it is yellow (and red, obviously). It's easy enough to have the Processing sketch not draw anything when the connection is not strong.

References:

Hacking the USB dongle: http://developer.neurosky.com/docs/doku.php?id=arduino_tutorial

http://www.neurosky.com/AboutUs/BrainwaveTechnology.aspx

http://developer.neurosky.com/

http://frontiernerds.com/brain-hack

http://en.wikipedia.org/wiki/Electroencephalography

In the News:

At the 2011 Gadget Show: http://www.youtube.com/watch?v=1tr4CjtGtvg

Keywords:

EEG, Mindwave, NeuroSky, electrode, brainwaves