Foveal

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

Retinal image shifts, but not eye movements per se, cause alternations in awareness during binocular rivalry

Abstract: Particularly promising studies on visual awareness exploit a generally used perceptual bistability phenomenon, "binocular rivalry"--in which the two eyes' images alternately dominate--because it can dissociate the visual input from the perceptual output. To successfully study awareness, it is crucial to know the extent to which eye movements alter the input. Although there is convincing evidence that perceptual alternations can occur without eye movements, the literature on their exact role is mixed. Moreover, recent work has demonstrated that eye movements, first, correlate positively with perceptual alternations in binocular rivalry, and second, often accompany covert attention shifts (that were previously thought to be purely mental). Here, we asked whether eye movements cause perceptual alternations, and if so, whether it is either the execution of the eye movement or the resulting retinal image change that causes the alternation. Subjects viewed repetitive line patterns, enabling a distinction of saccades that did produce foveal image changes from those that did not. Subjects reported binocular rivalry alternations. We found that, although a saccade is not essential to initiate percept changes, the foveal image change resulting from a (micro)saccade is a deciding factor for percept dominance. We conclude that the foveal image must change to have a saccade cause a change in awareness. This sheds new light on the interaction between spatial attention shifts and perceptual alternations.

Color cell groups in foveal striate cortex of the behaving macaque.

Abstract: Color-tuning curves were obtained for 218 cells in the foveal striate cortex of behaving macaques. Each cell was tested with its optimal spatial stimulus. Test colors (14 interference filters, 4 Wr...

Noninvasive imaging of human foveal capillary network using dual-conjugate adaptive optics.

Abstract: PURPOSE. To demonstrate noninvasive imaging of human foveal capillary networks with a high-resolution, wide-field, dual-conjugate adaptive optics (DCAO) imaging instrument. METHODS. The foveal capillary networks of five healthy subjects with no previous history of ocular or neurologic disease or surgery were imaged with a novel high-resolution, wide-field DCAO instrument. The foveal avascular zone (FAZ) in each image was defined using a manual procedure. An automated algorithm based on publicly available and custom-written software was used to identify vessels and extract morphologic FAZ and vessel parameters. Capillary densities were calculated in two annular regions of interest (ROIs) outside the FAZ (500 mu m and 750 mu m outer radius from the foveal center) and in the superior, inferior, temporal, and nasal quadrants within the two ROIs. RESULTS. Mean FAZ area was 0.302 +/- 0.100 mm(2), and mean capillary density (length/area) in the inner ROI was 38.0 +/- 4.0 mm(-1) and 36.4 +/- 4.0 mm(-1) in the outer ROI. The difference in ROI capillary density was not significant. There was no significant difference in quadrant capillary density within the two ROIs or between quadrants irrespective of ROI. CONCLUSIONS. The authors have demonstrated a technique for noninvasive imaging and semiautomated detection and analysis of foveal capillaries. In comparison with other studies, their method yielded lower capillary densities than histology but similar results to the current clinical gold standard, fluorescein angiography. The increased field of view of the DCAO instrument opens up new possibilities for high-resolution noninvasive clinical imaging of foveal capillaries. (Invest Ophthalmol Vis Sci. 2011;52:2649-2655) DOI:10.1167/iovs.10-6054 (Less)

Foveal anatomic associations with the secondary peak and the slope of the macular pigment spatial profile.

Abstract: PURPOSE To investigate the reproducibility of the macular pigment (MP) spatial profile by using heterochromatic flicker photometry (HFP) and to relate the MP spatial profile to foveal architecture. METHODS Sixteen healthy subjects (nine had the typical exponential MP spatial profile [group 1]; seven had a secondary peak MP spatial profile [group 2]) were recruited. The MP spatial profile was measured on three separate occasions. Six radiance measurements were obtained at each locus (0.25 degrees , 0.5 degrees , 1 degrees , and 1.75 degrees eccentricity; reference point, 7 degrees ). Foveal architecture was assessed by optical coherence tomography (OCT). RESULTS Subjects who had the typical decline profile, had this profile after averaging repeated measures (group 1). Subjects who had a secondary peak, displayed the secondary peak after repeated measures were averaged (group 2). Mean SD foveal width in group 1 was significantly narrower than mean SD foveal width in group 2 (1306 +/- 240 microm and 1915 +/- 161 microm, respectively; P < 0.01). This difference remained after adjustment for sex (P < 0.001). Foveal width was significantly related to mean foveal MP, with adjustment for sex (r = 0.588, P = 0.021). Foveal profile slope was significantly related to MP spatial profile slope, after removal of an outlier (r = 0.591, P = 0.020). CONCLUSIONS HFP reproducibly measures MP spatial profile. Secondary peaks seen in the MP spatial profile cannot be attributed to measurement error and are associated with wider foveas. The slope of an individual's MP spatial profile is related to foveal slope, with a steeper MP distribution associated with a steeper foveal depression.