Patent ID: 7657318

Claim:
An apparatus for inducing action potentials at an adjustable locus of electrically excitable tissue of an organism, comprising in combination: (A) a plurality of electrodes forming an array adapted to be implanted adjacent to the tissue, the array having a first group of electrodes and a second group of electrodes, the second group of electrodes located at an outer position relative to the first group of electrodes; (B) at least one return electrode capable of being disposed within the organism; (C) a first set of at least one electrode of the first group of electrodes capable of being driven with a first pulse, the first pulse having a pulse parameter to generate a first subthreshold potential area in the tissue; (D) a second set of at least one electrode of the second group of electrodes capable of being driven with a second pulse, the second pulse having a pulse parameter to generate a second subthreshold potential in the tissue; (E) a generator configured to provide the first and second pulses between the return electrode and the first and second sets to cause a steerable electric field; and wherein a superposition of the first subthreshold potential area with the second subthreshold potential area results in a suprathreshold potential area of the adjustable locus where the action potentials are induced.