Visual Periphery Research Articles

An eccentricity gradient reversal across high-level visual cortex.

Human visual cortex contains regions selectively involved in perceiving and recognizing ecologically important visual stimuli such as people and places. Located in the ventral temporal lobe, these regions are organized consistently relative to cortical folding, a phenomenon thought to be inherited from how centrally or peripherally these stimuli are viewed with the retina. While this eccentricity theory of visual cortex has been one of the best descriptions of its functional organization, whether or not it accurately describes visual processing in all category-selective regions is not yet clear. Through a combination of behavioral and functional MRI measurements in 27 participants (17 females), we demonstrate that a limb-selective region neighboring well-studied face-selective regions shows tuning for the visual periphery in a cortical region originally thought to be centrally-biased. We demonstrate that the spatial computations performed by the limb-selective region are consistent with visual experience, and in doing so, make the novel observation that there may in fact be two eccentricity gradients, forming an eccentricity reversal across high-level visual cortex. These data expand the current theory of cortical organization to provide a unifying principle that explains the broad functional features of many visual regions, showing that viewing experience interacts with innate wiring principles to drive the location of cortical specialization.Significance Statement What is the organizing principle of high-level visual cortex? Visual stimuli experienced extensively during childhood, like faces or scenes, give rise to specialized regions in visual cortex. These regions emerge in consistent locations across individuals, thought to result from the retinotopic input of earlier visual cortex. The field has quantified this input as a medial-lateral gradient of retinotopic eccentricity in ventrotemporal cortex that has not yet been mapped beyond the fusiform gyrus. By performing receptive field mapping in limb-selective cortex for the first time we uncover a u-shaped eccentricity gradient which reverses near the lateral Fusiform. These findings produce a parsimonious model of cortical organization incorporating previously uncharacterized regions, offering a new organizing principle of high-level vision.

Oculomotor contributions to foveal crowding.

Crowding, the phenomenon of impaired visual discrimination due to nearby objects, has been extensively studied and linked to cortical mechanisms. Traditionally, crowding has been studied extrafoveally; its underlying mechanisms in the central fovea, where acuity is highest, remain de-bated. While low-level oculomotor factors are not thought to play a role in crowding, this study shows that they are key factors in defining foveal crowding. Here we investigate the influence of fixational behavior on foveal crowding and provide a comprehensive assessment of the magnitude and extent of this phenomenon (N=13 human participants, 4 males). Leveraging on a unique blend of tools for high-precision eyetracking and retinal stabilization, we show that removing the retinal motion introduced by oculomotor behavior with retinal stabilization, diminishes the negative effects of crowding. Ultimately, these results indicate that ocular drift contributes to foveal crowding re-sulting in the same pooling region being stimulated both by the target and nearby objects over the course of time, not just in space. The temporal aspect of this phenomenon is peculiar to crowding at this scale and indicates that the mechanisms contributing to foveal and extrafoveal crowding differ.Significance Statement: Foveated stimuli are often crowded. The effects of crowding have been extensively studied in the visual periphery and are thought to have a cortical origin. Nonetheless, foveal crowding mechanisms remain elusive. Here we show that acuity drops by two lines on a Snellen Chart when flankers surround a stimulus presented at the very center of gaze. Further, at this scale, crowding cannot be regarded as a purely cortical phenomenon. Because foveal neurons' receptive fields are the smallest, eye jitter during fixation introduces spatial uncertainty by sweeping target and surrounding distractors over the same cortical pooling region even during short fixation periods, exacerbating crowding effects.

Foveal crowding in children with developmental dyslexia.

Excessive crowding in the visual periphery has been demonstrated in children with developmental dyslexia (DD). However, less is known about crowding in the fovea, even though foveal crowding is at least equally important, as reading is mostly accomplished through foveal vision. Here we used a special set of digitstimuli (Pelli fonts) to measure foveal crowding in DD and DD + ADHD children, and compared it to that in TD (typically developing) and ADHD children. We also used the Chinese reading acuity charts (C-READ) to assess the maximum reading speed and reading acuity, along with tests to evaluate cognitive attributes including phonological awareness, rapid automatized naming, morphological awareness, and orthographic knowledge. The results indicate significantly stronger foveal crowding in the DD and DD + ADHD groups, as well as in the ADHD group, than in the TD group. Furthermore, the DD and DD + ADHD groups exhibited poorer maximum reading speed and reading acuity compared to the ADHD and TD groups.Within the two DD groups, theslower maximum reading speed and higher reading acuitycan be predicted bystronger foveal crowding. In addition, the DD and DD + ADHD groups performed the worst in four cognitive skills, with the DD group showing negative correlations between foveal crowding and performances across all these skills. Our findings thus move beyond previously well-documented peripheral crowding in dyslexia, and the easy administration of the Pelli-font-based crowding test may be useful for early diagnosis of developmental dyslexia in young children.

