Context Of Navigation Research Articles

Aging and spatial cues influence the updating of navigational memories

Updating navigational memories is important for everyday tasks. It was recently found that older adults are impaired in updating spatial representations in small, bi-dimensional layouts. Because performance in small-scale areas cannot predict navigational behavior, we investigated how aging affects the updating of navigational memories encoded in large, 3-dimensional environments. Moreover, since locations can be encoded relative to the observer (egocentric encoding) or relative to landmarks (allocentric encoding), we tested whether the presumed age-related spatial updating deficit depends on the available spatial cues. By combining whole-body motion tracking with immersive virtual reality, we could dissociate egocentric and allocentric spatial cues and assess navigational memory under ecologically valid conditions (i.e., providing body-based and visual cues). In the task, objects were relocated overnight, and young and older participants had to navigate to the updated locations of the objects. In addition to replicating age-related deficits in allocentric memory, we found age-related impairments in updating navigational memories following egocentric encoding. Finally, older participants depicted stronger representations of the previous navigational context that were correlated with their spatial updating deficits. Given that these effects may stem from inefficient suppression of former navigational memories, our findings propose a mechanism that helps explain the navigational decline in aging.

Wideband Air–Ground Channel Model for a Regional Airport Environment

In the air–ground propagation channel, multipath propagation severely affects the performance of communication, navigation, and surveillance systems used in civil aviation. To verify the performance of aeronautical wireless transmission systems independently from expensive flight trials, a channel model for computer simulations is required. Based on an exhaustive propagation measurement campaign, we propose a geometry-based stochastic channel model for the air–ground channel in a regional airport environment in the L -band. The proposed channel model allows us to correctly reproduce the non-stationarity of the channel impulse response. Thus, the channel model is suitable not only to assess the performance of communication systems, but also for ranging, i.e., for navigation systems. We validate the channel model using data from both channel sounding and as well as flight measurements performed in a navigation context.

Magnetic body alignment in migratory songbirds: a computer vision approach.

Several invertebrate and vertebrate species have been shown to align their body relative to the geomagnetic field. Many hypotheses have been proposed to explain the adaptive significance of magnetic body alignment outside the context of navigation. However, experimental evidence to investigate alternative hypotheses is still limited. We present a new setup to track the preferential body alignment relative to the geomagnetic field in captive animals using computer vision. We tested our method on three species of migratory songbirds and provide evidence that they align their body with the geomagnetic field. We suggest that this behaviour is involved in the underlying mechanism for compass orientation and calibration, which may occur near to sunrise and sunset periods. Our method could easily be extended to other species and used to test a large set of hypotheses to explain the mechanisms behind the magnetic body alignment and the magnetic sense in general.

Emergent neural turing machine and its visual navigation

Traditional Turing Machines (TMs) are symbolic whose hand-crafted representations are static and limited. Developmental Network 1 (DN-1) uses emergent representation to perform Turing Computation. But DN-1 lacks hierarchy in its internal representations, and is hard to handle the complex visual navigation tasks. In this paper, we improve DN-1 with several new mechanisms and presenta new emergent neural Turing Machine — Developmental Network 2 (DN-2). By neural, we mean that the control of the TM has neurons as basic computing elements. The major novelty of DN-2 over DN-1 is that the representational hierarchy inside DN-2 is emergent and fluid. DN-2 grows complex hierarchies by dynamically allowing initialization of neurons with different ranges of connection. We present a complex task — vision guided navigation in simulated and natural worlds using DN-2. A major function that has not been demonstrated before is that the hierarchy enables attention that disregards distracting features based on the navigation context. In simulated navigation experiments, DN-2 can perform with no errors, and in real-world navigation experiments, the error rate is only 0.78%. These experimental results showed that DN-2 successfully learned rules of navigation with image inputs.

