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The primate superior colliculus (SC) has recently been shown to possess both a large foveal representation as well as a varied visual processing repertoire. This structure is also known to contribute to eye movement generation. Here, we describe our current understanding of how SC visual and movement-related signals interact within the realm of small eye movements associated with the foveal scale of visuomotor behavior. Within the SC's foveal representation, there is a full spectrum of visual, visual-motor, and motor-related discharge for fixational eye movements. Moreover, a substantial number of neurons only emit movement-related discharge when microsaccades are visually guided, but not when similar movements are generated toward a blank. This represents a particularly striking example of integrating vision and action at the foveal scale. Beyond that, SC visual responses themselves are strongly modulated, and in multiple ways, by the occurrence of small eye movements. Intriguingly, this impact can extend to eccentricities well beyond the fovea, causing both sensitivity enhancement and suppression in the periphery. Because of large foveal magnification of neural tissue, such long-range eccentricity effects are neurally warped into smaller differences in anatomical space, providing a structural means for linking peripheral and foveal visual modulations around fixational eye movements. Finally, even the retinal-image visual flows associated with tiny fixational eye movements are signaled fairly faithfully by peripheral SC neurons with relatively large receptive fields. These results demonstrate how studying active vision at the foveal scale represents an opportunity for understanding primate vision during natural behaviors involving ever-present foveating eye movements. NEW & NOTEWORTHY The primate superior colliculus (SC) is ideally suited for active vision at the foveal scale: it enables detailed foveal visual analysis by accurately driving small eye movements, and it also possesses a visual processing machinery that is sensitive to active eye movement behavior. Studying active vision at the foveal scale in the primate SC is informative for broader aspects of active perception, including the overt and covert processing of peripheral extra-foveal visual scene locations.

By attending to part of a visual scene, we can prioritize processing of the most relevant visual information and so use our limited resources effectively. Previous functional magnetic resonance imaging (fMRI) work has shown that attention can increase overall blood-oxygen-level-dependent (BOLD) signal responsiveness but also enhances the stimulus information in terms of classifier performance. Here, we investigate how these effects vary across the visual field. We compare attention-enhanced fMRI-BOLD amplitude responses and classifier accuracy in fovea and surrounding stimulus regions using a set of four simple stimuli subdivided into a foveal region (1.4° diameter) and a surround region (15° diameter). We found dissociations between the effects of attention on average response and in enhancing stimulus information. In early visual cortex, we found that attention increased the amplitude of responses to both foveal and surround parts of the stimuli and increased classifier performance only for the surround stimulus. Conversely, ventral visual areas showed less change in average response but greater changes in decoding. Unlike for early visual cortex, in the ventral visual cortex attention produced similar changes in decoding for center and surround stimuli.

Visual processing varies dramatically across the visual field. These differences start in the retina and continue all the way to the visual cortex. Despite these differences in processing, the perceptual experience of humans is remarkably stable and continuous across the visual field. Research in the last decade has shown that processing in peripheral and foveal vision is not independent, but is more directly connected than previously thought. We address three core questions on how peripheral and foveal vision interact, and review recent findings on potentially related phenomena that could provide answers to these questions. First, how is the processing of peripheral and foveal signals related during fixation? Peripheral signals seem to be processed in foveal retinotopic areas to facilitate peripheral object recognition, and foveal information seems to be extrapolated toward the periphery to generate a homogeneous representation of the environment. Second, how are peripheral and foveal signals re-calibrated? Transsaccadic changes in object features lead to a reduction in the discrepancy between peripheral and foveal appearance. Third, how is peripheral and foveal information stitched together across saccades? Peripheral and foveal signals are integrated across saccadic eye movements to average percepts and to reduce uncertainty. Together, these findings illustrate that peripheral and foveal processing are closely connected, mastering the compromise between a large peripheral visual field and high resolution at the fovea.

Scarce previous data on how the location where an emotional stimulus appears in the visual scene modulates its perception suggest that, for functional reasons, a perceptual advantage may exist, vertically, for stimuli presented at the lower visual field (LoVF) and, horizontally, for stimuli presented at the left visual field (LeVF). However, this issue has been explored through a limited number of spatial locations, usually in a single spatial dimension (e.g., horizontal) and invariant eccentricities. Event-related potentials (ERPs) were recorded from 39 participants perceiving brief neutral (wheels) and emotional stimuli (spiders) presented at 17 different locations, one foveal and 16 at different peripheral coordinates. As a secondary scope, we explored the role of the magnocellular (M) and the parvocellular (P) visual pathways by presenting an isoluminant/heterochromatic (P-biased) and a heteroluminant/isochromatic version (M-biased) of each stimulus. Emo > Neu effects were observed in PN1 (120 ms) for stimuli located at fovea, and in PN2 (215 ms) for stimuli located both at fovea and diverse peripheral regions. A factorial approach to these effects further revealed that: (a) emotional stimuli presented in the periphery are efficiently perceived, without evident decrease from para- to perifovea; (b) peripheral Emo > Neu effects are reflected 95 ms later than foveal Emo > Neu effects in ERPs; (c) LoVF is more involved than UVF in these effects; (d) our data fail to support the LeVF advantage previously reported, and (e) Emo > Neu effects were significant for both M and P stimuli., (© 2019 The Authors. Human Brain Mapping published by Wiley Periodicals, Inc.)

Object perception across saccadic eye movements is assumed to result from integrating two information sources: incoming peripheral object information and information from a foveal prediction (Herwig and Schneider, J Exp Psychol Gen 143(5):1903-1922, 2014, Herwig, J Vis 15(16), 7, 2015). Predictions are supposed to be based on transsaccadic associations of peripheral and foveal object information. The main function of these predictions may be to conceal discrepancies in resolution and locations across saccades. Here we ask how predictions are affected by discrepancies between peripheral and foveal objects. Participants learned unfamiliar transsaccadic associations by making saccades to objects whose shape systematically changed during the saccade. Importantly, we manipulated the size of this change between participants to induce different magnitudes of object discrepancy. In a subsequent test, we found that judgment shifts of peripheral shape perception toward the predicted foveal input depended on change size during acquisition. Specifically, the contribution of prediction decreased for large changes but did not reach zero, showing that even for large changes (i.e., square to circle or vice versa) the prediction was not ignored completely. These findings indicate that object discrepancy during learning determines how much the resulting foveal prediction contributes to perception in the periphery.

