Importance of phase alignment for interocular suppression.
We measured contrast thresholds for Gabor targets in the presence of maskers which had higher or lower spatial frequencies than the targets. A high-pass fractal masker elevated target contrast thresholds at low and intermediate pedestal contrasts in both monocular and dichoptic modes of presentation, suggesting that the masking occurs after a monocular processing stage. Moreover we found that a high-pass checkerboard masker elevated thresholds at the low and intermediate pedestal contrasts and that most of this threshold elevation disappeared when the phase of the masker's spatial components were scrambled. This masking was effective only in the dichoptic presentation, not in the monocular presentation. These results indicate that phase alignment of the high spatial frequency components plays a crucial role for interocular suppression. We speculate that phase alignments signal the existence of a luminance contour in the monocular image and that this signal suppresses processing of information in the other eye when there is no corresponding signal in that eye.
Maehara
Goro
G
McGill Vision Research Unit, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada. goro.maehara@mail.mcgill.ca
Huang
Pi-Chun
PC
Hess
Robert F
RF
D015350:Contrast Sensitivity / Q000502:physiology*; D017709:Fractals; D006801:Humans; D008029:Lighting; D016013:Likelihood Functions; D010470:Perceptual Masking / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D012684:Sensory Thresholds / Q000502:physiology; D015357:Vision Disparity / Q000502:physiology