Answer: A sleep spindle is a particular waveform that is observed in the EEG traces of a person in the early stages of non-REM sleep.
Dynamic coupling between slow waves and sleep spindles during slow wave sleep in humans is modulated by functional pre-sleep activation
Travelling spindles create necessary conditions for spike-timing-dependent plasticity in humans
Hemodynamic cerebral correlates of sleep spindles during human non-rapid eye movement sleep
Abnormal spindle activity during periods of non-REM sleep. (A) Epidural
Rotating waves during human sleep spindles organize global patterns of activity that repeat precisely through the night
Sleep Spindles: Mechanisms and Functions
Frontiers A Novel Approach to Estimating the Cortical Sources of Sleep Spindles Using Simultaneous EEG/MEG
Sleep spindles mediate hippocampal-neocortical coupling during long-duration ripples
Sleep Spindles – As a Biomarker of Brain Function and Plasticity
Frontiers A Novel Approach to Estimating the Cortical Sources of Sleep Spindles Using Simultaneous EEG/MEG