When periphery rules: Enhanced sampling weights of the visual periphery in crowding across dimensions

When periphery rules: Enhanced sampling weights of the visual periphery in crowding across dimensions

Near-optimal metacognition across the visual periphery

Near-optimal metacognition across the visual periphery

A continuous tracking measure of orientation sensitivity and bias in the visual periphery

A continuous tracking measure of orientation sensitivity and bias in the visual periphery

Consistent metacognitive efficiency and variable response biases in peripheral vision.

Across the visual periphery, perceptual and metacognitive abilities differ depending on the locus of visual attention, the location of peripheral stimulus presentation, the task design, and many other factors. In this investigation, we aimed to illuminate the relationship between attention and eccentricity in the visual periphery by estimating perceptual sensitivity, metacognitive sensitivity, and response biases across the visual field. In a 2AFC detection task, participants were asked to determine whether a signal was present or absent at one of eight peripheral locations (±10°, 20°, 30°, and 40°), using either a valid or invalid attentional cue. As expected, results revealed that perceptual sensitivity declined with eccentricity and was modulated by attention, with higher sensitivity on validly cued trials. Furthermore, a significant main effect of eccentricity on response bias emerged, with variable (but relatively unbiased) c'a values from 10° to 30°, and conservative c'a values at 40°. Regarding metacognitive sensitivity, significant main effects of attention and eccentricity were found, with metacognitive sensitivity decreasing with eccentricity, and decreasing in the invalid cue condition. Interestingly, metacognitive efficiency, as measured by the ratio of meta-d'a/d'a, was not modulated by attention or eccentricity. Overall, these findings demonstrate (1) that in some circumstances, observers have surprisingly robust metacognitive insights into how performance changes across the visual field and (2) that the periphery may be subject to variable detection biases that are contingent on the exact location in peripheral space.

Greater benefits of deep learning-based computer-aided detection systems for finding small signals in 3D volumetric medical images.

Radiologists are tasked with visually scrutinizing large amounts of data produced by 3D volumetric imaging modalities. Small signals can go unnoticed during the 3D search because they are hard to detect in the visual periphery. Recent advances in machine learning and computer vision have led to effective computer-aided detection (CADe) support systems with the potential to mitigate perceptual errors. Sixteen nonexpert observers searched through digital breast tomosynthesis (DBT) phantoms and single cross-sectional slices of the DBT phantoms. The 3D/2D searches occurred with and without a convolutional neural network (CNN)-based CADe support system. The model provided observers with bounding boxes superimposed on the image stimuli while they looked for a small microcalcification signal and a large mass signal. Eye gaze positions were recorded and correlated with changes in the area under the ROC curve (AUC). The CNN-CADe improved the 3D search for the small microcalcification signal ( , ) and the 2D search for the large mass signal ( , ). The CNN-CADe benefit in 3D for the small signal was markedly greater than in 2D ( , ). Analysis of individual differences suggests that those who explored the least with eye movements benefited the most from the CNN-CADe ( , ). However, for the large signal, the 2D benefit was not significantly greater than the 3D benefit ( , ). The CNN-CADe brings unique performance benefits to the 3D (versus 2D) search of small signals by reducing errors caused by the underexploration of the volumetric data.

The disengagement deficit after right-hemisphere damage: Distinct roles of lateral frontal and parietal damage

An influential model of spatial attention postulates three main attention-orienting mechanisms: disengagement, shifting, and engagement. Early research linked disengagement deficits with superior parietal damage, regardless of hemisphere or presence of spatial neglect. Subsequent studies supported the involvement of more ventral parietal regions, especially in the right hemisphere, and linked spatial neglect to deficient disengagement from ipsilateral cues. However, previous lesion studies faced serious limitations, such as small sample sizes and the lack of brain-injured controls without neglect. Additionally, some studies employed symbolic cues or used long cue-target intervals, which may fail to reveal impaired disengagement. We here used a machine-learning approach to conduct lesion-symptom mapping (LSM) on 89 patients with focal cerebral lesions to the left (LH) or right (RH) cerebral hemisphere. A group of 54 healthy participants served as controls. The paradigm used to uncover disengagement deficits employed non-predictive cues presented in the visual periphery and at short cue-target intervals, targeting exogenous attention. The main factors of interest were group (healthy participants, LH, RH), target position (left, right hemifield) and cue validity (valid, invalid). LSM-analyses were performed on two indices: the validity effect, computed as the absolute difference between reaction times (RTs) following invalid compared to valid cues, and the disengagement deficit, determined by the difference between contralesional and ipsilesional validity effects. While LH patients showed general slowing of RTs to contralesional targets, only RH patients exhibited a disengagement deficit from ipsilesional cues. LSM associated the validity effect with a right lateral frontal cluster, which additionally affected subcortical white matter of the right arcuate fasciculus, the corticothalamic pathway, and the superior longitudinal fasciculus. In contrast, the disengagement deficit was related to damage involving the right temporoparietal junction. Thus, our results support the crucial role of right inferior parietal and posterior temporal regions for attentional disengagement, but also emphasize the importance of lateral frontal regions, for the reorienting of attention.

