Target Localization Task Research Articles

Differential radio map-based robust indoor localization

While wireless local area network-based indoor localization is attractive, the problems concerning how to capture the signal-propagating character in the complex dynamic environment and how to accommodate the receiver gain difference of different mobile devices are challenging. In this article, we solve these problems by modeling them as common mode noise and develop a localization algorithm based on a novel differential radio map approach. We propose a differential operation to improve the performance of the radio map module, where the location is estimated according to the difference of received signal strength (RSS) instead of RSS itself. The particle filter algorithm is adopted to realize the target localization and tracking task. Furthermore, to calculate the particle weight at arbitrary locations, we propose a local linearization technique to realize continuous interpolation of the radio map. The indoor experiment results demonstrate the effectiveness and robustness of our approach.

Value associations of irrelevant stimuli modify rapid visual orienting

In familiar environments, goal-directed visual behavior is often performed in the presence of objects with strong, but task-irrelevant, reward or punishment associations that are acquired through prior, unrelated experience. In a two-phase experiment, we asked whether such stimuli could affect speeded visual orienting in a classic visual orienting paradigm. First, participants learned to associate faces with monetary gains, losses, or no outcomes. These faces then served as brief, peripheral, uninformative cues in an explicitly unrewarded, unpunished, speeded, target localization task. Cues preceded targets by either 100 or 1,500 msec and appeared at either the same or a different location. Regardless of interval, reward-associated cues slowed responding at cued locations, as compared with equally familiar punishment-associated or no-value cues, and had no effect when targets were presented at uncued locations. This localized effect of reward-associated cues is consistent with adaptive models of inhibition of return and suggests rapid, low-level effects of motivation on visual processing.

Improvements in proprioceptive functioning influence multisensory-motor integration in 7- to 13-year-old children

Accurate and efficient sensorimotor behavior depends on precise localization of the body in space, which may be estimated using multiple sensory modalities (i.e., vision and proprioception). Although age-related differences in multisensory-motor integration across childhood have been previously reported, the extent to which age-related changes in unimodal functioning affect multisensory-motor integration is unclear. The purpose of the current study was to address this knowledge gap. Thirty-seven 7- to 13-year-old children moved their dominant hand in a target localization task to visual, proprioceptive, and concurrent visual and proprioceptive stimuli. During a subsequent experimental phase, we introduced a perturbation that placed the concurrent visual and proprioceptive stimuli in conflicting locations (incongruent condition) to determine the relative contributions of vision and proprioception to the multisensory estimate of target position. Results revealed age-related differences in the localization of incongruent stimuli in which the visual estimate of target position contributed more to the multisensory estimate in the younger children whereas the proprioceptive estimate was up-weighted in the older children. Moreover, above and beyond the effects of age, differences in proprioceptive functioning systematically influenced the relative contributions of vision and proprioception to the multisensory estimate during the incongruent trials. Specifically, improvements in proprioceptive functioning resulted in an up-weighting of proprioception, suggesting that the central nervous system of school-aged children utilizes information about unimodal functioning to integrate redundant sensorimotor inputs.

Evaluation of three types of reference image data for external beam radiotherapy target localization using digital tomosynthesis (DTS)

