Our objective is to find precise measures of how color and pattern information are jointly processed in the human visual system. A major study examines the detection mechanisms fed by long (L) and medium (M) wave cones. The combinations of cone inputs comprising luminance and chromatic (red-green) mechanisms for coarse patterns have been shown to depend on adapting color: we intend to qualify this. We will also make an accurate measure of the sensitivity of these mechansms to stimulus temporal frequency. Studies at higher spatial frequency (approximately 4 c/degrees) will determine whether such patterns are processed by mechanisms combining luminance and chromaticity. Existing data are contradictory. The second major study examines detection mechanisms fed by short wave (S) cones in opposition to L and M. This blue-yellow system has clearly identified, post-cone adaptation. However, data on the effects of yellow luminance pedestals on chromatic sensitivity conflict. We will extend such studies for a full range of positive and negative pedestals using also a full range of test chromatic and luminance combinations so as to portray completely the responses of this opponent system. As in the L-M system, the effects of stimulus spatial and temporal frequencies are likely to be important. To permit such tests we have developed specialized apparatus which delivers any desired positive and negative stimulus increments for the M vs. L cones or S vs. M+L cones. Complete test threshold detection contours are measured for these paired variables, providing a powerful method of data interpretation. Stimuli can have various patterns, spatially (spots, sine gratings) and temporally (flashes, sinusoidal flicker), on different chromatic adapting fields. Tests are computer-controlled in a forced-choice staircase paradigm. The long term objective is to provide precise noninvasive diagnoses of visual system dysfunction. The vocabulary of visual stimuli is complex and consequently the diagnostic distinctions are potentially very subtle. Contemporary electrophysiological studies employ the same visual stimuli as do psychophysical studies, and there is a good probability of drawing close correspondences between anatomical sites and specific visual discriminations.
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