LIBRARYWhat Is EEG & How Does It Work?
EEG (electroencephalography) records the brain's electrical activity from the scalp. What the signal actually is, what it can tell you, and what it can't.
EEG (electroencephalography) is a way to record the brain's electrical activity using electrodes placed on the scalp. When large populations of neurons fire together, the tiny voltages they produce sum up and reach the scalp as a fluctuating signal of a few microvolts. EEG measures that signal as voltage over time. It is a recording of electrical rhythm, not a picture of the brain.
What makes EEG special: timing
What makes EEG special is its timing. It captures changes millisecond by millisecond, so it's superb at telling you when something happens in the brain. The trade-off is location: because the signal is blurred crossing the skull and scalp, EEG has poor spatial resolution and can't pinpoint where deep in the brain an event came from. It is also strictly a measurement: it reads the brain's own activity and puts nothing in.
EEG vs fMRI, MEG, and fNIRS
| Method | Strength | Trade-off |
|---|---|---|
| EEG | Millisecond timing, cheap, portable, non-invasive | Poor spatial resolution; noisy |
| fMRI | Excellent spatial detail, whole brain | Slow (seconds), huge & expensive, not portable |
| MEG | Good timing + better localization than EEG | Enormous, shielded-room cost |
| fNIRS | Portable, tolerant of movement | Slow (blood-flow based), shallow |
EEG is not mind-reading and not brain imaging. It can't recover words, images, or specific thoughts. What it can do is detect patterns (rhythms, responses to stimuli, and states like relaxed-vs-alert) reliably enough to drive a brain-computer interface. Powerful, but pattern detection, not telepathy.
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Curious how the microvolt signal actually gets captured and digitized? That's the hardware story: start with the chip at the center of most DIY EEG, then build the front-end in the OTD Academy EEG front-end project.
One Thousand Drones Academy · reviewed June 2026
Coming soon
8-Channel EEG Front-End on ESP32 →Design the analog board that reads real brainwaves: the BCI.
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