Spatial Manipulations Research Articles

Visual Servoing and Kalman Filter Applied to Parallel Manipulator 3-RRR

This study introduces a novel methodology integrating computer vision, visual servo control, and the Kalman Filter to precisely estimate object locations for a 3-RRR planar type parallel manipulator. Through kinematic analysis and the development of a vision system using color indicators, the research enhances the ability of the manipulator to track object trajectories, especially in cases of occlusion. Employing Eye-to-Hand visual servo control, the research further refines the visual orientation of the sensor for optimal end effector and object identification. The incorporation of the Kalman Filter as a robust estimator for occluded objects underscores the predictive accuracy of the system. Results demonstrate the effectiveness of the methodology in trajectory generation and object tracking, with potential implications for improving robotic manipulators in dynamic environments. This comprehensive approach not only advances the fields of kinematic control and visual servoing but also opens new avenues for future research in complex spatial manipulations.

On the relationship between spatial attention and semantics in the context of a Stroop paradigm.

A controversial issue in the literature on single word reading concerns whether semantic activation from a printed word can be stopped. Several reports have claimed that, even when attention is directed to a single letter in a word, semantic interference persists full blown in the context of variants of Stroop's paradigm. Incidental word recognition is thus claimed to be unaffected by directed spatial attention and hence to be automatic by this criterion. In contrast, the literature examining the relation between intentional visual word recognition and spatial attention in tasks like lexical decision and reading aloud suggests that spatial attention is a necessary preliminary to lexical/semantic processing of a word. These opposing conclusions raise the question of whether there is a qualitative difference between incidental and intentional visual word recognition when spatial attention is considered. We first consider the methodology from Stroop experiments in which putatively narrowed spatial attention manipulations failed to prevent interference from semantics. We then report a new experiment that better promotes focused spatial attention. The results yield clear evidence that the effect of semantic activation can indeed be sidelined because one or more prior processes were in large measure stopped. We conclude that incidental word recognition is not automatic in the sense of occurring without any kind of attention.

ExMove: An open-source toolkit for processing and exploring animal-tracking data in R.

Ongoing technological advances have led to a rapid increase in the number, type and scope of animal-tracking studies. In response, many software tools have been developed to analyse animal movement data. These tools generally focus on movement modelling, but the steps required to clean raw data files from different tracking devices have been largely ignored. Such pre-processing steps are often time-consuming and involve a steep learning curve but are crucial for the creation of high-quality, standardised and shareable data. Moreover, decisions made at this early stage can substantially influence subsequent analyses, and in the current age of reproducibility crisis, the transparency of this process is vital. Here we present an open-access, reproducible toolkit written in the programming language R for processing raw data files into a single cleaned data set for analyses and upload to online tracking databases (found here: https://github.com/ExMove/ExMove). The toolkit comprises well-documented and flexible code to facilitate data processing and user understanding, both of which can increase user confidence and improve the uptake of sharing open and reproducible code. Additionally, we provide an overview website (found here: https://exmove.github.io/) and a Shiny app to help users visualise tracking data and assist with parameter determination during data cleaning. The toolkit is generalisable to different data formats and device types, uses modern 'tidy coding' practices, and relies on a few well-maintained packages. Among these, we perform spatial manipulations using the package sf. Overall, by collating all required steps from data collection to archiving on open access databases into a single, robust pipeline, our toolkit provides a valuable resource for anyone conducting animal movement analyses and represents an important step towards increased standardisation and reproducibility in animal movement ecology.

In Case of Doubt, One Follows One's Self: The Implicit Guidance of the Embodied Self-Avatar.

