Control a computer with just your mind. On one hand, it sounds almost like a sci-fi fantasy. On the other, EEG (electroencephalography) was first used in the early 20th century. What kept you waiting for the future?
EEG is the recording of electrical activity of the brain from the scalp, produced by neurons firing in the brain. The brain cortex produces tiny electrical voltages (1–100 µV on the scalp). EEG doesn’t read your thoughts, but it can tell your general state. For example, EEG can show if you are paying attention or meditating.
The tiny voltages are easily masked by electrical noise from muscles and ambient sources. EEG currents are measured in microvolts (µV), which are millionths of a volt:
1 µV = 0.001 mV = 10-6 V
Noise from muscle and eye movement can be quite powerful compared to this. In normal buildings, the electrical main’s current radiates a 50Hz or 60Hz electromagnetic field. In a laboratory setting, EEG is usually measured in a room that has less interference. At home, the EEG unit must filter out the troublesome signals.
EEG devices used to be prohibitively expensive and annoying to connect, and the data required expert knowledge to interpret. For many years, a starting price for the cheapest EEG units was thousands of dollars. They required conductive gel to connect. Having very clean hair and skin was recommended. Most units used at least 19 electrodes. EEG results were printed on paper and doctors had to take a course to be able to analyze ...