On route with harbor seals – how their senses contribute to orientation, navigation and foraging

Summary Summary: Seals and sea lions are well-oriented in their habitat, the coastal regions and oceans, and are, moreover, successful hunters. During their movements between haul-out places and foraging grounds as well as during foraging, the sensory systems of seals and sea lions provide useful information, although the animals, and thus their sensory systems, face considerable challenges in their habitat and due to their amphibious lifestyle. In this review, in the first chapter, we compiled and later (chapter 4) discuss the information on the senses of seals and sea lions in general and their specific adaptations to habitat and lifestyle in particular. We hereby focus on the senses of harbor seals. Harbor seals turned into a model organism regarding the sensory systems due to intensive sensory research of the last decades. In the second and third chapter, the sensory basics are put into the context of orientation, navigation, and foraging. This allows formulating new research questions, such as where and how the information from different senses is integrated.

EVALUATING ROUTE LEARNING PERFORMANCE OF OLDER AND YOUNGER ADULTS IN DIFFERENTLY-DESIGNED VIRTUAL ENVIRONMENTS: A TASK-DIFFERENTIAL ANALYSIS

Abstract. Navigating in unfamiliar environments is a complex task that requires considerable cognitive resources to memorize (and eventually learn) a route. In general, virtual environments (VEs) can be useful tools in training for route learning and improving route recall. However, the visual information presented in VEs, that is, what we choose to present in a virtual scene, can strongly affect the ability to recall a route. This is especially relevant when we consider individual differences, and people’s varying abilities to navigate effectively. Taking various cognitive processes involved in route learning into account, we designed a multi-level experiment that examines route recall effectiveness in a navigation context. We conceptualized that the participants would have to recall information related to the route that is demanding on primarily visual, spatial, or visuospatial memory systems. Furthermore, because there is a clear link between memory capacity and ageing; we conducted our experiment with two different age groups (total 81 participants: 42 young people aged 20–30 yo and 39 older people aged 65–76 yo). We also measured participants’ spatial abilities and visuospatial memory capacity for control purposes. After experiencing a pre-determined route in three different VEs (that we varied in levels of visual realism, and named as AbstractVE, MixedVE, and RealisticVE), each participant solved a list of tasks that was designed to measure visual, spatial, and visuospatial recall of the scene elements and information about the route. Participants solved these tasks immediately after experiencing the route in each VE, as well as after a week, thus we could measure ‘learning’ (delayed recall). Results from our study confirm the well-known decline in recall with age (young vs. older), provide new information regarding memorability of routes and VE scene elements over time (immediate vs. delayed), and most importantly demonstrate the crucial role the visual design decisions play in route learning and memorability of visuospatial displays.

Fusion of 3D GIS, Vision, Inertial and Magnetic Data for Improved Urban Pedestrian Navigation and Augmented Reality Applications

n the context of pedestrian navigation and Augmented Reality applications in urban environments, we propose to fuse the pose estimated through a vision process, thanks to a precisely known 3D model, with inertial and magnetic measurements. First, this allows for updating a Pedestrian DeadReckoning process and improving the positioning accuracy. Second, a trusted pose estimate allows us to reproject 3D Geographical Information System content in Augmented Reality with qualified confidence. Because 3D Geographical Information System data are provided by many sources inducing an inhomogeneous precision and level of quality, being able to qualify these 3D contents is important to validate their relevance to use them. A long pedestrian path of 3 km in an urban environment with a sparsely known 3D model of urban furniture was conducted. This has permitted validation of the contribution of sensor fusion that improves the positioning accuracy and allows characterization of the 3D Geographical Information System content directly onsite using Augmented Reality. Performance is presented in terms of positioning accuracy in urban spaces. © 2018 Institute of Navigation.

The Complex Nature of Hippocampal-Striatal Interactions in Spatial Navigation.

