Anomalous contrast as an adaptive violation of the Talbot-Plateau law

To better understand anomalous contrast mechanisms that allow flicker-fused stimuli to be visible even when they provide the same physical contrast as background.

Stimulus flicker was used to elicit differential activation of ON and OFF retinal channels at frequencies above the flicker-fusion threshold. Providing balanced light energy to ON and OFF channels will normally cause the stimulus to vanish into the background.

We used ultrabrief bright pulses, combined with ultralong dark pulses, to elicit "anomalous contrast" that rendered the stimulus visible, even though it had the same average luminance as the background. The duration and intensity of flicker components were varied to gain insight into the conditions that would elicit this effect.

Anomalous contrast displays violated the Talbot-Plateau law, but in doing so, provided an adaptive way to register and signal contours that matched background luminance. These findings contribute additional details about this visual adaptation, and we discuss how the retinal circuitry provides for stimulus visibility.