The time-course of chromatic facilitation by luminance contours.

The threshold for detecting an equiluminant chromatic spot is approximately halved by the presentation of a coincident, suprathreshold luminance pedestal flash. The dynamics of this facilitation were studied by varying the duration and temporal asynchrony of the chromatic test flash and luminance pedestal. Facilitation occurs in a narrow temporal window near the chromatic test presentation; masking may occur when the pedestal is temporally displaced from the test by longer times. The mechanism producing facilitation lags behind the chromatic signal by at least 20 msec.