Peripheral vision is mainly for looking rather than seeing

Identification of Distinct Visual Scan Paths for Pathologists in Rare-Element Search Tasks

BackgroundThe search for rare elements, like mitotic figures, is crucial in pathology. Combining digital pathology with eye-tracking technology allows for the detailed study of how pathologists complete these important tasks.ObjectivesTo determine if pathologists have distinct search characteristics in domain- and nondomain-specific tasks.DesignSix pathologists and six graduate students were recruited as observers. Each observer was given five digital "Where's Waldo?" puzzles and asked to search for the Waldo character as a nondomain-specific task. Each pathologist was then given five images of a breast digital pathology slide to search for a single mitotic figure as a domain-specific task. The observers' eye gaze data were collected.ResultsPathologists' median fixation duration was 244 ms, compared to 300 ms for nonpathologists searching for Waldo (P < .001), and compared to 233 ms for pathologists searching for mitotic figures (P = .003). Pathologists' median fixation and saccade rates were 3.17/second and 2.77/second, respectively, compared to 2.61/second and 2.47/second for nonpathologists searching for Waldo (P < .001), and compared to 3.34/second and 3.09/second for pathologists searching for mitotic figures (P = .222 and P = .187, respectively). There was no significant difference between the two cohorts in their accuracy in identifying the target of their search.ConclusionsWhen searching for rare elements during a nondomain-specific search task, pathologists' search characteristics were fundamentally different compared to nonpathologists, indicating pathologists can rapidly classify the objects of their fixations without compromising accuracy. Further, pathologists' search characteristics were fundamentally different between a domain-specific and nondomain-specific rare-element search task.

Testing the top-down feedback in the central visual field using the reversed depth illusion

In a new framework to understand vision, an information bottleneck impoverishes visual input information downstream of the primary visual cortex along the visual pathway; to aid ongoing visual recognition given the bottleneck, feedback from downstream to upstream visual stages queries for additional information. According to the central-peripheral dichotomy theory, this feedback is primarily directed to the central, rather than the peripheral, visual field. Counterintuitively, this theory predicts illusions visible only in the peripheral visual field, which lacks the feedback query to veto the illusions arising from misleading and impoverished feedforward signals. A paradigmatic example is the predicted and confirmed reversed depth illusion in random-dot stereograms. This theory further predicts that disrupting the feedback renders this illusion visible in the central visual field. We test and confirm this prediction using visual backward masking to disrupt the feedback. This feedback privilege for the central visual field underpins visual understanding through analysis-by-synthesis.

Spatial properties of scintillating grid illusion through visual experiments and numerical simulations

This study investigated the spatial properties of the scintillating grid illusion through three visual experiments and numerical simulations using differential equations. Experiment 1 was conducted to confirm that the scintillating grid illusion occurred in the peripheral vision under binocular viewing. The results showed that illusory blackness was perceived on the white disk at the horizontal viewing angles of ±6.0, ±9.0, and ±12.0 degrees stronger than ±0.6 and ±3.0 degrees. Experiment 2 investigated the area where the scintillating grid illusion occurred not only in the horizontal orientation but also in the vertical orientation. The results showed that the area of the scintillating grid illusion was farther from the fixation point in the horizontal orientation than in the vertical orientation under binocular viewing. Experiment 3 examined the spatial properties of the scintillating grid illusion under monocular viewing, revealing that the area of the scintillating grid illusion was wider in the horizontal orientation than in the vertical orientation. These results suggest that the scintillating grid illusion has spatial anisotropy, regardless of binocular or monocular viewing. Based on the findings in the visual experiments and electrophysiology, this study improved a mathematical model using differential equations for retinal information processing. The improved model demonstrated the results of numerical simulations similar to the spatial properties of the scintillating grid illusion under experimental results. The numerical simulations suggested that the blurring and inhibitory effects could be involved in the spatial properties of the scintillating grid illusion.

Spatial comparison of disappearance and scintillation phenomena using a single-unit scintillating grid illusion

The scintillating grid illusion induces the phenomena of disappearance and scintillation. However, it is unclear in which peripheral region these phenomena occur. This study aimed to investigate the spatial properties of disappearance and scintillation phenomena in the scintillating grid illusion. In Experiment 1, participants binocularly observed a single-unit scintillating grid illusion and responded whether a white disk and illusory blackness were perceived. As a result, the perceptual region of the white disk was larger in the horizontal direction than in the vertical direction, as well as the perceptual region of the illusory blackness. This result indicates that both perceptual regions have spatial anisotropy. In Experiment 2, the same task as in Experiment 1 was performed with monocular viewing. The results did not exactly reject spatial anisotropy in monocular vision, regardless of the perceptual regions. This study may contribute to understanding how disappearance and scintillation phenomena coexist in the scintillating grid illusion.

