STXBP1 and Down syndrome: The developmental profile of low-frequency power was altered in STXBP1 syndrome: while low-frequency power decreased with age in TDC [linear regression; slope = −0.04, t(48) = −8.35, p = 6.5e-11], power remained high in children with STXBP1 syndrome [slope = 0.003, t(12) = 0.08, p = 0.94; Supplementary Figure 6A].