Visual Occlusion Research Articles

Incremental Visual Occlusion During Split-Belt Treadmill Walking Has No Gradient Effect on Adaptation or Retention.

Split-belt treadmills have become an increasingly popular means of quantifying ambulation adaptability. Multiple sensory feedback mechanisms, including vision, contribute to task execution and adaptation success. No studies have yet explored visual feedback effects on locomotor adaptability across a spectrum of available visual information. In this study, we sought to better understand the effects of visual information on locomotor adaptation and retention by directly comparing incremental levels of visual occlusion. Sixty healthy young adults completed a split-belt adaptation protocol, including a baseline, asymmetric walking condition (adapt), a symmetric walking condition (de-adapt), and another asymmetric walking condition (re-adapt). We randomly assigned participants into conditions with varied visual occlusion (i.e., complete and lower visual field occlusion, or normal vision). We captured kinematic data, and outcome measures included magnitude of asymmetry, spatial and temporal contributions to step length asymmetry, variability of the final adapted pattern, and magnitude of adaptation. We used repeated measures and four-way MANOVAs to examine the influence of visual occlusion and walking condition. Participants with complete, compared to lower visual field visual occlusion displayed less consistency in their walking pattern, evident via increased step length standard deviation (p = .007, d = 0.89), and compared to normal vision groups (p = .003 d = 0.81). We found no other group differences, indicating that varying levels of visual occlusion did not significantly affect locomotor adaptation or retention. This study offers insight into the role vision plays in locomotor adaptation and retention with clinical utility for improving variability in step control.

Inattention and Uncertainty in the Predictive Brain.

Negative effects of inattention on task performance can be seen in many contexts of society and human behavior, such as traffic, work, and sports. In traffic, inattention is one of the most frequently cited causal factors in accidents. In order to identify inattention and mitigate its negative effects, there is a need for quantifying attentional demands of dynamic tasks, with a credible basis in cognitive modeling and neuroscience. Recent developments in cognitive science have led to theories of cognition suggesting that brains are an advanced prediction engine. The function of this prediction engine is to support perception and action by continuously matching incoming sensory input with top-down predictions of the input, generated by hierarchical models of the statistical regularities and causal relationships in the world. Based on the capacity of this predictive processing framework to explain various mental phenomena and neural data, we suggest it also provides a plausible theoretical and neural basis for modeling attentional demand and attentional capacity "in the wild" in terms of uncertainty and prediction error. We outline a predictive processing approach to the study of attentional demand and inattention in driving, based on neurologically-inspired theories of uncertainty processing and experimental research combining brain imaging, visual occlusion and computational modeling. A proper understanding of uncertainty processing would enable comparison of driver's uncertainty to a normative level of appropriate uncertainty, and thereby improve definition and detection of inattentive driving. This is the necessary first step toward applications such as attention monitoring systems for conventional and semi-automated driving.

Nature Experiences of Older People for Active Ageing: An Interdisciplinary Approach to the Co-Design of Community Gardens

In Western countries, the concepts of healthy ageing and active ageing, that is, concepts that favour health, participation, and security to increase the quality of life of older people, have become key issues. Hence, the effective design of public green spaces in urban areas is crucial, as visiting these areas encourages social relations and interactions in natural, healthy contexts. Consistent with these perspectives, existing landscape design criteria emphasise the importance of considering not only the functional and aesthetic elements, but also the ecosystemic and biophilic relationships between people and the environment, producing positive effects for both. To maximise the impact of such design criteria, proper engagement strategies are desirable, both to assign an active role to older people themselves and to inform the fine-tuning of the design process according to the specific needs of the local population. This study presents an interdisciplinary co-design method that encourages and informs a biophilic approach by describing the experiences of people in natural environments, actual and designed, through the application of attention restoration theory (ART). The case study was developed through six focus group meetings with older people for the co-design of a restorative area in a community garden in the Ortica district in Milan (Italy). Results show how the main needs expressed by participants can be classified into the ART factors of “compatibility” (a multifunctional garden), “fascination” (sense of contact with nature), and “being away” (metaphorical escape from nursing homes). The garden designed includes biophilic principles that respond to such needs, and specific links with designed elements were identified. For example, “being away” (e.g., isolation from daily routine and visual occlusion of the surroundings) and “compatibility” (e.g., pergola and aesthetic value) are the factors that include the elements that more satisfactorily answer previous needs. “Fascination” also includes many positive aspects, allowing space for improvements (e.g., more water elements, interaction with animals). Implications of the method are discussed, including the importance of subjective experience in informing design, the use of different psychological constructs to describe it, and the methodological alternatives for psychological assessment.

