Displacement Of Object Research Articles

Tracking and inferring spatial rotation by children and great apes.

Finding hidden objects in space is a fundamental ability that has received considerable research attention from both a developmental and a comparative perspective. Tracking the rotational displacements of containers and hidden objects is a particularly challenging task. This study investigated the ability of 3-, 5-, 7-, and 9-year-old children and great apes (chimpanzees, bonobos, gorillas, and orangutans) to (a) visually track rotational displacements of a baited container on a platform and (b) infer its displacements by using the changes of position or orientation of 3 landmarks: an object on a container, the color of the containers, and the color of the platform on which the containers rested. Great apes and 5-year-old and older children successfully tracked visible rotations, but only children were able to infer the location of a correct cup (with the help of landmarks) after invisible rotations. The ability to use landmarks changed with age so that younger children solved this task only with the most explicit marker on the baited container, whereas older children, particularly 9-year-olds, were able to use landmark orientation to infer correct locations.

New Motion Illusion Caused by Pictorial Motion Lines

Motion lines (MLs) are a pictorial technique used to represent object movement in a still picture. This study explored how MLs contribute to motion perception. In Experiment 1, we reported the creation of a motion illusion caused by MLs: random displacements of objects with MLs on each frame were perceived as unidirectional global motion along the pictorial motion direction implied by MLs. In Experiment 2, we showed that the illusory global motion in the peripheral visual field captured the perceived motion direction of random displacement of objects without MLs in the central visual field, and confirmed that the results in Experiment 1 did not stem simply from response bias, but resulted from perceptual processing. In Experiment 3, we showed that the spatial arrangement of orientation information rather than ML length is important for the illusory global motion. Our results indicate that the ML effect is based on perceptual processing rather than response bias, and that comparison of neighboring orientation components may underlie the determination of pictorial motion direction with MLs.

USE OF SINGLE‐VISION EYEGLASSES IMPROVES STEPPING PRECISION AND SAFETY WHEN ELDERLY HABITUAL MULTIFOCAL WEARERS NEGOTIATE A RAISED SURFACE

USE OF SINGLE‐VISION EYEGLASSES IMPROVES STEPPING PRECISION AND SAFETY WHEN ELDERLY HABITUAL MULTIFOCAL WEARERS NEGOTIATE A RAISED SURFACE

Altered emotionality, spatial memory and cholinergic function in caveolin-1 knock-out mice

Neurological phenotypes associated with loss of caveolin 1 (cav-1) (the defining structural protein in caveolar vesicles, which regulate signal transduction and cholesterol trafficking in cells) in mice have been reported recently. In brain, cav-1 is highly expressed in neurons and glia. We investigated emotional and cognitive behavioural domains in mice deficient in cav-1 (CavKO mice). CavKO mice were more anxious and spent more time in self-directed grooming behaviour than wild-type (wt) mice. In a spatial/working memory task, CavKO mice failed to recognize the object displacement, thus showing a spatial memory impairment. CavKO mice showed higher locomotor activity than wt mice, thus suggesting reduced inhibitory function by CNS cholinergic systems. Behavioural response to the cholinergic muscarinic antagonist, scopolamine (2 mg/Kg), was decreased in CavKO mice. Few behavioural sex differences emerged in mice; whereas the sex differences were generally attenuated or even reverted in the null genotype. Our data confirm a distinct behavioural phenotype in CavKO mice and indicate a selective alteration in central cholinergic function.

Theoretical principles of optical measurements on the components of multicomponent displacements for mobile objects on the basis of multivariate tests

The principles are considered of a multivariate test method for optical measurements on the components of complicated displacements of mobile objects, which includes combinational models for such displacements and tests, with examples of realization.

Collision avoidance behavior as a function of aging and tennis playing

Daily living often requires pedestrians and drivers to adapt their behavior to the displacement of other objects in their environment in order to avoid collision. Yet little research has paid attention to the effect of age on the completion of such a challenging task. The purpose of this study was to examine the relationship between age and collision avoidance skill and whether a sporting activity affects this. Three age groups (20-30, 60-70, and 70-80 years) of tennis players and non-players launched a projectile toward a target in order to hit it before it was hit by another "object" (a stimulus represented by apparent motion of lights). If the participant judged that time-to-collision (TTC) of the moving stimulus was not long enough for him/her to launch the projectile in time to arrive before the stimulus, the participant had to inhibit the launching. Results showed that for the non-players the number of errors in the 70-80 year-old group was significantly higher than those of the 20-30 and 60-70 year-old groups, which did not differ from each other. However, this increase was not observed in the 70-80 year-old tennis players, demonstrating a beneficial effect of playing tennis on collision avoidance skill. Results also revealed that the older groups of both tennis players and non-players were subject to the typical age-related increase in response time. Additional analyses indicated that the 70-80 year-old non-players did not adjust their actions to these age-related changes in response time. The older tennis-playing participants, however, were more likely to adjust collision avoidance behavior to their diminished response times.

