For decades neurophysiology has successfully contributed to research and clinical care in child psychiatry. Recently, methodological progress has led to a revival of interest in brain oscillations (i.e., a band of periodic neuronal frequencies with a wave-duration from milliseconds to several seconds which may code and decode information). These oscillations will nurture future information processing research during normal and pathological brain development, allowing us to investigate basic neuronal connectivity as well as interactions of brain systems and their modulation (e.g., by temporal neuronal synchronisation) as close correlates of behaviour and intermediate phenotypes from genes to behavioural variations. Especially, a systematic neurodynamic look at transitional processes from rest to stimulus-triggered goal-directed performance will aid behavioural understanding and guidance of children. Preliminary data suggest two separate oscillatory mechanisms in this respect. One is ongoing from pre- to post-stimulus processing and related to quantitative modification of behaviour, while another is merely related to qualitative effects of behaviour and reflects "on-top" post-stimulus processing by temporal neuronal synchronisation of the oscillatory network in question. Suggested neurodynamic models may be tested in multilevel clinical experiments as well as in the framework of computational neuropsychiatry.