Virtual Floor Research Articles

Visual boundary cues suffice to anchor place and grid cells in virtual reality

The hippocampal formation contains neurons responsive to an animal's current location and orientation, which together provide the organism with a neural map of space.1,2,3 Spatially tuned neurons rely on external landmark cues and internally generated movement information to estimate position.4,5 An important class of landmark cue are the boundaries delimiting an environment, which can define place cell field position6,7 and stabilize grid cell firing.8 However, the precise nature of the sensory information used to detect boundaries remains unknown. We used 2-dimensional virtual reality (VR)9 to show that visual cues from elevated walls surrounding the environment are both sufficient and necessary to stabilize place and grid cell responses in VR, when only visual and self-motion cues are available. By contrast, flat boundaries formed by the edges of a textured floor did not stabilize place and grid cells, indicating only specific forms of visual boundary stabilize hippocampal spatial firing. Unstable grid cells retain internally coherent, hexagonally arranged firing fields, but these fields "drift" with respect to the virtual environment over periods >5 s. Optic flow from a virtual floor does not slow drift dynamics, emphasizing the importance of boundary-related visual information. Surprisingly, place fields are more stable close to boundaries even with floor and wall cues removed, suggesting invisible boundaries are inferred using the motion of a discrete, separate cue (a beacon signaling reward location). Subsets of place cells show allocentric directional tuning toward the beacon, with strength of tuning correlating with place field stability when boundaries are removed.

Collision Detection of Virtual Powered Support Groups Under Complex Floors

Abnormal relative position and attitude offset may cause powered supports to collide during movement, affecting the stability of a longwall operation. This study proposed a collision detection method for virtual powered support groups in the undulating strata condition. First, a support workspace was developed by defining key points, and the Denavit-Hartenberg (DH) matrix coordinate system of powered supports was established to solve the key points. Then, based on the intersection rule of plane line segments, collision detection between powered supports was realized by calculating the coordinates of the key points. According to actual coal face data, a virtual simulation platform is established, and the sequential movement of support groups on the virtual floor was realized. Finally, contrast experiments of different virtual floor models were conducted, and the Mesh floor, which is closer to the actual coal seam, was selected for subsequent virtual simulation. The collision detection experiments of powered supports were conducted in both virtual and physical environments, and the results validated the feasibility of the collision detection method. This method improves the virtual simulation degree of longwall coal mining, and provides simulation reference for the attitude adjustment of actual powered support groups before moving.

Child-Computer Interaction in times of a pandemic.

The increasing presence of interactive technologies in children’s lives poses critical ethical questions for researchers and designers. Discourse specific to these intersecting topics is nascent, spread across communities and largely developed retrospectively. In a series of workshops and panels at the annual ACM Interaction Design for Children (ACM IDC) conference, a small group from the community has aimed to provide a central space and continuity for this discourse. The most recent of these spaces was the ACM IDC 2020 workshop entitled, “Emergent, Situated and Prospective Ethics for Child–Computer Interaction Research” that brought together a small group of researchers interested in sharing and discussing ethical issues arising when researching, designing, and deploying technologies for children [1]. When we, as the two main organizers of the workshop, wrote the workshop proposal we were particularly interested in how the ethical challenges in Child–Computer Interaction (CCI) were changing in the face of a rapidly changing world. At that time, it was completely unknown to us how different the world would be when we conducted the workshop. When the participants eventually met online for this workshop in late June 2020, a global pandemic had changed public life as we knew it and social justice issues, as manifested in the Black Lives Matter movement, were causing widespread unrest. Layered on these immediate challenges was the looming climate crisis that poses one of the most existential threats to humans yet. When we ran the workshop, we decided to focus our discussions on sharing thoughts and experiences of what these monumental shifts might mean for our community. The question, which we put onto the virtual floor was: How is the ethics of your research changing in the face of the Covid-19 Pandemic and recent social justice issues, as manifested in the Black Live Matters movement? What followed was a rich and thoughtful discussion. Every participant was affected by the pandemic in different ways, both personally and professionally. In the 45 min session we had reserved for this part of the workshop, we were all not only connected via video link, but also collaboratively worked on a shared virtual whiteboard at the same time. In a very productive mix of show and tell, we collected sticky notes, online resources, quotes and other bits of information; all the while making connections and categorizations. Later, we, as the two main organizers, discussed our observations from the workshop, and then reviewed the data and our own notes to informally look for themes related to our original question. We wrote up the themes individually, and worked collaboratively to refine, clarify, and contextualize them. From this exercise, four main themes emerged, which all included perceived challenges as well as the participants’ recommendations for how these concerns might be addressed moving forward. The following briefly summarizes these themes.

