Technique for adjusting the locus of excitation of electrically excitable tissue

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 a two dimensional array adapted to be implanted adjacent to the tissue, the two dimensional array having a first group of electrodes and a second group of electrodes, the second group of electrodes being located at a more lateral position relative to the first group of electrodes;
• (B) 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;
• (C) 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;
• (D) a generator configured to provide the first and second pulses to 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.

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 first group of electrodes in an inner ring formation, the second group of electrodes in an outer ring formation;
• (B) at least one electrode of the first group of electrodes capable of being driven with a first pulse, the first pulse having a first pulse width to generate a first subthreshold potential area in the tissue;
• (D) at least one electrode of the second group of electrodes capable of being driven with a second pulse, the second pulse having a second pulse width to generate a second subthreshold potential in the tissue;
• (E) a generator configured to provide the first and second pulses 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.