Apparatus (18) for treating a condition of a subject is provided. An electrode device (100) is adapted to be coupled to longitudinal nervous tissue (40) of the subject, and a control unit (50) is adapted to drive the electrode device to apply to the nervous tissue a current which is capable of inducing action potentials that propagate in the nervous tissue in a first direction, so as to treat the condition. The control unit is further adapted to suppress action potentials from propagating in the nervous tissue in a second direction opposite to the first direction.