Rigorous behavioral studies made in human subjects have shown that small-eccentricity target displacements are associated with increased saccadic reaction times, but the reasons for this remain unclear. Before characterizing the neurophysiological foundations underlying this relationship between the spatial and temporal aspects of saccades, we tested the triggering of small saccades in the male rhesus macaque monkey. We also compared our results to those obtained in human subjects, both from the existing literature and through our own additional measurements. Using a variety of behavioral tasks exercising visual and nonvisual guidance of small saccades, we found that small saccades consistently require more time than larger saccades to be triggered in the nonhuman primate, even in the absence of any visual guidance and when valid advance information about the saccade landing position is available. We also found a strong asymmetry in the reaction times of small upper versus lower visual field visually guided saccades, a phenomenon that has not been described before for small saccades, even in humans. Following the suggestion that an eye movement is not initiated as long as the visuo-oculomotor system is within a state of balance, in which opposing commands counterbalance each other, we propose that the longer reaction times are a signature of enhanced times needed to create the symmetry-breaking condition that puts downstream premotor neurons into a push-pull regime necessary for rotating the eyeballs. Our results provide an important catalog of nonhuman primate oculomotor capabilities on the miniature scale, allowing concrete predictions on underlying neurophysiological mechanisms. NEW & NOTEWORTHY Leveraging a multitude of neurophysiological investigations in the rhesus macaque monkey, we generated and tested hypotheses about small-saccade latencies in this animal model. We found that small saccades always take longer, on average, than larger saccades to trigger, regardless of visual and cognitive context. Moreover, small downward saccades have the longest latencies overall. Our results provide an important documentation of oculomotor capabilities of an indispensable animal model for neuroscientific research in vision, cognition, and action.

What we see is influenced by where we look. When confronted with multiple relevant targets, inaccurate saccade target selection can impair perceptual performance. Here we ask whether endpoint selection can be optimized by the mechanism maintaining saccade accuracy: saccade adaptation. Therefore, we introduce a double-target adaptation task, where a presaccadic peripheral stimulus (plaid) splits vertically into its two components (Gabor patches) during horizontal saccades. While both targets were task-relevant, one of them provided more information for the perceptual task, because it could only be identified after the saccade with near-foveal vision. The other target was highly salient and could also be identified in the presaccadic plaid using peripheral vision. This double-target paradigm induced saccade adaptation: Without a perceptual task, participants adapted to the salient target. When both targets were judged sequentially, participants mostly adapted to the target they had to judge first. When targets were judged simultaneously, endpoints were biased toward the informative target but showed no gradual learning and fell short of optimality. We observed gradual adaptation when targets shifted randomly such that a strategic adjustment of endpoints was not possible. Overall, these findings show that when multiple targets compete, our oculomotor system can learn to adjust endpoints in order to maximize information for perception. Yet individual variability and other factors affecting target priority play a crucial role.

A defining feature of the primate visual system is its foveated nature. Processing of foveal retinal input is important not only for high-quality visual scene analysis but also for ensuring precise, albeit tiny, gaze shifts during high-acuity visual tasks. The representations of foveal retinal input in the primate lateral geniculate nucleus and early visual cortices have been characterized. However, how such representations translate into precise eye movements remains unclear. Here, we document functional and structural properties of the foveal visual representation of the midbrain superior colliculus. We show that the superior colliculus, classically associated with extra-foveal spatial representations needed for gaze shifts, is highly sensitive to visual input impinging on the fovea. The superior colliculus also represents such input in an orderly and very specific manner, and it magnifies the representation of foveal images in neural tissue as much as the primary visual cortex does. The primate superior colliculus contains a high-fidelity visual representation, with large foveal magnification, perfectly suited for active visuomotor control and perception., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Humans use saccades to inspect objects of interest with the foveola, the small region of the retina with highest acuity. This process of visual exploration is normally studied over large scenes. However, in everyday tasks, the stimulus within the foveola is complex, and the need for visual exploration may extend to this smaller scale. We have previously shown that fixational eye movements, in particular microsaccades, play an important role in fine spatial vision. Here, we investigate whether task-driven visual exploration occurs during the fixation pauses in between large saccades. Observers judged the expression of faces covering approximately 1°, as if viewed from a distance of many meters. We use a custom system for accurately localizing the line of sight and continually track gaze position at high resolution. Our findings reveal that active spatial exploration, a process driven by the goals of the task, takes place at the foveal scale. The scanning strategies used at this scale resemble those used when examining larger scenes, with idiosyncrasies maintained across spatial scales. These findings suggest that the visual system possesses not only a coarser priority map of the extrafoveal space to guide saccades, but also a finer-grained priority map that is used to guide microsaccades once the region of interest is foveated., Competing Interests: The authors declare no conflict of interest., (Copyright © 2019 the Author(s). Published by PNAS.)

Saccades constitute a major source of artifacts and confounds in brain imaging studies. Whereas some artifacts can be removed by omitting segments of data, saccadic artifacts cannot be typically eliminated by this method because of their high occurrence rate even during fixation (1-3 per second). Some saccadic artifacts can be alleviated by offline-correction algorithms, but these methods leave nonnegligible residuals and cannot mitigate the saccade-related visual activity. Here, we propose a novel yet simple approach for diminishing saccadic artifacts and confounds through experimental design. We suggest that specific tasks can lead to substantially less saccade occurrences around the time of stimulus presentation, starting from slightly before its onset and lasting for a few hundred milliseconds. In three experiments, we compared the frequency and size of saccades in a variety of tasks. Results of Experiment 1 showed that a foveal change-detection task reduced the number and sizes of saccades, relative to a parafoveal orientation-discrimination task. Experiment 2 replicated this finding with a parafoveal object recognition task. Experiment 3 showed that both foveal and parafoveal continuous change detection tasks induced fewer and smaller saccades than a discrete orientation-discrimination task. We conclude that adding a foveal or a parafoveal continuous task reduces saccades' number and size. This would lead to better artifact correction and enable the omission of contaminated data segments. This study may be the first step toward developing saccade-free experimental designs., (© 2018 Society for Psychophysiological Research.)

