An implant unit according to some embodiments may include a flexible carrier, at least one pair of modulation electrodes on the flexible carrier, and at least one implantable circuit in electrical communication with the at least one pair of modulation electrodes. The at least one pair of modulation electrodes and the at least one circuit may be configured for implantation through derma on an underside of a subject's chin and for location proximate to terminal fibers of the medial branch of the subject's hypoglossaS nerve, such that an electric field extending from the at least one pair of modulation electrodes can modulate one or more of the terminal fibers of the medial branch of the hypoglossal nerve.