A holy grail of BCI research is to be able to control complex devices using noninvasive recordings of brain signals at high spatial and temporal resolution. Current noninvasive recording techniques capture changes in blood flow or fluctuations in electric/magnetic fields caused by the activity of large populations of neurons, but we are still far from a recording technique that can capture neural activity at the level of spikes noninvasively. In the absence of such a recording technique, researchers have focused on noninvasive techniques such as EEG, MEG, fMRI, and fNIR, and studied how the large-scale population-level brain signals recorded by these techniques can be used for BCI.

Electroencephalographic (EEG) BCIs

The technique of EEG involves recording electrical signals from the scalp (Section 3.1.2). The idea of using EEG to build a BCI was first suggested by Vidal (1973), but progress was limited until the 1990s when the advent of fast and cheap processors sparked a surge of interest in this area, leading to the development of a variety of EEG-based BCI techniques.