Sleep is a very active state. Sleep is important to a number of brain functions and important to maintain the functioning of neurons including how nerve cells communicate with each other. In fact, the brain and body stay remarkably active during sleep. Sleep disturbances and sleep deprivation are considered as a necessity and in some quarters considered to be fashionable for night time activities. Sleep loss and sleep disturbances in modern society are due to changes in a variety of environmental and social conditions for example less dependence on daylight for most activities, extended shift work and 24/7 round-the-clock activities. Sleep deprivation and sleep disorders have great impact on both memory function and non-memory function of cognitive processes.