Development of a Virtual Floor Maze Test - Effects of Distal Visual Cues and Correlations With Executive Function in Healthy Adults.

Virtual reality (VR) is a useful tool to assess and improve spatial navigation, a complex skill and relevant marker for progression of dementia. A fully-immersive VR system that allows the user to physically navigate in the space can provide an ecologically valid environment for early detection and remediation of cognitive and navigational deficits. The aim of this study was to develop a virtual version of the floor maze test (VR-FMT), a navigational test that requires navigating through an unfamiliar two-dimensional floor maze. With the VR-FMT, mazes of desired complexity and walls of preferred height can be built to challenge navigational ability and mask visual clues. Fifty-five healthy adults completed the FMT in three different conditions: real environment (RE), virtual environment with no walls (VE-NW), and virtual environment with walls (VE-W). In addition, they completed two neuropsychological tests, the Trail Making Test and Digit Symbol Substitution Test. Results showed that the time to complete the maze in the VE was significantly higher than in the RE. The introduction of walls increased the number of errors, the completion time, and the length of the path. Only time to exit in the VE-W correlated with results of the cognitive tests. Participants were further subdivided on the basis of their time to exit the maze in the RE, VE-NW, and VE-W (low navigational time - LNT, and high navigational time - HNT). Only when analyzing the time to exit the maze in the VE-W, the LNT group outperformed the HNT group in all cognitive tests.

Pavement patterns can be designed to improve gait in Parkinson's disease patients.

Public spaces are usually designed with respect to various patient populations, but not Parkinson's disease. The objective of this study was to explore what type of easily applicable visual cueing might be used in public spaces and some interiors to improve gait in people with Parkinson's disease. Thirty-two patients with freezing of gait walked an 8-meter track on 6 different floor patterns in single- and dual-task conditions in random sequence. The reference pattern was a virtual large transverse chessboard, and the other patterns differed either in size (small floor stones), orientation (diagonal), nature (real paving), regularity (irregular), or no pattern. Time, number of steps, velocity, step length, cadence, and dual-task effect were calculated. The number and total duration of freezing episodes were analyzed. Virtual, large, transverse floor stones improve time (P = 0.0101), velocity (P = 0.0029), number of steps (P = 0.0291), and step length (P = 0.0254) in Parkinson's disease patients compared with walking on no pattern. Virtual floor stones were superior in time and velocity to the real ones. Transverse floor stones were better than diagonal, whereas regular pattern stones were superior to irregular in some gait parameters. Subjectively, the reference pattern was preferred to the irregular one and to no pattern. No direct effect on freezing of gait was observed. Parkinson's disease patients may benefit from floor patterns incorporating transverse oriented large rectangular visual cues. Because public space can be regulated with respect to people with medical conditions, the relevant legislative documents should be extended to allow for parkinsonian gait disorder. © 2019 International Parkinson and Movement Disorder Society.

The Dominant Role of Visual Motion Cues in Bumblebee Flight Control Revealed Through Virtual Reality.

Flying bees make extensive use of optic flow: the apparent motion in the visual scene generated by their own movement. Much of what is known about bees' visually-guided flight comes from experiments employing real physical objects, which constrains the types of cues that can be presented. Here we implement a virtual reality system allowing us to create the visual illusion of objects in 3D space. We trained bumblebees, Bombus ignitus, to feed from a static target displayed on the floor of a flight arena, and then observed their responses to various interposing virtual objects. When a virtual floor was presented above the physical floor, bees were reluctant to descend through it, indicating that they perceived the virtual floor as a real surface. To reach a target at ground level, they flew through a hole in a virtual surface above the ground, and around an elevated virtual platform, despite receiving no reward for avoiding the virtual obstacles. These behaviors persisted even when the target was made (unrealistically) visible through the obstructing object. Finally, we challenged the bees with physically impossible ambiguous stimuli, which give conflicting motion and occlusion cues. In such cases, they behaved in accordance with the motion information, seemingly ignoring occlusion.

Virtual Seafloor Reduces Internal Wave Generation by Tidal Flow

Our numerical simulations of tidal flow of a stratified fluid over periodic knife-edge ridges and random topography reveal that the time-averaged tidal energy converted into internal gravity wave radiation arises only from the section of a ridge above a virtual seafloor. The average radiated power is approximated by the power predicted by linear theory if the height of the ridge is measured relative to the virtual floor. The concept of a virtual floor can extend the applicability of linear theory to global predictions of the conversion of tidal energy into internal wave energy in the oceans.