Trans-saccadic integration for object recognition peters out with pre-saccadic object eccentricity as target-directed saccades become more saliency-driven

Bringing objects from peripheral locations to fovea via saccades facilitates their recognition. Human observers integrate pre- and post-saccadic information for recognition. This integration has only been investigated using instructed saccades to prescribed locations. Typically, the target has a fixed pre-saccadic location in an uncluttered scene and is viewed by a pre-determined post-saccadic duration. Consequently, whether trans-saccadic integration is limited or absent when the pre-saccadic target eccentricity is too large in cluttered scenes in unknown. Our study revealed this limit during visual exploration, when observers decided themselves when and to where to make their saccades. We asked thirty observers (400 trials each) to find and report as quickly as possible a target amongst 404 non-targets in an image spanning 57.3°×33.8° in visual angle. We measured the target's pre-saccadic eccentricity e, the duration Tpre of the fixation before the saccade, and the post-saccadic foveal viewing duration Tpost. This Tpost increased with e before starting to saturate around eccentricity ep=10°-20°. Meanwhile, Tpre increased much more slowly with e and started decreasing before ep. These observations imply the following at sufficiently large pre-saccadic eccentricities: the trans-saccadic integration ceases, target recognition relies exclusively on post-saccadic foveal vision, decision to saccade to the target relies exclusively on target saliency rather than identification. These implications should be applicable to general behavior, although ep should depend on object and scene properties. They are consistent with the Central-peripheral Dichotomy that central and peripheral vision are specialized for seeing and looking, respectively.

Attention moderates the motion silencing effect for dynamic orientation changes in a discrimination task

Being able to detect changes in our visual environment reliably and quickly is important for many daily tasks. The motion silencing effect describes a decrease in the ability to detect feature changes for faster moving objects compared with stationary or slowly moving objects. One theory is that spatiotemporal receptive field properties in early vision might account for the silencing effect, suggesting that its origins are low-level visual processing. Here, we explore whether spatial attention can modulate motion silencing of orientation changes to gain greater understanding of the underlying mechanisms. In Experiment 1, we confirm that the motion silencing effect occurs for the discrimination of orientation changes. In Experiment 2, we use a Posner-style cueing paradigm to investigate whether manipulating covert attention modulates motion silencing for orientation. The results show a clear spatial cueing effect: Participants were able to discriminate orientation changes successfully at higher velocities when the cue was valid compared to neutral cues and performance was worst when the cue was invalid. These results show that motion silencing can be modulated by directing spatial attention toward a moving target and provides support for a role for higher level processes, such as attention, in motion silencing of orientation changes.

Neural manifolds in V1 change with top-down signals from V4 targeting the foveal region

High-dimensional brain activity is often organized into lower-dimensional neural manifolds. However, the neural manifolds of the visual cortex remain understudied. Here, we study large-scale multi-electrode electrophysiological recordings of macaque (Macaca mulatta) areas V1, V4, and DP with a high spatiotemporal resolution. We find that the population activity of V1 contains two separate neural manifolds, which correlate strongly with eye closure (eyes open/closed) and have distinct dimensionalities. Moreover, we find strong top-down signals from V4 to V1, particularly to the foveal region of V1, which are significantly stronger during the eyes-open periods. Finally, in silico simulations of a balanced spiking neuron network qualitatively reproduce the experimental findings. Taken together, our analyses and simulations suggest that top-down signals modulate the population activity of V1. We postulate that the top-down modulation during the eyes-open periods prepares V1 for fast and efficient visual responses, resulting in a type of visual stand-by state.

Looking with or without seeing in an individual with age-related macular degeneration impairing central vision

Looking leads gaze to objects; seeing recognizes them. Visual crowding makes seeing difficult or impossible before looking brings objects to the fovea. Looking before seeing can be guided by saliency mechanisms in the primary visual cortex (V1). We have proposed that looking and seeing are mainly supported by peripheral and central vision, respectively. This proposal is tested in an observer with central vision loss due to macular degeneration, using a visual search task that can be accomplished solely through looking, but is actually impeded through seeing. The search target is an uniquely oriented, salient, bar among identically shaped bars. Each bar, including the target, is part of an " " X " shape. The target's " X is identical to, although rotated from, the other " X 's in the image, which normally causes confusion. However, this observer exhibits no such confusion, presumably because she cannot see the " X 's shape, but can look towards the target. This result demonstrates a critical dichotomy between central and peripheral vision.