Topic
Contrast (vision)
About: Contrast (vision) is a research topic. Over the lifetime, 10379 publications have been published within this topic receiving 221480 citations.
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TL;DR: It is concluded that a single mechanism sensitive to both LM and CM cannot predict the pattern of results for mixtures, while a model containing separate pathways for LM andCM, followed by energy summation, does so successfully and is quantitatively consistent with the finding of order-specific facilitation.
142 citations
TL;DR: Neuroimaging measurements reveal several differences among MM, sighted controls, Sighted monocular, and early blind subjects, and it is speculated that these differences stem from damage during the critical period in development of retinal neurons with small, foveal receptive fields.
142 citations
TL;DR: The results, reported here, show that the energy detection properties of both foveal and peripheral vision are comparable, however, independently of scale, peripheral vision ignores the relative position of image components.
Abstract: Objects in peripheral vision are not simply blurred but lack quality of form. Assuming that the visual system performs a (patchwise) Fourier analysis of the retinal image (for review see ref. 2), it has been suggested that this disadvantage of peripheral vision may be due to the inability to encode properly spatial phase relationships. This is of great interest for neurological research as certain visual pathologies imply alterations of perceived form. Previous attempts at measuring phase sensitivities failed to distinguish between the detection of phase-related changes in contrast and phase coding in the visual system. We separated these processing strategies by applying the iso-second-order texture paradigm of Julesz to the discrimination of compound gratings. Our results, reported here, show that the energy detection properties of both foveal and peripheral vision are comparable, however, independently of scale, peripheral vision ignores the relative position of image components.
141 citations
TL;DR: To investigate amblyopic contrast vision at threshold and above, pedestal-masking (contrast discrimination) experiments with a group of eight strabismic amblyopes using horizontal sinusoidal gratings in monocular, binocular and dichoptic configurations balanced across eye were performed.
140 citations
TL;DR: These results provide first insights into basic visual responses of the human SC and show the feasibility of studying subcortical structures using high-resolution fMRI.
Abstract: The superior colliculus (SC) is a multimodal laminar structure located on the roof of the brain stem. The SC is a key structure in a distributed network of areas that mediate saccadic eye movements and shifts of attention across the visual field and has been extensively studied in nonhuman primates. In humans, it has proven difficult to study the SC with functional MRI (fMRI) because of its small size, deep location, and proximity to pulsating vascular structures. Here, we performed a series of high-resolution fMRI studies at 3 T to investigate basic visual response properties of the SC. The retinotopic organization of the SC was determined using the traveling wave method with flickering checkerboard stimuli presented at different polar angles and eccentricities. SC activations were confined to stimulation of the contralateral hemifield. Although a detailed retinotopic map was not observed, across subjects, the upper and lower visual fields were represented medially and laterally, respectively. Responses were dominantly evoked by stimuli presented along the horizontal meridian of the visual field. We also measured the sensitivity of the SC to luminance contrast, which has not been previously reported in primates. SC responses were nearly saturated by low contrast stimuli and showed only small response modulation with higher contrast stimuli, indicating high sensitivity to stimulus contrast. Responsiveness to stimulus motion in the SC was shown by robust activations evoked by moving versus static dot stimuli that could not be attributed to eye movements. The responses to contrast and motion stimuli were compared with those in the human lateral geniculate nucleus. Our results provide first insights into basic visual responses of the human SC and show the feasibility of studying subcortical structures using high-resolution fMRI.
140 citations