Sensory neurophysiologic functions participating in active sleep processes

The main concepts presented in this review are that sleep is not a function but a state diverse from the waking one. A lot of physiologic functions are carried out during sleep, cardiovascular, respiratory, endocrine, sensory, etc., although in a different way. This state occurs because there is a shifts in all/some cell assemblies-neuronal networks passing from a waking mode into a sleeping mode, perhaps organized by some unknown hub neurons. Since Bremer (1935) postulated a passive sleep theory i.e., the lack of sensory input would be the sleep cause, many active processes have being described. Moreover, since the nineteen sixties, several sensory approaches began to emphasize the role of the sensory input regarding sleep. We are proposing that at least a percentage of sleep generation is due to shifts in the sensory input to the brain determining changes in the cell assemblies-neuronal networks shift into a different mode the sleeping one. Many experimental data, from unitary recordings to every sensory system evoked potentials in human and animals as well as more recent magnetic evoked responses and brain imaging, support the notion of a sensory participation on sleep. The auditory, olfactory, vestibular and somesthetic system, developed introducing more sensory data which progressively shaped a brain that began to reach its completion, leading to a dynamic end: the genetically established sleep-waking cycle features. A proportion of “passive” effects must be associated with active functions for entering and maintaining normal sleep. Sleep generation, maintenance and every related event, are part of central processes that involve the whole brain.