The brain can only attend to a fraction of all the information that is entering the visual system at any given moment. One way of overcoming the so-called bottleneck of selective attention (e.g., J. M. Wolfe, Võ, Evans, & Greene, 2011) is to make use of redundant visual information and extract summarized statistical information of the whole visual scene. Such ensemble representation occurs for low-level features of textures or simple objects, but it has also been reported for complex high-level properties. While the visual system has, for example, been shown to compute summary representations of facial expression, gender, or identity, it is less clear whether perceptual input from all parts of the visual field contributes equally to the ensemble percept. Here we extend the line of ensemble-representation research into the realm of race and look at the possibility that ensemble perception relies on weighting visual information differently depending on its origin from either the fovea or the visual periphery. We find that observers can judge the mean race of a set of faces, similar to judgments of mean emotion from faces and ensemble representations in low-level domains of visual processing. We also find that while peripheral faces seem to be taken into account for the ensemble percept, far more weight is given to stimuli presented foveally than peripherally. Whether this precision weighting of information stems from differences in the accuracy with which the visual system processes information across the visual field or from statistical inferences about the world needs to be determined by further research.

Humans achieve a stable and homogeneous representation of their visual environment, although visual processing varies across the visual field. Here we investigated the circumstances under which peripheral and foveal information is integrated for numerosity estimation across saccades. We asked our participants to judge the number of black and white dots on a screen. Information was presented either in the periphery before a saccade, in the fovea after a saccade, or in both areas consecutively to measure transsaccadic integration. In contrast to previous findings, we found an underestimation of numerosity for foveal presentation and an overestimation for peripheral presentation. We used a maximum-likelihood model to predict accuracy and reliability in the transsaccadic condition based on peripheral and foveal values. We found near-optimal integration of peripheral and foveal information, consistently with previous findings about orientation integration. In three consecutive experiments, we disrupted object continuity between the peripheral and foveal presentations to probe the limits of transsaccadic integration. Even for global changes on our numerosity stimuli, no influence of object discontinuity was observed. Overall, our results suggest that transsaccadic integration is a robust mechanism that also works for complex visual features such as numerosity and is operative despite internal or external mismatches between foveal and peripheral information. Transsaccadic integration facilitates an accurate and reliable perception of our environment.

Efficient control of attentional resources and high-acuity vision are both fundamental for survival. Shifts in visual attention are known to covertly enhance processing at locations away from the center of gaze, where visual resolution is low. It is unknown, however, whether selective spatial attention operates where the observer is already looking-that is, within the high-acuity foveola, the small yet disproportionally important rod-free region of the retina. Using new methods for precisely controlling retinal stimulation, here we show that covert attention flexibly improves and speeds up both detection and discrimination at loci only a fraction of a degree apart within the foveola. These findings reveal a surprisingly precise control of attention and its involvement in fine spatial vision. They show that the commonly studied covert shifts of attention away from the fovea are the expression of a global mechanism that exerts its action across the entire visual field.

Our visual environment is full of texture-"stuff" like cloth, bark, or gravel as distinct from "things" like dresses, trees, or paths-and humans are adept at perceiving subtle variations in material properties. To investigate image features important for texture perception, we psychophysically compare a recent parametric model of texture appearance (convolutional neural network [CNN] model) that uses the features encoded by a deep CNN (VGG-19) with two other models: the venerable Portilla and Simoncelli model and an extension of the CNN model in which the power spectrum is additionally matched. Observers discriminated model-generated textures from original natural textures in a spatial three-alternative oddity paradigm under two viewing conditions: when test patches were briefly presented to the near-periphery ("parafoveal") and when observers were able to make eye movements to all three patches ("inspection"). Under parafoveal viewing, observers were unable to discriminate 10 of 12 original images from CNN model images, and remarkably, the simpler Portilla and Simoncelli model performed slightly better than the CNN model (11 textures). Under foveal inspection, matching CNN features captured appearance substantially better than the Portilla and Simoncelli model (nine compared to four textures), and including the power spectrum improved appearance matching for two of the three remaining textures. None of the models we test here could produce indiscriminable images for one of the 12 textures under the inspection condition. While deep CNN (VGG-19) features can often be used to synthesize textures that humans cannot discriminate from natural textures, there is currently no uniformly best model for all textures and viewing conditions.

The blur experienced by our visual system is not uniform across the visual field. Additionally, lens designs with variable power profile such as contact lenses used in presbyopia correction and to control myopia progression create variable blur from the fovea to the periphery. The perceptual changes associated with varying blur profile across the visual field are unclear. We therefore measured the perceived neutral focus with images of different angular subtense (from 4° to 20°) and found that the amount of blur, for which focus is perceived as neutral, increases when the stimulus was extended to cover the parafovea. We also studied the changes in central perceived neutral focus after adaptation to images with similar magnitude of optical blur across the image or varying blur from center to the periphery. Altering the blur in the periphery had little or no effect on the shift of perceived neutral focus following adaptation to normal/blurred central images. These perceptual outcomes should be considered while designing bifocal optical solutions for myopia or presbyopia., (Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Peripheral viewing is characterized by poor resolution and distortions as compared to central viewing; nevertheless, when we move our gaze around, the visual scene does not appear to change. One possible mechanism leading to perceptual uniformity would be that peripheral appearance is extrapolated based on foveal information. Here we investigate foveal-to-peripheral extrapolation in the case of the perceived brightness of an object's surface. While fixating a spot on the rendered object, observers were asked to adjust the brightness of a disc to match a peripherally viewed target area on the surface of the same object. Being forced to fixate a better illuminated point led to brighter matches as compared to fixating points in the shadow, indicating that foveal brightness information was extrapolated. When observers fixated additional points outside of the object on the scene's background, fixated brightness had no effect on the brightness match. Results indicate that our visual system uses the brightness of the foveally viewed surface area to estimate the brightness of areas in the periphery. However, this mechanism is selectively applied within an object's boundary.

Understanding software engineers' behaviour plays a vital role in the software development industry. It also provides helpful guidelines for teaching and learning. In this article, we conduct a study of the extrafoveal vision and its role in information processing. This is a new perspective on source code comprehension. Despite its major importance, the extrafoveal vision has been largely ignored by previous studies. The available research has been focused entirely on the foveal information processing and the gaze fixation position. In this work, we share the results of a gaze-contingent study of source code comprehension by expert ( N = 12) and novice ( N = 12) programmers in conditions of the restricted extrafoveal vision. The window-moving paradigm was employed to restrict the extrafoveal area of vision as participants comprehend two source code examples. The results indicate that the semantic preview allowed by the extrafoveal vision provides tangible benefits to expert programmers. When the experts could not use the semantic information from the extrafoveal area, their fixation duration increased to duration similar to novices. The experts' performance dropped in the restricted-view mode, and they required more time to solve the tasks.

