Polygraphic studies of kitten development: sleep state patterns.

The sequence of developmental changes in sleep pattern organization was derived from 12-hr recordings in 10-, 20 and 40-day-old kittens. Each characteristic of sleep patterning exhibited a distinct maturational sequence. Earlier changes (10-20 days) included quiet sleep (QS) increments and somatic activity decrements; later changes (20-40 days) included emergence of EEG slow waves and spindles, decrements in active sleep (AS), and diminution of QS respiratory variability. Changes in the lengths of state epochs and the types of state transitions spanned the period studied. We suggest that the differential development of the characteristics of sleep patterns reflects differential maturation of distinct nervous system elements.