The EEG 10-20 system shows where to place electrodes on the scalp for qEEG assessments and evoke potentials tests. Specialists also use it for LORETA-type brain biofeedback. The placements correspond to specific locations in the brain. The system was designed to ensure rigor, reliability, and effective comparability between EEG recordings.
The “10” and “20” refer to the actual distances between adjacent electrodes as being either 10 percent or 20 percent of the total front–back or right–left distance of the skull. (Wikipedia)
The skull cap they place on you for your qEEG test has built-in electrodes that follow the 10-20 system. Each electrode in the cap has a label with a letter that corresponds to the underlying brain lobe and a number that corresponds to hemispheric locations.
The letters stand for:
- C: Central
- Fp: Pre-frontal
- F: Frontal
- T: Temporal
- P: Parietal
- O: Occipital
Numbers range from 1 to 6. Odd numbers refer to the left side of the head. Even to the right side. All the electrodes placed along the centreline of the head are labelled “Z.” Z stands for zero, that is, the midline sagittal plane of the skull.
For more detailed information, see Wikipedia.