What technology is commonly used to monitor brain activity during sleep?

Electroencephalography (EEG) is the technology commonly used to monitor brain activity during sleep. This technique involves placing electrodes on the scalp to detect electrical activity generated by neurons in the brain. The resulting data provides insights into the different stages of sleep, such as REM and non-REM sleep, by recording the brain's electrical patterns. EEG is particularly valuable in polysomnography, the comprehensive study of sleep, as it helps to evaluate sleep disorders and understand the overall sleep architecture.

Other technologies mentioned, such as magnetoencephalography (MEG), while useful for monitoring brain activity, are not typically employed in sleep studies due to their complexity and cost. Electromyography (EMG) measures muscle activity and is generally used in conjunction with EEG in polysomnography, but it does not specifically monitor brain activity. Computed tomography (CT), a form of imaging, is used primarily for structural imaging of the brain but does not provide information on brain activity as it relates to sleep. Thus, EEG clearly stands out as the primary method for monitoring brain activity during sleep.