Decades of research have established the importance of the hippocampus for episodic and spatial memory. In spatial navigation tasks, the role of the hippocampus has been classically juxtaposed with the role of the dorsal striatum, the latter of which has been characterized as a system important for implementing stimulus-response and action-outcome associations. In many neuroimaging paradigms, this has been explored through contrasting way finding and route-following behavior. The distinction between the contributions of the hippocampus and striatum to spatial navigation has been supported by extensive literature. Convergent research has also underscored the fact that these different memory systems can interact in dynamic ways and contribute to a broad range of navigational scenarios. For example, although familiar routes may often be navigable based on stimulus-response associations, hippocampal episodic memory mechanisms can also contribute to egocentric route-oriented memory, enabling recall of context-dependent sequences of landmarks or the actions to be made at decision points. Additionally, the literature has stressed the importance of subdividing the striatum into functional gradients—with more ventral and medial components being important for the behavioral expression of hippocampal-dependent spatial memories. More research is needed to reveal how networks involving these regions process and respond to dynamic changes in memory and control demands over the course of navigational events. In this Perspective article, we suggest that a critical direction for navigation research is to further characterize how hippocampal and striatal subdivisions interact in different navigational contexts.

Transcranial Magnetic Stimulation to the Occipital Place Area Biases Gaze During Scene Viewing.

We can understand viewed scenes and extract task-relevant information within a few hundred milliseconds. This process is generally supported by three cortical regions that show selectivity for scene images: parahippocampal place area (PPA), medial place area (MPA) and occipital place area (OPA). Prior studies have focused on the visual information each region is responsive to, usually within the context of recognition or navigation. Here, we move beyond these tasks to investigate gaze allocation during scene viewing. Eye movements rely on a scene’s visual representation to direct saccades, and thus foveal vision. In particular, we focus on the contribution of OPA, which is: (i) located in occipito-parietal cortex, likely feeding information into parts of the dorsal pathway critical for eye movements; and (ii) contains strong retinotopic representations of the contralateral visual field. Participants viewed scene images for 1034 ms while their eye movements were recorded. On half of the trials, a 500 ms train of five transcranial magnetic stimulation (TMS) pulses was applied to the participant’s cortex, starting at scene onset. TMS was applied to the right hemisphere over either OPA or the occipital face area (OFA), which also exhibits a contralateral visual field bias but shows selectivity for face stimuli. Participants generally made an overall left-to-right, top-to-bottom pattern of eye movements across all conditions. When TMS was applied to OPA, there was an increased saccade latency for eye movements toward the contralateral relative to the ipsilateral visual field after the final TMS pulse (400 ms). Additionally, TMS to the OPA biased fixation positions away from the contralateral side of the scene compared to the control condition, while the OFA group showed no such effect. There was no effect on horizontal saccade amplitudes. These combined results suggest that OPA might serve to represent local scene information that can then be utilized by visuomotor control networks to guide gaze allocation in natural scenes.

Attitude estimation for indoor navigation and augmented reality with smartphones

We investigate the precision of attitude estimation algorithms in the particular context of pedestrian navigation with commodity smartphones and their inertial/magnetic sensors. We report on an extensive comparison and experimental analysis of existing algorithms. We focus on typical motions of smartphones when carried by pedestrians. We use a precise ground truth obtained from a motion capture system. We test state-of-the-art and built-in attitude estimation techniques with several smartphones, in the presence of magnetic perturbations typically found in buildings. We discuss the obtained results, analyze advantages and limits of current technologies for attitude estimation in this context. Furthermore, we propose a new technique for limiting the impact of magnetic perturbations with any attitude estimation algorithm used in this context. We show how our technique compares and improves over previous works. A particular attention was paid to the study of attitude estimation in the context of augmented reality motions when using smartphones.

