OPM-MEG reveals protracted maturation of visual phase-amplitude coupling from early childhood to adulthood

Cross-frequency coupling describes interactions between neural ensembles operating at different frequency bands, and has been proposed to underlie coordination of brain activity over multiple temporal and spatial scales. Phase amplitude coupling (PAC) describes modulation of the amplitude of high-frequency oscillations by the phase of low frequency oscillations. MEG work in adults has demonstrated that alpha-gamma PAC may support visual perception. However, very little work has investigated visual PAC in children, or the development of this process between childhood and adulthood. Here we investigated the development of PAC in a sample of 101 individuals, comprising 50 children (aged 2-13 years) and 51 adults (21-34 years). Participants completed a passive visual stimulation paradigm while neural responses were recorded using a wearable whole-head OPM-MEG system. Sensor-level data were spatially resolved to visual cortex, and we quantified coupling between the phase of low-frequency oscillations (5-13 Hz) and the amplitude of broadband gamma oscillations (28-100 Hz) in each participant. In the adult data, we identified a cluster of phase-amplitude frequency pairs (phase: 7-11 Hz, amplitude: 52-66 Hz) in which there was strong evidence for an increase in PAC following stimulus presentation relative to baseline. Within this cluster, the magnitude of stimulus-induced PAC was positively correlated with age across all participants. Meanwhile, we did not see credible evidence for visual PAC at any frequency pair(s) within the child group. These results suggest that, alongside well-documented developmental changes in band-specific oscillatory power and connectivity, visual PAC represents a distinct functional process which matures with age.