Electroencephalography (EEG) EEG records the brain's spontaneous electrical activity over a short period of time, usually 20–40 minutes, as recorded from multiple electrodes on the scalp.[20] Microsleeps have EEG shift to slower frequencies (from alpha to theta waves).[21] Functional magnetic resonance imaging (fMRI) A functional neuroimaging procedure using MRI technology that measures brain activity by detecting associated changes in blood flow (detects what regions of brain are active during microsleep events).[22] Psychological tests Reaction time test, Karolinska Sleepiness Scale (KSS),[23] Maintenance of Wakefulness Test (MWT),[24] Multiple Sleep Latency Test (MSLT).[25] Electrooculogram (EOG) EOG is a technique for measuring the resting potential of the retina in the human eye.[26] Eye-video test Measures eyes blinking and eye movements to detect microsleep events.[27][28] Mouth yawning test Counts number of yawns over a period of time.[29] Speech tests Examines emotions and/or prosody in speech to predict microsleep episodes.[23][30][31]