Schematic description of the stimulus set used to generate each response data set.

For each data set (1 to 7) we describe the stimulus set, we report the parameters spatial spread (σ), peak response amplitude (reported in units of mean spike count per trial and varied to model the different amplitudes of stimulation), the value of the scaling factor and the geometry of the grid of both stimulated and recording electrodes. We use square grids of electrodes, but for stimulation we only use the “external” sites, located on the perimeter of the array. The recording electrodes are all used. So for data set 5, the matrix of electrodes is and we use all of them. For data set 6, the grid is , and since we do not stimulate with the central one, we use 8 stimulation electrodes, while all 9 recording electrodes are used. The grid used in data set 7 is and we do not stimulate with the 9 internal electrodes.