Consentiva can record an EEG spectrum from an OpenBCI Cyton board next to everything else it measures. It's a lab experiment, and a good way to see how signals in the body compare with the signals in the air. This guide covers what you will see, how to do it safely, what Consentiva stores, and one thing people often get wrong: brain activity can't be picked up from a distance.
What EEG is
Electroencephalography (EEG) measures tiny voltage changes, a few to a few hundred microvolts, between electrodes on the scalp. It reflects the combined electrical activity of large groups of neurons. The signal stays in the body: it isn't a broadcast, so no antenna or radio receiver can read it. Systems that decode brain activity (for example, research that reconstructs words from brain scans) rely on electrodes, MEG or fMRI scanners in the lab, not on remote sensing.
The bands you will see
| Band | Frequency | Often linked with |
|---|---|---|
| Delta | 1 to 4 Hz | Deep sleep, and slow movement artefacts |
| Theta | 4 to 8 Hz | Drowsiness, some focus tasks |
| Alpha | 8 to 12 Hz | Relaxed wakefulness, stronger with eyes closed |
| Beta | 12 to 30 Hz | Active thinking, muscle tension |
| Gamma | 30 Hz and up | Mixed; often mostly muscle and mains noise |
A reliable first experiment: sit still with electrodes at the back of the head, and compare a minute with eyes open against a minute with eyes closed. Many people see the 8 to 12 Hz alpha peak grow when their eyes are closed. You will also see a sharp line at 50 or 60 Hz: that's the mains wiring, not you.
Setting up
- Plug the Cyton's USB dongle into a computer and switch the board to PC. Use Chrome or Edge; Android Chrome and iPhone can't use USB serial.
- Prepare the skin and attach gold-cup electrodes with conductive paste, following OpenBCI's instructions. Run the board on its battery.
- In the app choose Lab: OpenBCI EEG board under Receiver and start the walk. Pick the dongle when Chrome asks.
Channels with no electrode are ignored, so you can start with one or two electrodes.
What Consentiva stores
One spectrum per second, from 1 to about 125 Hz. Never the raw waveform. The report and share page are labelled "Test data: EEG, not radio," and sharing an EEG walk shows an extra warning, because brain-wave data is personal even as a summary.
Where the electrodes go
EEG placement follows the international 10-20 system, which names scalp positions by letters and numbers. A few positions are enough to start:
- O1 and O2 (back of the head, over the visual cortex): the best place to see alpha rhythm when your eyes are closed.
- Cz (top of the head, midline): a common general-purpose position.
- Fp1 and Fp2 (forehead): show blinks and eye movements very strongly, which is useful for checking that the board works.
The board also needs a reference and a ground (a "bias") electrode, usually placed on the earlobes or the bony part behind the ear (the mastoid). Follow OpenBCI's instructions for which pins to use, because the wiring depends on your setup.
Getting a good signal
- Clean the skin where each electrode goes (an alcohol wipe, or a mild abrasive prep gel) and let it dry.
- Part the hair and place a gold cup electrode with conductive paste such as Ten20, so the paste fills the cup and touches the scalp.
- Keep cables short, tidy and still. A swinging cable creates large slow waves.
- Sit comfortably, with your jaw relaxed and your eyes on a fixed point, for the first minute.
Channels with no electrode attached are ignored by Consentiva, so you can start with one or two electrodes and add more later.
What is not brain activity
EEG is small, a few microvolts to a few tens of microvolts, so many other things are larger. These are called artefacts, and learning to recognise them matters more than anything else in EEG:
| Artefact | What it looks like |
|---|---|
| Blinks and eye movements | Large, slow bumps in the 1 to 4 Hz range, strongest on the forehead |
| Jaw, face and neck muscle | A broad rise from about 20 Hz upward, and noisy readings in the gamma range |
| Mains interference | A sharp line at exactly 50 or 60 Hz, sometimes with harmonics |
| Movement and loose electrodes | Large, irregular jumps across all frequencies |
| Sweat | Very slow drifts below 1 Hz |
Experiments to try
- Eyes open, eyes closed. Record one minute of each with electrodes at O1 and O2. The 8 to 12 Hz alpha band usually rises with eyes closed.
- Blink test. Blink deliberately every few seconds with a forehead electrode and watch the low-frequency bumps.
- Jaw clench. Clench your jaw briefly and watch the high-frequency noise: a clear lesson in muscle artefact.
- Mental arithmetic. Count backwards from 500 by sevens for a minute and compare it with resting. Changes are subtle and vary from person to person.
Reading the Consentiva spectrum
Each sweep is the spectrum of the latest second of signal, averaged over the channels that carry a signal, from about 1 to 124 Hz in steps of about 1 Hz, in decibels relative to one microvolt. EEG naturally falls with frequency (lower frequencies are stronger), so a smooth downward slope is normal. Look for peaks above that slope, and for how they change when you change what you are doing. A single second can be noisy, so watch the trend over a minute.
Safety and consent
- Run the board from its battery, not from mains power, while electrodes are on your head.
- Stop if the skin becomes irritated. Clean off paste after each session.
- Record only yourself, or someone who understands and agrees. Children need a guardian's agreement.
- Don't use a recording to draw conclusions about health. If you have a medical concern, see a clinician.
Why decoding is not remote
Published work that decodes the meaning of language from brain activity, such as the 2023 University of Texas study, used fMRI recordings: the person lay inside a scanner for many hours listening to stories while a model was trained on that one person's brain. It required their cooperation, a large magnet and a shielded room, and it worked only for the person it was trained on. Other research uses MEG, or electrodes implanted in the brain. None of these works from across a street, and none depends on a radio signal that a receiver could pick up.
Limits and honesty
EEG readings are easily distorted by blinking, jaw tension, movement and loose electrodes. Consentiva's support for the Cyton is a beta, checked against a simulated board and not yet a real one. Nothing here is a medical measurement, and a spectrum doesn't tell you what a person is thinking or feeling. See what to buy.
Common questions
Can an antenna or receiver pick up brain signals from a distance?
No. EEG is a microvolt-level electrical signal measured by electrodes touching the scalp. It isn't radiated, so a radio receiver can't detect it. Research systems that decode brain activity use contact sensors, or MRI or MEG machines in shielded rooms.
Does Consentiva store my raw EEG?
No. Only a spectrum, about one reading a second, is stored. The raw waveform is never uploaded.
Is this a medical device?
No. It is an experimental tool, and every report says so. It says nothing about thoughts, feelings or health.
Which devices work?
The OpenBCI Cyton board with its USB dongle, in Chrome or Edge on a computer. Other headsets are not supported yet, and support for the Cyton is a beta tested against a simulated board.
Where should I put the electrodes to see alpha rhythm?
At the back of the head, around O1 and O2 in the 10-20 system, with a reference and ground on the earlobes or mastoids. Alpha around 8 to 12 Hz usually rises when your eyes are closed.
Why is there a sharp line at 50 or 60 Hz?
That is mains interference from nearby wiring and equipment. It shows the board is connected and picking up signals, but it is not brain activity.