Why are three electrodes placed on the chin during polysomnography?

In polysomnography, the placement of three electrodes on the chin serves primarily to enhance the clarity of the electromyographic signals that monitor muscle activity, particularly the activity of the submental muscles. By using multiple electrodes, the system can achieve a more reliable reading of muscle tone during sleep stages, especially during rapid eye movement (REM) sleep, when muscle atonia is a key characteristic. This redundancy ensures that if one electrode fails or provides noise interference, the others can still provide consistent data, thus improving overall signal integrity.

Furthermore, this setup allows for effective differentiation between wakefulness and various sleep stages, assists in the identification of sleep disorders (such as sleep apnea), and contributes to a better understanding of the patient’s sleep architecture. While monitoring additional muscle activity could be a consideration, the primary benefit is indeed focusing on achieving a clear and stable signal, which is critical for accurate sleep analysis and diagnosis.