What Is EEG? Acquisition Principles and Common Misconceptions

Electroencephalography (EEG) records signals of the brain's electrical activity over time via electrodes on the scalp. It is a measurement method; a single segment of EEG data alone cannot directly read out thoughts, make a complete diagnosis, or prove training effects.

Where do EEG signals come from?

In a routine EEG examination, electrodes are placed on the surface of the scalp; the device records potential changes, and professionals analyze them in combination with recording conditions and clinical background. EEG has relatively high temporal resolution, but the signal is affected by factors such as blinking, muscle activity, and electrode contact.

NINDS describes EEG as an examination that monitors brain electrical activity and can be used for the evaluation of certain paroxysmal disorders, sleep-related observations, and other clinical scenarios. The specific purpose of the examination and the interpretation of results should be based on a qualified physician's assessment.

The relationship between EEG, EEG biofeedback, and brain-computer interfaces

EEG provides a signal source. EEG biofeedback translates selected EEG metrics into real-time visual or auditory cues for participants to practice with; brain-computer interfaces further decode neural signals into device commands. The latter two can use EEG, but not every EEG system has training or control functions.

FAQ: Can EEG devices “read minds”?

Ordinary scalp EEG should not be understood as directly reading a person's thoughts. The measured signals require processing and task design, and results are limited by noise, individual differences, and validation conditions. When claims such as “precise mind reading” appear in promotional materials, clearly defined tasks, evaluation metrics, and reproducible evidence should be required.

Further Reading

EEG Biofeedback,Brain-Computer Interface,Biofeedback