Sleep is an Auto-Regulatory Global Phenomenon

for the regulation of sleep-wakefulness (Urbano et al., 2012). From the evolutionary point of view it can be assumed that the primitive brain had auto-regulatory oscillations between awake-like and sleep-like states (Cirelli, 2009). As evolution progressed, and as the brainstem, diencephalon, and neocortex were formed, they also became part of the oscillating network. Prior activity in the network determines the probability of the network entering the sleep-like state or awake-like state (Krueger et al., 2008). Hess had shown in the 1930s that the same locus in the thalamus can produce sleep-like and awake-like activity by varying the frequency of stimulation. Chemical stimulation studies have shown that either sleep or wakefulness could be elicited from the same loci by application of different neurotransmitters. Even the same transmitter under different experimental conditions can produce opposing responses (Kumar, 2005; Kumar et al., 2006, 2007). These findings question the very idea of assigning a sleep regulatory role to any one particular brain region. There are external and internal factors that influence the swing of sleep-wakefulness toward either sleep or wake state. There are several internal signals, including sleep inducing substances, which are sleep facilitating. It was suggested that the auto-regulatory/auto-modulatory characteristic of sleep and/or its homeostatic part operate through adenosine and other sleep regulatory substances (Manzar and Hussain, 2012). Basal forebrain and hypothalamus should be considered as part of the neural mechanism through which many of these internal signals act. These brain regions integrate sleep with body temperature, hunger, thirst, circadian cycles, neuroendocrine outputs, homeostatic mechanisms, autonomic responses, and stereotyped behaviors (Kumar, 2005). There is growing evidence to show that the thermoregulatory system is part of the global homeostatic sleep regulatory mechanism (Mallick and Kumar, 2012). The research on the effects of exercise on sleep have provided enough evidences to conclude that the auto-regulatory, global regulation of sleep is not the exclusive domain of the central nervous system, but it is heavily influenced by inputs from the rest of the body (Uchida et al., 2012). Even meditation practices influence brain functions, modulate autonomic, metabolic, endocrine, and immune functions, and thus mediate global regulatory changes in various behavioral states including sleep (Nagendra et al., 2012). It can be concluded that normal sleep is an auto-regulated global phenomenon. Sleep and vigilance emerge from the dynamic interaction of neuronal network throughout the brain. The tendency for sleep-wake oscillation is derived from a collective response of the several hundreds of neurons with oscillating membrane potential.