The estimation of gaze shift has been an important research area in saliency modeling. Gaze movement is a dynamic progress, yet existing estimation methods are limited to estimating scanpaths within only one saliency map, providing results with unsatisfactory accuracy. A bio-inspired method for gaze shift prediction is thus proposed. We take the effect of foveation into account in the proposed model, which plays an important role in the search for dynamic salient regions. The saccadic bias of gaze shifts and the mechanism of inhibition of return in short-term memory are also considered. Based on the probability map derived from these factors, candidates for the next fixation can be randomly generated, and the final scanpath can be acquired point by point. By the evaluation of objective measures, experimental results show that this method possesses better performance in several datasets than many existing models do.

The fovea is a specialized region of the retina that dominates the visual perception of primates by providing high chromatic and spatial acuity. While the foveal and peripheral retina share a similar core circuit architecture, they exhibit profound functional differences whose mechanisms are unknown. Using intracellular recordings and structure-function analyses, we examined the cellular and synaptic underpinnings of the primate fovea. Compared to peripheral vision, the fovea displays decreased sensitivity to rapid variations in light inputs; this difference is reflected in the responses of ganglion cells, the output cells of the retina. Surprisingly, and unlike in the periphery, synaptic inhibition minimally shaped the responses of foveal midget ganglion cells. This difference in inhibition cannot however, explain the differences in the temporal sensitivity of foveal and peripheral midget ganglion cells. Instead, foveal cone photoreceptors themselves exhibited slower light responses than peripheral cones, unexpectedly linking cone signals to perceptual sensitivity., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Vision in the fovea, the center of the visual field, is much more accurate and detailed than vision in the periphery. This is not in line with the rich phenomenology of peripheral vision. Here, we investigated a visual illusion that shows that detailed peripheral visual experience is partially based on a reconstruction of reality. Participants fixated on the center of a visual display in which central stimuli differed from peripheral stimuli. Over time, participants perceived that the peripheral stimuli changed to match the central stimuli, so that the display seemed uniform. We showed that a wide range of visual features, including shape, orientation, motion, luminance, pattern, and identity, are susceptible to this uniformity illusion. We argue that the uniformity illusion is the result of a reconstruction of sparse visual information (from the periphery) based on more readily available detailed visual information (from the fovea), which gives rise to a rich, but illusory, experience of peripheral vision.

Numerous previous studies have shown that healthy aging results in increased foveal center surround contrast suppression when the center and surround patterns are presented to both eyes. The mechanistic cause of this observation is not well established. Neurophysiological and psychophysical studies have shown that different mechanisms of parafoveal center surround suppression can be tapped by manipulating viewing conditions to present the center and surround to the same eye (intraocular viewing) or to different eyes (interocular viewing), or by manipulating stimulus parameters such as duration. Here, we tested intraocular and interocular foveal center surround contrast suppression for stimuli of 40 ms and 200 ms duration in 18 younger and 18 older adults. For both groups, foveal intraocular center surround contrast suppression decreased with longer stimulus duration whereas interocular surround suppression did not, confirming contributions from separate mechanisms to these forms of suppression. Intraocular center surround contrast suppression was increased in older adults compared to younger adults; however, interocular suppression was similar in both groups. Our results indicate that aging differentially affects distinct forms of suppression arising at various levels of the visual pathway.

A previous study by Williams et al. (2008) provided evidence for a novel form of feedback in the visual system, whereby peripheral information is contained in foveal retinotopic cortex. Beyond its possible implication for peripheral object recognition, few studies have examined the effect of a direct behavioral manipulation of the foveal feedback representation. To address this question, we measured participants' peripheral visual discrimination performance while modulating their foveal representation in a series of psychophysical experiments. On each trial, participants discriminated the identities of briefly presented novel, three-dimensional objects or the orientations of gratings in a peripheral location while fixating at the center. Besides the peripheral target, another stimulus (foil) was also presented and masked at the fovea. Our results showed that for objects, when the foveal foil that was identical to the peripheral target was presented 150 ms after the onset of the peripheral target, visual discrimination of the peripheral target was improved. This congruency effect occurred even though participants did not consciously perceive the foveal stimulus. No such effect was observed when the foveal foil was presented simultaneously with the peripheral target, or when the foil was presented in a parafoveal location. The foil effect in gratings was different from that in objects in terms of its effective timing and foveal specificity, suggesting that foveal feedback may be specific to high-level objects. These results indicate that modulating foveal information can affect individuals' ability to discriminate peripheral objects, suggesting a functional role of foveal representations in peripheral visual perception.

Due to capacity limitation, visual attention must be focused to a limited region of the visual field. Nevertheless, it is assumed that the size of that region may vary with task demands. We aimed to obtain direct evidence for the modulation of visuospatial attention as a function of foveal and parafoveal task load. Participants were required to fixate the center word of word triplets. In separate task blocks, either just the fixated word or both the fixated and the parafoveal word to the right should be semantically classified. The spatiotemporal distribution of attention was assessed with task-irrelevant probes flashed briefly at center or parafoveal positions, during or in between word presentation trials. The N1 component of the ERP elicited by intertrial probes at possible target positions increased with task demands within a block. These results suggest the recruitment of additional attentional resources rather than a redistribution of a fixed resource pool, which persists across trials., (© 2015 Society for Psychophysiological Research.)

Most approaches to visual prostheses have focused on the retina, and for good reasons. The earlier that one introduces signals into the visual system, the more one can take advantage of its prodigious computational abilities. For methods that make use of microelectrodes to introduce electrical signals, however, the limited density and volume occupying nature of the electrodes place severe limits on the image resolution that can be provided to the brain. In this regard, non-retinal areas in general, and the primary visual cortex in particular, possess one large advantage: "magnification factor" (MF)-a value that represents the distance across a sheet of neurons that represents a given angle of the visual field. In the foveal representation of primate primary visual cortex, the MF is enormous-on the order of 15-20 mm/deg in monkeys and humans, whereas on the retina, the MF is limited by the optical design of the eye to around 0.3m m/deg. This means that, for an electrode array of a given density, a much higher-resolution image can be introduced into V1 than onto the retina (or any other visual structure). In addition to this tremendous advantage in resolution, visual cortex is plastic at many different levels ranging from a very local ability to learn to better detect electrical stimulation to higher levels of learning that permit human observers to adapt to radical changes to their visual inputs. We argue that the combination of the large magnification factor and the impressive ability of the cerebral cortex to learn to recognize arbitrary patterns, might outweigh the disadvantages of bypassing earlier processing stages and makes V1 a viable option for the restoration of vision., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The visual wulst of the zebra finch comprises at least two retinotopic maps of the contralateral eye. As yet, it is not known how much of the visual field is represented in the wulst neuronal maps, how the organization of the maps is related to the retinal architecture, and how information from the ipsilateral eye is involved in the activation of the wulst. Here, we have used autofluorescent flavoprotein imaging and classical anatomical methods to investigate such characteristics of the most posterior map of the multiple retinotopic representations. We found that the visual wulst can be activated by visual stimuli from a large part of the visual field of the contralateral eye. Horizontally, the visual field representation extended from -5° beyond the beak tip up to +125° laterally. Vertically, a small strip from -10° below to about +25° above the horizon activated the visual wulst. Although retinal ganglion cells had a much higher density around the fovea and along a strip extending from the fovea towards the beak tip, these areas were not overrepresented in the wulst map. The wulst area activated from the foveal region of the ipsilateral eye, overlapped substantially with the middle of the three contralaterally activated regions in the visual wulst, and partially with the other two. Visual wulst activity evoked by stimulation of the frontal visual field was stronger with contralateral than with binocular stimulation. This confirms earlier electrophysiological studies indicating an inhibitory influence of the activation of the ipsilateral eye on wulst activity elicited by stimulating the contralateral eye. The lack of a foveal overrepresentation suggests that identification of objects may not be the primary task of the zebra finch visual wulst. Instead, this brain area may be involved in the processing of visual information necessary for spatial orientation.

