What is it?

Electroencephalography (EEG) is a non-invasive method used to record electrical activity of the brain. EEG data is typically collected using electrodes placed on the scalp, which measure voltage fluctuations resulting from ionic current flows within the neurons of the brain.

Taken from https://my.clevelandclinic.org/health/diagnostics/9656-electroencephalogram-eeg

This is a good picture to see how EEG data is collected using multiple electrodes placed on the scalp. All electrodes work together to capture the brain's electrical activity from different regions, providing a comprehensive view of neural function.

Electrodes

Electrodes are small metal discs or sensors that are placed on the scalp to detect electrical activity in the brain. They serve as the primary interface between the brain and the EEG recording system. The number and arrangement of electrodes can vary depending on the specific EEG system and the research or clinical requirements.

Taken from https://www.researchgate.net/figure/EEG-electrode-placement-based-on-international-10-20-system-The-18-electrodes-cover-5_fig4_371908856

For example, an electrode labeled "Fz" is positioned on the frontal midline of the scalp, while "P3" is located over the left parietal region. Each electrode captures electrical signals from the underlying brain tissue, allowing for the analysis of brain wave patterns and neural activity.

Electrode Placement

Electrodes are strategically placed on the scalp according to standardized systems, such as the 10-20 system, to ensure consistent and reproducible measurements across different sessions and subjects. Each electrode corresponds to a specific area of the brain, allowing researchers and clinicians to analyze brain activity related to various cognitive and physiological functions.

Commonly, EEG datasets will contain electrodes that goes in multiples of 4, such as 16, 32, 64, or 128 channels. This allows for a more detailed spatial resolution of brain activity.