The role of prediction and visual tracking strategies during manual interception: An exploration of individual differences.

The interception (or avoidance) of moving objects is a common component of various daily living tasks; however, it remains unclear whether precise alignment of foveal vision with a target is important for motor performance. Furthermore, there has also been little examination of individual differences in visual tracking strategy and the use of anticipatory gaze adjustments. We examined the importance of in-flight tracking and predictive visual behaviors using a virtual reality environment that required participants (n = 41) to intercept tennis balls projected from one of two possible locations. Here, we explored whether different tracking strategies spontaneously arose during the task, and which were most effective. Although indices of closer in-flight tracking (pursuit gain, tracking coherence, tracking lag, and saccades) were predictive of better interception performance, these relationships were rather weak. Anticipatory gaze shifts toward the correct release location of the ball provided no benefit for subsequent interception. Nonetheless, two interceptive strategies were evident: 1) early anticipation of the ball's onset location followed by attempts to closely track the ball in flight (i.e., predictive strategy); or 2) positioning gaze between possible onset locations and then using peripheral vision to locate the moving ball (i.e., a visual pivot strategy). Despite showing much poorer in-flight foveal tracking of the ball, participants adopting a visual pivot strategy performed slightly better in the task. Overall, these results indicate that precise alignment of the fovea with the target may not be critical for interception tasks, but that observers can adopt quite varied visual guidance approaches.

Unique yellow shifts for small and brief stimuli in the central retina.

The spectral locus of unique yellow was determined for flashes of different sizes (<11 arcmin) and durations (<500 ms) presented in and near the fovea. An adaptive optics scanning laser ophthalmoscope was used to minimize the effects of higher-order aberrations during simultaneous stimulus delivery and retinal imaging. In certain subjects, parafoveal cones were classified as L, M, or S, which permitted the comparison of unique yellow measurements with variations in local L/M ratios within and between observers. Unique yellow shifted to longer wavelengths as stimulus size or duration was reduced. This effect is most pronounced for changes in size and more apparent in the fovea than in the parafovea. The observed variations in unique yellow are not entirely predicted from variations in L/M ratio and therefore implicate neural processes beyond photoreception.

Avian eye-inspired perovskite artificial vision system for foveated and multispectral imaging.

Avian eyes have deep central foveae as a result of extensive evolution. Deep foveae efficiently refract incident light, creating a magnified image of the target object and making it easier to track object motion. These features are essential for detecting and tracking remote objects in dynamic environments. Furthermore, avian eyes respond to a wide spectrum of light, including visible and ultraviolet light, allowing them to efficiently distinguish the target object from complex backgrounds. Despite notable advances in artificial vision systems that mimic animal vision, the exceptional object detection and targeting capabilities of avian eyes via foveated and multispectral imaging remain underexplored. Here, we present an artificial vision system that capitalizes on these aspects of avian vision. We introduce an artificial fovea and vertically stacked perovskite photodetector arrays whose designs were optimized by theoretical simulations for the demonstration of foveated and multispectral imaging. The artificial vision system successfully identifies colored and mixed-color objects and detects remote objects through foveated imaging. The potential for use in uncrewed aerial vehicles that need to detect, track, and recognize distant targets in dynamic environments is also discussed. Our avian eye-inspired perovskite artificial vision system marks a notable advance in bioinspired artificial visions.

Evolutionary and developmental specialization of foveal cell types in the marmoset.

In primates, high-acuity vision is mediated by the fovea, a small specialized central region of the retina. The fovea, unique to the anthropoid lineage among mammals, undergoes notable neuronal morphological changes during postnatal maturation. However, the extent of cellular similarity across anthropoid foveas and the molecular underpinnings of foveal maturation remain unclear. Here, we used high-throughput single-cell RNA sequencing to profile retinal cells of the common marmoset (Callithrix jacchus), an early divergent in anthropoid evolution from humans, apes, and macaques. We generated atlases of the marmoset fovea and peripheral retina for both neonates and adults. Our comparative analysis revealed that marmosets share almost all their foveal types with both humans and macaques, highlighting a conserved cellular structure among primate foveas. Furthermore, by tracing the developmental trajectory of cell types in the foveal and peripheral retina, we found distinct maturation paths for each. In-depth analysis of gene expression differences demonstrated that cone photoreceptors and Müller glia (MG), among others, show the greatest molecular divergence between these two regions. Utilizing single-cell ATAC-seq and gene-regulatory network inference, we uncovered distinct transcriptional regulations differentiating foveal cones from their peripheral counterparts. Further analysis of predicted ligand-receptor interactions suggested a potential role for MG in supporting the maturation of foveal cones. Together, these results provide valuable insights into foveal development, structure, and evolution.

