(A) Cathode- and anode- first stimulus regimes with varying charge-balancing phases of 100%, 50%, 25%, 10%, 5%, and 2.5% of the leading phase amplitude. (B) Strength duration curve for the charge-balancing phase for passing fibers (blue) or orthogonal fibers (red) for neurons 3 mm away from the contact center. (C) Cathode-first stimulation with varying amplitudes of the anodic charge balancing phase. Changes to the balancing either select against or in favor of orthogonally oriented fibers (third eigenvector). (D) Anode-first stimulation with varying amplitudes of the charge-balancing phase. Orthogonal fibers are highly excitable in all anode-first waveform scenarios.