During non-rapid eye movement (NREM) sleep, brief brain states lasting less than a second, called EEG microstates, determine whether a person will recall a dream upon waking. Two microstates (3 and 4) dominated NREM sleep compared to wakefulness. Within NREM sleep, microstate 3 was more present before dream recall, while microstate 4 was less present. Microstate 3 involved the medial frontal lobe, suggesting deeper local deactivation and executive disconnection that keeps the brain asleep. Microstate 4 involved the occipital cortex, thalamus, and brainstem, and its reduced presence may indicate local activation enabling rich perceptual dream content. The temporal dynamics of these alternating brain states determine whether conscious experience arises during NREM sleep.
Conscious experience feels continuous but actually consists of brief, discrete brain states lasting 60–120 milliseconds, called EEG microstates. These stable scalp electric field patterns, measured with high temporal resolution, may represent the basic building blocks of thought. Altered states of consciousness—including sleep, anesthesia, meditation, and psychiatric conditions—change the dynamics of these microstates. This perspective argues that studying EEG microstates can reveal underlying features of self-consciousness, summarizing recent findings on microstate alterations during mind-wandering, meditation, sleep, and anesthesia.