Healthy adult non-REM sleep was recorded using 64-channel electroencephalogram (EEG) to image millisecond changes in the scalp topography of individual sleep spindles. Matched frequency filtering isolated fast (13-15 Hz) and slow (11-13 Hz) ends of the spindle spectrum. Sequential voltage maps of filtered data across time produced topographically precise movies of individual spindles. Slow spindles (centered around 12 Hz) show a more dynamic topography, primarily over the frontal cortex and with bilateral variability between and within spindles. Fast spindles (centered at 14 Hz) are topographically and dynamically limited to the superior central and parietal cortex. Peak activity patterns suggest that slow spindles result from cortical-cortical activation following spindle initiation, while fast spindles in the EEG reflect only cortico-thalamic activation.