Collective decision-making for dynamic environments with visual occlusions

Collective decision-making for dynamic environments with visual occlusions

Industrial robot programming by demonstration using stereoscopic vision and inertial sensing

PurposeThe purpose of this paper is to present a programming by demonstration (PbD) system based on 3D stereoscopic vision and inertial sensing that provides a cost-effective pose tracking system, even during error-prone situations, such as camera occlusions.Design/methodology/approachThe proposed PbD system is based on the 6D Mimic innovative solution, whose six degrees of freedom marker hardware had to be revised and restructured to accommodate an IMU sensor. Additionally, a new software pipeline was designed to include this new sensing device, seeking the improvement of the overall system’s robustness in stereoscopic vision occlusion situations.FindingsThe IMU component and the new software pipeline allow the 6D Mimic system to successfully maintain the pose tracking when the main tracking tool, i.e. the stereoscopic vision, fails. Therefore, the system improves in terms of reliability, robustness, and accuracy which were verified by real experiments.Practical implicationsBased on this proposal, the 6D Mimic system reaches a reliable and low-cost PbD methodology. Therefore, the robot can accurately replicate, on an industrial scale, the artisan level performance of highly skilled shop-floor operators.Originality/valueTo the best of the authors’ knowledge, the sensor fusion between stereoscopic images and IMU applied to robot PbD is a novel approach. The system is entirely designed aiming to reduce costs and taking advantage of an offline processing step for data analysis, filtering and fusion, enhancing the reliability of the PbD system.

Ecological design of augmentation improves helicopter ship landing maneuvers: An approach in augmented virtuality.

Helicopter landing on a ship is a visually regulated "rendezvous" task during which pilots must use fine control to land a powerful rotorcraft on the deck of a moving ship tossed by the sea while minimizing the energy at impact. Although augmented reality assistance can be hypothesized to improve pilots' performance and the safety of landing maneuvers by guiding action toward optimal behavior in complex and stressful situations, the question of the optimal information to be displayed to feed the pilots' natural information-movement coupling remains to be investigated. Novice participants were instructed to land a simplified helicopter on a ship in a virtual reality simulator while minimizing energy at impact and landing duration. The wave amplitude and related ship heave were manipulated. We compared the benefits of two types of visual augmentation whose design was based on either solving cockpit-induced visual occlusion problems or strengthening the online regulation of the deceleration by keeping the current [Formula: see text] variable around an ideal value of -0.5 to conduct smooth and efficient landing. Our results showed that the second augmentation, ecologically grounded, offers benefits at several levels of analysis. It decreases the landing duration, improves the control of the helicopter displacement, and sharpens the sensitivity to changes in [Formula: see text]. This underlines the importance for designers of augmented reality systems to collaborate with psychologists to identify the relevant perceptual-motor strategy that must be encouraged before designing an augmentation that will enhance it.

Visual Effect on Brain Connectome That Scales Feedforward and Feedback Processes of Aged Postural System During Unstable Stance.