Visually induced postural reactivity is velocity-dependent at low temporal frequencies and frequency-dependent at high temporal frequencies

Visual stimulation alone is sufficient to produce visually induced postural reactivity (VIPR). While some studies have shown that VIPR increases with the velocity of a moving visual stimulus, others have shown that it decreases with the temporal frequency of an oscillating visual stimulus. These results seem contradictory given that these two variables co-vary in the same direction. The purpose of this study is to determine whether the VIPR can be different depending on the frequency range being considered. Twelve subjects were placed standing up in a virtual reality environment that simulated a black and white checkerboard at floor level. This checkerboard oscillated at seven frequencies (0.03–2.0 Hz) and three amplitudes (2, 4, and 8°), corresponding to nine velocities (0.125–32°/s). The virtual floor oscillated from left to right (mediolateral) or from front to back (anteroposterior). We calculated the subjects’ mean velocity (Ω) based on data from electromagnetic sensors positioned on the head and lower back. Our experiment shows that for temporal frequencies below 0.12 Hz, VIPR is visually dependent and increases with stimulus velocity. When stimulus velocity becomes too high, the body becomes incapable of following, and the VIPR saturates between 0.12 and 0.25 Hz. In this frequency range, maximal postural oscillation seems to depend on biomechanical constraints imposed by the positioning of the feet. For frequencies above 0.5 Hz, the body can no longer maintain the same oscillation state. This saturation may be linked to proprioceptive feedback mechanisms in the postural system.

2D and 3D Traveling Salesman Problem

When a two-dimensional (2D) traveling salesman problem (TSP) is presented on a com- puter screen, human subjects can produce near-optimal tours in linear time. In this study we tested human performance on a real and virtual floor, as well as in a three- dimensional (3D) virtual space. Human performance on the real floor is as good as that on a computer screen. Performance on a virtual floor is very similar, while that in a 3D space is slightly but systematically worse. We modeled these results by a graph pyramid algorithm. The same algorithm can account for the results with 2D and 3D problems, which suggests that deterioration of performance in the 3D space can be attributed to geometrical relations between hierarchical clustering in a 3D space and coarse-to-fine production of a tour.

The Influence of Downstream Diurnal Heating on the Descent of Flow across the Sierras

Abstract The potential for a stably stratified air mass upstream of the Sierra Nevada (California) to descend as foehn into the nearly 3-km-deep Owens Valley was studied for the 2 March 2006 case with observations from sondes, weather stations, and two aircraft flights. While upstream conditions remained almost unchanged throughout the day, strong diurnal heating on the downstream side warmed the valley air mass sufficiently to permit flow through the passes to descend to the valley floor only in the late afternoon. Potential temperatures of air crossing the crest were too warm to descend past a virtual floor formed by the strong potential temperature step at the top of the valley air mass, the height of which changed throughout the day primarily due to diurnal heating in the valley. The descending stably stratified flow and its rebound with vertical velocities as high as 8 m s−1 were shaped by the underlying topography and the virtual valley floor.

Modeling the effect of facial topographies upon the visual field of humans and primates

To establish a virtual device that can predict the effect of facial features on the visual field of humans and primates. Virtual masks were obtained from human subjects, and macaque, chimpanzee and baboon taxidermic specimens, and aligned with upright head orientation at the center of a virtual perimeter-like dome (radius = 50 m) developed with Cinema 4D. Virtual searchlights positioned at the masks' pupils were then allowed to 'paint' facial elements obstructing their path, and demarcate the unobstructed rays at the perimetric surface and on a virtual ground floor related to eye level. Searchlight positions along the human mask's pupillary axis were identified by maximum congruence to Goldmann visual field limits. The human contours largely concur with large-stimulus isopters displaying the limiting role of the nasal ridge, and the relatively extended ventral and temporal limits. In contrast, the facial design of chimpanzees and baboons obstructs significant portions of the ventral foreground (>2 m cf < 0.5 m in human), while there appear to be larger binocular overlaps (125 degrees in chimp cf 90 degrees in human). The model provides information on anatomical constraints for monocular and binocular visual field extensions including projection of the ventral field on a virtual floor.

Spatial knowledge of children with spina bifida in a virtual large-scale space

The spatial knowledge of 18 children with spina bifida and 18 healthy control children (matched according to sex, age, and verbal IQ) was investigated in a computer-simulated environment. All children had to learn a route through a virtual floor system containing 18 landmarks. Controlling for cognitive abilities, the results revealed that children with spina bifida showed impaired route knowledge but not an impaired landmark knowledge. Thus the results suggest that children with spina bifida are not impaired in all large-scale abilities similarly. The impairments of the children with spina bifida are more accentuated in more behaviour based measurements, which indicates a relation to the reduced mobility of the children with spina bifida.