Figure 1.

Characteristic patterns of physical activity and glucose associated with time of day and sleep/wake intervals for a single subject (top) and the time- and frequency-dependent coherence between these two processes as a heat map (bottom). The top panel illustrates raw activity (total activity counts per 5 min [blue]) and glucose values (mg/dl [green]) over a single 60-hr recording period, with clear daily (circadian) variations in both activity and glucose. Vertical shaded regions denote the recorded sleep periods for this subject. The bottom panel illustrates the time-varying and frequency-specific coherence between activity and glucose. The color bar at the right of this panel provides the scale for coherence (ranging from 0 to 1), with intervals of statistically significant coherence shaded red and enclosed by a black border.