Foveal

About: Foveal is a research topic. Over the lifetime, 2652 publications have been published within this topic receiving 94120 citations.

Feature integration in pattern perception.

Abstract: The human visual system is able to effortlessly integrate local features to form our rich perception of patterns, despite the fact that visual information is discretely sampled by the retina and cortex. By using a novel perturbation technique, we show that the mechanisms by which features are integrated into coherent percepts are scale-invariant and nonlinear (phase and contrast polarity independent). They appear to operate by assigning position labels or “place tags” to each feature. Specifically, in the first series of experiments, we show that the positional tolerance of these place tags in foveal, and peripheral vision is about half the separation of the features, suggesting that the neural mechanisms that bind features into forms are quite robust to topographical jitter. In the second series of experiment, we asked how many stimulus samples are required for pattern identification by human and ideal observers. In human foveal vision, only about half the features are needed for reliable pattern interpolation. In this regard, human vision is quite efficient (ratio of ideal to real ≈ 0.75). Peripheral vision, on the other hand is rather inefficient, requiring more features, suggesting that the stimulus may be relatively underrepresented at the stage of feature integration.

Rapid communication Foveal and peripheral thresholds for detection and resolution of vanishing optotype tumbling E's

Abstract: We measured detection and resolution acuity for vanishing optotype tumbling E stimuli in both the fovea and at 30° in the periphery to determine if peripheral resolution is sampling limited for this stimulus. In the fovea, where acuity is optically limited, detection and resolution were the same. At 30°, however, detection was markedly better than resolution indicating that peripheral resolution is sampling limited for this stimulus. Detection acuity was higher when contrast was 90% rather than 40%, but resolution did not change with contrast. The vanishing optotype is a legitimate perimetric stimulus to measure retinal ganglion cell density provided the task is resolution and not detection. © 1999 Elsevier Science Ltd. All rights reserved.

Visual Development and Amblyopia

Abstract: At birth, visual acuity is poor, in the range of hand motions to count fingers. For the most part, this is due to immaturity of visual centers in the brain responsible for vision processing. Visual acuity rapidly improves during the first few months of life as clear in-focus retinal images stimulate neurodevelopment of visual centers, including the lateral geniculate nucleus and striate cortex.52 Dropout and growth of neuronal connections give rise to the organizational refinement and establish high-resolution receptive fields corresponding to the central foveal area.18,23 Normal visual development requires appropriate visual stimulation, including clear retinal images, with equal image clarity in both eyes (Table 10-1).