Melanopsin Stimulation Modulates Blackness Induction

ABSTRACT A central field will become darker with increasing intensity of a surrounding annulus until it appears uniformly black. We investigated the relation between blackness induction of a central field and the stimulation of melanopsin cells in a surrounding field. Silent substitution was used to selectively modulate melanopsin cells while the tristimulus values were kept constant (melanopic/photopic ratio = 0.51–1.21). Eight participants judged the perceived blackness of the center field using a pairwise comparison method for all visual stimulus combinations. Stimuli were presented monocularly for 0.5 or 5 s with 2‐s inter‐stimulus intervals. Statistical analysis was performed using Scheffé's pairwise comparison method (Nakaya variation). The results showed that perceived blackness of the center decreased significantly under the 5‐s presentation condition with increasing stimulation of melanopsin cells in the surround, although perceived blackness of the center increased with increasing luminance in the surround. In contrast, under the 0.5‐s presentation condition, no significant difference in perceived blackness of the center with stimulus intensity to melanopsin cells was found. These results demonstrate that the stimulation of melanopsin cells of the surround modulates blackness induction of the center at longer stimulus durations.