In this study, the investigator evaluates whether there are age-specific diurnal changes in markers of cortical plasticity in children, adolescents and adults. The question will be investigated by the quantification of brain metabolites and structural brain volumes using magnet resonance imaging (MRI) and electrophysiological markers using sleep encephalography (sleep EEG). In a second step, it will be tested how these markers of cortical plasticity change depending on a modulation of sleep by applying tones during deep sleep.