According to the 10-20 international electrode placement system, where are electrodes O1 and O2 placed?

In the 10-20 international electrode placement system, electrodes O1 and O2 are strategically placed in reference to the Oz (occipital midline) electrode. Specifically, they are positioned at a distance of 5% of the total distance from the nasion (the bridge of the nose) to the inion (the bony protrusion at the back of the skull) on either side of the Oz. This placement is important for accurately capturing electrical activity from the occipital region of the brain, which is essential in sleep studies and various neurophysiological assessments.

The 10-20 system is designed to ensure consistency in electrode placement across different studies and among practitioners, thereby improving the reliability of the recorded data. In expressing the distances as percentages of the total measurement, precise locations can be maintained, allowing for comparisons between different individuals and studies. The use of 5% on either side of Oz for O1 and O2 provides an appropriate balance for analyzing brain waves associated with visual processing and other functions related to the occipital lobe.