Electroencephalography

Otherwise known as EEG, or electrical recording along the scalp.

“An EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain. In clinical contexts, EEG refers to the recording of the brain’s spontaneous electrical activity over a short period of time, usually 20–40 minutes, as recorded from multiple electrodes placed on the scalp. Diagnostic applications generally focus on the spectral content of EEG, that is, the type of neural oscillations that can be observed in EEG signals. In neurology, the main diagnostic application of EEG is in the case of epilepsy, as epileptic activity can create clear abnormalities on a standard EEG study.” – Wikipedia

If you are still reading this and the Wikipedia definition above didn’t completely lose you, we would first off like to congratulate you. Secondly, you can now breath a sigh of relief because the rest of this document will help you understand the science behind an EEG in a rather simple manner.   To begin, think of the brain as an electrical center.  The brain is estimated to contain between 10 billion and 100 billion neurons which are basically tiny electrical spark plugs. These neurons fire electrical charges to other neurons throughout the brain every time we have a thought.  In fact, neurons are firing when we are not even thinking.  While it is inconceivable to map the billions of neurons and figure out which ones fire in which order, it is possible to understand the overall charge of the brain created from neurons firing. It would stand to reason, the more spark plugs lighting up in our brain, the more electrical activity could be monitored with special equipment.  This is, in effect, the basic principle behind an EEG.  The placement of sensors around the cranium can detect how strong and how weak the electrical charge is at the given point of each individual sensor.

EEGs are manufactured in a variety of ways.  Most EEGs use somewhere between 10 and 20 sensors arranged in a standardized pattern along the cranium, but it is not uncommon to see EEGs with upwards of a hundred sensors.  The greater number of sensors utilized, the more information is able to be gleaned from the study.  The results of the information are commonly seen in television shows and movies as a large printout of jagged lines. In modern technology, the results are handled digitally (as expected) and each sensor will show an electrical line that bounces up and down over time.  By combining the information from each sensor, it is possible to determine how the brain is operating. For example, by reading the charts produced from an EEG, a neurologist could determine the amount of brain activity, check for seizures, check for epilepsy, check for different sleep states (REM), and can even tell if a patient opens their eyes or attempts to talk.  Basically every action we perform has an electrical signature – though every brain operates a little differently.  Broad generalizations can be made on activity, but a detailed diagnosis can not necessarily be made through the results of an EEG alone.

EEGs are now becoming more widely available for independent research and study.  Originally, the cost of a complete EEG setup was prohibitive for the casual researcher. But, with the advances in technology and the desires for an open source software community, many of the original price barriers are beginning to break down.  We are truly in a fascinating time where widespread adoption and understanding of EEGs is no longer limited to expensive laboratories and medical facilities. We expect in the coming years that EEG tools and resources will continue to become more widely available and allow even the casual consumer to measure his or her own brain activity at their own leisure.

The Measurement of Sleep States

One of the more fascinating features to explore with an EEG is the varying sleep cycles of the brain.

Similar to the concept discussed on our binaural frequency page, whereas binaural frequencies can induce different sleep states (Alpha/Mu, Beta, Delta, Theta), an EEG can be used to interpret the sleep state. So wherein we can attempt to trick the brain into falling into different states through these binaural frequencies, we can also measure how well we perform these tasks through the use of an EEG.