Polysomnography is a diagnostic test used to evaluate sleep disorders. It involves the continuous monitoring of various physiological parameters during sleep, including brain activity (electroencephalography), eye movements (electrooculography), muscle activity (electromyography), heart rate, and respiratory function. This test helps in the diagnosis of conditions such as sleep apnea, narcolepsy, and other sleep-related disorders. Polysomnography is typically performed in a sleep lab overnight, where a trained technologist monitors the data and recordings to analyze the patient's sleep patterns and identify any abnormalities.