Which sleep stage is characterized by the presence of sleep spindles and k-complexes?

The stage of sleep characterized by the presence of sleep spindles and K-complexes is NREM Stage 2. During this stage, which typically accounts for a significant portion of the sleep cycle, individuals experience a decrease in heart rate and body temperature, preparing the body for deeper sleep.

Sleep spindles are sudden bursts of oscillatory brain activity that occur during this stage and serve a role in processing memory and learning. K-complexes, which are sudden spikes of brain activity, may be triggered by external stimuli and play a role in maintaining sleep by protecting against awakenings. These features are crucial in differentiating NREM Stage 2 from other sleep stages.

In contrast, NREM Stage 1 is a light sleep stage where alpha brain waves transition to theta waves, and it is not characterized by sleep spindles or K-complexes. NREM Stage 3, also known as deep sleep, is where delta waves are predominant, indicating the deepest form of non-REM sleep, and it lacks the defining features present in Stage 2. REM sleep, on the other hand, is marked by rapid eye movements, vivid dreaming, and a different brain wave pattern, moving away from the characteristics distinctive of Stage 2