Which brainwaves signify deep sleep as observed through an EEG?

Delta waves are indeed associated with deep sleep, particularly during the stages of non-rapid eye movement (NREM) sleep, especially in NREM stage 3. These waves have a frequency of 0.5 to 4 Hz and are characterized by their high amplitude. During deep sleep, the brain is in a restorative state, which is crucial for physical recovery, memory consolidation, and the overall maintenance of health.

In contrast, alpha waves are typically present when a person is awake but relaxed and alert. Theta waves are associated with light sleep and the transitional state between wakefulness and sleep, often appearing during NREM stages 1 and 2. Gamma waves are linked to cognitive processing and are actually seen during periods of intense focus and problem-solving. Thus, delta waves are the clear indicator of deep sleep as measured by EEG, fostering the understanding of sleep architecture and the phases of sleep.