Older adults with degenerative declines in sensory systems depend strongly on visual input for postural control. By connecting advanced neural imaging and a postural control model, this study investigated the visual effect on the brain functional network that regulates feedback and feedforward processes of the postural system in older adults under somatosensory perturbations. Thirty-six older adults conducted bilateral stance on a foam surface in the eyes-open (EO) and eyes-closed (EC) conditions while their center of pressure (COP) and scalp EEG were recorded. The stochastic COP trajectory was modeled with non-linear stabilogram diffusion analysis (SDA) to characterize shifts in postural control in a continuum of feedback and feedforward processes. The EEG network was analyzed with the phase-lag index (PLI) and minimum spanning tree (MST). The results indicated that visual input rebalanced feedforward and feedback processes for postural sway, resulting in a greater critical point of displacement (CD), short-term effective diffusion coefficients (Ds) and short-term exponent (Hs), but the smaller critical point of time (CT) and long-term exponent (Hl) for the EC state. The EC network demonstrated stronger frontoparietal-occipital connectivity but weaker fronto-tempo-motor connectivity of the theta (4–7 Hz), alpha (8–12 Hz), and beta (13–35 Hz) bands than did the EO network. MST analysis revealed generally greater leaf fraction and maximal betweenness centrality (BCmax) and kappa of the EC network, as compared with those of the EO network. In contrast, the EC network exhibited a smaller diameter and average eccentricity than those of the EO network. The modulation of long-term negative feedback gain of the aged postural system with visual occlusion was positively correlated with leaf fraction, BCmax, and kappa, but negatively correlated with the diameter and average eccentricity for all EEG sub-bands. In conclusion, the aged brain functional network in older adults is tuned to visual information for modulating long-term negative feedback of the postural system under somatosensory perturbations.

Self-organization in natural swarms of Photinus carolinus synchronous fireflies.

Fireflies flashing in unison is a mesmerizing manifestation of animal collective behavior and an archetype of biological synchrony. To elucidate synchronization mechanisms and inform theoretical models, we recorded the collective display of thousands of Photinus carolinus fireflies in natural swarms, and provide the first spatiotemporal description of the onset of synchronization. At low firefly density, flashes appear uncorrelated. At high density, the swarm produces synchronous flashes within periodic bursts. Using three-dimensional reconstruction, we demonstrate that flash bursts nucleate and propagate across the swarm in a relay-like process. Our results suggest that fireflies interact locally through a dynamic network of visual connections defined by visual occlusion from terrain and vegetation. This model illuminates the importance of the environment in shaping self-organization and collective behavior.

Solution for vision occlusion based on binocular line-structured light

Solution for vision occlusion based on binocular line-structured light

Multi-Sensor Perception Strategy to Enhance Autonomy of Robotic Operation for Uncertain Peg-in-Hole Task.

The peg-in-hole task with object feature uncertain is a typical case of robotic operation in the real-world unstructured environment. It is nontrivial to realize object perception and operational decisions autonomously, under the usual visual occlusion and real-time constraints of such tasks. In this paper, a Bayesian networks-based strategy is presented in order to seamlessly combine multiple heterogeneous senses data like humans. In the proposed strategy, an interactive exploration method implemented by hybrid Monte Carlo sampling algorithms and particle filtering is designed to identify the features’ estimated starting value, and the memory adjustment method and the inertial thinking method are introduced to correct the target position and shape features of the object respectively. Based on the Dempster–Shafer evidence theory (D-S theory), a fusion decision strategy is designed using probabilistic models of forces and positions, which guided the robot motion after each acquisition of the estimated features of the object. It also enables the robot to judge whether the desired operation target is achieved or the feature estimate needs to be updated. Meanwhile, the pliability model is introduced into repeatedly perform exploration, planning and execution steps to reduce interaction forces, the number of exploration. The effectiveness of the strategy is validated in simulations and in a physical robot task.

Anxiety does not always affect balance: the predominating role of cognitive engagement in a video gaming task.