Toward a theory of perspective perception in pictures.

This paper reviews projection models and their perception in realistic pictures, and proposes hypotheses for three-dimensional (3D) shape and space perception in pictures. In these hypotheses, eye fixations, and foveal vision play a central role. Many past theories and experimental studies focus solely on linear perspective. Yet, these theories fail to explain many important perceptual phenomena, including the effectiveness of nonlinear projections. Indeed, few classical paintings strictly obey linear perspective, nor do the best distortion-avoidance techniques for wide-angle computational photography. The hypotheses here employ a two-stage model for 3D human vision. When viewing a picture, the first stage perceives 3D shape for the current gaze. Each fixation has its own perspective projection, but, owing to the nature of foveal and peripheral vision, shape information is obtained primarily for a small region of the picture around the fixation. As a viewer moves their eyes, the second stage continually integrates some of the per-gaze information into an overall interpretation of a picture. The interpretation need not be geometrically stable or consistent over time. It is argued that this framework could explain many disparate pictorial phenomena, including different projection styles throughout art history and computational photography, while being consistent with the constraints of human 3D vision. The paper reviews open questions and suggests new studies to explore these hypotheses.

Processing difficulty while reading words with neighbors is not due to increased foveal load: Evidence from eye movements.

Words with high orthographic relatedness are termed "word neighbors" (angle/angel; birch/birth). Activation-based models of word recognition assume that lateral inhibition occurs between words and their activated neighbors. However, studies of eye movements during reading have not found inhibitory effects in early measures assumed to reflect lexical access (e.g., gaze duration). Instead, inhibition in eye-movement studies has been found in later measures of processing (e.g., total time, regressions in). We conducted an eye-movement boundary change study (Rayner, Cognitive Psychology, 7(1), 65-81, 1975) that manipulated the parafoveal preview of the word following the neighbor word (word N+1). In this way, we explored whether the late inhibitory effects seen with transposed letter words and words with higher-frequency neighbors result from reduced parafoveal preview due to increased foveal load and/or interference during late stages of lexical processing (the L2 stage within the E-Z Reader framework). For word N+1, while there were clear preview effects, there was not an effect of the neighborhood status of word N, nor a significant interaction. This suggests that the late inhibitory effects of earlier eye-movement studies are driven by misidentification of neighbor words rather than being due to increased foveal load.

Cone-Opponent Ganglion Cells in the Primate Fovea Tuned to Noncardinal Color Directions.

A long-standing question in vision science is how the three cone photoreceptor types-long (L), medium (M), and short (S) wavelength sensitive-combine to generate our perception of color. Hue perception can be described along two opponent axes: red-green and blue-yellow. Psychophysical measurements of color appearance indicate that the cone inputs to the red-green and blue-yellow opponent axes are M vs. L + S and L vs. M + S, respectively. However, the "cardinal directions of color space" revealed by psychophysical measurements of color detection thresholds following adaptation are L vs. M and S vs. L + M. These cardinal directions match the most common cone-opponent retinal ganglion cells (RGCs) in the primate retina. Accordingly, the cone opponency necessary for color appearance is thought to be established in the cortex. While neurons with the appropriate M vs. L + S and L vs. M + S opponency have been reported in the retina and lateral geniculate nucleus, their existence continues to be debated. Resolving this long-standing debate is necessary because a complete account of the cone opponency in the retinal output is critical for understanding how downstream neural circuits process color. Here, we performed adaptive optics calcium imaging to noninvasively measure foveal RGC light responses in the living Macaca fascicularis eye. We confirm the presence of L vs. M + S and M vs. L + S neurons with noncardinal cone opponency and demonstrate that cone-opponent signals in the retinal output are more diverse than classically thought.

Featural Representation and Internal Noise Underlie the Eccentricity Effect in Contrast Sensitivity.