Due to the inhomogenous visual representation across the visual field, humans use peripheral vision to select objects of interest and foveate them by saccadic eye movements for further scrutiny. Thus, there is usually peripheral information available before and foveal information after a saccade. In this study we investigated the integration of information across saccades. We measured reliabilities--i.e., the inverse of variance-separately in a presaccadic peripheral and a postsaccadic foveal orientation--discrimination task. From this, we predicted trans-saccadic performance and compared it to observed values. We show that the integration of incongruent peripheral and foveal information is biased according to their relative reliabilities and that the reliability of the trans-saccadic information equals the sum of the peripheral and foveal reliabilities. Both results are consistent with and indistinguishable from statistically optimal integration according to the maximum-likelihood principle. Additionally, we tracked the gathering of information around the time of the saccade with high temporal precision by using a reverse correlation method. Information gathering starts to decline between 100 and 50 ms before saccade onset and recovers immediately after saccade offset. Altogether, these findings show that the human visual system can effectively use peripheral and foveal information about object features and that visual perception does not simply correspond to disconnected snapshots during each fixation.

The visual system extracts average features from groups of objects (Ariely, 2001; Dakin & Watt, 1997; Watamaniuk & Sekuler, 1992), including high-level stimuli such as faces (Haberman & Whitney, 2007, 2009). This phenomenon, known as ensemble perception, implies a covert process, which would not require fixation of individual stimulus elements. However, some evidence suggests that ensemble perception may instead be a process of averaging foveal input across sequential fixations (Ji, Chen, & Fu, 2013; Jung, Bulthoff, Thornton, Lee, & Armann, 2013). To test directly whether foveating objects is necessary, we measured observers' sensitivity to average facial emotion in the absence of foveal input. Subjects viewed arrays of 24 faces, either in the presence or absence of a gaze-contingent foveal occluder, and adjusted a test face to match the average expression of the array. We found no difference in accuracy between the occluded and non-occluded conditions, demonstrating that foveal input is not required for ensemble perception. Unsurprisingly, without foveal input, subjects spent significantly less time directly fixating faces, but this did not translate into any difference in sensitivity to ensemble expression. Next, we varied the number of faces visible from the set to test whether subjects average multiple faces from the crowd. In both conditions, subjects' performance improved as more faces were presented, indicating that subjects integrated information from multiple faces in the display regardless of whether they had access to foveal information. Our results demonstrate that ensemble perception can be a covert process, not requiring access to direct foveal information.

Human peripheral vision appears vivid compared to foveal vision; the subjectively perceived level of detail does not seem to drop abruptly with eccentricity. This compelling impression contrasts with the fact that spatial resolution is substantially lower at the periphery. A similar phenomenon occurs in visual attention, in which subjects usually overestimate their perceptual capacity in the unattended periphery. We have previously shown that at identical eccentricity, low spatial attention is associated with liberal detection biases, which we argue may reflect inflated subjective perceptual qualities. Our computational model suggests that this subjective inflation occurs because under the lack of attention, the trial-by-trial variability of the internal neural response is increased, resulting in more frequent surpassing of a detection criterion. In the current work, we hypothesized that the same mechanism may be at work in peripheral vision. We investigated this possibility in psychophysical experiments in which participants performed a simultaneous detection task at the center and at the periphery. Confirming our hypothesis, we found that participants adopted a conservative criterion at the center and liberal criterion at the periphery. Furthermore, an extension of our model predicts that detection bias will be similar at the center and at the periphery if the periphery stimuli are magnified. A second experiment successfully confirmed this prediction. These results suggest that, although other factors contribute to subjective inflation of visual perception in the periphery, such as top-down filling-in of information, the decision mechanism may be relevant too.

In the present study, we examined how gaze guidance is affected by immediately available information in the periphery and investigated how search strategies differed across manipulations in the availability of scene context and object content information. Across 3 experiments, participants performed a visual search task in scenes while using a gaze-contingent moving-window paradigm. Extrafoveal information was manipulated across conditions to examine the contributions of object content, scene context, or some combination of the two. Experiment 1 demonstrated a possible interaction between scene context and object content information in improving guidance. Experiments 2 and 3 supported the notion that object content is selected for further scrutiny based on its position within scene context. These results suggest a prioritization of object information based on scene context, such that contextual information acts as a framework in the selection of relevant regions, and object information can then affect which specific locations in those regions are selected for further examination.

Spatial processing resolution of a particular object in the visual field can differ considerably due to eye movements. The same object will be represented with high acuity in the fovea but only coarsely in periphery. Herwig and Schneider (in press) proposed that the visual system counteracts such resolution differences by predicting, based on previous experience, how foveal objects will look in the periphery and vice versa. They demonstrated that previously learned transsaccadic associations between peripheral and foveal object information facilitate performance in visual search, irrespective of the correctness of these associations. False associations were learned by replacing the presaccadic object with a slightly different object during the saccade. Importantly, participants usually did not notice this object change. This raises the question of whether perception of object continuity is a critical factor in building transsaccadic associations. We disturbed object continuity during learning with a postsaccadic blank or a task-irrelevant shape change. Interestingly, visual search performance revealed that neither disruption of temporal object continuity (blank) nor disruption of spatial object continuity (shape change) impaired transsaccadic learning. Thus, transsaccadic learning seems to be a very robust default mechanism of the visual system that is probably related to the more general concept of action-effect learning., (© 2014 ARVO.)