CT image registration in sinogram space

Object displacement in a CT scan is generally reflected in CT projection data or sinogram. In this work, the direct relationship between object motion and the change of CT projection data (sinogram) is investigated and this knowledge is applied to create a novel algorithm for sinogram registration. Calculated and experimental results demonstrate that the registration technique works well for registering rigid 2D or 3D motion in parallel and fan beam samplings. Problem and solution for 3D sinogram-based registration of metallic fiducials are also addressed. Since the motion is registered before image reconstruction, the presented algorithm is particularly useful when registering images with metal or truncation artifacts. In addition, this algorithm is valuable for dealing with situations where only limited projection data are available, making it appealing for various applications in image guided radiation therapy.

Modified temporal-phase-unwrapping method for measuring in real time the out-of-plane displacements of the tympanic membrane of Mongolian Gerbil

A technique for measuring in real-time continuous out-of-plane displacements of delicate objects is proposed, and demonstrated on the tympanic membrane of Mongolian Gerbil. The technique is based on the combination of two methods: the spatial phase shifting (SPS) and the modified temporal phase unwrapping (TPU). The combination allows to obtain, in several steps, the phase values of the points that undergo out-of-plane displacement as the object is deformed. The technique reduces the frame acquisition time of the standard TPU used in moiré interferometry by a factor of 4, which is important to diminish post-mortem artifacts during in-vitro experiments and to reduce motion artifacts in in-vivo tests. The proposed technique is robust against problems associated with the temporal phase-shifting method, such as nonlinear phase shift and noise. The advantages and disadvantages are discussed.

Behavior on the water maze platform: Relationship to learning and open field exploration in aged and adult rats

In the present study we examined whether age-related deficits in the water maze could be accounted for by changes in the behavior on the platform, and whether platform behavior represents some form of exploration, akin to that seen in the open field. Twenty-seven aged and 8 adult rats (26 and 3 months old Wistar rats, respectively) were tested in an empty open field and spatial object exploration task, followed by 9 days of escape learning in a water maze. The aged as compared to the adults exhibited lower levels of open field activity and were deficient in the object displacement task. Escape deficits in the water maze and reduced activity levels on the platform were also found. In the aged, water maze performance was correlated with behavior on the platform, including quiescence, orienting-like activity and turning behavior, a form of axial rotation. In both age groups, turning behavior was also correlated with exploratory activity in the open field. In conclusion, the results support the hypothesis that age-related impairments in the water maze relate to changes in platform behavior, which, in turn, might reflect exploratory activity.

TH‐D‐M100J‐07: CT Image Registration in Sinogram Space

Purpose: Object displacement in a CT scan is generally reflected in CT projection data or sinogram. Conventional registrations in the image space are often adversely influenced by the reconstruction‐induced artifacts. A direct sinogram‐based registration has been studied. Method and Materials: It is found that a rigid motion only affects the projection angle and radial distance of the CT projections instead of the intensity. Simple equations have been successfully deduced.A simulated 2D phantom model was adopted and modified to test the algorithm. A physical head phantom was scanned using a kV cone beam scanner. Fan beam sinograms were then generated for the central axial plane.Upon random 2D rigid motions, registrations were carried out in the sinogram space. For every possible motion, the relevant sinogram was generated according to the discovered relationship and compared with the reference sinogram, as a result, the most likely motion was obtained. Results: Simulated and experimental results demonstrate that the new registration technique works well for registration of rigid motion in parallel beam sampling and fan beam sampling CT scans. The images were reconstructed from the registered sinograms and the spatial accuracy of this new registration was better than 2 mm.It is also found that this sinogram registration couldn't be affected by the metal filling, the truncation, or uncompleted projection set. This makes it appealing for various applications in image guided radiation therapy (IGRT). Conclusions: The direct relationships between the object motion and the change of CT projection data (sinogram) were studied and this knowledge was successfully applied to a novel algorithm for sonogram‐based registration. Calculated and experimental results demonstrate that the new registration technique works well particularly when registering images with metal or truncation artifacts.

Minimising algorithm‐induced artefacts in true ortho‐image generation: a direct method implemented in the vector domain

AbstractTrue ortho‐images are generated from perspective images with both object and terrain displacement distortion corrected and with occlusions removed. However, widely used algorithms based on a Z‐buffer have drawbacks and may result in artefacts in the generated ortho‐images. This paper analyses the artefacts induced by Z‐buffer algorithms in true ortho‐image generation, and proposes a vector‐based method to avoid algorithm‐induced artefacts. The proposed method treats a perspective image pixel as a square patch instead of an image pixel point, and generates ortho‐images in the vector domain. Under the vector implementation, occlusion detection is a simple process, and image resampling becomes a straightforward procedure. Most importantly, this method can minimise artefacts in the ortho‐images so generated.

