We compared the curvature response to three prominent component responses (0, 45, 135 deg as revealed by Fourier 2D transform). Three reasons why it is unlikely that curvature domain response is due to component response: (1) Curvature domains and orientation domains are spatially distinct (2) Curvature domains respond weakly to component orientations (by roughly an order of magnitude) and (3) orientation domains are weakly activated by curvature stimuli, only curvature domains show strong response (A-D: Case 1, E-G: Case 3). (A) Component orientations in the stimuli. Central (red) and flanking parts (blue) of the curvature stimuli. (B) Functional domains from the FOV in Figure 7E (red dotted rectangle). From left to right: curvature domains (all curved minus all straight), 0 deg, 45 deg, 135 deg orientation domains. (C, D) Response timecourses. In each of the curvature panels, these red lines correspond to the three orientations (horizontal, 45, 135). In each of the orientation panels, red lines correspond to the optimal orientations of the orientation domains (shown in the corner of each panel). The gray lines correspond to the identified curvature stimuli. (E) Functional domains. From left to right: curvature domains (all curved minus all straight), 90 deg, 45 deg domains, 135 deg orientation domains. (F, G) Response timecourses. Gray lines: see legend at left. Red lines: see legend within graph. Not due to a weighted sum. To do a quick calculation of a weighted sum of 0, 45, 135 orientation response. For upwards curvature (from C, a/b ratio = 7), Response0 = −0.0026%, Response45 = −0.0027%, Response135 = 0.0006%, Wi = 1/3, Response = −0.0016%, much weaker (by almost an order of magnitude) than the response in curvature domains −0.0115% (responses were calculated by average of the response amplitudes from the last 10 frames). While we are not able to test the weighted sum of all possible orientations, at least with this simple test, we do not see any indication of component summation.