Figure 2.

Top three rows depict results from the SEM analysis. In these topographic maps the amount of variance (percentage) explained by A, C, and E to slow (10–12 Hz) and fast (12–16 Hz) sleep-spindle amplitude and ISA is shown. Data for SEM analyses are scaled from 0 to 100% and warm colors indicate that a large portion of the variance is explained by the plotted factor, whereas cool colors indicate little or no contribution to the variance of the plotted factor. The bottom (i.e., fourth) row shows the topographic distribution of spindle amplitude (measured in microvolts) and ISA (measured in microvolts per second) averaged across all subjects (independent of twin status). The minima and maxima for each of these maps are shown at the top right of the map. Electrode locations are shown with a black dot in all topographic maps.