Sleep and mental deficiency.

The nocturnal sleep of 54 young, organic and functional, institutionalized mentally deficients was recorded and analyzed according to Rechtschaffen and Kales (1968) and compared to that of 17 normal subjects of the same age. The paradoxical sleep (PS) rate of mental deficients is significantly lower than that of normals, as is the number of PS phases. On the other hand, the rate of intermediary sleep (IS) is increased, as is the latency of the first PS phases. The analysis of intervals between consecutive horizontal eye movements showed that intervals less than 1 sec (I less than 1 sec) are shorter in mental deficients. The ratio between high frequency (I less than 1 sec) and low frequency intervals (I greater than or equal to 2 sec) increases with age in normals and remains at a constant low level in mental deficients.