Abstract
<p>The emergence of the alpha peak is a milestone in brain development. For decades, metrics commonly used to quantify alpha have collapsed its temporal dimension, which can obscure the course of alpha development when the rhythm is not yet sustained. Here, we leveraged over 600 resting EEG recordings from 207 children aged 1–48 months to chart alpha development through its rhythmic structure and transient recruitment (bursts) and related these time-resolved measures to traditional measures of alpha from the power spectrum. We show that early alpha (1 to 12 months) depended largely on transient bursts. As alpha became more rhythmic with age, alpha power relied progressively less on burst activity. These findings indicate that the development of the alpha peak may reflect a fundamental shift from a transient to a more sustained rhythm. Time-resolved metrics are therefore essential for characterizing alpha accurately in early development.</p>