The measured distance from pre-auricular to pre-auricular is 40 cm. What is the distance from Cz to C3?

To determine the distance from Cz to C3 based on the measured distance from pre-auricular to pre-auricular being 40 cm, it’s essential to understand the International 10-20 system of EEG electrode placement. This system provides a standardized way to position electrodes on the scalp relative to specific anatomical landmarks.

In this system, the distance between the pre-auricular points (these are the points located in front of the ears) corresponds to a defined measurement. The points Cz (the central midline electrode) and C3 (the electrode located on the left side of the scalp) are positioned relative to these predetermined landmarks.

The distance from Cz to C3 is derived from the overall measurement. With the total distance from pre-auricular to pre-auricular being 40 cm, the distance between the midline (Cz) and the left side (C3) is approximately 10% of that distance, considering there are generally two regions spanning from the midline to each ear. This places the distance from Cz to C3 at about 4 cm, ultimately leading to a more accurate interpretation of the measurement data derived from the standard.

Through this understanding, it’s clear that the value of 8.