Brain Oscillatory Signatures of Auditory Stimuli Across Different Vigilance and Sedation States

The investigators want to explore how presenting acoustic stimuli influences brain oscillatory signatures and heart rhythm- dynamics across different vigilance and sedation states. The investigators will administer acoustic stimuli during sedation and anaesthesia while brain activity and heart activity are being recorded by electroencephalogram and electrocardiogram. On the day following anaesthesia an optional nap/sleep period's EEG and ECG will be recorded. During this short sleep, patients will again be exposed to acoustic stimuli. The recorded EEG and ECG will be compared intra-and inter-individually to recordings from sedation and anaesthesia.