A brain computer interface takes a biosignal measured from EEG and predicts cognitive state. There are 3 types of BCI.
1. Active BCI – You control by conscious voluntary thought, like consciously moving a limb.
2. Reactive BCI – Utilizes brain responses to outside events, like a flickering light.
3. Passive BCI – Picks up any brain processes, utilizes the information to add to your life. Can have many passive BCI’s running in parallel.
The key modality is EEG is because it’s relatively cheap to measure. Functional Near-Infrared Spectroscopy(fNIRS) is another modality. BCI experiments are also happening with invasive sensors, microarrays, neurotics, ECoG. Magnetoencephalography(MEG) and functional Magnetic Resonance Imaging(fMRI) are other methods. fMRI has the benefit of very high resolution. Non-brain signals can also be very useful. Motion capture can show you artifacts. Any aspect of the physical brain sate can be measured with sufficient single-trial reliability.
Tonic state: slow changing brain states such as cognitive load and degree of relaxation
Phasic state: switching attention, and imagined movement
Event-related state: surprised/not surprised, committed error, event noticed/not noticed
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