Foveal

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

Functional Division of the Visual Field: Moving Masks and Moving Windows

Abstract: Publisher Summary The human eyes do not have the same resolution and sensitivity at every position of the retina. Fine details can only be discriminated efficiently by the fovea (the central part of the retina). At higher eccentricities, perceptual acuity decreases rapidly, and only coarse-grained information can be resolved. Consequently, peripheral vision is not particularly suited for object identification or word recognition, as these processes rely on detailed image analyses. Eye movements, or saccades, are required to project image areas onto the fovea. Saccades are not made to random image locations. Most fixations occur on interesting parts of the stimulus, such as words in a text or objects in a scene. Extrafoveal information can be used successfully to guide saccades to informative stimulus locations. By disentangling foveal and peripheral vision the concepts of moving mask and moving window are studied. Coarse peripheral information is preferred to obtain global image characteristics, while object localization gets benefited most from a high resolution peripheral image.

Contrast thresholds for letter identification in retinitis pigmentosa.

Abstract: To assess mechanisms of foveal vision loss in retinitis pigmentosa (RP), contrast thresholds were measured for the identification of Sloan letters at four adapting field luminances (0.4, 1.4, 2.4, and 3.4 log td) in a group of 16 patients with RP who had best-corrected Snellen visual acuities of 20/30 or better, minimal or no posterior subcapsular cataracts, and no atrophic or cystic-appearing foveal lesions. Letter contrast sensitivities of the patients with RP were reduced below those of a group of ten subjects with normal vision for all letter sizes and at all adapting field luminances. The overall pattern of these results indicated that neither a reduced quantal absorption by foveal cones nor spatial undersampling from a loss of foveal cones accounted for the reductions in letter contrast sensitivities. The findings were most consistent with a uniform increase in intercone spacing in the foveas of this group of patients with RP and mild visual acuity loss.

Parafoveal Previews and Lexical Frequency in Natural Reading: Evidence from Eye Movements and Fixation-Related Potentials

Abstract: Participants' eye movements and electroencephalogram (EEG) signal were recorded as they read sentences displayed according to the gaze-contingent boundary paradigm. Two target words in each sentence were manipulated for lexical frequency (high vs. low frequency) and parafoveal preview of each target word (identical vs. string of random letters vs. string of Xs). Eye movement data revealed visual parafoveal-on-foveal (PoF) effects, as well as foveal visual and orthographic preview effects and word frequency effects. Fixation-related potentials (FRPs) showed visual and orthographic PoF effects as well as foveal visual and orthographic preview effects. Our results replicated the early preview positivity effect (Dimigen, Kliegl, & Sommer, 2012) in the X-string preview condition, and revealed different neural correlates associated with a preview comprised of a string of random letters relative to a string of Xs. The former effects seem likely to reflect difficulty associated with the integration of parafoveal and foveal information, as well as feature overlap, while the latter reflect inhibition, and potentially disruption, to processing underlying reading. Interestingly, and consistent with Kretzschmar, Schlesewsky, and Staub (2015), no frequency effect was reflected in the FRP measures. The findings provide insight into the neural correlates of parafoveal processing and written word recognition in reading and demonstrate the value of utilizing ecologically valid paradigms to study well established phenomena that occur as text is read naturally. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Effect of stimulus size, duration, and retinal location upon the appearance of color.

Abstract: The names given to spectral stimuli from 480 to 610 mμ and to a white-light test stimulus were obtained using 11′ or 21′ diam stimulus fields, exposed for 20 msec in the fovea and for 20 and 200 msec at 5° and 10° in the periphery The experiment was designed to test the hypothesis that normal color vision is replaced by tritanopic vision in all parts of the retina if the total luminous energy is sufficiently reduced The results obtained with four observers confirm the presence of tritanopia when small brief stimuli are viewed foveally but fail to confirm it in the periphery Rather, reduced color vision in the periphery is more nearly characteristic of deuteranomaly which ends ultimately in colorless vision These results are discussed as giving support to the notion that foveal tritanopia is due to the depressed sensitivity of the blue receptor mechanism found in the central fovea