Aperiodic exponent did not significantly change with age in TDC [slope = −0.01, t(48) = −1.82, p = 0.08], or in STXBP1 syndrome [slope = 0.03, t(12) = 0.90, p = 0.38; Supplementary Figure 6D]. Here, STXBP1 is linked to Down syndrome.