Spatial summation of peripheral Gabor patches

Previous studies have specified the foveal pattern that is seen most effici ently, with the assumption that the waveform of the bust pattern matches th e impulse response of the most sensitive visual filter. We measured the thr eshold contrast for circular, collinear, and orthogonal Gabor stimuli of 6 Hz temporal frequency presented 7 deg above the fixation point. We found th at the threshold contrast energy is minimal for a class of stimuli whose Fo urier-spectra bandwidth is less than similar to1 octave. These findings sug gest that an energy algorithm might underlie spatial summation of periphera l Gabor patches. The different behavior of spatial summation in fovea and p eriphery might reflect the differences in pattern detectability across spac e in the central and peripheral visual fields. It is also possible that a c oherent (cross-correlation! algorithm is employed in detection of foveal st imuli and that an incoherent (energy) algorithm is employed in detection of peripheral stimuli. (C) 2001 Optical Society of America OCIS codes: 330.73 10, 330.1880, 330.5000, 330.1800, 330.6110, 330.4060.