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.
After six weeks of breath-focused, digital meditation training, young adults showed changes in resting-state brain networks measured by EEG microstates, particularly in the right insula, superior temporal gyrus, superior parietal lobule, and superior frontal gyrus bilaterally. These topographical changes were not seen in an active placebo control group. The results suggest that this low-cost, digital meditation practice can reorganize brain network connectivity and may offer a novel, noninvasive approach for treating neuropathological conditions.
The study used ultra-high field fMRI and high-density EEG to investigate the neural basis of self-generated thoughts. Participants engaged in two conditions: retrieving self-relevant past memories or performing serial mental arithmetic. fMRI showed increased activity in temporal, parietal, and occipital areas during memory retrieval, organized into subsystems for scene reconstruction and self-experience. EEG microstate analysis revealed that specific brief periods of stable brain activity were modulated differently between conditions, linking these fast temporal dynamics to the slower fMRI changes. The findings suggest that fMRI networks related to mental activity can be captured by EEG as brief, recurring periods of coherent neuronal activity.