Figure 6.

Schematic of the integration of sleep inertia, sleep homeostatic and circadian control systems that modulate cognition, affect, physiology and behavior. Homeostatic sleep drive, circadian rhythms and sleep inertia all interact to influence human cognition, physiology and behavior. Arrows represent direction of influence. Circadian phase and homeostatic sleep drive interact to influence each other and both processes modulate sleep inertia. All three processes independently, and perhaps interactively, influence cognition, affect, physiology, and behavior. Behavior also feeds back to alter sleep homeostasis (e.g., choice to sleep versus engage in other activities) and circadian physiology (e.g., gating of exposure to light).