When observing a talking face, it has often been argued that visual speech to the left and right of fixation may produce differences in performance due to divided projections to the two cerebral hemispheres. However, while it seems likely that such a division in hemispheric projections exists for areas away from fixation, the nature and existence of a functional division in visual speech perception at the foveal midline remains to be determined. We investigated this issue by presenting visual speech in matched hemiface displays to the left and right of a central fixation point, either exactly abutting the foveal midline or else located away from the midline in extrafoveal vision. The location of displays relative to the foveal midline was controlled precisely using an automated, gaze-contingent eye-tracking procedure. Visual speech perception showed a clear right hemifield advantage when presented in extrafoveal locations but no hemifield advantage (left or right) when presented abutting the foveal midline. Thus, while visual speech observed in extrafoveal vision appears to benefit from unilateral projections to left-hemisphere processes, no evidence was obtained to indicate that a functional division exists when visual speech is observed around the point of fixation. Implications of these findings for understanding visual speech perception and the nature of functional divisions in hemispheric projection are discussed.

The visual span (or ‘‘uncrowded window’’), which limits the sensory information on each fixation, has been shown to determine reading speed in tasks involving rapid serial visual presentation of single words. The present study investigated whether this is also true for fixation durations during sentence reading when all words are presented at the same time and parafoveal preview of words prior to fixation typically reduces later word-recognition times. If so, a larger visual span may allow more efficient parafoveal processing and thus faster reading. In order to test this hypothesis, visual span profiles (VSPs) were collected from 60 participants and related to data from an eye-tracking reading experiment. The results confirmed a positive relationship between the readers’ VSPs and fixation-based reading speed. However, this relationship was not determined by parafoveal processing. There was no evidence that individual differences in VSPs predicted differences in parafoveal preview benefit. Nevertheless, preview benefit correlated with reading speed, suggesting an independent effect on oculomotor control during reading. In summary, the present results indicate a more complex relationship between the visual span, parafoveal processing, and reading speed than initially assumed., (© 2014 ARVO.)

Visual crowding, as context modulation, reduce the ability to recognize objects in clutter, sets a fundamental limit on visual perception and object recognition. It's considered that crowding does not exist in the fovea and extensive efforts explored crowding in the periphery revealed various models that consider several aspects of spatial processing. Studies showed that spatial and temporal crowding are correlated, suggesting a tradeoff between spatial and temporal processing of crowding. We hypothesized that limiting stimulus availability should decrease object recognition in clutter. Here we show, for the first time, that robust contour interactions exist in the fovea for much larger target-flanker spacing than reported previously: participants overcome crowded conditions for long presentations times but exhibit contour interaction effects for short presentation times. Thus, by enabling enough processing time in the fovea, contour interactions can be overcome, enabling object recognition. Our results suggest that contemporary models of context modulation should include both time and spatial processing.

An important factor constraining visual search performance is the inhomogeneity of the visual system. Engaging participants in a scene search task, the present study explored how the different regions of the visual field contribute to search. Gaze-contingent Blindspots and Spotlights were implemented to determine the absolute and relative importance of the different visual regions for object-in-scene search. Three Blindspot/Spotlight radii (1.6°, 2.9°, and 4.1°) were used to differentiate between foveal, parafoveal, and peripheral vision. When searching the scene with artificially impaired foveal or central vision (Blindspots), search performance was surprisingly unimpaired. Foveal vision was not necessary to attain normal search performance. When high-resolution scene information was withheld in both foveal and parafoveal vision (4.1° Blindspot), target localization was unimpaired but it took longer to verify the identity of the target. Artificially impairing extrafoveal scene analysis (Spotlights) affected attentional selection and visual processing; shrinking the Spotlight of high resolution led to longer search times, shorter saccades, and more and longer fixations. The 4.1° radius was identified as the crossover point of equal search times in Blindspot and Spotlight conditions. However, a gaze-data based decomposition of search times into behaviorally defined epochs revealed differences in particular subprocesses of search., (PsycINFO Database Record (c) 2014 APA, all rights reserved.)

Human vision is an active process in which information is sampled during brief periods of stable fixation in between gaze shifts. Foveal analysis serves to identify the currently fixated object and has to be coordinated with a peripheral selection process of the next fixation location. Models of visual search and scene perception typically focus on the latter, without considering foveal processing requirements. We developed a dual-task noise classification technique that enables identification of the information uptake for foveal analysis and peripheral selection within a single fixation. Human observers had to use foveal vision to extract visual feature information (orientation) from different locations for a psychophysical comparison. The selection of to-be-fixated locations was guided by a different feature (luminance contrast). We inserted noise in both visual features and identified the uptake of information by looking at correlations between the noise at different points in time and behavior. Our data show that foveal analysis and peripheral selection proceeded completely in parallel. Peripheral processing stopped some time before the onset of an eye movement, but foveal analysis continued during this period. Variations in the difficulty of foveal processing did not influence the uptake of peripheral information and the efficacy of peripheral selection, suggesting that foveal analysis and peripheral selection operated independently. These results provide important theoretical constraints on how to model target selection in conjunction with foveal object identification: in parallel and independently.

Previous studies have shown that subjects require less time to process a stimulus at the fovea after a saccade if they have viewed the same stimulus in the periphery immediately prior to the saccade. This extrafoveal preview benefit indicates that information about the visual form of an extrafoveally viewed stimulus can be transferred across a saccade. Here, we extend these findings by demonstrating and characterizing a similar extrafoveal preview benefit in monkeys during a free-viewing visual search task. We trained two monkeys to report the orientation of a target among distractors by releasing one of two bars with their hand; monkeys were free to move their eyes during the task. Both monkeys took less time to indicate the orientation of the target after foveating it, when the target lay closer to the fovea during the previous fixation. An extrafoveal preview benefit emerged even if there was more than one intervening saccade between the preview and the target fixation, indicating that information about target identity could be transferred across more than one saccade and could be obtained even if the search target was not the goal of the next saccade. An extrafoveal preview benefit was also found for distractor stimuli. These results aid future physiological investigations of the extrafoveal preview benefit.

