A brief light reduction induces a significant delay in the previously dimmed eye.

Purpose: We investigated how a short-term luminance reduction in one eye can influence temporal processing of that eye after luminance is restored by measuring the relative delay between the eyes.

Methods: A paradigm based on the Pulfrich effect, which is a visual illusion of depth when no depth cue is present, was used to measure relative delay in visual processing between the eyes. We deprived the monocular luminance in adults with normal vision across different intensities. In the first experiment, the ratio of the light level between the eyes stayed constant, whereas the absolute value was allowed to vary. In the second experiment, both the ratio and the absolute light level stayed constant, by controlling the environmental light level. In both experiments, we measured the changes in relative delay before and after 60 min of light deprivation.

Results: Our results indicated that short-term monocular deprivation of luminance slows the processing in the previously dimmed eye and that the magnitude of the delay is correlated with the degree of luminance reduction. In addition, we observed that the absolute luminance difference, rather than the absolute luminance levels seen by the dimmed eye, is important in determining the magnitude of delay in the previously dimmed eye. These findings differ from what has been reported previously for the monocular deprivation of contrast.

Conclusions: Taken together, these findings support the view that short-term deprivation of visual information could affect two distinct mechanisms (contrast gain and temporal dynamics) of neural plasticity.