Fig. 1.

Power spectrum as an aperiodic signal with superimposed periodic signal(s) (A) An illustration of the power spectrum as two separable signal sources: the aperiodic background signal (dashed line), and one or more periodic components (dark purple “bump”). Analysis of the aperiodic and periodic signals separately allows for a more accurate estimate of changes in oscillatory activity with age. The canonical alpha-band (α) is highlighted in light purple. (B, C) Two example participants, one age 4.5 years (light purple line) and the other age 15 (dark purple line), have different aperiodic slopes (B) and offsets (C). The solid grey lines show the raw power spectra. The aperiodic signal slope was estimated as the exponent of the equation in (B) and the offset as the intercept in (C). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).