Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for developing transcranial electrical stimulation protocols are disclosed. In one aspect, a method includes forming a first array of electrodes and optimizing a plurality of electrode parameters within the first array of electrodes to achieve a desired physiological response; identifying one or more electrodes within the optimized first array that have relatively low current compared to the remaining electrodes in the first array; removing the identified low current electrodes from the first array to form a second array of electrodes, wherein the number of electrodes in the second array is less than the number of electrodes in the first array and optimizing a plurality of electrode parameters with the second array of electrodes to achieve a desired physiological response.