These changes take place over a few seconds or less in rodents but may take 10 sec to a minute in humans ( Takahashi et al., 2010 Wright. Hence the mechanisms for wake-sleep state transitions potentially have broad implications for a variety of behavioral states.Īs an individual falls asleep, the EEG initially transitions from a state of high frequency, low voltage waves in the waking state to higher voltage, slower waves representing NREM sleep. The principles that govern these models for state transitions may ultimately apply to many other state changes, such as emotional responses, sexual arousal, or cognitive state changes such as reorienting attention. Recent advances in understanding the brain circuitry underlying the waking and sleeping states have given rise to models that may explain these transitions. Similarly, during the sleep period, animals and people rapidly transition between rapid eye movement (REM) and non-REM (NREM) sleep states. We measure the changes in cortical activity and muscle tone, respectively, by recording the electroencephalogram (EEG) and electromyogram (EMG), and the actual transitions in electrophysiologically monitored state occur over just a few seconds ( Takahashi et al., 2010). These state transitions involve dramatic alterations in easily observed physiological variables, including eye closure, breathing, arousability, and muscle tone. Conversely, it is common experience that one can fall asleep over just a few seconds or minutes. Because sleeping animals are inherently more vulnerable, it is necessary for an animal to be able to awaken quickly so it can flee or defend itself. We spend nearly one-third of our lives asleep, and many mammals, including small laboratory rodents, spend half or more of their existence in this state ( Savage and West, 2007 Siegel, 2009).
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