Digital tomosynthesis (DTS) is a fast, low-dose three-dimensional (3D) imaging approach which yields slice images with excellent in-plane resolution, though low plane-to-plane resolution. A stack of DTS slices can be reconstructed from a single limited-angle scan, with typical scan angles ranging from 10 degrees to 40 degrees and acquisition times of less than 10 s. The resulting DTS slices show soft tissue contrast approaching that of full cone-beam CT. External beam radiotherapy target localization using DTS requires the registration of on-board DTS images with corresponding reference image data. This study evaluates three types of reference volume: original reference CT, exact reference DTS (RDTS), and a more computationally efficient approximate reference DTS (RDTSapprox), as well as three different DTS scan angles (22 degrees, 44 degrees, and 65 degrees) for the DTS target localization task. Three-dimensional mutual information (MI) shared between reference and onboard DTS volumes was computed in a region surrounding the spine of a chest phantom, as translations spanning +/-5 mm and rotations spanning +/-5 degrees were simulated along each dimension in the reference volumes. The locations of the MI maxima were used as surrogates for registration accuracy, and the width of the MI peaks were used to characterize the registration robustness. The results show that conventional treatment planning CT volumes are inadequate reference volumes for direct registration with on-board DTS data. The efficient RDTSapprox method also appears insufficient for MI-based registration without further refinement of the technique, though it may be suitable for manual registration performed by a human observer. The exact RDTS volumes, on the other hand, delivered a 3D DTS localization accuracy of 0.5 mm and 0.50 along each axis, using only a single 44 degrees coronal on-board DTS scan of the chest phantom.

Congruency between Visual and Auditory Displays on Spatial Tasks Using Different Reference Frames

This study investigated the effectiveness of spatial auditory cues for tasks using different reference frames, and examined how congruency between auditory and visual displays affected performance. Performance with three types of auditory cues (egocentric, exocentric and non-spatial) was compared on three spatial tasks: target search, target localization and target recall. There was a clear effect of reference frame congruency between auditory and visual displays on target search and target localization tasks. Interestingly, even incongruent auditory cues improved performance relative to non-spatial control conditions. In addition, egocentric auditory cues facilitated performance more than exocentric cues on incongruent trials. The findings have important implications for display design in work environments that involve diverse spatial tasks and displays that use different reference frames.

Interaction between location- and frequency-based inhibition of return in human auditory system

Using a cue-target paradigm, this study investigated the interaction between location and frequency information processing in human auditory inhibition of return (IOR). The cue and the target varied in terms of location and frequency and participants were asked to perform a target detection, localization or frequency discrimination task. Results showed that, when neither location nor frequency of auditory stimuli was particularly relevant to the target detection task, there was a location-based IOR only if the cue and the target were identical in frequency and there was a frequency-based IOR only if the cue and the target were presented at the same location. When a particular feature of auditory stimuli, whether location or frequency, was directly relevant to the current task, the IOR effect was evident for this feature only if the cue and the target differed on the task-irrelevant feature, while the IOR effect was eliminated for the task-relevant feature when the cue and the target had the same task-irrelevant feature. Similarly, the IOR effect based on the task-irrelevant feature was evident when the cue and the target differed on the task-relevant feature, and was eliminated or reversed when the cue and the target shared the task-relevant feature. Theoretical implications of these findings for auditory IOR are discussed.

Right hemispheric dominance in gaze-triggered reflexive shift of attention in humans

Recent findings suggest a right hemispheric dominance in gaze-triggered shifts of attention. The aim of this study was to clarify the dominant hemisphere in the gaze processing that mediates attentional shift. A target localization task, with preceding non-predicative gaze cues presented to each visual field, was undertaken by 44 healthy subjects, measuring reaction time (RT). A face identification task was also given to determine hemispheric dominance in face processing for each subject. RT differences between valid and invalid cues were larger when presented in the left rather than the right visual field. This held true regardless of individual hemispheric dominance in face processing. Together, these results indicate right hemispheric dominance in gaze-triggered reflexive shifts of attention in normal healthy subjects.

Effect of action video games on the spatial distribution of visuospatial attention.

The authors investigated the effect of action gaming on the spatial distribution of attention. The authors used the flanker compatibility effect to separately assess center and peripheral attentional resources in gamers versus nongamers. Gamers exhibited an enhancement in attentional resources compared with nongamers, not only in the periphery but also in central vision. The authors then used a target localization task to unambiguously establish that gaming enhances the spatial distribution of visual attention over a wide field of view. Gamers were more accurate than nongamers at all eccentricities tested, and the advantage held even when a concurrent center task was added, ruling out a trade-off between central and peripheral attention. By establishing the causal role of gaming through training studies, the authors demonstrate that action gaming enhances visuospatial attention throughout the visual field.

