Spontaneous episodic thoughts about the past and future are common during waking but rarely occur during N2 or REM sleep. Analysis of thought reports from 138 participants who underwent experience-sampling while awake and serial awakenings during sleep shows that waking spontaneous thought frequently includes autobiographical planning with a strong bias toward the future. In contrast, dreaming sleep states rarely feature such mental time travel. This suggests that human consciousness differs substantially across the sleep-wake cycle in how it typically engages with episodic past and future events.
A state called pure presence, reported in meditative traditions as a vivid experience without thoughts, perceptions, or self, was examined in twenty-two long-term meditators using high-density EEG. During pure presence, brain activity showed widespread reductions in gamma and delta power compared to mind-wandering, watching a movie, active thinking, and dreamless sleep. The strongest gamma decreases occurred in the posteromedial cortex. These findings align with integrated information theory's prediction that vivid consciousness can arise when the brain's cortical substrate is largely quiet yet highly awake.