Table 2.

Objective and constraints for all three methods used in the comparison study.

	Dmochowski et al. [31]	Ruffini et al. [32]	Guler et al.
Objective:	Minimize least squares error between desired and achievable electric field in the brain	Minimize least squares error between desired and achievable electric field component normal to the cortex	Maximize integral of current density component normal to the cortex over the ROI
Constraints:	Individual electrode currents	Individual electrode currents and total injected current	Individual electrode currents, total injected current and current power in the brain outside ROI