ABSTRACT
As stated previously, during sleep the central nervous system (CNS) remains active and in fact determines the behavioural state in an active process. It is beyond the scope of this book to go into details of the function of the various regions of the brain in the different sleep stages. Briefly, it is generally believed that the cerebral cortex does not possess an intrinsic mechanism for its own activation, and thus the maintenance of wakefulness requires ascending excitatory input from the subcortical structures and brain stem.