The sense of embodiment in virtual reality (VR) is commonly understood as the subjective experience that one's physical body is substituted by a virtual counterpart, and is typically achieved when the avatar's body, seen from a first-person view, moves like one's physical body. Embodiment can also be experienced in other circumstances (e.g., in third-person view) or with imprecise or distorted visuo-motor coupling. It was moreover observed, in various cases of small or progressive temporal and spatial manipulations of avatars' movements, that participants may spontaneously follow the movement shown by the avatar. The present work investigates whether, in some specific contexts, participants would follow what their avatar does even when large movement discrepancies occur, thereby extending the scope of understanding of the self-avatar follower effect beyond subtle changes of motion or speed manipulations. We conducted an experimental study in which we introduced uncertainty about which movement to perform at specific times and analyzed participants' movements and subjective feedback after their avatar showed them an incorrect movement. Results show that, when in doubt, participants were influenced by their avatar's movements, leading them to perform that particular error twice more often than normal. Importantly, results of the embodiment score indicate that participants experienced a dissociation with their avatar at those times. Overall, these observations not only demonstrate the possibility of provoking situations in which participants follow the guidance of their avatar for large motor distortions, despite their awareness about the avatar movement disruption and on the possible influence it had on their choice, and, importantly, exemplify how the cognitive mechanism of embodiment is deeply rooted in the necessity of having a body.

Coherent Spatial Control of Wave Packet Dynamics on Quantum Lattices.

Quantum lattices are pivotal in the burgeoning fields of quantum materials and information science. Novel experimental techniques allow the preparation and monitoring of wave packet dynamics on quantum lattices with high spatiotemporal resolution. We present an analytical study of wave packet diffusivity and diffusion length on tight-binding quantum lattices subject to stochastic noise. Our analysis reveals the crucial role of spatial coherence and predicts a set of novel phenomena: (1) noise can enhance the transient diffusivity and diffusion length of spatially extended initial states; (2) standing or traveling initial states, with large momentum, spread faster than a localized initial state and exhibit a noise-induced peak in the transient diffusivity; (3) the differences in the diffusivity or diffusion length of extended and localized initial states have a universal dependence on initial width. These predictions suggest the possibility of controlling the wave packet dynamics by spatial manipulations, which will have implications for materials science and quantum technologies.

A Fragile Watermarking Method for Content-Authentication of H.264-AVC Video

This work proposes a blind fragile GOP-based watermarking technique that ensures the H.264-AVC video's content authenticity. In the H.264 video, the self-authentication code is created by securely hashing a number of intra prediction modes of I-frames in addition to motion vectors of P-frames and B-frames. The resulting authentication code is subsequently injected into the IPCM-Least block's Significant Bits (LSB) of some I-frames' luma and chroma pixel samples. To manage and regulate authentication data and watermark processes (embedding, detection, and verification), a key based on video footage and a secret key has been created. Intra prediction modes and motion vectors from the bitstream can be partially decoded to detect and confirm the hidden watermark data without the need for the original movie or complete video decoding. Several experiments were conducted to assess the sensitivity of the proposed method against signal processing, rate control and transcoding, conventional GOP-based and Frame-based attacks. Experimental simulations demonstrate that the implanted fragile watermark is sensitive to several low to harmful and content-preserving attacks. With only a modest bit-rate increase and hardly any perceptual quality deterioration, a large payload capacity is achieved. Experimental results show that the proposed method is suburb in term of imperceptibility, and lower effect on bit-rate. Applications like tamper-proofing, content-authentication, and covert communication are ideally suited for this technique. Based on achieved results, the devised method is capable of detecting any form of spatial and/or temporal manipulations which make it ideal for real-time applications.

