Temporal summation for grating patches detected at low light levels.

It is not known if temporal integration for periodic stimuli is affected by changes in scotopic luminance. Contrast thresholds were measured as a function of duration for 0.25 cpd grating patches across a 2.3 log-unit scotopic range. Threshold vs. duration (TVD) functions were identical in shape regardless of mean luminance once scaled by translating along log-log axes. Critical duration decreased 0.09 log-units per log-unit increase in retinal illuminance. This slope is identical to that reported for photopic conditions, suggesting that temporal integration may be determined by the same neural pathway at all light levels.