REM sleep deprivation diminishes fear in rats.

To test the hypothesis that REM sleep deprivation decreases fear, the behavior of 44 rats was measured in an open-field test. Prior to this test, the animals were exposed to 4 days to one of four treatments, i.e., either a dry environment control, a wet environment control, a 2-day REM deprivation period, or a 4-day REM deprivation period. During the test both exploration and three parameters of emotionality were recorded. The results offered convincing evidence in support of the hypothesis.