What is the role of an electrode in polysomnography?

In polysomnography, electrodes play a critical role in detecting and recording electrical activity in the brain. This activity is primarily captured through electroencephalography (EEG), which utilizes electrodes placed on the scalp to measure the brain's electrical signals. These signals help identify different sleep stages, such as REM (rapid eye movement) and non-REM sleep, by analyzing patterns and frequencies that indicate distinct neural activities associated with various phases of sleep.

While other aspects of sleep monitoring, such as eye movement, heart rate variability, and muscle tone are also important, they are typically measured using different specialized methods or sensors. For example, electrooculography (EOG) is used to monitor eye movements, whereas electromyography (EMG) measures muscle tone. These methods involve separate electrodes or sensors specifically designed for their respective functions. Thus, the primary and fundamental role of electrodes in polysomnography is to facilitate the capture of brain activity, making option B the most accurate choice.