Scientists have predominantly assessed anxiety's impact on postural control when anxiety is created by the need to maintain balance (e.g., standing at heights). In the present study, we investigate how postural control and its mechanisms (i.e., vestibular function) are impacted when anxiety is induced by an unrelated task (playing a video game). Additionally, we compare watching and playing a game to dissociate postural adaptations caused by increased engagement rather than anxiety. Participants [N = 25, female = 8, M (SD) age = 23.5 (3.9)] held a controller in four standing conditions of varying surface compliance (firm or foam) andwith or without peripheral visual occlusion across four blocks: quiet standing (baseline), watching the game with a visual task (watching), playing the game (low anxiety), and playing under anxiety (high anxiety). We measured sway area, sway frequency, root mean square (RMS) sway, anxiety, and mental effort. Limited sway differences emerged between anxiety blocks (only sway area on firm surface). The watching block elicited more sway than baseline (greater sway area and RMS sway; lower sway frequency), and the low anxiety block elicited more sway than the watching block (greater sway area and RMS sway; higher sway frequency). Mental effort was associated with increased sway area and RMS sway. Our findings indicate that anxiety, when generated through competition, has minimal impact on postural control. Postural control primarily adapts according to mental effort and more cognitively engaging task constraints (i.e., playing versus watching). We speculate increased sway reflects the prioritization of attention to game performance over postural control.

Pupillary Response to Postural Demand in Parkinson's Disease.

Background: Individuals with Parkinson’s disease (PD) may need to spend more mental and physical effort (i.e., cognitive workload) to maintain postural control. Pupillary response reflects cognitive workload during postural control tasks in healthy controls but has not been investigated as a measure of postural demand in PD.Objectives: To compare pupillary response during increased postural demand using vision occlusion and dual tasking between individuals with PD and healthy controls.Methods: Thirty-three individuals with PD and thirty-five healthy controls were recruited. The four conditions lasted 60 s and involved single balance task with eyes open; single balance task with eyes occluded; dual task with eyes open; dual task with eyes occluded. The dual task comprised the Auditory Stroop test. Pupillary response was recorded using an eye tracker. The balance was assessed by using a force plate. Two-way Repeated Measures ANOVA and LSD post-hoc tests were employed to compare pupillary response and Center of Pressure (CoP) displacement across the four conditions and between individuals with PD and healthy controls.Results: Pupillary response was higher in individuals with PD compared to healthy controls (p = 0.009) and increased with more challenging postural conditions in both groups (p < 0.001). The post-hoc analysis demonstrated increased pupillary response in the single balance eyes occluded (p < 0.001), dual task eyes open (p = 0.01), and dual task eyes occluded (p < 0.001) conditions compared to single task eyes open condition.Conclusion: Overall, the PD group had increased pupillary response with increased postural demand compared to the healthy controls. In the future, pupillary response can be a potential tool to understand the neurophysiological underpinnings of falls risk in the PD population.

Object-Wise Video Editing

Beyond time frame editing in video data, object level video editing is a challenging task; such as object removal in a video or viewpoint changes. These tasks involve dynamic object segmentation, novel view video synthesis and background inpainting. Background inpainting is a task of the reconstruction of unseen regions presented by object removal or viewpoint change. In this paper, we propose a video editing method including foreground object removal background inpainting and novel view video synthesis under challenging conditions such as complex visual pattern, occlusion, overlaid clutter and variation of depth in a moving camera. Our proposed method calculates a weighted confidence score on the basis of normalized difference between observed depth and predicted distance in 3D space. A set of potential points from epipolar lines from neighbor frames are collected, refined, and weighted to select a few number of highly qualified observations to fill the desired region of interest area in the current frame from video. Based on the background inpainting method, novel view video synthesis is conducted with arbitrary viewpoint. Our method is evaluated with both a public dataset and our own video clips and compared with multiple state of the art methods showing a superior performance.

골프퍼팅시 시각차단연습과 시각허용연습이 수행지각거리와 실제수행거리의 정확성에 미치는 영향

Purpose: The purpose of this study was to investigate the potential applicability of visual occlusion training as a physical intervention by comparing the accuracy of perceptual distance and actual performance distance according to visual occlusion training and visual allowance training. Methods: 36 male college students with no previous experience in golf participated in the experiment. They were randomly assigned to one of three groups; visual occlusion training group, visual allowance training group, and control group. In the pre-test, participants performed a total of 15 putts once at each distance (1-15m). In the block 1, 2, 3, a total of 90 putts were performed twice for each distance in each block. After the block practice, the post-test was conducted in the same way as the pre-test. The absolute error value for putting performance was used to analyze the accuracy of perceptual distance and actual performance distance. Results: Visual occlusion training and visual allowance training groups were significantly higher than control group in the accuracy of perceptual and actual performance distance. However, there was no difference between the two training groups. Conclusion: The results suggest that visual occlusion and visual allowance training can enhance perceptual judgment and skill performance, in particular, the potential applicability of visual occlusion training as an effective physical intervention for combining with visual allowance training.

