[00:05.20]1995

[00:07.51]Sleep is divided into periods of so-called REM sleep,

[00:11.56]characterized by rapid eye movements and dreaming,

[00:14.68]and longer periods of non-REM sleep.

[00:17.50](1)Neither kind of sleep is at all well-understood,

[00:20.52]but REM sleep is (2)assumed

[00:22.44]to serve some restorative function of the brain.

[00:25.57]The purpose of non-REM sleep is even more (3)mysterious.

[00:29.20]The new experiments, such as

[00:31.02]those (4)described for the first time

[00:32.94]at a recent meeting of the Society

[00:35.35]for Sleep Research in Minneapolis,

[00:37.87]suggest fascinating explanations

[00:40.09](5)for the purpose of non-REM sleep.

[00:42.75]For example, it has long been known

[00:45.59]that total sleep (6)deprivation is 100 percent fatal to rats,

[00:50.14]yet, (7)upon examination of the dead bodies,

[00:52.87]the animals look completely normal.

[00:55.31]A researcher has now (8)cast light on the mystery

[00:58.33]of why the aninlals die.

[01:00.05]The rats (9)develop bacterial infections of the blood,

[01:03.28](10)as if their immune systems

[01:05.11]--the self-protecting mechanism against disease--had crashed.