During which sleep stage is the EEG most likely to show a predominance of delta waves?

The primary characteristic of Stage 3 and Stage 4 sleep, collectively referred to as slow-wave sleep (SWS), is the predominance of delta waves on the EEG. Delta waves are high-amplitude, low-frequency brain waves that are typically found in the deeper sleep stages, reflecting increased synchronization of neural activity. This stage is crucial for restorative processes, growth, and overall brain health.

During Stage 3 and 4, the body experiences significant physical restoration, and the presence of delta waves indicates that the brain is engaged in deep, slow-wave activity. This contrasts with the other stages of sleep, such as Stage 1 and Stage 2, where theta waves and sleep spindles are more common, and REM sleep, which is characterized by a different wave pattern where theta and beta waves become prominent. Thus, the answer is supported by the understanding of EEG wave patterns associated with different sleep stages.