Which technique is used to measure physiological processes during sleep?

Polysomnography is the key technique for measuring physiological processes during sleep. It is a comprehensive test that records various physiological activities while a person sleeps. This includes brain waves (through EEG), oxygen levels in the blood, heart rate, and breathing patterns, as well as eye and leg movements. By monitoring these different metrics, polysomnography helps assess sleep stages, identify sleep disorders, and evaluate sleep quality.

The other techniques mentioned have specific applications that do not encompass the full range of physiological monitoring required during sleep. Electrocardiography primarily assesses heart activity rather than a comprehensive overview of sleep physiology. Magnetic resonance imaging is focused on detailed imaging of the body's internal structures and does not capture the dynamic processes occurring during sleep. Functional magnetic resonance imaging, while useful for assessing brain activity based on blood flow, is not typically employed for sleep studies in a conventional sense and does not measure the full spectrum of physiological changes related to sleep patterns.