This image demonstrates a 30-second recording (Compumedics) of stage N1 sleep, notable for the theta activity throughout the first three quarters of the epoch. An arousal occurs at that time (arrow), with a return of alpha activity. The top two leads represent the eyes (right and left), the next lead is the chin, then the following six leads are EEG (right and left frontal, central, and occipital), ECG with heart rate below (R-R), and the leg EMG lead.