Background: The priority processing of peripherally presented affective stimuli was recently shown in healthy individuals to divert attentional resources dedicated to foveal processing. Here we investigated the influence of sub-clinical levels of anxiety and depression on this bias., Methods: Eighty-four participants were submitted to psychological tests that evaluate anxiety and depression levels. Then, they had to make speeded responses to the direction of left- or right-oriented arrows that were presented foveally at fixation. Each arrow was preceded by a peripherally presented pair of pictures, one neutral and one emotional, unpleasant or pleasant. Thus, the direction of the foveal arrow was either congruent or not with the peripheral location of the previously presented emotional picture. Data analysis focused on the differences of reaction times between congruent and incongruent conditions, which assess the spatial response bias in the task., Results: A main effect of state-anxiety was observed suggesting that the higher the level of state-anxiety, the greater the congruence effect., Limitations: Since the obtained result relates to subclinical anxiety levels, its generalization to anxiety disorders remains tentative., Conclusions: State-anxiety appears to modulate the propensity to be influenced by emotionally salient information occurring in peripheral vision, independently of its relevance to the ongoing behavior. The long-term persistence of a high level of alertness for emotional cues in visual periphery could contribute to the causation and the maintenance of anxiety disorders., (© 2013 Elsevier B.V. All rights reserved.)

A general method for compressing the modulation time-bandwidth product of analog signals is introduced. As one of its applications, this physics-based signal grooming, performed in the analog domain, allows a conventional digitizer to sample and digitize the analog signal with variable resolution. The net result is that frequency components that were beyond the digitizer bandwidth can now be captured and, at the same time, the total digital data size is reduced. This compression is lossless and is achieved through a feature selective reshaping of the signal's complex field, performed in the analog domain prior to sampling. Our method is inspired by operation of Fovea centralis in the human eye and by anamorphic transformation in visual arts. The proposed transform can also be performed in the digital domain as a data compression algorithm to alleviate the storage and transmission bottlenecks associated with "big data."

A glare source in the visual field modifies the brightness of a test patch surrounded by a mesopic background. In this study, we investigated the effect of two levels of transient glare on brightness perception for several combinations of mesopic reference test luminances (Lts) and background luminances (Lbs). While brightness perception was affected by Lb, there were no appreciable effects for changes in the Lt. The highest brightness reduction was found for Lbs in the low mesopic range. Considering the main proposal that brightness can be inferred from contrast and the Lb sets the mesopic luminance adaptation, we hypothesized that contrast gain and retinal adaptation mechanisms would act when a transient glare source was present in the visual field. A physiology-based model that adequately fitted the present and previous results was developed.

Little is known as to how visual systems and visual behaviors vary within guilds in which species share the same micro-habitat types but use different foraging tactics. We studied different dimensions of the visual system and scanning behavior of Carolina chickadees, tufted titmice, and white-breasted nuthatches, which are tree foragers that form heterospecific flocks during the winter. All species had centro-temporally located foveae that project into the frontal part of the lateral visual field. Visual acuity was the highest in nuthatches, intermediate in titmice, and the lowest in chickadees. Chickadees and titmice had relatively wide binocular fields with a high degree of eye movement right above their short bills probably to converge their eyes while searching for food. Nuthatches had narrower binocular fields with a high degree of eye movement below their bills probably to orient the fovea toward the trunk while searching for food. Chickadees and titmice had higher scanning (e.g., head movement) rates than nuthatches probably due to their wider blind areas that limit visual coverage. The visual systems of these three species seem tuned to the visual challenges posed by the different foraging and scanning strategies that facilitate the partitioning of resources within this guild.

Recent neuroimaging evidence suggests that visual inputs arising beyond the fovea can be 'fed back' to foveal visual cortex to construct a new retinotopic representation. However, whether these representations are critical for extra-foveal perception remains unclear. Using transcranial magnetic stimulation we found that relatively late (350-400 msec) disruption of foveal retinotopic cortex impaired perceptual discrimination of objects in the periphery. These results are consistent with the hypothesis that feedback to the foveal retinotopic cortex is crucial for extra-foveal perception, and provide additional evidence for 'constructive' feedback in human vision., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Inhibition of return (IOR) has been described as a hallmark of externally controlled orienting of attention using extrafoveal cues and targets. This paper describes an IOR like inhibition of reaction time for the detection of targets at the fovea that cannot be explained by shift of covert attention. This foveal RT inhibition adds to the evidence that challenges the view of IOR-like phenomena as obligatory expressions of orienting and attentional control., (Copyright © 2012 Elsevier B.V. All rights reserved.)

During reading information is acquired from word(s) beyond the word that is currently looked at. It is still an open question whether such parafoveal information can influence the current viewing of a word, and if so, whether such parafoveal-on-foveal effects are attributable to distributed processing or to mislocated fixations which occur when the eyes are directed at a parafoveal word but land on another word instead. In two display-change experiments, we orthogonally manipulated the preview and target difficulty of word n+2 to investigate the role of mislocated fixations on the previous word n+1. When the eyes left word n, an easy or difficult word n+2 preview was replaced by an easy or difficult n+2 target word. In Experiment 1, n+2 processing difficulty was manipulated by means of word frequency (i.e., easy high-frequency vs. difficult low-frequency word n+2). In Experiment 2, we varied the visual familiarity of word n+2 (i.e., easy lower-case vs. difficult alternating-case writing). Fixations on the short word n+1, which were likely to be mislocated, were nevertheless not influenced by the difficulty of the adjacent word n+2, the hypothesized target of the mislocated fixation. Instead word n+1 was influenced by the preview difficulty of word n+2, representing a delayed parafoveal-on-foveal effect. The results challenge the mislocated-fixation hypothesis as an explanation of parafoveal-on-foveal effects and provide new insight into the complex spatial and temporal effect structure of processing inside the perceptual span during reading.

Our eyes move constantly, even when we try to fixate our gaze. Fixational eye movements prevent and restore visual loss during fixation, yet the relative impact of each type of fixational eye movement remains controversial. For over five decades, the debate has focused on microsaccades, the fastest and largest fixational eye movements. Some recent studies have concluded that microsaccades counteract visual fading during fixation. Other studies have disputed this idea, contending that microsaccades play no significant role in vision. The disagreement stems from the lack of methods to determine the precise effects of microsaccades on vision versus those of other eye movements, as well as a lack of evidence that microsaccades are relevant to foveal vision. Here we developed a novel generalized method to determine the precise quantified contribution and efficacy of human microsaccades to restoring visibility compared with other eye movements. Our results indicate that microsaccades are the greatest eye movement contributor to the restoration of both foveal and peripheral vision during fixation. Our method to calculate the efficacy and contribution of microsaccades to perception can determine the strength of connection between any two physiological and/or perceptual events, providing a novel and powerful estimate of causal influence; thus, we anticipate wide-ranging applications in neuroscience and beyond.