The development of processing second-order spatial relations of faces in Chinese preschoolers

Second-order relational information processing is the perception of the relative distance between facial features. Previous studies ignored the effect of different spatial manipulations on second-order sensitivity in face processing, and little is known about its developmental trajectory in East Asian populations, who have stronger holistic face processing than Western populations. We addressed these gaps in the literature through an experiment with four groups of Chinese preschool children (aged 3–6 years; n = 157) and a group of adults (n = 25). The participants were presented with face pairs displaying features with various spatial distance manipulations (Change 1: changes in the spacing between eyes; Change 2: nose–mouth spacing changes; Change 3: a combination of Changes 1 and 2) using a simultaneous two-alternative forced-choice task. Second-order sensitivity was already present in 3-year-old children across all manipulations and became more pronounced in 4-year-old children. Second-order sensitivity to the spatial distance between the eyes (i.e., Changes 1 and 3) among 4-year-olds was higher than that of 3-year-olds and was similar to that of adults, suggesting a key increase of this sensitivity from 3 to 4 years of age. Regarding the Change 2 condition, preschoolers aged 5 and 6 years had higher sensitivity than 3-year-olds; however, all preschoolers’ sensitivity was inferior to that of adults. These findings show that the development of Chinese preschoolers’ sensitivity for detecting spatial relations between the eyes might be faster than that for detecting nose–mouth spacing, supporting the importance of eyes in face processing.

Event-Related Potentials Index Prediction Error Signalling During Perceptual Processing of Emotional Facial Expressions

Humans use socially relevant stimuli to guide perceptual processing of the surrounding environment, with emotional stimuli receiving preferential attention due to their social importance. Predictive coding theory asserts this cognitive process occurs efficiently by combining predictions about what is to be perceived with incoming sensory information, generating prediction errors that are then used to update future predictions. Recent evidence has identified differing neural activity that demonstrates how spatial and feature-based attention may interact with prediction, yet how emotion-guided attention may influence this relationship remains unknown. In the present study, participants viewed a display of two faces in which attention, prediction, and emotion were manipulated, and responded to a face expressing a specific emotion (anger or happiness). The N170 was found to be enhanced by unpredictable as opposed to predictable stimuli, indicating that it indexes general prediction error signalling processes. The N300 amplitudes were also enhanced by unpredictable stimuli, but they were also affected by the attentional status of angry but not happy faces, suggesting that there are differences in prediction error processes indexed by the N170 and N300. Overall, the findings suggest that the N170 and N300 both index violations of expectation for spatial manipulations of stimuli in accordance with prediction error responding processes.

Emerging Nonplanar van der Waals Nanoarchitectures from 2D Allotropes for Optoelectronics

AbstractThe unique atomic thickness and mechanical flexibility of 2D van der Waals (vdW) materials endow them with spatial designability and constructability. It is easy to break the inherent planar construction through various spatial manipulations, thus creating vdW nanoarchitectures with nonplanar topologies. The basic properties before evolution are retained and tunable by architecture‐related feature sizes, and other newly generated properties are inspiring as they are beyond the reach of 2D allotropes, bringing great competitiveness for their encouraging applications in optoelectronics. Here, these representative nonplanar vdW nanoarchitectures (i.e., nanoscrolls, nanotubes, spiral nanopyramids, spiral nanowires, nanoshells, etc.) are summarized and their structural evolution processes are elucidated. Their fascinating nascent properties based on their distinctive structural features, focusing on generally enhanced light–matter interactions and device physics, are further introduced. Finally, their opportunities and challenges for in‐depth experimental exploration are prospected. It is a brand‐new idea to modify the properties of 2D vdW materials from micro‐ and nanostructural design and evolution, offering a solid platform for twistronics, valleytronics, and integrated nanophotonics.

Effects of task load, spatial attention, and trait anxiety on neuronal responses to fearful and neutral faces

There is an ongoing debate on how different components of the event-related potential (ERP) to threat-related facial expressions are modulated by attentional conditions and interindividual differences in trait anxiety. In the current study (N=80), we examined ERPs to centrally presented, task-irrelevant fearful and neutral faces, while participants had to solve a face-unrelated visual task, which differed in difficulty and spatial position. Critically, we used a fixation-controlled experimental design and ensured the spatial attention manipulation by spectral analysis of the EEG. Besides the factors emotion, spatial attention, and perceptual load, we also investigated correlations between trait anxiety and ERPs. While P1 emotion effects were insignificant, the N170 was increased to fearful faces regardless of load and spatial attention conditions. During the EPN time window, a significantly increased negativity for fearful faces was observed only during low load and spatial attention to the face. We found no significant relationship between ERPs and trait anxiety, questioning the hypothesis of a general hypersensitivity toward fearful expressions in anxious individuals. These results show a high resistance of the N170 amplitude increase for fearful faces to spatial attention and task load manipulations. By contrast, the EPN modulation by fearful faces index a resource-dependent stage of the ERP, requiring both spatial attention at the location of faces and low load of the face-irrelevant task.

