The restrictions of measuring sleep at short 30-second epochs limits the ability to record events shorter than 30 seconds; hence, the macrostructure of sleep can be evaluated while the microstructure is not. The sleep process is smoothened out in<unk>  results unlike it occurs naturally. Also some specific features of sleep such as sleep spindles and K complexes may not be defined in the<unk> ; this is particularly true for sleep scoring that is automated. The method of obtaining the data used in a<unk>  is restricted to the input from an EEG, EOG or EMG. The interval of recording may include features from several stages, in which case it is recorded as the stage whose features occupy the recording for the longest duration. For this reason, the stage of sleep may be misrepresented on the<unk> .
Hypnogram
Polysomnography
Magnetoencephalography
Otoacoustic emission
Somnology
Audiometry
Echoencephalography
Hemoencephalography