Human visual performance for basic visual dimensions (e.g., contrast sensitivity and acuity) peaks at the fovea and decreases with eccentricity. The eccentricity effect is related to the larger visual cortical surface area corresponding to the fovea, but it is unknown if differential feature tuning contributes to this eccentricity effect. Here, we investigated two system-level computations underlying the eccentricity effect: featural representation (tuning) and internal noise. Observers (both sexes) detected a Gabor embedded in filtered white noise which appeared at the fovea or one of four perifoveal locations. We used psychophysical reverse correlation to estimate the weights assigned by the visual system to a range of orientations and spatial frequencies (SFs) in noisy stimuli, which are conventionally interpreted as perceptual sensitivity to the corresponding features. We found higher sensitivity to task-relevant orientations and SFs at the fovea than that at the perifovea, and no difference in selectivity for either orientation or SF. Concurrently, we measured response consistency using a double-pass method, which allowed us to infer the level of internal noise by implementing a noisy observer model. We found lower internal noise at the fovea than that at the perifovea. Finally, individual variability in contrast sensitivity correlated with sensitivity to and selectivity for task-relevant features as well as with internal noise. Moreover, the behavioral eccentricity effect mainly reflects the foveal advantage in orientation sensitivity compared with other computations. These findings suggest that the eccentricity effect stems from a better representation of task-relevant features and lower internal noise at the fovea than that at the perifovea.

Dynamic changes in ocular shape during human development and its implications for retina fovea formation.

The human fovea is known for its distinctive pit-like appearance, which results from the displacement of retinal layers superficial to the photoreceptors cells. The photoreceptors are found at high density within the foveal region but not the surrounding retina. Efforts to elucidate the mechanisms responsible for these unique features have ruled out cell death as an explanation for pit formation and changes in cell proliferation as the cause of increased photoreceptor density. These findings have led to speculation that mechanical forces acting within and on the retina during development underly the formation of foveal architecture. Here we review eye morphogenesis and retinal remodeling in human embryonic development. Our meta-analysis of the literature suggests that fovea formation is a protracted process involving dynamic changes in ocular shape that start early and continue throughout most of human embryonic development. From these observations, we propose a new model for fovea development.

Foveal feedback in perceptual processing: Contamination of neural representations and task difficulty effects.

Visual object recognition was traditionally believed to rely on a hierarchical feedforward process. However, recent evidence challenges this notion by demonstrating the crucial role of foveal retinotopic cortex and feedback signals from higher-level visual areas in processing peripheral visual information. The nature of the information conveyed through foveal feedback remains a topic of debate. To address this, we conducted a study employing a foveal mask paradigm with varying stimulus-mask onset asynchronies in a peripheral same/different task, where peripheral objects exhibited different degrees of similarity. Our hypothesis posited that simultaneous arrival of feedback and mask information in the foveal cortex would lead to neural contamination, biasing perception. Notably, when the two peripheral objects were identical, we observed a significant increase in the number of "different" responses, peaking at approximately 100 ms. Similar effect was found when the objects were dissimilar, but with an overall later timing (around 150 ms). No significant difference was found when comparing easy (dissimilar objects) and difficult trials (similar objects). The findings challenge the hypothesis that foveation planning alone accounts for the observed effects. Instead, these and previous observations support the notion that the foveal cortex serves as a visual sketchpad for maintaining and manipulating task-relevant information.

Parafoveal processing in bilingual readers: Semantic access within but not across languages.

Prior research has investigated the quality of information a reader can extract from upcoming parafoveal words. However, very few studies have considered parafoveal processing in bilingual readers, who may differ from monolinguals due to slower lexical access and susceptibility to cross-language activation. This eye-tracking experiment, therefore, investigated how bilingual readers process parafoveal semantic information within and across languages. We used the boundary technique to replace a preview word in a sentence with a different target word during the first rightward saccade from the pretarget region. We manipulated both preview language (nonswitch vs. code-switch) and semantic relatedness (synonym/translation vs. unrelated) between previews and targets. Upon fixation, target words always appeared in the same language as the rest of the sentence to create an essentially monolingual language context. Semantic preview benefits emerged for nonswitched synonym previews but not for code-switched translation previews. Furthermore, participants skipped code-switched previews less often than nonswitched previews and no more often than previews that were unfamiliar to them. These data suggest that bilinguals can extract within-language semantic information from the parafovea in both native and nonnative languages, but that cross-language words are not accessible while reading in a monolingual language mode, as per the partial selectivity hypothesis of bilingual language control. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Maturation and refinement of the maculae and foveae in the Anolis sagrei lizard.

The fovea is a pit in the center of the macula, which is a region of the retina with a high concentration of photoreceptor cells, which accounts for a large degree of visual acuity in primates. The maturation of this primate visual acuity area is characterized by the shallowing and widening of the foveal pit, a decrease in the diameter of the rod-free zone, and an increase in photoreceptor cells packing after birth. Maturation occurs concurrently with progressing age, increasing eye size, and retinal length/area. These observations have led to the hypothesis that the maturation of the fovea might be a function of mechanical variables that remodel the retina. However, this has never been explored outside of primates. Here, we take advantage of the Anolis sagrei lizard, which has a bifoveated retina, to study maturation of the fovea and macula. Eyes were collected from male and female lizards-hatchling, 2-month, 4-month, 6-month, and adult. We found that Anolis maculae undergo a maturation process somewhat different than what has been observed in primates. Anole macular diameters actually increase in size and undergo minimal photoreceptor cell packing, possessing a near complete complement of these cells at the time of hatching. As the anole eye expands, foveal centers experience little change in overall retina cell density with most cell redistribution occurring at macular borders and peripheral retina areas. Gene editing technology has recently been developed in lizards; this study provides a baseline of normal retina maturation for future genetic manipulation studies in anoles.