Selection drives divergence of eye morphology in sympatric Heliconius butterflies.

When populations experience different sensory conditions, natural selection may favor sensory system divergence, affecting peripheral structures and/or downstream neural pathways. We characterized the outer eye morphology of sympatric Heliconius butterflies from different forest types and their first-generation reciprocal hybrids to test for adaptive visual system divergence and hybrid disruption. In Panama, Heliconius cydno occurs in closed forests, whereas Heliconius melpomene resides at the forest edge. Among wild individuals, H. cydno has larger eyes than H. melpomene, and there are heritable, habitat-associated differences in the visual brain structures that exceed neutral divergence expectations. Notably, hybrids have intermediate neural phenotypes, suggesting disruption. To test for similar effects in the visual periphery, we reared both species and their hybrids in common garden conditions. We confirm that H. cydno has larger eyes and provide new evidence that this is driven by selection. Hybrid eye morphology is more H. melpomene-like despite body size being intermediate, contrasting with neural trait intermediacy. Overall, our results suggest that eye morphology differences between H. cydno and H. melpomene are adaptive and that hybrids may suffer fitness costs due to a mismatch between the peripheral visual structures and previously described neural traits that could affect visual performance.

High visual salience of alert signals can lead to a counterintuitive increase of reaction times

It is often assumed that rendering an alert signal more salient yields faster responses to this alert. Yet, there might be a trade-off between attracting attention and distracting from task execution. Here we tested this in four behavioral experiments with eye-tracking using an abstract alert-signal paradigm. Participants performed a visual discrimination task (primary task) while occasional alert signals occurred in the visual periphery accompanied by a congruently lateralized tone. Participants had to respond to the alert before proceeding with the primary task. When visual salience (contrast) or auditory salience (tone intensity) of the alert were increased, participants directed their gaze to the alert more quickly. This confirms that more salient alerts attract attention more efficiently. Increasing auditory salience yielded quicker responses for the alert and primary tasks, apparently confirming faster responses altogether. However, increasing visual salience did not yield similar benefits: instead, it increased the time between fixating the alert and responding, as high-salience alerts interfered with alert-task execution. Such task interference by high-salience alert-signals counteracts their more efficient attentional guidance. The design of alert signals must be adapted to a “sweet spot” that optimizes this stimulus-dependent trade-off between maximally rapid attentional orienting and minimal task interference.

The Role of Uniform Textures in Making Texture Elements Visible in the Visual Periphery.

There are important differences between central and peripheral vision. With respect to shape, contours retain phenomenal sharpness, although some contours disappear if they are near other contours. This leads to some uniform textures to appear non-uniform (Honeycomb illusion, Bertamini et al., 2016). Unlike other phenomena of shape perception in the periphery, this illusion is showing how continuity of the texture does not contribute to phenomenal continuity. We systematically varied the relationship between central and peripheral regions, and we collected subjective reports (how far can one see lines) as well as judgments of line orientation. We used extended textures created with a square grid and some additional lines that are invisible when they are located at the corners of the grid, or visible when they are separated from the grid (control condition). With respects to subjective reports, we compared the region of visibility for cases in which the texture was uniform (Exp 1a), or when in a central region the lines were different (Exp 1b). There were no differences, showing no role of objective uniformity on visibility. Next, in addition to the region of visibility we measured sensitivity using a forced-choice task (line tilted left or right) (Exp 2). The drop in sensitivity with eccentricity matched the size of the region in which lines were perceived in the illusion condition, but not in the control condition. When participants were offered a choice to report of the lines were present or absent (Exp 3) they confirmed that they did not see them in the illusion condition, but saw them in the control condition. We conclude that mechanisms that control perception of contours operate differently in the periphery, and override prior expectations, including that of uniformity. Conversely, when elements are detected in the periphery, we assign to them properties based on information from central vision, but these shapes cannot be identified correctly when the task requires such discrimination.

