Objective: Adolescence is characterised by a genuine interest in new experiences and an increased sense of responsibility. The aim of this study was to investigate changes in brain maturation that underlie task-relevant behaviour and the relation of these changes to novel impressions during the transition from childhood into adolescence and then young adulthood. We hypothesized that, with development, improved target detection abilities and reduced distractibility will be characterised by an increased involvement of frontal brain regions within the fronto-parietal brain network during novel processing and target detection. Methods: In a cross-sectional study, a classical visual oddball task (n = 159) and a novelty visual oddball task (n = 84) were utilized in combination with EEG measurements to investigate brain maturation between late childhood and young adulthood (8 to 30 years of age). Developmental changes of late ERP components and concurrent delta (0.5 - 4 Hz) and theta (4 - 7 Hz) oscillations were analysed using regression models. Pre-stimulus amplitude and post-stimulus amplitude modulation, inter-trial phase coherence of local maxima and inter-electrode spatial phase coherence were assessed. Results and Discussion: A general decline in reaction time and late ERP latency (novelty N2, P3a and P3b) with age was observed and may depend on task performance. The frontal novelty N2 amplitude decreased while the P3a amplitude increased with age. This opposing developmental trend may relate to a compensatory mechanism for immature P3a-related cognitive functions, such as attention control. The pre-stimulus amplitudes of delta and theta oscillations decreased while post-stimulus amplitude enhancements and inter-trial phase coherence increased with age. Both effects seem to underlie maturation of the P3b amplitude, even though this cannot be observed directly in ERP amplitude measurements. Post-stimulus theta inter-electrode spatial phase coherence originating from frontal electrode sites increased with age during novel and target stimulus processing, indicating prolonged maturation of the fronto-parietal network that underlies target detection and novel processing. Conclusion: Functional brain networks involving the frontal cortex, such as the fronto-parietal network, mature until young adulthood, thereby affecting slow-wave oscillations on a local and global scale alongside late frontal ERP components. Brain maturation during adolescence may lead to a reduction of spontaneous slow-wave oscillations and an enhancement of amplitude modulation and regional and inter-regional precision of timing of event-related oscillations within the P3 time-window. Thus, brain maturation underlying task-related behaviour and reduced distractibility is versatile. Significance: Combined analysis of developmental trajectories of late ERPs, concurrent changes in spontaneous and task-modulated brain oscillations and their embedding within functional brain networks (e.g., the fronto-parietal network) is important to estimate how brain maturation relates to abilities of cognitive control during the transition into adolescence and young adulthood. It is critical to extend our understanding of healthy brain maturation as excessive brain plasticity during adolescence raises the sensitivity to the environment and learning experiences, and its outcome may have long-term positive or negative impact on personal opportunities in life and mental health
