"Theophilus Samuels" <theophilus.samuels at btinternet.com>:
> Technically, the proportion of quiet sleep (i.e. greater muscle tone, steady
> respiration and adequate temperature homeostasis) remains much the same from
> birth to old age, at about 5 hours per night. But rather it's the amount of
> active sleep or REM sleep (i.e. eye movements, flaccid skeletal musculature,
> erratic respiration and heart-beat, loss of temperature control) that
> decreases with age.
Agreed, just want to add that REM sleep is when dreams occur, and dreams are
usually _not_ the exact play-back of daytime activities. Freud has pointed
out an example where the alarm clock ran off while a person was sleeping and
in his dream he heard an ambulance passing by (or something like that). This
seems more like free association to me. REM sleep also has a *higher* meta-
-bolic rate than wakefulness, thats why its also called paradoxical sleep.
So, why does the brain engage in costly REM sleep?
(To generate random connections?)