A system configured to enhance deep sleep in a subject during positive airway pressure therapy, the system comprising: a pressure generator configured to generate a pressurized flow of breathable gas for delivery to an airway of the subject; one or more sensors configured to generate output signals conveying information related to breathing of the subject; and one or more hardware processors operatively coupled to the pressure generator and the one or more sensors, the one or more hardware processors configured by machine-readable instructions to: cause the pressure generator to generate the pressurized flow of breathable gas in accordance with a positive airway pressure therapy regime based on the information in the output signals; determine sleep stages of the subject based on the information in the output signals; and responsive to the sleep stages indicating the subject is in deep sleep, cause the pressure generator to adjust the pressurized flow of breathable gas to deliver a stimulus to the subject, the stimulus configured to enhance deep sleep in the subject; and characterized in that the one or more hardware processors are further configured to cause pressure generator to adjust the pressurized flow of breathable gas to deliver the stimulus to subject comprises causing motor oscillations in pressure generator, which in turn, cause oscillations in the pressure and/or flow rate of the pressurized flow of breathable gas delivered to subject. a pressure generator configured to generate a pressurized flow of breathable gas for delivery to an airway of the subject; one or more sensors configured to generate output signals conveying information related to breathing of the subject; and one or more hardware processors operatively coupled to the pressure generator and the one or more sensors, the one or more hardware processors configured by machine-readable instructions to: cause the pressure generator to generate the pressurized flow of breathable gas in accordance with a positive airway pressure therapy regime based on the information in the output signals; determine sleep stages of the subject based on the information in the output signals; and responsive to the sleep stages indicating the subject is in deep sleep, cause the pressure generator to adjust the pressurized flow of breathable gas to deliver a stimulus to the subject, the stimulus configured to enhance deep sleep in the subject; and characterized in that the one or more hardware processors are further configured to cause pressure generator to adjust the pressurized flow of breathable gas to deliver the stimulus to subject comprises causing motor oscillations in pressure generator, which in turn, cause oscillations in the pressure and/or flow rate of the pressurized flow of breathable gas delivered to subject. cause the pressure generator to generate the pressurized flow of breathable gas in accordance with a positive airway pressure therapy regime based on the information in the output signals; determine sleep stages of the subject based on the information in the output signals; and responsive to the sleep stages indicating the subject is in deep sleep, cause the pressure generator to adjust the pressurized flow of breathable gas to deliver a stimulus to the subject, the stimulus configured to enhance deep sleep in the subject; and characterized in that the one or more hardware processors are further configured to cause pressure generator to adjust the pressurized flow of breathable gas to deliver the stimulus to subject comprises causing motor oscillations in pressure generator, which in turn, cause oscillations in the pressure and/or flow rate of the pressurized flow of breathable gas delivered to subject.