THE TIME-COURSE OF CHROMATIC FACILITATION BY LUMINANCE CONTOURS

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