Which stages of sleep include both theta waves and sleep spindles?

Stage 2 of sleep is characterized by the presence of both theta waves and sleep spindles. This stage is crucial for memory consolidation and is generally considered a deeper sleep than Stage 1. During Stage 2, the brain begins to exhibit specific waveforms associated with sleep, such as sleep spindles—brief bursts of brain activity that are believed to play a role in memory processing and protection against external stimuli.

Theta waves, which are slower than alpha waves, also dominate this stage, indicating a transition from light sleep to deeper sleep. The combination of these brain waves reflects important physiological and neurological processes occurring during this stage, making it distinct from the other sleep stages. Stages 1 and 3 have different wave patterns, and REM sleep is marked by a different activity state, primarily with beta waves similar to alertness. Thus, Stage 2 stands out for its characteristic wave patterns, confirming it as the correct choice.