A push-pull training protocol is applied to reduce sensory eye dominance in the foveal region. The training protocol consists of cueing the weak eye to force it to become dominant while the strong eye is suppressed when a pair of dichoptic orthogonal grating stimulus is subsequently presented to it (Ooi & He, 1999). We trained with four pairs of dichoptic orthogonal gratings (0°/90°, 90°/0°, 45°/135° and 135°/45° at 3cpd) to affect the interocular inhibitory interaction tuned to the four trained orientations (0°, 45°, 90° and 135°). After a 10-day training session, we found a significant learning effect (reduced sensory eye dominance) at the trained orientations as well as at two other untrained orientations (22.5° and 67.5°). This suggests that the four pairs of oriented training stimuli are sufficient to produce a learning effect at any other orientation. The nearly complete transfer of the learning effect across orientation is attributed to the fact that the trained and untrained orientations are close enough to fall in the same orientation tuning function of the early visual cortical neurons (∼37.5°). Applying the same notion of transfer of learning within the same feature channel, we also found a large transfer effect to an untrained spatial frequency (6cpd), which is 1 octave higher than the trained spatial frequency (3cpd). Furthermore, we found that stereopsis is improved, as is the competitive ability between the two eyes, after the push-pull training. Our data analysis suggests that these improvements are correlated with the reduced sensory eye dominance after the training, i.e., due to a more balanced interocular inhibition. We also found that the learning effect (reduced SED and stereo threshold) can be retained for more than a year after the termination of the push-pull training., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

We investigated whether the control of movement of the left hand is more likely to involve the use of allocentric information than movements performed with the right hand. Previous studies (Gonzalez et al. in J Neurophys 95:3496-3501, 2006; De Grave et al. in Exp Br Res 193:421-427, 2009) have reported contradictory findings in this respect. In the present study, right-handed participants (N = 12) and left-handed participants (N = 12) made right- and left-handed grasps to foveated objects and peripheral, non-foveated objects that were located in the right or left visual hemifield and embedded within a Müller-Lyer illusion. They were also asked to judge the size of the object by matching their hand aperture to its length. Hand apertures did not show significant differences in illusory bias as a function of hand used, handedness or visual hemifield. However, the illusory effect was significantly larger for perception than for action, and for the non-foveated compared to foveated objects. No significant illusory biases were found for reach movement times. These findings are consistent with the two-visual system model that holds that the use of allocentric information is more prominent in perception than in movement control. We propose that the increased involvement of allocentric information in movements toward peripheral, non-foveated objects may be a consequence of more awkward, less automatized grasps of nonfoveated than foveated objects. The current study does not support the conjecture that the control of left-handed and right-handed grasps is predicated on different sources of information.

On average our eyes make 3-5 saccadic movements per second when we read, although their neural mechanism is still unclear. It is generally thought that saccades help redirect the retinal fovea to specific characters and words but that actual discrimination of information only occurs during periods of fixation. Indeed, it has been proposed that there is active and selective suppression of information processing during saccades to avoid experience of blurring due to the high-speed movement. Here, using a paradigm where a string of either lexical (Chinese) or non-lexical (alphabetic) characters are triggered by saccadic eye movements, we show that subjects can discriminate both while making saccadic eye movement. Moreover, discrimination accuracy is significantly better for characters scanned during the saccadic movement to a fixation point than those not scanned beyond it. Our results showed that character information can be processed during the saccade, therefore saccades during reading not only function to redirect the fovea to fixate the next character or word but allow pre-processing of information from the ones adjacent to the fixation locations to help target the next most salient one. In this way saccades can not only promote continuity in reading words but also actively facilitate reading comprehension.

To foveate a visual target, subjects usually execute a primary hypometric saccade (S1) bringing the target in perifoveal vision, followed by a corrective saccade (S2) or by more than one S2. It is still debated to what extent these S2 are pre-programmed or dependent only on post-saccadic retinal error. To answer this question, we used a visually-triggered saccade task in which target position and target visibility were manipulated. In one-third of the trials, the target was slightly displaced at S1 onset (so-called double step paradigm) and was maintained until the end of S1, until the start of the first S2 or until the end of the trial. Experiments took place in two visual environments: in the dark and in a dimly lit room with a visible random square background. The results showed that S2 were less accurate for shortest target durations. The duration of post-saccadic visual integration thus appears as the main factor responsible for corrective saccade accuracy. We also found that the visual context modulates primary saccade accuracy, especially for the most hypometric subjects. These findings suggest that the saccadic system is sensitive to the visual properties of the environment and uses different strategies to maintain final gaze accuracy., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Words are processed as units. This is not as evident as it seems, given the division of the human cerebral cortex in two hemispheres and the partial decussation of the optic tract. In two experiments, we investigated what underlies the unity of foveally presented words: A bilateral projection of visual input in foveal vision, or interhemispheric inhibition and integration as proposed by the SERIOL model of visual word recognition. Experiment 1 made use of pairs of words and nonwords with a length of four letters each. Participants had to name the word and ignore the nonword. The visual field in which the word was presented and the distance between the word and the nonword were manipulated. The results showed that the typical right visual field advantage was observed only when the word and the nonword were clearly separated. When the distance between them became smaller, the right visual field advantage turned into a left visual field advantage, in line with the interhemispheric inhibition mechanism postulated by the SERIOL model. Experiment 2, using 5-letters stimuli, confirmed that this result was not due to the eccentricity of the word relative to the fixation location but to the distance between the word and the nonword., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Event-related potentials and behavioural performance as a function of target eccentricity were measured while subjects performed a texture segmentation task. Fit-of-structures, i.e. easiness of target detection was varied: in Experiment 1, a texture with peripheral fit (easier detection of peripheral presented targets) and in Experiment 2, a texture with foveal fit (easier detection of foveal presented targets) was used. In the two experiments, the N2p was sensitive to target eccentricity showing larger amplitudes for foveal targets compared to peripheral targets, and at the foveal position, a reversal of the N2p differential amplitude effect was found. The anterior P2 seemed sensitive to the easiness of target detection. In both experiments the N2pc varied as a function of eccentricity. However, the P3 was neither sensitive to target eccentricity nor to the fit-of-structures. Results show the existence of a P2/N2 complex (Potts and Tucker, 2001) indicating executive functions located in the anterior cortex and perceptual processes located in the posterior cortex. Furthermore, the N2p might indicate the existence of a foveal vs. peripheral subsystem in visual processing., (2011 Elsevier B.V. All rights reserved.)