Participants will be divided into two groups: healthy controls and persons with OSA. Both groups will undergo standard overnight sleep study or PSG. In addition to the standard PSG (with or without Continuous Positive Airway Pressure (CPAP)), the study researchers will add the OxiplexTS—allowing them to assess brain oxygenation and hemodynamics during sleep. The hemodynamic patterns of the healthy controls will be compared to those of persons with OSA. Participants with OSA who undergo PSG/CPAP will be tested with the OxiplexTS, as well. Their PSG and PSG/CPAP data will be compared.