Ultradian and circadian modulation of dream recall: EEG correlates and age effects

• Dream recall, particularly after REM sleep, is modulated by the circadian system.
• Dream recall is predicted by specific frequency- and topography-NREM and REM sleep EEG activity.
• Dreaming in older people is linked to specific differences in NREM and REM sleep.
• Specific regional brain function directly modulates dreaming.

Dreaming occurs during non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, which both are regulated by homeostatic, ultradian, and circadian processes. However, the magnitude of how ultradian REM and NREM sleep and its EEG correlates impact onto dream recall remains fairly unknown. In this review, we address three questions: 1. Is there an ultradian NREM–REM sleep modulation in successful dream recall, which is gated by the circadian clock? 2. What are the key electrophysiological correlates that account for dream recall during NREM and REM sleep and 3. Are there age-related changes in the ultradian and circadian regulation in dream recall and its electrophysiological correlates? Knowledge on the specific frequency and topography NREM and REM sleep differences prior to dream recall may pinpoint to the cerebral correlates that account for this cognitive process, and hint to their possible physiological meaning.