researchers have called “effort” and “arousal” strongly suggests that REM sleep
facilitates the re-energization of the brain. Hippocampal functioning depends
significantly on the presence of ATP (e.g., Inoue, 1998; Inoue, Koizumi, Ueno, Kita, &
Tsuda, 1999), and the hippocampus is the part of the brain that becomes especially active
during REM sleep (Lerma-Garcia-Austt, 1985; Rimbaud, Passouant, & Cadilhac, 1955).
In this paper, physiological features associated with tonic REM sleep, phasic
REM sleep, effort, and arousal are reviewed. It is then noted that tonic REM sleep and
effort share a number of significant physiological similarities, and phasic REM sleep and
arousal also appear to share a common underlying biological process. It is argued that
REM sleep replenishes depleted ATP reserves in the hippocampus and associated brain
structures, such as the amygdala. A preliminary interpretation of the physiological
features associated with REM sleep is offered.
2. REM sleep
REM sleep was initially discovered by researchers at the University of Chicago in
the mid-twentieth century (Aserinsky & Kleitman, 1953), and it has become clear that it
fulfills some critical biological function in nearly all mammals and birds (Zepelin, Siegel,
& Tobler, 2005). REM sleep and non-REM (NREM) sleep alternate cyclically
throughout the sleep cycle. Human infants typically enter REM sleep directly after the
initial onset of sleep and spend approximately 50% of their total sleep time in REM sleep.
Humans older than two years old typically enter NREM sleep before REM sleep and
spend approximately 20% to 25% of their total sleep time in REM sleep “across
preliminary draft (9/24/2006)