In the case of some sensory attributes (e.g., luminance), differential thresholds increase with the spatial separation between the stimuli to be compared, but in other cases (e.g., spatial frequency, hue) thresholds vary little whether the stimuli are close together or separated by 10 degrees of arc. To this latter class of sensory attributes, we here add two dimensions: Speed of motion and chromatic purity. Stimuli were presented too briefly for an eye movement and could fall at any positions on an imaginary circle centered on the fixation point. What neural mechanisms underlie discrimination in such tasks? We doubt discrimination depends on a large array of dedicated "comparator neurons," one for each possible pair of positions in the visual field and for each sensory attribute. Instead we suggest that information about local sensory properties is carried to the cortical site of comparison by neural connections that resemble the man-made Internet insofar as the same physical substrate from moment to moment carries different information in a symbolic code.