Visual Odometry and Place Recognition Fusion for Vehicle Position Tracking in Urban Environments

In this paper, we address the problem of vehicle localization in urban environments. We rely on visual odometry, calculating the incremental motion, to track the position of the vehicle and on place recognition to correct the accumulated drift of visual odometry, whenever a location is recognized. The algorithm used as a place recognition module is SeqSLAM, addressing challenging environments and achieving quite remarkable results. Specifically, we perform the long-term navigation of a vehicle based on the fusion of visual odometry and SeqSLAM. The template library for this latter is created online using navigation information from the visual odometry module. That is, when a location is recognized, the corresponding information is used as an observation of the filter. The fusion is done using the EKF and the UKF, the well-known nonlinear state estimation methods, to assess the superior alternative. The algorithm is evaluated using the KITTI dataset and the results show the reduction of the navigation errors by loop-closure detection. The overall position error of visual odometery with SeqSLAM is 0.22% of the trajectory, which is much smaller than the navigation errors of visual odometery alone 0.45%. In addition, despite the superiority of the UKF in a variety of estimation problems, our results indicate that the UKF performs as efficiently as the EKF at the expense of an additional computational overhead. This leads to the conclusion that the EKF is a better choice for fusing visual odometry and SeqSlam in a long-term navigation context.

What in the World Is North? Translating Cardinal Directions across Languages, Cultures and Environments

What in the World Is North? Translating Cardinal Directions across Languages, Cultures and Environments

Regulatory Aspects of Optical Methods and Exogenous Targets for Cancer Detection.

Considerable advances in cancer-specific optical imaging have improved the precision of tumor resection. In comparison to traditional imaging modalities, this technology is unique in its ability to provide real-time feedback to the operating surgeon. Given the significant clinical implications of optical imaging, there is an urgent need to standardize surgical navigation tools and contrast agents to facilitate swift regulatory approval. Because fluorescence-enhanced surgery requires a combination of both device and drug, each may be developed in conjunction, or separately, which are important considerations in the approval process. This report is the result of a one-day meeting held on May 4, 2016 with officials from the National Cancer Institute, the FDA, members of the American Society of Image-Guided Surgery, and members of the World Molecular Imaging Society, which discussed consensus methods for FDA-directed human testing and approval of investigational optical imaging devices as well as contrast agents for surgical applications. The goal of this workshop was to discuss FDA approval requirements and the expectations for approval of these novel drugs and devices, packaged separately or in combination, within the context of optical surgical navigation. In addition, the workshop acted to provide clarity to the research community on data collection and trial design. Reported here are the specific discussion items and recommendations from this critical and timely meeting. Cancer Res; 77(9); 2197-206. ©2017 AACR.

Spatial Navigation and the Central Complex: Sensory Acquisition, Orientation, and Motor Control.

Cockroaches are scavengers that forage through dark, maze-like environments. Like other foraging animals, for instance rats, they must continually asses their situation to keep track of targets and negotiate barriers. While navigating a complex environment, all animals need to integrate sensory information in order to produce appropriate motor commands. The integrated sensory cues can be used to provide the animal with an environmental and contextual reference frame for the behavior. To successfully reach a goal location, navigational cues continuously derived from sensory inputs have to be utilized in the spatial guidance of motor commands. The sensory processes, contextual and spatial mechanisms, and motor outputs contributing to navigation have been heavily studied in rats. In contrast, many insect studies focused on the sensory and/or motor components of navigation, and our knowledge of the abstract representation of environmental context and spatial information in the insect brain is relatively limited. Recent reports from several laboratories have explored the role of the central complex (CX), a sensorimotor region of the insect brain, in navigational processes by recording the activity of CX neurons in freely-moving insects and in more constrained, experimenter-controlled situations. The results of these studies indicate that the CX participates in processing the temporal and spatial components of sensory cues, and utilizes these cues in creating an internal representation of orientation and context, while also directing motor control. Although these studies led to a better understanding of the CX's role in insect navigation, there are still major voids in the literature regarding the underlying mechanisms and brain regions involved in spatial navigation. The main goal of this review is to place the above listed findings in the wider context of animal navigation by providing an overview of the neural mechanisms of navigation in rats and summarizing and comparing our current knowledge on the CX's role in insect navigation to these processes. By doing so, we aimed to highlight some of the missing puzzle pieces in insect navigation and provide a different perspective for future directions.