The magnitude of the sound-induced flash illusion does not increase monotonically as a function of visual stimulus eccentricity

The sound-induced flash illusion (SIFI) occurs when a rapidly presented visual stimulus is accompanied by two auditory stimuli, creating the illusory percept of two visual stimuli. While much research has focused on how the temporal proximity of the audiovisual stimuli impacts susceptibility to the illusion, comparatively less research has focused on the impact of spatial manipulations. Here, we aimed to assess whether manipulating the eccentricity of visual flash stimuli altered the properties of the temporal binding window associated with the SIFI. Twenty participants were required to report whether they perceived one or two flashes that were concurrently presented with one or two beeps. Visual stimuli were presented at one of four different retinal eccentricities (2.5, 5, 7.5, or 10 degrees below fixation) and audiovisual stimuli were separated by one of eight stimulus-onset asynchronies. In keeping with previous findings, increasing stimulus-onset asynchrony between the auditory and visual stimuli led to a marked decrease in susceptibility to the illusion allowing us to estimate the width and amplitude of the temporal binding window. However, varying the eccentricity of the visual stimulus had no effect on either the width or the peak amplitude of the temporal binding window, with a similar pattern of results observed for both the “fission” and “fusion” variants of the illusion. Thus, spatial manipulations of the audiovisual stimuli used to elicit the SIFI appear to have a weaker effect on the integration of sensory signals than temporal manipulations, a finding which has implications for neuroanatomical models of multisensory integration.

Exploring 4D Image Sets of Early Heart Development Using Gesture and an Immersive, Spatial Operating Environment

Abstract Scientists today can collect more data than they can perceive using traditional visualization methods. New technologies and sensors allow researchers to gather dynamic, complex multidimensional datasets—all of which must be carefully studied to reveal hidden patterns and narratives. The authors used an immersive platform to design a new visualization for real-time, intuitive spatial manipulations of time-based volumetric datasets via a wand-based gestural interface. The resulting work resolves microscopic tissue structures at a human scale in a room-based pixel space, facilitating research, discovery and in-person teaching and collaboration.

Binocular contrast perception of gratings, noise, and natural images

The visual system is tasked with combining the two eye’s views into a single percept of the world. To understand the principles that underlie this combination, dichoptic stimuli (stimuli that have different levels of luminance and/or contrast in the two eyes) can be used to probe how each eye’s input contributes to the ultimate binocular percept. For example, contrast perception of simple dichoptic stimuli, such as sine wave gratings, is well-predicted as a weighted combination of the two eyes inputs typically biased towards the eye seeing higher contrast. We aimed to examine contrast perception of more complex dichoptic stimuli to determine how higher-order visual properties may influence the binocular percept. Using a perceptual matching task in which participants adjusted one stimulus (which was non-dichoptic) to match the perceived contrast of another stimulus (which was dichoptic), we examined the perceived contrast of three classes of stimuli: gratings, 1/f noise, and natural image patches. In addition to finding the closest perceptual match, we also asked participants to report on whether and how the two stimuli differed in appearance. We found that: 1) Spatial variation in the stimuli modulated binocular contrast perception; however, the effect depended on the stimulus type. Specifically, spatial manipulations that affected the perceptual matches for gratings (i.e., increasing or decreasing the contrast of the surrounding area in either eye) did not have a systematic effect on the matches for the noise and natural images. 2) Across all stimulus types, however, spatial manipulations did affect the proportion of trials in which participants reported finding an “exact match”. These results suggest that spatial frequency interactions and higher-level inferences can modulate both the interocular weighting and the perceptual interpretation during binocular combination.

