Human Brain Mapping of the Apparent Diffusion Coefficient (ADC) During Sleep and Wakefulness

Two MRI scanning session will be obtained for each participant both at the same time of day (9AM 12 PM). In one occasion they will be scanned after a night of rested sleep while awake and on another day they will be scanned after one night of sleep deprivation while sleeping in the scanner. In addition to the most sensitive technique selected in the development phase (either DWI or MT), each imaging MRI session will include (1) a resting-state functional connectivity (RSFC; 10 minutes) scan using single-shot T2\*-weighted EPI; and (2) quantitative T1 relaxometry (T1) in a CSF voxel (1mL; cubic) using an inversion recovery experiment with increased interpulse intervals (TI = 200, 300, 400, 500, 700, 1000, 1500, 2000, 3000, 5000, 10000 ms) and a long TR (10000 ms; scan time 2 min) to assess the level of solutes in CSF.

ECG will be used to monitor heart rate variability (HRV), which differ significantly between the waking state and the different sleep stages