Developmental Changes in EEG Phase Amplitude Coupling and Phase Preference over the First Three Years After Birth

The coupling of the phase of slower electrophysiological oscillations with the amplitude of faster oscillations, termed phase-amplitude coupling (PAC), is thought to facilitate dynamic connectivity in the brain. Though the brain undergoes dramatic changes in connectivity during the first few years of life, how PAC changes through this developmental period has not been studied. Here, we examined PAC through electroencephalography (EEG) data collected longitudinally during an awake, eyes-open EEG collection paradigm in 98 children between the ages of 3 months and 3 years. We implement a novel technique developed for capturing both PAC strength and phase preference (i.e., where in the slower oscillation waveform the faster oscillation shows increased amplitude) simultaneously, and employed non-parametric clustering methods to evaluate our metrics across a range of frequency pairs and electrode locations. We found that frontal and occipital PAC, primarily between the alpha-beta and gamma frequencies, increased from early infancy to early childhood (p = 1.35 x 10-5). Additionally, we found frontal gamma coupled with the trough of the alpha-beta waveform, while occipital gamma coupled with the peak of the alpha-beta waveform. This opposing trend may reflect each regions specialization towards feedback or feedforward processing, respectively.\n\nSignificance StatementThe brain undergoes significant changes in functional connectivity during infancy and early childhood, enabling the emergence of higher-level cognition. Phase-amplitude coupling (PAC) is thought to support the functional connectivity of the brain. Here, we find PAC increases from 3 months to 3 years of age. We additionally report the frontal and occipital brain areas show opposing forms of PAC; this difference could facilitate each regions tendency towards bottom-up or top-down processing.