How they work
Neurons communicate with tiny electrical signals. Electrodes pick these up, either from outside the skull (EEG, which is safe but coarse) or from electrodes placed on or in the brain (which gives much clearer signals but needs surgery). Software then learns to match patterns of activity to an intended action, such as moving a hand or forming a word.
What has been shown
In clinical studies, people with paralysis or loss of speech have used implanted interfaces to control a computer cursor, a robotic arm or a speech synthesiser. These are research trials with small numbers of participants, and each system needs careful calibration.
Open questions
Long-term safety and durability of implants, how to make systems simple enough for use at home, regulatory approval, and the privacy of brain data. A brain–computer interface does not read private thoughts; it decodes specific signals it has been trained to recognise.
Where it is used
- Communication Spelling or speech synthesis for people who cannot speak or move.
- Control Moving a cursor or a robotic arm.
- Rehabilitation Training after a stroke, often with non-invasive EEG.
Invasive compared with non-invasive interfaces
Non-invasive interfaces, such as EEG caps, are safe and easy to wear, but their signals are blurry. Implanted electrodes read much clearer signals but need surgery and carry risks, so they are used mainly in clinical trials for severe disability.
The right choice depends on the balance of risk and benefit for each person.
Key terms
- Electroencephalography (EEG)
- Recording the brain’s electrical activity from outside the head.
- Decoding
- Turning recorded brain signals into an intended action.
- Implant
- A device placed inside the body, here in or on the brain.
- Calibration
- Tuning a system to one person’s signals.
Common questions
Can a brain–computer interface read my mind?
- No. It detects trained patterns linked to intended movements or speech, not general thoughts.
Are they approved for patients?
- Some non-invasive devices exist for rehabilitation. Implanted systems are still mainly in clinical trials in most countries.
What are the risks?
- Implants carry surgical risks such as infection, and devices may degrade over time. Researchers and regulators weigh these against the benefits for each patient group.
Sources and further reading
Independent pages we checked while writing this guide. They are not Reinnder products, and Reinnder is not affiliated with them.
- Nature Reviews Bioengineering: Clinical trials of implantable brain–computer interfaces (opens in a new tab)
- Nature Reviews Bioengineering: Translation of neurotechnologies (opens in a new tab)
- Nature Reviews Neurology: Brain–computer interfaces for communication and rehabilitation (opens in a new tab)
Reinnder’s angle
How Reinnder looks at brain–computer interfaces
Reinnder Health lists brain–computer interfaces as a long-horizon interest, to be pursued only within medical regulation.
This guide explains the technology in general terms. It is not advice, and it does not describe a Reinnder product on sale.