Abstract
Rods recover sensitivity after turning off a light-adapting field, an effect known as dark adaptation. Recovery is assessed behaviorally by measuring the threshold for just detecting a test flash on the field, compared to just after turning the field off. In the present experiment, tests were presented for 2s and flickered at 4 Hz or 8Hz (100% modulation). Subjects adjusted test radiance to bring the flicker to threshold. Flicker thresholds at 4 Hz recovered 600 ms after turning off a dim (0.00158 sc td) field, paralleling the recovery found for detections. However, flickers at 8 and 10 Hz did not recover after turning off the field, but needed intensification to become visible. In this respect the rod pathway parallels the cone pathway, as cone-mediated luminance flickers also recover at lower Hz but rise at higher Hz (Reeves & Wu, Vis. Res., 2004). We had named this effect 'transient lumanopia' as it is reminiscent of transient tritanopia in the yellow-blue pathway and its analogues in the red-green pathway. Current data show that transient lumanopia is a property of the entire luminance pathway, not just of the photopic branch, and add to the remarkable series of phenomena in which visual sensitivity decreases, not increases, in early dark adaptation.
Meeting abstract presented at VSS 2017