Dipole Cancellation as an Artifact Suppression Technique in Simultaneous Electrocorticography Stimulation and Recording

Fully-implantable, bi-directional brain-computer interfaces (BCIs) necessitate simultaneous cortical recording and stimulation. This is challenging since electrostimulation of cortical tissue typically causes strong artifacts that may saturate ultra-low power (ULP) analog front-ends of fully-implantable BCIs. To address this problem, we propose an efficient hardware-based method for artifact suppression that employs an auxiliary stimulator with polarity opposite to that of the primary stimulator. The feasibility of this method was explored first in simulations, and then experimentally with brain phantom tissue and electrocorticogram (ECoG) electrode grids. We find that the canceling stimulator can reduce stimulation artifacts below the saturation limit of a typical ULP front-end, while delivering only ~10% of the primary stimulator's voltage.