from SECTION 1 - NORMAL SLEEP
Published online by Cambridge University Press: 08 August 2009
Overview
Sleep is not an inactive state.
Dating back to early modern classifications of sleep based on electrophysiological measurements, the inherent activities of various neural substrates in sleep have been readily recognized.
Normal sleep has been classified as having two characteristic divisions: non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. These sleep states are defined by neurophysiological parameters of electroencephalogram (EEG), electrooculogram (EOG), and surface electromyogram (EMG), as detailed by Dr. Billiard in the following chapter. These characteristics clearly distinguish the NREM and REM sleep states from the wakefulness state.
Behaviorally, sleep is a reversible state characterized by perceptual disengagement and apparent unresponsiveness to the environment with closed eyes, reduced movements, and recumbency. Early behaviorally based studies revealed that even in those with unequivocal electrophysiologic correlates of being asleep, arousal to one's own name and responsiveness to other auditory stimuli persist.
Additionally, the understanding that continues to evolve of the neurophysiology and neurochemistry of normal sleep suggests that many of the neurologic substrates involved are by no means passive, but rather very active in sleep. An example is the increase in cerebral blood flow that occurs in normal sleep. Both animal and human studies have shown that cerebral blood flow in NREM sleep may increase up to 25% greater than in wakefulness, and up to 80% greater in REM sleep. These changes in cerebral blood flow, at least in part, correlate with concomitant increased brain oxygen metabolism in sleep.
To save this book to your Kindle, first ensure [email protected] is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.