Useful Visual Field Reduction as a Function of Age and Risk of Accident in Simulated Car Driving

To study the relationships between the reduction of the useful visual field, age, and driving performance. Forty-eight subjects, aged from 23 to 77 years performed a test to evaluate the size of their useful visual fields. The test involved the detection and localization of peripheral signals that could appear in an area of 70 degrees of visual angle. The subjects then performed a simulated car-driving task involving the management of a situation that could lead to an accident. The analysis of the data revealed that the ability to process peripheral signals and simulated driving performance (vehicle speed) deteriorate with age. Simulated driving performance and useful visual field measurement have been analyzed jointly. The results indicate that the reduction of the useful visual field, estimated using a target-localization task, is related to the individual's ability to manage the simulated driving situation (correlation coefficient with speed = -0.43 and with reaction time for avoidance of a mobile obstacle = +0.30) and the deterioration of the useful visual field estimated using a target detection task is related only to vehicle speed (correlation coefficient = -0.32). The adoption of a lower speed by the drivers with a reduced visual field (the elderly ones) is probably an adaptation strategy to process the peripheral information. All useful visual field measurements do not seem to be equivalent to estimate the ability to process information relative to the mobile obstacle. The risk of collision should be estimated only with a useful visual field test using a target localization task.

La signature spatiale de l'objet : une information essentielle pour la localisation de cibles dans une scène naturelle

Scenes of the outside world do not look like any artificial image. They exhibit a specific spatial frequency content and a global structure evocative of their category membership. This information characteristic of natural scenes leads to define the concept of scene spatial signature. What is the respective role of this specific global information related to the scene and of the local information related to the image components in a target localization task ? Two experiments investigate the relative weight of both levels of information. Results show that initially, when images are blurred, the global structure plays a major role. However, after a familiarization period, subjects start using the invariant distinctive features of the target to localize it regardless of the aspect of the scene. Analogous to the scene spatial signature, the local information distinguishing the target from its close environment defines the object spatial signature. This perceptual adaptation process frees subjects from having to rely on global information. Results show that perceptual strategies are not determined once and for all. The visual system is flexible and is able to juggle the various available information at both global and local levels to adapt to the demand.

Searching Visual Displays: The Role of Attention

Previous research suggests that (a) target localization tasks, (b) apprehension of spatial relations among stimuli, (c) critical features shared between target and non-target stimuli, and (d) mirror-image symmetry between target and non-targets each place demands on attention, resulting in poor search performance caused by capacity limitations. But, are these performance deficits actually caused by capacity limitations? Perhaps they are caused by early, pre-attentive visual processing or by noisy decision making instead of capacity limitations. If so, this has implications for the design of “user-friendly” displays to facilitate search performance. To address these questions, we controlled sensory effects and systematically varied the complexity and number of stimuli as well as whether non-targets were mirror-images of the target. Comparisons of data to theoretical predictions showed that capacity limitations occurred only when the target shared critical features with complex non-target stimuli, so that one must apprehend spatial relations of each object's component parts. No other factors resulted in capacity limitations. Moreover, although mirror-image symmetry adversely affected early visual preattentive processing, it did not place additional demands on attention.

Differential effects of visual context on pattern discrimination by pigeons (Columba livia) and humans (Homo sapiens).

Three experiment examined the role of contextual information during line orientation and line position discriminations by pigeons (Columba livia) and humans (Homo sapiens). Experiment 1 tested pigeons' performance with these stimuli in a target localization task using texture displays. Experiments 2 and 3 tested pigeons and humans, respectively, with small and large variations of these stimuli in a same-different task. Humans showed a configural superiority effect when tested with displays constructed from large elements but not when tested with the smaller, more densely packed texture displays. The pigeons, in contrast, exhibited a configural inferiority effect when required to discriminate line orientation, regardless of stimulus size. These contrasting results suggest a species difference in the perceptionand use of features and contextual information in the discrimination of line information.

