Inclusion Criteria:  Healthy males with age between 18 and 40 years Body Mass Index (BMI) = weight (kg) / height (m)2 between 18.5 to 25 kg/m2 Able to understand and to sign a written informed consent prior to the study Informed consent signed Normal or corrected-to-normal vision Completed the Morningness-Eveningness Questionnaire (MEQ - Appendix B) and obtained a score between 30 and 70. No consumption of any beverages or foods with caffeine such as coffee and tea, within 24 hours prior to and during the experiment No strenuous exercise the day before the experiment. No strenuous exercise on the day of the experiment. Completed the one-week sleeping diary over the week before the experiment (Appendix A) showing habitually good sleep, such as falling asleep no later than midnight, waking up no later than 8:00 AM, and regularly having 7-9 hours of sleep every night.  Exclusion Criteria:  Having any metallic, electronic, magnetic, or mechanical implants, devices, or objects, for safety reason linked to magnetic field exposure:  Aneurysm clip(s) Cardiac pacemaker Implanted cardioverter defibrillator (ICD) Electronic implant or device Magnetically-activated implant or device Neurostimulation system Spinal cord stimulator Cochlear implant or implanted hearing aid Insulin or infusion pump Implanted drug infusion device, like portacath® for instance Any type of prosthesis or implant Artificial or prosthetic limb Any metallic fragment or foreign body Hearing aid Other implants Claustrophobia Inability to perform tasks Significant psychological disorders Performing shift work or trans-meridian travel within one month before the study initiation Use of medication or nutritional supplements known to affect the circadian system or the NAD levels, including NAD precursor supplements. Hearing disorders (for safety purpose the participant should be able to hear from the operators during MRS scans) Subject having a hierarchical link with the investigator or co-investigators. Subject does not want to be informed of fortuitous discovery that could have an effect on his health