A goalkeeper's performance in stopping free kicks reduces when the defensive wall blocks their initial view of the ball.

Free kicks are an important goal scoring opportunity in football. It is an unwritten rule that the goalkeeper places a wall of defending players with the aim of making scoring harder for the attacking team. However, the defensive wall can occlude the movements of the kicker, as well as the initial part of the ball trajectory. Research on one-handed catching suggests that a ball coming into view later will likely delay movement initiation and possibly affect performance. Here, we used virtual reality to investigate the effect of the visual occlusion of the initial ball trajectory by the wall on the performance of naïve participants and skilled goalkeepers. We showed that movements were initiated significantly later when the wall was present, but not by the same amount as the duration of occlusion (~200ms, versus a movement delay of ~70-90ms); movements were thus initiated sooner after the ball came into view, based on less accumulated information. For both naïve participants and skilled goalkeepers this delayed initiation significantly affected performance (i.e., 3.6cm and 1.5cm larger spatial hand error, respectively, not differing significantly between the groups). These performance reductions were significantly larger for shorter flight times, reaching increased spatial errors of 4.5cm and 2.8cm for both groups, respectively. Further analyses showed that the wall-induced performance reduction did not differ significantly between free kicks with and without sideward curve. The wall influenced early movement biases, but only for free kicks with curve in the same direction as the required movement; these biases were away from the final ball position, thus hampering performance. Our results cannot suggest an all-out removal of the wall-this study only considered one potential downside-but should motivate goalkeepers to continuously evaluate whether placing a wall is their best option. This seems most pertinent when facing expert free kick takers for whom the wall does not act as a block (i.e., whose kicks consistently scale the wall).

Generation mechanism and simulation research of zipper phenomenon of pedestrian flow in corridor

In this study, the unidirectional pedestrian flow in the corridor is taken as a research object, the generation mechanism of the pedestrian zipper phenomenon is analyzed, and a velocity correction model based on the Voronoi diagram is established for the simulation research. First, the generation mechanism of the pedestrian zipper phenomenon is analyzed from the perspective of optimal visual field and walking comfort of pedestrians. Then the visual attention and visual occlusion of pedestrians are used to describe the factors which affect the zipper deviation during pedestrian movement, the local density of pedestrians is used to describe the walking comfort of pedestrians, the zipper sensitivity coefficient is adopted to describe the willingness of pedestrians to move objectively, and the mechanism of lateral deviation of a single pedestrian is considered to obtain the optimal deviation position of pedestrians. Besides, the Voronoi diagram is introduced to effectively determine the pedestrians surrounding the target pedestrian within the visual field. And the influence of surrounding pedestrians with different distances and directions on the moving velocity of the target pedestrian based on the Voronoi diagram is considered. Then, a velocity correction model of pedestrians based on the Voronoi diagram is constructed, whether the pedestrian has a subjective willingness to deviate is considered, and the deviation rule is embedded to simulate and reproduce the zipper phenomenon of pedestrians. The simulation results truly reproduce the normal pedestrian flow through the corridor and show that our model can overcome the deficiency of the jitter and overlap phenomenon of the traditional social force model. The self-organized pedestrian flow with uniform distribution and the pedestrian zipper effect can also be observed. Furthermore, through the simulation results, we can see that the number of zipper layers for pedestrians is proportional to the width of the corridor. The comparison of simulated pedestrian data with the empirical data indicates that the fundamental diagram of velocity-density relation of our model is in good agreement with the empirical data. A comparison between with and without considering the zipper effect shows that the larger the proportion of pedestrians actively willing to laterally deviate, the more helpful it will be to improve the moving velocity, comfort and space utilization of pedestrians in the corridor.

