Sleep spindles are a pattern of brain waves that occur during non-rapid eye movement (NREM) sleep. They are bursts of neural oscillatory activity that are generated by the interplay of the thalamic reticular nucleus (TRN) and other thalamic nuclei in a frequency range of ~11 to 16 Hz with a duration of 0.5 seconds. Sleep spindles are identified by electroencephalography (EEG), which measures electrical activity in the brain.

The purpose and meaning of sleep spindles are not fully understood, but they are thought to play a role in brain plasticity, or the process of learning and integrating new memories. They also appear to diminish our response to outside stimuli while sleeping. Recent research has revealed that spindles distort the transmission of auditory information to the cortex, isolating the brain from external disturbances during sleep.

Sleep spindles are being further studied in both animals and humans, and they are believed to mediate many sleep-related functions, from memory consolidation to cortical development. They play an essential role in both sensory processing and long-term memory consolidation because they are generated in the TRN.

Sleep spindles look like a burst of activity in the midst of less dense, less frequent waves. They first increase and then decrease in amplitude, giving them a characteristic appearance that resembles a wool spindle. A single sleep spindle generally lasts between 0.5 and three seconds, and they occur every three to six seconds.

In summary, sleep spindles are a pattern of brain waves that occur during NREM sleep, and they are generated by the interplay of the thalamic reticular nucleus and other thalamic nuclei. Although their purpose and meaning are not fully understood, they are thought to play a role in brain plasticity, memory consolidation, and cortical development.