Words in this series

• EEG. The electrical activity of the brain, picked up by electrodes on the scalp. The voltages are measured in microvolts, millionths of a volt.
• Electrode, reference. An electrode is a contact on the scalp. Each electrode's voltage is measured against a reference contact.
• Window. Four seconds of signal, the piece the models work on.
• Corpus. The collection of public EEG recordings the models learned from.
• Artifact. Any part of a recording that is not brain activity, such as a blink or a loose electrode.
• ADS1299. The chip in the IntoMind One that measures the electrodes and turns each measurement into a number. It is an ADC, the kind of chip that turns an analog voltage into digital numbers.
• Sample rate. How many measurements are taken each second. 500 samples per second is 500 measurements on each electrode every second.
• nRF52840. The small processor with a Bluetooth radio that runs the IntoMind One.
• Firmware. The software that runs inside a device.
• Model. A program that is trained on examples rather than written line by line.
• Parameter. One of the numbers a model learns. Mu 171K has 170,772 of them.
• Training step. One round of learning, on a batch of examples.
• Without labels. Learning from the recordings alone, without being told anything about the people in them.
• Foundation model. A model trained on a great deal of data without labels, so that it can later be put to many uses.
• Teacher, student, distillation. A small model, the student, is trained to reproduce what a large model, the teacher, says about the same data.
• Mu 17.8M, Mu 492K, Mu 171K. The IntoMind Mu models: the teacher, the larger student, and the student that runs on the IntoMind One.
• Encoder. A model that turns EEG into numbers. The IntoMind Mu models are encoders.
• Embedding. The list of numbers a model produces to describe a window of EEG.
• Token. The list of numbers a model produces to describe one short slice of the signal.
• Decoder. A map from a model's numbers back to the signal. The open reconstruction head is a decoder.
• Head. A small add-on that turns a model's numbers into an answer, such as an estimate of age.
• Pass. One run of a model over one window.
• Multiply-add. The basic arithmetic step a model takes. Counting them measures how much computing a model needs.
• Band power. The classic summary of EEG: how strong each of the brain's rhythms is.
• PSD. The power spectral density, the measurement band power is computed from.
• AUC. How well a test separates two groups. 0.5 is a coin toss, and 1.0 is perfect.
• R². How much of a signal's variation is recovered. 1 is all of it, and 0 is no better than a flat line.
• Real time. Finishing each window of EEG before the next one is ready.
• Synthetic signal. EEG-like signal produced by a model rather than by a brain.
• Noise floor. The level of a measuring chip's own electrical noise, below which it cannot see a signal.
• Datasheet. The manufacturer's document that specifies a chip.
• Short circuit. An unintended electrical connection.
• Acceptance test. The full set of checks a unit has to pass.
• Over the air. Sent to the device by Bluetooth, with no cable.
• Packet. A small bundle of samples sent over Bluetooth.
• BCI. A brain-computer interface.
• API, SDK. The API is the set of commands through which programs talk to the device. An SDK is a developer kit built on it.
• Repository, repo. A place where code is published and kept.
• PCB. A printed circuit board.
• LiPo. A lithium-polymer battery.
• Mains. Power from the wall.
• Bring-up. The first power-on and testing of a new device.