EEG provides the recording of electrical activity of the brain from the surface of the scalp
it is portable, it can fit into a small suitcase (vs MEG which requires special built rooms). Lab grade EEG systems may be expensive, but they are cheaper than other BCI methods.
contains rhythmic activity, which reflects neural oscillations. Oscillations are described by frequency, power and phase. delta, theta, alpha, meta, and gamma waves can be picked up.
Main benefit is time resolution
Electrodes are placed on the scalp to pickup the electrical current generated by the brain.
When firing, a neuron forms a dipole, with a lower voltage at synapses and higher voltage at the axon. If it’s an inhibitory neuron, the dipole is flipped.
When groups of neurons fire together, they provide enough signal for us to measure from the scalp.
What is recorded is the voltage difference between minimum 2 electrodes.
Minimal configuration is composed by three electrodes: active electrode, reference electrode and ground electrode. The EEG measures the potential difference over time between signal or active electrode and the reference electrode
The ground electrode is used to measure the differential voltage between the active and the reference points.
Wet - using saline solution of gel. Conductivity is increased because the electrical distance is minimized. The majority are made of stainless steel, tin, gold or silver and which are covered with a silver chloride coating
Dry - more convenient and easier to use, but can lose higher frequencies. Dampen electrodes for better conductivity
https://www.ers-education.org/lrmedia/2016/pdf/298830.pdf
EEG Montages and Technical Components
locations of International 10-20 system for EEG