This disclosure describes techniques for delivering electrical stimulation at one or more phases relative to an ongoing oscillating signal in a patient, and then mapping the response to the oscillating signal. The techniques may reduce or eliminate the oscillating signal. In one example, the disclosure is directed to a method that includes delivering a set of first electrical stimulation at a plurality of phases relative to an oscillating signal, measuring a response in the oscillating signal to the set of first electrical stimulation after delivering electrical stimulation at each respective phase of the plurality of phases, determining a phase at which to deliver second electrical stimulation based on the measured responses, and delivering the second electrical stimulation to the patient at the determined phase to produce a therapeutic effect.