Investigating the Effects of Interruptions and Reliable Cueing on Change Detection within Dynamic Scenes

The goal of the present study was to examine the effects of cuing and task interruptions on change detection within dynamic scenes. Undergraduate students watched 24 brief videos (12 containing interruptions) for anomalous feature changes appearing in 8 videos. Half of the object changes occurred during a visual occlusion, while the others contained no interruption. All videos were unique and depicted various dynamic scenes. Participants were assigned at random to one of three conditions containing cues to the changes (reliable, unreliable, or no cue). The results showed that more object changes were detected during uninterrupted vs. interrupted trials. More object changes were detected with reliable vs. unreliable cues for uninterrupted trials. Providing reliable cues had no benefit over the other conditions when interruptions were present. Overall, these results suggest that visual interruptions may degrade information stored in memory, which could compromise visual monitoring tasks.

Facing Repeated Stressors in a Motor Task: Does it Enhance or Diminish Resilience?

The aim of the present research is to test whether resilience in a motor task enhances or diminishes when encountering stressors. We conducted a lateral movement task during which we induced stressors and tracked the movement accuracy of each participant over time. Stressors corresponded to organismic constraints (i.e., visual occlusion), task constraints (i.e., movement sensitivity), or both types of constraints in an alternating pattern. In order to determine resilience, we introduced a measure combining the strength of a stressor and the relaxation time. Across the three conditions, we found that resilience was enhanced rather than diminished over time. This supports the notion that stressors in the form of constraint alterations can be beneficial to human motor performance.

The influence of the Sander parallelogram illusion and early, middle and late vision on goal-directed reaching and grasping

Vision is one of the most robust sensory inputs used for the execution of goal-directed actions. Despite a history of extensive visuomotor research, how individuals process visual context for the execution of movements continues to be debated. This experiment examines how early, middle and late visuomotor control is impacted by illusory characteristics in a reaching and grasping task. Participants either manually estimated or reached out and picked up a three-dimensional target bar resting on a two-dimensional picture of the Sander parallelogram illusion. Participants performed their grasps within a predefined time movement window based on their own average grasp time, allowing for the manipulation of visual feedback. On some trials, vision was only available before the response cue (an auditory tone), while on others vision was occluded until the response cue, becoming available for either the full, early, middle or late portions of the movement. While results showed that the effect of the illusion was stronger on manual estimations than on grasping, maximum grip apertures in the occluded vision and early vision grasping conditions were also consistent to a lesser extent with the illusion. The late vision condition showed longer movement time, wrist deceleration period, time to maximum grip aperture and lower maximum velocity. These findings indicate that visual context affects visuomotor control distinctly depending on when vision is available, and supports the notion that human vision is comprised of two functionally and anatomically distinct systems.

The Time Course of Perceptual Closure of Incomplete Visual Objects: An Event-Related Potential Study.

Perceptual organization is an important part of visual and auditory information processing. In the case of visual occlusion, whether the loss of information in images could be recovered and thus perceptually closed affects object recognition. In particular, many elderly subjects have defects in object recognition ability, which may be closely related to the abnormalities of perceptual functions. This phenomenon even can be observed in the early stage of dementia. Therefore, studying the neural mechanism of perceptual closure and its relationship with sensory and cognitive processing is important for understanding how the human brain recognizes objects, inspiring the development of neuromorphic intelligent algorithms of object recognition. In this study, a new experiment was designed to explore the realistic process of perceptual closure under occlusion and intact conditions of faces and building. The analysis of the differences in ERP components P1, N1, and Ncl indicated that the subjective awareness of perceptual closure mainly occurs in Ncl, but incomplete information has been processed and showed different manners compared to complete stimuli in N170 for facial materials. Although occluded, faces, but not buildings, still maintain the specificity of perceptual processing. The Ncl by faces and buildings did not show significant differences in both amplitude and latency, suggesting a “completing” process regardless of categorical features.