Retrieving true images through fine grid steps for enhancing the resolution beyond the classical limits: theory and simulations

We developed the theory of, and tested by extended simulations, a novel method for retrieving true images in a grid step much finer than both the acquisition and the optical microscope limits. We believe that the method is promising in view of avoiding the limitations on the resolution improvement in direct imaging mode systems. Two basic concepts are involved: (i) random (up to 3D) relative displacements of objects with respect to the receiving matrix and (ii) the use of a reference object firmly fixed to small signal objects for avoiding the displacement measurements. The retrieved images are created by rearranging a set of true images acquired with a lower resolution equal to the matrix pixel size. We demonstrate the good quality of the retrieved images and the possibility to visualize and detect small (convolved) objects not observed into the captured images. The method provides good opportunities for effective applications of different inverse algorithms for improving the resolution requiring, as a rule, more precisely sampled images, but at arbitrary relations between the pixel size and the optical diffraction limit. We further demonstrated the application of some deconvolution procedures for extracting highly resolved images in the object and image planes in the presence of noise. The possibility to resolve small objects beyond the two classical limits is shown by means of simulations. The estimates for the method's limiting resolution, combined with proper deconvolution processing, show that resolution in the lower nano-dimension scale (below 10 nm) could be achieved. The requirements to the implementation of the novel method are commented as well.

Triple-sensor multiplexed frequency-modulated continuous-wave interferometric fiber-optic displacement sensor

A triple-sensor multiplexed fiber-optic displacement sensor, which can measure the displacements of three different objects or the three-dimensional displacement of a single object, is introduced. The sensor is based on the principles of optical frequency-modulated continuous-wave interference and frequency-division multiplexing. The beat signals from the individual sensors are assigned in the frequency domain and separated with different electrical bandpass filters. The displacements of objects can be determined simultaneously by detecting the phase shifts of the corresponding signals. The cross talk between the individual sensors is evaluated, and an accuracy of 0.08 microm in a dynamic range of 1000 microm is achieved.

Effect of Pulse Width on Object MovementIn VitroUsing Holmium:YAG Laser

The holmium:YAG laser is an effective modality for intracorporeal lithotripsy. The fiber tip needs to be in contact with the calculus for maximal effect. Laser energy can cause stone retropulsion, necessitating cumbersome repositioning of the fiber. We examined the effect of varying the laser pulse width on object movement in vitro. Two experiments were conducted using a holmium:YAG laser at the 350-microsec and 700-microsec pulse-width settings. In the first experiment, one pulse was delivered to a non-fragmentable ball bearing at increasing energy settings, and object displacement was measured. In the second experiment, a train of pulses was delivered to a fragmentable soda lime phantom at increasing energy settings, and the total energy delivered before movement from the tip of the fiber was determined. The mean ball bearing movement was significantly greater at the 350-microsec setting with a 200-microm fiber (P < 0.0001), as well as a 400-microm fiber (P < 0.0069). More disparity in movement was noted at higher energy settings. The total energy delivered to the soda lime phantom before migration was significantly greater using the 700-microsec setting (P < 0.0018). Pressure waves from Ho:YAG lithotripsy are less than with other modalities, yet some retropulsion occurs. The duration of the laser pulse can influence shockwave generation and object migration. Longer pulse width results in less object movement after one shock and more energy delivery during repetitive shocks. Clinically, this regimen may reduce the need for fiber readjustment and lead to more efficient stone fragmentation.

Neurotoxic doses of methamphetamine cause neurocognitive abnormalities in mice

Methamphetamine (METH) is a neurotoxic psychostimulant that causes damage to striatal dopamine (DA) terminals and to non-monoaminergic cells in the striatum (STR) and cortex of rodents. The aim of the present study was to investigate short- and long-term consequences of neurotoxic METH doses on mice behaviors. Male BALB/c mice, 12–14 weeks old, were injected with dl-METH (i.p., 7.5 mg/kg x 4 times, every 2 hours) or saline. Behaviors were accessed at 10 days after drug treatment. METH administration caused significant decreases in responding to object displacement using an Open Field Object Recognition test. In contrast, METH caused increased response to object novelty. There were no drug-induced effects on locomotor activity. Moreover, repeated METH injections resulted in significant decreases in dopamine (DA) levels in the STR, frontal cortex (FC) and olfactory bulb (OB) in mice sacrificed 10 days after drug treatment. Furthermore, as previously reported for the cortex and striatum, METH administration caused marked increases in the number of cells that were positive for TUNEL staining in the OB at 3 days, observations that are indicative of drug-induced enhancement of cell death in that structure. When taken together, these results suggest that METH caused impairments in spatial learning and/or memory as a consequence of its neurodegenerative effects. This research was supported by the Intramural Research Program of the NIH, NIDA.