Out of sight, out of mind: Foveal processing is necessary for semantic integration of words into sentence context.

Word recognition begins before a reader looks directly at a word, as demonstrated by the parafoveal preview benefit and word skipping. Both low-level form and high-level semantic features can be accessed in parafoveal vision and used to promote reading efficiency. However, words are not recognized in isolation during reading; once a semantic representation is retrieved, it must be integrated with the broader sentence context. One open question about parafoveal processing is whether it is limited to shallow stages of lexico-semantic activation or extends to semantic integration. In the present two-experiment study, we recorded event-related brain potentials in response to a sentence-final word that was presented in foveal or parafoveal vision and was either expected, unexpected, or anomalous in the sentence context. We found that word recognition, indexed by the N400, ensued regardless of perception location whereas identification of the semantic fit of a word in its sentence context, indexed by the late positive component, was only observed for foveally perceived but not parafoveally perceived words. This pattern was not sensitive to task differences that promote different levels of orthographic scrutiny, as manipulated between the two experiments. These findings demonstrate separate roles for parafoveal and foveal processing in reading. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Cross-language semantic parafoveal preview benefits in bilinguals.

The aim of this project was to identify factors contributing to cross-language semantic preview benefits. In Experiment 1, Russian-English bilinguals read English sentences with Russian words presented as parafoveal previews. The gaze-contingent boundary paradigm was used to present sentences. Critical previews were cognate translations of the target word (CTAPT-START), noncognate translations (CPOK-TERM), or interlingual homograph translations (MOPE-SEA). A semantic preview benefit (i.e., shorter fixation durations for related than unrelated previews) was observed for cognate and interlingual homograph translations, but not for noncognate translations. In Experiment 2, English-French bilinguals read English sentences with French words used as parafoveal previews. Critical previews were interlingual homograph translations of the target word (PAIN-BREAD) or interlingual homograph translations with a diacritic added (PÁIN-BREAD). A robust semantic preview benefit was found only for interlingual homographs without diacritics, although both preview types produced a semantic preview benefit in the total fixation duration. Our findings suggest that semantically related previews need to have substantial orthographic overlap with words in the target language to produce cross-language semantic preview benefits in early eye fixation measures. In terms of the Bilingual Interactive Activation+ model, the preview word may need to activate the language node for the target language before its meaning is integrated with that of the target word. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Investigating the role of the foveal cortex in peripheral object discrimination.

Peripheral object discrimination is hindered by a central dynamic mask presented between 150 and 300 ms after stimulus onset. The mask is thought to interfere with task-relevant feedback coming from higher visual areas to the foveal cortex in V1. Fan et al. (2016) supported this hypothesis by showing that the effect of mask can be further delayed if the task requires mental manipulation of the peripheral target. The main purpose of this study was to better characterize the temporal dynamics of foveal feedback. Specifically, in two experiments we have shown that (1) the effect of foveal noise mask is sufficiently robust to be replicated in an online data collection (2) in addition to a change in sensitivity the mask affects also the criterion, which becomes more conservative; (3) the expected dipper function for sensitivity approximates a quartic with a global minimum at 94 ms, while the best fit for criterion is a quintic with a global maximum at 174 ms; (4) the power spectrum analysis of perceptual oscillations in sensitivity data shows a cyclic effect of mask at 3 and 12 Hz. Overall, our results show that foveal noise affects sensitivity in a cyclic manner, with a global dip emerging earlier than previously found. The noise also affects the response bias, even though with a different temporal profile. We, therefore, suggest that foveal noise acts on two distinct feedback mechanisms, a faster perceptual feedback followed by a slower cognitive feedback.

Fixation-related fMRI analysis reveals the neural basis of parafoveal processing in self-paced reading of Chinese words.

