Fig. 2: Transient and nonlinear changes in periodic power between 4 and 12 Hz.

a, b Individual periodic power spectra for 2–4 months, and 6–8 months old. Red markers show peaks between 4 and 12 Hz. c Proportion (mean of binary data) of infants with two peaks identified between 4 and 12 Hz at each age bin. d Proportion of infants with an identified peak between 6.5 and 12 Hz at each age bin. For c and d, shaded areas represent 95% confidence intervals. e–i GAMMs modeled trajectories for males (orange) and females (blue). Lines are the model predicted value with the shaded area representing 95% confidence intervals. Relative inflection points are shown with circular markers. Source data are provided as a Source Data file. Below, heatmaps show the standardized change in offset or slope per day, defined as [change per day]/[standard deviation of measures across full age range]. Both male and female heatmaps shown for models with significant age × sex interaction.