The adaptive character of the attentional system: statistical sensitivity in a target localization task.

A localization task required participants to indicate which of 4 locations contained a briefly displayed target. Most displays also contained a distractor that was not equally probable in these locations, affecting performance dramatically. Responses were faster when a display had no distractor and almost as fast when the distractor was in its frequent location. Conversely, responses were slower when targets appeared in frequent-distractor locations, even thou targets were equally likely in each location. Negative-priming effects were reliably smaller when targets followed distractors in the frequent-distractor location compared to the rare-distractor location, challenging the episodic-retrieval account Experiment 2 added a 5th location that rarely displayed distractors and never targets, yet responses slowed most when distractors appeared there. The results confirmed that the attentional system is sensitive to first- and higher-order statistical patterns and can make short- and long-term adjustments in preferences based on prior history of inspecting unsuccessful locations.

Pigeon perception and discrimination of rapidly changing texture stimuli.

The perception and discrimination of rapidly changing texture stimuli by pigeons was examined in a target localization task. Five experienced pigeons were rewarded for finding and pecking at a randomly placed odd target block of small repeated elements embedded in a larger rectangular array of contrasting distractor elements. On dynamic color test trials, the color of the target, distractor, or both of these regions changed at rates of 100, 250, 500, or 1000 ms per frame. The number of colors appearing within such trials also varied. Pigeons performed well above chance in all test conditions, with target-associated changes producing the best discrimination. The results suggest: (a) global relational information can exclusively guide target localization behavior, (b) pigeons can perceptually group and segregate colored textured differences quite rapidly (< or = 100 ms), and (c) pigeons may possess automatic search control processes that can be captured by stimulus-driven changes in the display.

Acquisition of Spatial Knowledge Through Visual Exploration of Simulated Environments

The capacity of observers to learn spatial layouts of objects located in a graphically displayed wall-limited space was tested in a target localization task after active or passive exploration of the simulated environment. The spatial layouts were composed of four target cubes of different colors and obstructing inner walls. In the active exploration condition, the observers freely explored the space, smoothly changing the view point by means of a joystick and attempting to locate each target cube. In two passive exploration conditions, the observers explored the environments by looking either at a continuous changing scene as viewed along a smoothly travelled path or at a series of static scenes as viewed from successive points of view along a path. Immediately after exploration, the observer's task was to reach, using the shortest path, a specified target not visible from the starting point situated near the center of the environment. We hypothesized that spatial acquisition resulting after active exploration would be more accurate than after passive exploration, and that dynamic visual information used to display the environment would be more efficient than static visual information. As expected, the performance was better for active exploration than for passive exploration, but dynamic and static passive conditions yielded equivalent performance. Further spatial analyses of the trajectories produced to reach the target and subsequent analyses between trajectories and corresponding target reaching score and target reaching time allowed us to classify the participants' strategies according to different levels of learning of the environment layouts. Some participants were able to build up an absolute representation of the environment, including the objects' locations and orientations, and others learned the spatial layouts of objects by relating spatial clues to each other. A few participants were unable to memorize the environment layouts and exhibited random-like search paths. These results show the link between the level of performance and the level of spatial knowledge, and confirm the importance of active motor behavior combined with active perception to extract invariants in the environment.

Visual‐motor localizations in normal and subnormal development

Subnormal and normal children, of like mental age, were compared on a visual target localization task. Severely subnormal children were found to be less accurate than normal children, in conditions where they visually directed or visually guided their hand to the target and received visual knowledge of results. On visually directed localizations without knowledge of results or with proprioceptive knowledge of results (same hand) no significant difference was found between normal and severely subnormal children. Another experiment with moderately subnormal children revealed that developmental changes on visually directed and visually guided localizations are a function of mental age rather than chronological age.