What is the primary characteristic of sleep spindles?

The primary characteristic of sleep spindles is that they occur at the onset of stage 2 sleep. Sleep spindles are brief bursts of brain activity that feature a distinct waveform, characterized by a frequency of 12-16 Hz, depending on the species. They play a critical role in sleep processes, particularly in the transition from lighter to deeper stages of sleep.

During stage 2 sleep, which is a light sleep stage, the presence of sleep spindles is a defining feature observed in the electroencephalogram (EEG). This activity contributes to the stabilization of sleep and is believed to aid in memory consolidation and the blocking of external sensory input, allowing for a more restorative sleep environment.

Understanding sleep spindles helps clarify their significance in the sleep cycle, including their absence during wakefulness, their non-exclusive nature in relation to REM sleep, and their limited presence in deeper sleep stages. This knowledge is fundamental when interpreting EEG readings in clinical and research settings.