Flights of Fancy and the Dissolution of Shakespearean Space-Time in Angela Carter’s Nights at the Circus

While much attention has been paid to Angela Carter’s intertextual appropriation of Shakespeare and her interrogation of the patriarchal ideology at work in his representations of familial strife, critics tend to focus on Carter’s final novel, Wise Children. Shakespeare’s influence on Carter’s earlier novel, Nights at the Circus, has gone largely unremarked. Like Wise Children, Nights at the Circus builds a bricolage of Shakespearean allusions, but it more subtly reconsiders the ontological issues of legitimacy by returning to Shakespeare’s interest in ambiguity, in deniability, in time, and in space. I argue that Nights at the Circus appropriates and shatters Shakespeare’s disruptive methods concerning the materiality of time in The Winter’s Tale and Hamlet. In so doing, Carter reverses time and dismembers space to criticise the masculine-made-legitimate at the expense of the feminine, which Shakespeare’s temporal and spatial manipulations ultimately uphold.

Entorhinal mismatch: A model of self-supervised learning in the hippocampus

SummaryThe hippocampal formation displays a wide range of physiological responses to different spatial manipulations of the environment. However, very few attempts have been made to identify core computational principles underlying those hippocampal responses. Here, we capitalize on the observation that the entorhinal-hippocampal complex (EHC) forms a closed loop and projects inhibitory signals “countercurrent” to the trisynaptic pathway to build a self-supervised model that learns to reconstruct its own inputs by error backpropagation. The EHC is then abstracted as an autoencoder, with the hidden layers acting as an information bottleneck. With the inputs mimicking the firing activity of lateral and medial entorhinal cells, our model is shown to generate place cells and to respond to environmental manipulations as observed in rodent experiments. Altogether, we propose that the hippocampus builds conjunctive compressed representations of the environment by learning to reconstruct its own entorhinal inputs via gradient descent.

Individual Differences in Working Memory and the N2pc.

The lateralized ERP N2pc component has been shown to be an effective marker of attentional object selection when elicited in a visual search task, specifically reflecting the selection of a target item among distractors. Moreover, when targets are known in advance, the visual search process is guided by representations of target features held in working memory at the time of search, thus guiding attention to objects with target-matching features. Previous studies have shown that manipulating working memory availability via concurrent tasks or within task manipulations influences visual search performance and the N2pc. Other studies have indicated that visual (non-spatial) vs. spatial working memory manipulations have differential contributions to visual search. To investigate this the current study assesses participants' visual and spatial working memory ability independent of the visual search task to determine whether such individual differences in working memory affect task performance and the N2pc. Participants (n = 205) completed a visual search task to elicit the N2pc and separate visual working memory (VWM) and spatial working memory (SPWM) assessments. Greater SPWM, but not VWM, ability is correlated with and predicts higher visual search accuracy and greater N2pc amplitudes. Neither VWM nor SPWM was related to N2pc latency. These results provide additional support to prior behavioral and neural visual search findings that spatial WM availability, whether as an ability of the participant's processing system or based on task demands, plays an important role in efficient visual search.

