This document discusses medical device for coupling to a plurality of implantable electrodes. The medical device includes a therapy circuit configured to deliver electrical neurostimulation energy to the plurality of implantable electrodes； and a control circuit operatively coupled to the therapy circuit. The control circuit is configured to: initiate delivery of bursts of pulses of the electrical neurostimulation energy to the plurality of the implantable electrodes, wherein pulses within a burst include an intra-pulse period； change a combination of electrodes used to deliver the bursts of pulses according to an inter-burst period between bursts； and change the inter-burst period during the delivery of the electrical neuromodulation energy.
