The third trimester is a critical period for the development of functional networks that support the lifelong neurocognitive performance; yet the emergence of neuronal coupling in these networks is poorly understood. Here, we used longitudinal high-density electroencephalographic (EEG) recordings from preterm infants during the period from 33 to 45 weeks of conceptional age to characterize early spatiotemporal patterns in the development of local cortical function and the intrinsic coupling modes (phase-phase, amplitude-amplitude, and phase-amplitude correlations). Absolute local power showed a robust increase with conceptional age across the full frequency spectrum, while local phase-amplitude correlations showed sleep state –specific, biphasic development that peaked a few weeks before normal birth. Amplitude-amplitude and distant phase-amplitude correlations decreased globally at nearly all frequencies. In contrast, the phase-phase correlations showed frequency- and region-selective development, with an increase of coupling strength with conceptional age between frontal, central, and occipital regions at low-delta and alpha frequencies together with a wider-spread decrease at other frequencies. Our findings together present the spectrally and spatially differential development of the distinct intrinsic coupling modes during the neonatal period and provide their developmental templates for future basic and clinical research.Significance statementNeuronal activity coupling in cortical networks is a fundamental mechanism underlying higher brain functions. However, emergence of these functional networks within the structural connectome at early maturation is poorly understood. Here, we study the human development of cortical function and distinct neuronal coupling modes (amplitude-amplitude, phase-phase, and phase-amplitude coupling) by investigating longitudinal high-density electroencephalographic recordings in preterm-born infants and discussing their potential links to established neurophysiological processes. Our findings disclose robust, spatially and spectrally specific developmental trajectories for all coupling modes to be used as developmental baselines for future research. The findings together indicate that neuronal coupling modes develop independently during the early neonatal period, supporting the notion that these modes reflect different coupling mechanisms and should be considered separately.