Neural opponent interactions between cone outputs do not produce flicker-free visual signal. (A) Normalized output of the three real cones in adult Metriaclima zebra in response to light reflected off an achromatic target (50% reflectance) that was illuminated with flickering illumination. Cone output varied considerably over time, with the variation in cone output (estimated as the standard deviation over time) highest for SWS1, lower for Rh2b, and lowest for Rh2a. (B) Output of putative opponent channels (SWS1-Rh2b, SWS1-Rh2a, and Rh2b-Rh2a) varied over time, showing variation comparable to that in cone output. (C) Cone dynamic range adjusted such that the over time variation in cone output was similar for all cone classes and equaled that of SWS1 that exhibited the largest variation. (D) Following the dynamic range adjustment, the variation in opponent channels’ output decreased only slightly, and did not produce flicker-free visual signals. (E) Cone dynamic range adjusted such that the over time variation in cone output was similar for all cone classes and equaled to that of Rh2a that exhibited the smallest variation. (F) Following this dynamic range adjustment, the variation in opponent channels’ output decreased by an order of magnitude, producing a visual signal that is almost flicker-free. Colored values indicate the variation in the output of each of the cones and opponent channels.
Sabbah and Hawryshyn BMC Biology 2013 11:77 doi:10.1186/1741-7007-11-77