While parafoveal word processing plays an important role in natural reading, the underlying neural mechanism remains unclear. The present study investigated the neural basis of parafoveal processing during Chinese word reading with the co-registration of eye-tracking and functional magnetic resonance imaging (fMRI) using fixation-related fMRI analysis. In the gaze-contingent boundary paradigm, preview conditions (words that are identical, orthographically similar, and unrelated to target words), pre-target word frequency and target word frequency were manipulated. When fixating the pre-target word, the identical preview condition elicited lower brain activation in the left fusiform gyrus relative to unrelated and orthographically similar preview conditions and there were significant interactions of preview condition and pre-target word frequency on brain activation of the left middle frontal gyrus, left fusiform gyrus and supplementary motor area. When fixating the target word, there was a significant main effect of preview condition on brain activation of the right fusiform gyrus and a significant interaction of preview condition and pre-target word frequency on brain activation of the left middle frontal gyrus. These results suggest that fixation-related brain activation provides immediate measures and new perspectives to understand the mechanism of parafoveal processing in self-paced reading.

Severe distortion in the representation of foveal visual image locations in short-term memory.

The foveal visual image region provides the human visual system with the highest acuity. However, it is unclear whether such a high fidelity representational advantage is maintained when foveal image locations are committed to short-term memory. Here, we describe a paradoxically large distortion in foveal target location recall by humans. We briefly presented small, but high contrast, points of light at eccentricities ranging from 0.1 to 12°, while subjects maintained their line of sight on a stable target. After a brief memory period, the subjects indicated the remembered target locations via computer controlled cursors. The biggest localization errors, in terms of both directional deviations and amplitude percentage overshoots or undershoots, occurred for the most foveal targets, and such distortions were still present, albeit with qualitatively different patterns, when subjects shifted their gaze to indicate the remembered target locations. Foveal visual images are severely distorted in short-term memory.

Parafoveal words can modulate sentence meaning: Electrophysiological evidence from an RSVP-with-flanker task.

During natural reading, readers can take up some visual information from not-yet-fixated words to the right of the current fixation and it is well-established that this parafoveal preview facilitates the subsequent foveal processing of the word. However, the extraction and integration of word meaning from parafoveal words and their possible influence on the semantic content of the sentence are controversial. In the current study, we recorded event-related potentials (ERPs) in the RSVP-with-flankers paradigm to test whether and how updates of sentential meaning, based only on parafoveal information, may influence the subsequent foveal processing. In Chinese sentences, the congruency of parafoveal and foveal target words with the sentence was orthogonally manipulated. In contrast to previous research, we also controlled for potentially confounding effects of parafoveal-to-foveal repetition priming (identity preview effects) on the N400. Crucially, we found that the classic effect of foveal congruency on the N400 component only appeared when the word in preview had been congruent with sentence meaning; in contrast, there was no N400 as a function of foveal incongruency when the preview word had also been incongruent. These results indicate that sentence meaning rapidly adapts to parafoveal preview, altering the semantic context for the subsequently fixated word. We also show that correct parafoveal preview generally attenuates the N400 once a word is fixated, regardless of congruency. Taken together, our findings underline the highly generative and adaptive framework of language comprehension.

Achromatic doublet electrowetting prism array for beam steering device in foveated display.

A foveated display is a technology that can solve the problem of insufficient angular resolution (relative to the human eye) for near-eye display. In a high-resolution foveated display, a beam steering element is required to track the human gaze. An electrowetting prism array is a transmissive non-mechanical beam steering device, that allows a light and compact optical system to be configured and a large aperture possible. However, the view is obstructed by the sidewall of the prism array. When the size of the cell prism is 7mm, the prism array has an 87% fill-factor. To push the fill-factor to 100%, the cell prisms were magnified using a lens array. Image processing was performed such that the image produced by the lens array was identical to the original. Beam steering by refraction is accompanied by chromatic dispersion, which causes chromatic aberration, making colors appear blurry. The refractive index condition to reduce chromatic dispersion was obtained using the doublet structure of the electrowetting prism. The chromatic dispersion was reduced by 70% on average.

Preview frequency effects in reading: evidence from Chinese.

Studies about sentence reading have shown that visual and lexical information beyond the currently fixated word can be integrated across fixations. The gaze-contingent boundary paradigm has been used widely to explore the extent to which parafoveal information can be processed before a word is fixated on. However, a critical review of the current literature suggests that unrelated mask previews are an unlikely baseline control with zero lexical activation, blurring the nature of experimental effects observed in the paradigm. The present study, therefore, aimed at shedding light on the effect of parafoveal mask properties through a manipulation of preview word frequency. Low-frequency preview words that are unrelated to target words elicited a larger interference than high-frequency preview words. We discuss implications of the preview frequency effect for computational models of eye-movement control in reading.