“…During early prematurity they are more frequent during active than quiet sleep. From 29 to 34 weeks this changes and delta brushes are more frequent, and of higher amplitude, in quiet than active sleep (Goldie et al, 1971, Lombroso, 1979, Watanabe and Iwase, 1972, Scher, 2006, Koszer et al, 2006, Tharp et al, 1981, André et al, 2010). At later post-menstrual ages (34–42 weeks), although scattered delta brushes may be present during active sleep and wakefulness, quiet sleep is the only state in which they are prominent (Goldie et al, 1971, D’Allest and André, 2002, Niedermeyer, 2005, Statz et al, 1982).…”