Phase-locked loop to enhance slow wave sleep

A non-transitory tangible machine readable medium having instructions stored thereon, which when executed, cause a machine to implement a method, the method comprising:

• identifying a sleep stage for slow wave sleep in a subject being monitored;
• generating, following identification of slow wave sleep and using a processor including a phase locked loop, an output signal including tones based on a phase of a reference input signal, the reference input signal corresponding to an electroencephalogram obtained from the subject with a phase tracked by the phase locked loop to adapt the phase locked loop to a target phase for slow wave characteristics of the subject, the output signal phase locked according to the reference input signal;
• delivering, via an interface connected to the processor and at the target phase for slow wave characteristics of the subject during slow wave sleep for the subject, an acoustic stimulus signal to the subject formed from the phase locked output signal, the delivering comprising:
• providing the stimulus signal in a series of signal pulses for a first period of time;
• and
• providing a refractory period without pulses in a second period of time;
• measuring feedback from the stimulus signal;
• monitoring the phase of the reference input signal;
• and
• adjusting the output signal phase to keep the output signal phase matched to the reference input signal to produce the stimulus signal.

A system comprising:

• a memory and processor including a phase locked loop, the memory storing instructions which, when executed by the processor, cause the processor to:
• identify a sleep stage for slow wave sleep in a subject being monitored;
• generate, following identification of slow wave sleep, an output signal based on a phase of a reference input signal, the reference input signal corresponding to an electroencephalogram obtained from the subject with a phase tracked by the phase locked loop to adapt the phase locked loop to a target phase for slow wave characteristics of the subject, the output signal phase locked according to the reference input signal;
• deliver, via an interface connected to the processor and at the target phase for slow wave characteristics of the subject during slow wave sleep for the subject, an acoustic stimulus signal to the subject formed from the phase locked output signal, the delivering comprising:
• providing the stimulus signal in a series of signal pulses for a first period of time;
• and
• providing a refractory period without pulses in a second period of time;
• measure feedback from the stimulus signal;
• monitoring the phase of the reference input signal;
• and
• adjusting the output signal phase to keep the output signal phase matched to the reference input signal to produce the stimulus signal.