A method and neurostimulator for providing therapy to a patient is provided. In one technique, electrical background energy is conveyed to a first tissue region of the patient in accordance with stochastic parameter, thereby modulating the excitability of the first tissue region, and electrical stimulation energy is conveyed to the first tissue region when its excitability is modulated. In one example, the stimulation energy may be conveyed to a second tissue region of the patient, thereby therapeutically stimulating the second tissue region. In this case, the excitability of the first tissue region is decreased, thereby reducing any adverse effect that the conveyed stimulation energy has on the first tissue region. As another example, the conveyed stimulation energy stimulates the first tissue region, in which case, the excitability of the first tissue region may be increased, thereby enhancing the stimulation of the first tissue region by the conveyed stimulation energy.