SPECTRAL MECHANISMS OF SPATIALLY INDUCED BLACKNESS - DATA AND QUANTITATIVE MODEL

Spectral efficiency functions and tests of additivity were obtained wi th three observers to identify possible chromatic contributions to spa tially induced blackness. Stimuli consisted of a series of monochromat ic (400-700 nm; 10-nm steps), 52-arcmin circular test lights surrounde d by broadband (x = 0.31, y = 0.37), 63-138-arcmin annuli of fixed ret inal illuminance. The stimuli were imaged on the fovea in Maxwellian v iew as 500-ms flashes with 10-s interstimulus intervals. Observers dec reased the intensity of the test center until it was first perceived a s completely black. Action spectra determined for two surround levels [2.5 and 3.5 log trolands] had three sensitivity peaks (at approximate ly 440, 540, and 600 nm). However, when monochromatic surrounds were a djusted to induce blackness in a broadband center, action spectra were unimodal and identical to functions obtained by heterochromatic flick er photometry. when blackness is induced by a broadband surround into a bichromatic center, there is an additivity failure of the cancellati on type. This additivity failure indicates that blackness induction is influenced, in part, by signals from opponent-chromatic pathways. A q uantitative model is presented to account for these data. model assume s that blackness induction is determined by the ratio of responses to the stimulus center and the annulus, and while signals from the annulu s are based only on achromatic information, responses from the center are based on both chromatic and achromatic properties of the stimulus. (C) 1997 Optical Society of America [S0740-3232(97)00302-5]