This chapter provides a brief description of the main animal models used in the study of sleep and cognition, which reveals their intercomplementary strength and scope. Two types of sleep deprivation are commonly carried out in rodents: total sleep deprivation (TSD) and rapid eye movement (REM) sleep deprivation (RSD). Memory consolidation during sleep could be a passive and unselective process due to a prolonged quiet period without any flow of information. The study of sleep-dependent cognitive processes is relatively recent in birds and few studies have so far included sleep deprivation. Sleep deprivation protocols include gentle handling, placing birds in a running wheel, the disc-over-water method, and constant light. Drosophila serves as a model system for the investigation of many cellular, developmental, and behavioral processes common to other species, including humans.