Which electrode site is located at 20% of the distance from the nasion to the inion?

The electrode site located at 20% of the distance from the nasion to the inion is indeed Fz. This specific placement makes use of the 10-20 system, which is a standardized method for electrode placement used in EEG and polysomnography.

In this system, Fz signifies a frontal midline location situated near the forehead. The measurement is a percentage of the total distance from the nasion (the bridge of the nose) to the inion (the bony prominence at the back of the skull). Placing an electrode at 20% of that distance characterizes it as the Fz site, crucial for capturing frontal lobe activity.

Understanding the significance of these landmarks and percentages is essential for ensuring accurate and reliable readings during polysomnography, particularly when assessing brain activity and sleep cycles.