Sensitivity analysis wherein the horizontal axis is the first N% of accumulated luminance contrast-based neural spikes varying from 0.01% to 15%, for a constant-scale Gaussian on-/off-center contrast model. Note the images to the right shows the algorithm response is a point-cloud for organic scenes (bottom right) and strong vertical and horizontal lines for man-made scenes (top right). The algorithm was tested against 312 real-world, cultural images. The vertical axis plots the rotation angle percent correct for an upright orientation +/-0.5o. Three insert plots show the SNR over the run set for the temporal first 0.1%, 5%, and 12% of neural contrast spikes.