Optimal inference explains dimension-specific contractions of spatial perception

It is known that people misperceive scenes they see during rapid eye movements called saccades. It has been suggested that some of these misperceptions could be an artifact of neurophysiological processes related to the internal remapping of spatial coordinates during saccades. Alternatively, we have recently suggested, based on a computational model, that transsaccadic misperceptions result from optimal inference. As one of the properties of the model, sudden object displacements that occur in sync with a saccade should be perceived as contracted in a non-linear fashion. To explore this model property, here we use computer simulations and psychophysical methods first to test how robust the model is to close-to-optimal approximations and second to test two model predictions: (a) contracted transsaccadic perception should be dimension-specific with more contraction for jumps parallel to the saccade than orthogonal to it, and (b) contraction should rise as a function of visuomotor noise. Our results are consistent with these predictions. They support the idea that human transsaccadic integration is governed by close-to-optimal inference.

External Realism about Cinematic Motion

Cinematic motion is, I argue, a genuine and intrinsic property of some cinematic works and not just a matter of how things look to us. It is an event-an item's change of position-happening prior and external to our sensory responses to movies. I therefore defend against common-sense illusionism a minority opinion within cinema studies: that movie viewing normally occasions veridical perceptions of a kind of objective displacement. I also dispute another version of anti-illusionist realism about cinematic motion, the implication that cinematic motion, like colour, is a response-dependent property. The impression of motion, I contend, is not produced by the visual system's operations. It is a sensory representation of a physical property of a particular type of external object.

Creating and Analyzing a Mirage

Most people have witnessed mirages such as the distant “puddles” that appear on a highway when the pavement is warmed by the Sun. The warmed surface heats the nearby air creating a temperature gradient with the cooler (and more dense) air above. The apparent displacement of distant objects occurs as light refracts through the different air densities. Rays of light from the sky that are originally directed toward the ground can be bent upward, appearing to a viewer as though coming from the ground. This effect is known as an inferior mirage; a superior mirage occurs when cooler air is underneath.1,2 In this paper, a mirage is created indoors using an electric hotplate and a saucepan filled with ice water.

Beyond Retinotopic Mapping: The Spatial Representation of Objects in the Human Lateral Occipital Complex

The spatial representation in the human ventral object-related areas (i.e., the lateral occipital complex [LOC]) is currently unknown. It seems plausible, however, that it would diverge from the strict retinotopic mapping (characteristic of V1) to a more invariant coordinate frame, thereby allowing for reliable object recognition in the face of eye, head, or body movement. To study this, we compared the fMRI activation in LOC when object displacement was limited to either the retina or the screen by manipulating eye position and object locations. We found clear adaptation in LOC when the object's screen position was fixed, regardless of the object's retinal position. Furthermore, we found significantly greater activation in LOC in the hemisphere contralateral to the object's screen position, although the visual task was constructed in a way that the objects were present equally often on each of the 2 retinal hemifields. Together, these results indicate that a sizeable fraction of the neurons in LOC may have head-based receptive fields. Such an extraretinal representation may be useful for maintenance of object coherence across saccadic eye movements, which are an integral part of natural vision.

SU‐FF‐J‐24: An Optical Flow Based Motion Tracking Method Using Fluoroscopic Video

Purpose: To present an optical flow‐based method for tracking tumor motion and propose a noninvasive respiratory detection method using fluoroscopic video. Method and Materials: Fluoroscopic video of a patient is acquired. Only one frame is selected as the reference frame and objects in this frame are manually segmented. The motion of a segmented object is found by computing the average optical flow of pixels within the object. Optical flow provides a two‐dimensional motion vector for the displacement of pixels between two frames. The object is moved between frames by moving all pixels by the average velocity vector. Then the position of the object in the new frame is adjusted by applying a template matching algorithm. The algorithm moves the object over a search range of +/− 2 pixels. The object is placed at the position having the maximum correlation coefficient (CC) between the pixels in the original and new frames. This procedure is repeated to advance the object from frame to frame. Results:The outlines of tracked objects are viewed superimposed on the fluoroscopic videos. The outlines follow the general motion of the objects without drifting away for the approximately 30 seconds (300 images) and 8 respiratory cycles of a typical video. Objects that do not significantly deform are well tracked. The boundaries of objects that deform are not well described by the tracked outlines, however, the centroid motion of the objects is. The analysis yields the mean displacement of objects. As the distance an object moves away from the reference position increases, the CC decreases. A plot of the CC vs frame shows a sinusoidal curve with the breathing period as does the displacement plot, but with reversed phase. Conclusion: The mean motions of objects in fluoroscopic video are well tracked. The displacement and respiratory signal are also obtained.