In polysomnography, what characterizes stage N2 sleep?

Stage N2 sleep is characterized by the presence of sleep spindles and K-complexes, along with an overall slowing of the EEG activity compared to wakefulness. Sleep spindles are quick bursts of brain activity that serve as a marker for this stage and reflect the brain's processing and consolidation of information.

The presence of sleep spindles, which typically occur at frequencies of about 12-16 Hz, is crucial as they signify a transition into deeper sleep, allowing the body to maintain a state of sleep while still responding to external stimuli. The presence of these sleep spindles is one of the defining features that differentiate stage N2 from other sleep stages, especially from stages of lighter sleep like N1 and deeper sleep such as N3.

In contrast, aspects such as the dominance of fast brain waves would be characteristic of lighter sleep or wakefulness, while stating that there is an absence of sleep spindles would inaccurately describe stage N2, as spindles are fundamental to this sleep stage. Lower muscle tone might be present, but claiming there are no spindles misrepresents the significance of spindles in identifying N2 sleep. Thus, recognizing the presence of sleep spindles truly encapsulates what