Reversed Effect of Eccentricity: Perceived Duration of Peripherally Presented Stimuli Depends on Time Span

Abstract The perceived duration of stimuli presented in the visual periphery decreases with increasing eccentricity for brief durations. However, studies using different experimental methods or longer durations have reported inconsistent results. The present study aims to systematically explore the impact of stimulus eccentricity on perceived duration across various duration ranges. In three experiments employing the temporal bisection task, participants categorised the duration of stimuli presented at 3° or 9° of eccentricity as rather short or long, referred to two anchor durations previously learned. Stimulus durations varied between experiments and included short durations of 20–220 ms (Experiment 1), long durations of 400–1600 ms (Experiment 2), and intermediate durations of 160–660 ms (Experiment 3). For the short durations of Experiment 1, the results again replicated the decrease in perceived duration with increasing eccentricity. Interestingly, for the long durations, the effect was reversed, while subjective duration did not differ significantly between eccentricities for the intermediate durations. We discuss the findings with respect to prominent models of time perception, considering potential differences in attentional processing of short and long durations.

Tryptamine psychedelics shape population receptive fields in early visual cortex in the presence of perceptual distortions

Aims/Purpose: N, N‐dimethyltryptamine (DMT) is a psychedelic tryptamine associated with conspicuous visual hallucinatory phenomena and changes in perceived visual space. The neural basis of these effects remain unidentified. We asked whether changes in population receptive field properties in the primary visual cortex (V1) occur in parallel with changes in visual phenomenology.Methods: We tested this hypothesis using magnetic resonance imaging using a placebo‐controlled design of inhaled DMT. We used a population receptive field (pRF) mapping method, which assesses neural population visual response properties and retinotopic maps in visual cortex. One‐Way Repeated Measures ANOVA was performed to determine if populations of visual neurons do reorganize along eccentricity in response to inhaled DMT. We also tested the phenomenology of visual hallucinations using the Hallucinogen Rating scale (HRS) with a focus on the visual cluster of symptoms.Results: We show that the pRF sizes in V1 are significantly increased in peripherical field in the active condition (inhaled DMT) versus placebo (F (3, 54) = 22.6790, p‐value <0.0001). Post hoc Paired Sample T‐Tests were used to determine which pairs of bins of eccentricity were associated to significant differences. We found statistically significant differences for the peripherical bins of eccentricity (3.75 deg, 6.25 deg, 8.75 deg). These effects were accompanied by higher visual scores in Hallucinogen Rating scale (HRS) F(1,9) = 46 434, p < 0.05).Conclusions: This evidence for fast effects of DMT resulting in increased population receptive fields is consistent with the presence of visual manifestations and may explain perceptual distortions induced by psychedelics such as field blurring and the enlargement of nearby visual space, particularly at the visual periphery.

Using naturalistic and driving simulator data to model driver responses to unintentional lane departures

Unintentional lane departures on straight roads cause many road fatalities each year. The objective of this study was to explore and model drivers’ recovery steering maneuvers in unintentional drift situations, to enable the prospective safety benefit assessment of lane departure warning and avoidance systems through counterfactual simulations. The timing and amplitude of the steering adjustments drivers make to avoid lane departure were studied over three data sets with different origins, consisting of both naturalistic data and experimental data from a driving simulator study. With respect to timing, the main finding was that visually distracted drivers often initiate the corrective steering response prior to looking back towards the road, demonstrating that lane-keeping information in the visual periphery is sufficient to trigger the response. As for steering amplitude, the observed amplitudes were correlated against different lane departure risk metrics from the literature, resulting in a model capable of accounting for human behavior across all three data sets with good performance. Surprisingly, a very simple model (which describes the steering amplitude as increasing quadratically with the vehicle’s orientation to the road) predicted the amplitude of the primary corrective steering adjustment better than models based on more complex lane departure risk metrics. This result indicates that drivers scale the amplitude of their steering adjustment to the steering input needed to get the vehicle back in the lane already at first response. However, it was possible to obtain a similar model fit using a more complex threshold model, with different dynamics depending on the vehicle’s current orientation to the road. We discuss how these findings can be applied to models of human steering for safety benefit assessment.

Inferential eye movement control while following dynamic gaze.

