An implantable medical device, IMD, for deep brain stimulation, DBS, comprising: stimulation generation circuitry configured to deliver electrical stimulation therapy to tissue of a patient via electrodes (116, 118); and processing circuitry configured to adjust a level of at least one parameter of the electrical stimulation therapy such that a sensed signal indicative of a beta signal of a brain of the patient is not less than a lower bound and not greater than an upper bound of a range; wherein the lower bound is one of: a magnitude of the sensed signal while receiving a first level of the electrical stimulation therapy that is a minimum level sufficient to reduce one or more symptoms of a disease and while the patient is receiving medication for reduction of one or more symptoms of the disease or disorder; or a magnitude of the sensed signal while receiving a second level of the electrical stimulation therapy sufficient to cause maximum reduction of the one or more symptoms of the disease or disorder without inducing substantial side effects in the patient and while the patient is not receiving the medication for reduction of the one or more symptoms of the disease; and the upper bound is one of: a magnitude of the sensed signal while receiving a third level of the third electrical stimulation therapy that is a minimum level sufficient to reduce the one or more symptoms of the disease and while the patient is not receiving the medication for reduction of the one or more symptoms of the disease; or a magnitude of the sensed signal while receiving a fourth level of the electrical stimulation therapy, while the patient is not receiving the medication for reduction of the one or more symptoms of the disease, that is sufficient to reduce the one or more symptoms of the disease or disorder but which above the level, substantially no further substantial reduction in the one or more symptoms is achieved. stimulation generation circuitry configured to deliver electrical stimulation therapy to tissue of a patient via electrodes (116, 118); and processing circuitry configured to adjust a level of at least one parameter of the electrical stimulation therapy such that a sensed signal indicative of a beta signal of a brain of the patient is not less than a lower bound and not greater than an upper bound of a range; wherein the lower bound is one of: a magnitude of the sensed signal while receiving a first level of the electrical stimulation therapy that is a minimum level sufficient to reduce one or more symptoms of a disease and while the patient is receiving medication for reduction of one or more symptoms of the disease or disorder; or a magnitude of the sensed signal while receiving a second level of the electrical stimulation therapy sufficient to cause maximum reduction of the one or more symptoms of the disease or disorder without inducing substantial side effects in the patient and while the patient is not receiving the medication for reduction of the one or more symptoms of the disease; and a magnitude of the sensed signal while receiving a first level of the electrical stimulation therapy that is a minimum level sufficient to reduce one or more symptoms of a disease and while the patient is receiving medication for reduction of one or more symptoms of the disease or disorder; or a magnitude of the sensed signal while receiving a second level of the electrical stimulation therapy sufficient to cause maximum reduction of the one or more symptoms of the disease or disorder without inducing substantial side effects in the patient and while the patient is not receiving the medication for reduction of the one or more symptoms of the disease; and the upper bound is one of: a magnitude of the sensed signal while receiving a third level of the third electrical stimulation therapy that is a minimum level sufficient to reduce the one or more symptoms of the disease and while the patient is not receiving the medication for reduction of the one or more symptoms of the disease; or a magnitude of the sensed signal while receiving a fourth level of the electrical stimulation therapy, while the patient is not receiving the medication for reduction of the one or more symptoms of the disease, that is sufficient to reduce the one or more symptoms of the disease or disorder but which above the level, substantially no further substantial reduction in the one or more symptoms is achieved. a magnitude of the sensed signal while receiving a third level of the third electrical stimulation therapy that is a minimum level sufficient to reduce the one or more symptoms of the disease and while the patient is not receiving the medication for reduction of the one or more symptoms of the disease; or a magnitude of the sensed signal while receiving a fourth level of the electrical stimulation therapy, while the patient is not receiving the medication for reduction of the one or more symptoms of the disease, that is sufficient to reduce the one or more symptoms of the disease or disorder but which above the level, substantially no further substantial reduction in the one or more symptoms is achieved.