What is EEG used to measure during polysomnography?

EEG, or electroencephalography, is used during polysomnography to measure the electrical activity in the brain. This measurement is critical for assessing the various stages of sleep as it provides a direct indication of brain wave patterns. Different sleep stages are characterized by distinct EEG patterns, allowing trained professionals to identify whether the patient is in light sleep, deep sleep, or REM sleep, among others. This information is essential for diagnosing sleep disorders and understanding the overall sleep architecture of a patient.

While other physiological parameters, such as heart rate variability and muscle tone, are also monitored during polysomnography, they do not provide information about brain activity directly. Therefore, EEG's ability to measure brain electrical activities is central to the evaluation and understanding of sleep stages and patterns.