Spatial summation of peripheral Gabor patches.

Previous studies have specified the foveal pattern that is seen most efficiently, with the assumption that the waveform of the best pattern matches the impulse response of the most sensitive visual filter. We measured the threshold contrast for circular, collinear, and orthogonal Gabor stimuli of 6 Hz temporal frequency presented 7 deg above the fixation point. We found that the threshold contrast energy is minimal for a class of stimuli whose Fourier-spectra bandwidth is less than approximately 1 octave. These findings suggest that an energy algorithm might underlie spatial summation of peripheral Gabor patches. The different behavior of spatial summation in fovea and periphery might reflect the differences in pattern detectability across space in the central and peripheral visual fields. It is also possible that a coherent (cross-correlation) algorithm is employed in detection of foveal stimuli and that an incoherent (energy) algorithm is employed in detection of peripheral stimuli.