Attending to other people's gaze is evolutionary important to make inferences about intentions and actions. Gaze influences covert attention and triggers eye movements. However, we know little about how the brain controls the fine-grain dynamics of eye movements during gaze following. Observers followed people's gaze shifts in videos during search and we related the observer eye movement dynamics to the time course of gazer head movements extracted by a deep neural network. We show that the observers' brains use information in the visual periphery to execute predictive saccades that anticipate the information in the gazer's head direction by 190-350 ms. The brain simultaneously monitors moment-to-moment changes in the gazer's head velocity to dynamically alter eye movements and re-fixate the gazer (reverse saccades) when the head accelerates before the initiation of the first forward gaze-following saccade. Using saccade-contingent manipulations of the videos, we experimentally show that the reverse saccades are planned concurrently with the first forward gaze-following saccade and have a functional role in reducing subsequent errors fixating on the gaze goal. Together, our findings characterize the inferential and functional nature of social attention's fine-grain eye movement dynamics.

Exploring perceptual sensitivity and response bias in the visual periphery

Exploring perceptual sensitivity and response bias in the visual periphery

A 2D Synthesized Image Improves the 3D Search for Foveated Visual Systems.

Current medical imaging increasingly relies on 3D volumetric data making it difficult for radiologists to thoroughly search all regions of the volume. In some applications (e.g., Digital Breast Tomosynthesis), the volumetric data is typically paired with a synthesized 2D image (2D-S) generated from the corresponding 3D volume. We investigate how this image pairing affects the search for spatially large and small signals. Observers searched for these signals in 3D volumes, 2D-S images, and while viewing both. We hypothesize that lower spatial acuity in the observers' visual periphery hinders the search for the small signals in the 3D images. However, the inclusion of the 2D-S guides eye movements to suspicious locations, improving the observer's ability to find the signals in 3D. Behavioral results show that the 2D-S, used as an adjunct to the volumetric data, improves the localization and detection of the small (but not large) signal compared to 3D alone. There is a concomitant reduction in search errors as well. To understand this process at a computational level, we implement a Foveated Search Model (FSM) that executes human eye movements and then processes points in the image with varying spatial detail based on their eccentricity from fixations. The FSM predicts human performance for both signals and captures the reduction in search errors when the 2D-S supplements the 3D search. Our experimental and modeling results delineate the utility of 2D-S in 3D search-reduce the detrimental impact of low-resolution peripheral processing by guiding attention to regions of interest, effectively reducing errors.

Parallel motion vision pathways in the brain of a tropical bee

Spatial orientation is a prerequisite for most behaviors. In insects, the underlying neural computations take place in the central complex (CX), the brain’s navigational center. In this region different streams of sensory information converge to enable context-dependent navigational decisions. Accordingly, a variety of CX input neurons deliver information about different navigation-relevant cues. In bees, direction encoding polarized light signals converge with translational optic flow signals that are suited to encode the flight speed of the animals. The continuous integration of speed and directions in the CX can be used to generate a vector memory of the bee’s current position in space in relation to its nest, i.e., perform path integration. This process depends on specific, complex features of the optic flow encoding CX input neurons, but it is unknown how this information is derived from the visual periphery. Here, we thus aimed at gaining insight into how simple motion signals are reshaped upstream of the speed encoding CX input neurons to generate their complex features. Using electrophysiology and anatomical analyses of the halictic bees Megalopta genalis and Megalopta centralis, we identified a wide range of motion-sensitive neurons connecting the optic lobes with the central brain. While most neurons formed pathways with characteristics incompatible with CX speed neurons, we showed that one group of lobula projection neurons possess some physiological and anatomical features required to generate the visual responses of CX optic-flow encoding neurons. However, as these neurons cannot explain all features of CX speed cells, local interneurons of the central brain or alternative input cells from the optic lobe are additionally required to construct inputs with sufficient complexity to deliver speed signals suited for path integration in bees.

Short periods of perinatal acoustic experience alter the developmental trajectory of auditory cortex

Compared to hearing subjects, psychophysical studies have revealed specific superior visual abilities following hearing loss early in development. The neural substrate for these superior abilities resides in auditory cortex that have been reorganized through crossmodal plasticity. Furthermore, the cartography of auditory cortex is altered following the loss of auditory input early in life. This study examined how perinatal exposure to brief periods of acoustic stimulation alters the developmental trajectory of auditory cortex. Movement detection, localization in the visual periphery, and face discrimination learning are superior in congenitally deaf cats. To examine the role of acoustic experience in mediating these enhanced functions, hearing animals were chemically deafened at increasing ages postnatal. Animals had 1–16 weeks of acoustic exposure prior to deafness onset. Overall, >9 weeks of acoustic experience resulted in no enhanced visual abilities. With >4 weeks of acoustic exposure, enhanced motion detection was not evident. As acoustic experience increased during development, the overall size of auditory cortex, and the size of individual auditory areas also expanded. These results demonstrate that increasingly longer periods of perinatal acoustic experience result in reduced enhanced visual abilities and an increased size of auditory cortex.