Spatiotemporal Terahertz Metasurfaces for Ultrafast All‐Optical Switching with Electric‐Triggered Bistability

AbstractOptoelectronic terahertz switching achieved by dynamically tuning metamaterials is viewed as a major breakthrough in promoting the advancement of terahertz technology. However, the main thrust toward the development of ultrafast switchable components and optical logic operations is still in a catch‐up stage for progressively increasing information and communication demands. Here, a novel spatiotemporal metadevice is proposed for terahertz wave steering in multidimensional domains with ultrahigh spatial and ultrafast temporal manipulations. By spatially changing the interconnect architecture via the embedded vanadium dioxide bridges, the state of electromagnetically induced transparency resonance is switched between “1” and “0” states under electrical stimuli, exhibiting a typical 1 bit coding bistability with a long retention time. Furthermore, with the characteristic of writable/erasable logic operation, ultrafast photoswitching of each memorized state is manifested by delivering optical excitations. The high‐speed temporal response of terahertz radiation exhibits an on–off–on switching cycle within 16 ps, owing to the defect‐rich germanium photoactive layer. By leveraging both degrees of freedom in space and time domains, this multifunctional spatiotemporal metaphotonic device can upgrade and improve the current capabilities of optical computing, data storage, and ultrahigh‐speed information processing, paving the way for a highly unexplored territory toward manipulations of light.

The border as archive: reframing the crisis mode of governance at the Canada-US border

Starting in January 2017 there was a dramatic increase in the number of people crossing irregularly from the US to make a claim for refugee status in Canada. Officials declared a crisis and admonished those who, in the words of one official, were crossing ‘in between the border.’ It is important to pay close attention to these spaces in-between borders: those (un)intended and strategic openings left by the working out of nation-state policies (like the Canada-US Safe Third Country Agreement) and those paths that are opened through the transgressions of those borders by people on the move. Crisis is the necessary corollary of the ‘politics of anticipatory governance’ that scaffolds contemporary nation-statist border control policies and practices. Approaching the border as an archive means confronting the work that is done by such temporal and spatial manipulations, while placing contested border crossings at the centre of border formation. By examining a series of intersecting moments from the recent history of this border (1987–present), I seek to both ‘inhabit’ the crisis and understand what might remain once the crisis is declared over. I argue that migration management regimes produce the border crises they anticipate while simultaneously masking and revealing contested histories and geographies of migration.

Attention increases environmental risk perception.

The authors suggest that mere attention increases the perceived severity of environmental risks because attention increases the fear and distinctiveness of attended risks. In Experiments 1 and 2, participants were exposed to images of multiple environmental risks, with attention repeatedly oriented to a subset of these risks. Participants subsequently perceived attended risks to be more severe, more frightening, higher priority, and more distinctive than control risks. In Experiments 3 and 4, spatial cueing manipulations were used to briefly draw attention toward some risks and away from others. In Experiment 3, a briefly flashed rectangle drew attention toward one side of a computer screen just before 2 images depicting different risks appeared: 1 image near to where the rectangle appeared and 1 further away. In Experiment 4, incidental attention was cued toward some risks by giving participants an unrelated letter search task that required them to briefly attend near that location. Participants in Experiments 3 and 4 selected cued (attended) risks as more severe, distinctive, and frightening than noncued risks. Across experiments, serial mediation analyses indicated that the effect of the attention manipulation on severity was mediated by the effect of attention on fear which was mediated by distinctiveness. Across experiments, we equated duration of exposure to risks and sought to minimize demand characteristics. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Audiovisual processing and selective attention in adult dyslexic readers: Anevent‐related potential study

Developmental dyslexia is a specific reading disability characterized by decoding and spelling deficits that continue into adulthood. Because reading involves both attentional functions and audiovisual (AV) processing, the aim of this study was to explore the associations between the two factors in adult dyslexic readers. Adult non‐impaired and dyslexic readers undertook alphabetic and non‐alphabetic tasks, each composed of three experimental blocks. Two experimental blocks contained left and right spatial selective attention manipulations, and another block included central presentations of the stimuli. Event‐related potential (ERP) and behavioural parameters were collected and analysed, particularly with respect to the N1‐P2 ERP complex. The dyslexic readers showed deviant patterns of amplitudes when it came to alphabetic stimuli processing. However, there was no difference between the two groups with regard to the non‐alphabetic stimuli. These results imply that adult dyslexic readers allocate altered attentional resources when it comes to the processing of AV alphabetic stimuli.