Feature-Based Resource Allocation for Real-Time Stereo Disparity Estimation

The most accurate stereo disparity algorithms take dozens or hundreds of seconds to process a single frame. This timescale is impractical for many applications. However, high accuracy is often not needed throughout the scene. Here, we investigate a “foveation” approach (in which some parts of an image are processed more intensively than others) in the context of modern stereo algorithms. We consider two scenarios: disparity estimation with a convolutional network in a robotic grasping context, and disparity estimation with a Markov random field in a navigation context. In each case, combining fast and slow methods in different parts of the scene improves frame rates while maintaining accuracy in the most task-relevant areas. We also demonstrate a simple and broadly applicable utility function for choosing foveal regions, which combines image and task information. Finally, we characterize the benefits of defining multiple individually placed small foveae per image, rather than a single large fovea. We find little benefit, supporting the use of hardware foveae of fixed size and shape. More generally, our results reaffirm that foveation is a practical way to combine speed with task-relevant accuracy. Foveae are present in the most complex biological vision systems, suggesting that they may become more important in artificial vision systems, as these systems become more complex.

Randomized controlled dissemination study of community-to-clinic navigation to promote CRC screening: Study design and implications

IntroductionRegular screening facilitates early diagnosis of colorectal cancer (CRC) and reduction of CRC morbidity and mortality. Screening rates for minorities and low-income populations remain suboptimal. Provider referral for CRC screening is one of the strongest predictors of adherence, but referrals are unlikely among those who have no clinic home (common among poor and minority populations). Methods/study designThis group randomized controlled study will test the effectiveness of an evidence based tailored messaging intervention in a community-to-clinic navigation context compared to no navigation. Multicultural, underinsured individuals from community sites will be randomized (by site) to receive CRC screening education only, or education plus navigation. In Phase I, those randomized to education plus navigation will be guided to make a clinic appointment to receive a provider referral for CRC screening. Patients attending clinic appointments will continue to receive navigation until screened (Phase II) regardless of initial arm assignment. We hypothesize that those receiving education plus navigation will be more likely to attend clinic appointments (H1) and show higher rates of screening (H2) compared to those receiving education only. Phase I group assignment will be used as a control variable in analysis of screening follow-through in Phase II. Costs per screening achieved will be evaluated for each condition and the RE-AIM framework will be used to examine dissemination results. ConclusionThe novelty of our study design is the translational dissemination model that will allow us to assess the real-world application of an efficacious intervention previously tested in a randomized controlled trial.

Cellular Basis of Head Direction and Contextual Cues in the Insect Brain

Animals rely upon integrated sensory information for spatial navigation. A question of wide importance in navigation is how sensory cues get transformed into neural codes that represent the animal's orientation within its proximal environment. Here, we investigated the possibility of head-direction coding in the central complex of the cockroach, Blaberus discoidalis. We used extracellular recordings in restrained animals that were rotated on a platform relative to a fixed landmark. The passive rotations allowed us to test for head-direction coding in the absence of self-generated motion cues. Our results indicate that individual cells in the central complex encode the animal's heading relative to a landmark's position in several ways. In some cells, directional tuning was established even in the absence of visual cues, suggesting that the directional code can be maintained solely based on the internal motion cues derived from the passive rotations. Additionally, some cells in the central complex encoded rotation-direction history, a navigational context cue, by increasing or decreasing the firing rate during the stationary periods following clockwise or counterclockwise rotations. Together, these results unveil head-direction cell-like activity in the insect central complex, which highly resemble similarly functioning cells in the mammalian brain that encode head direction. We predict that the observed head-orientation coding and directionally sensitive cells are essential components of the brain circuitry mediating insect navigation.

Age-Related Differences in Associative Learning of Landmarks and Heading Directions in a Virtual Navigation Task.

Previous studies have showed that spatial memory declines with age but have not clarified the relevance of different landmark cues for specifying heading directions among different age groups. This study examined differences between younger, middle-aged and older adults in route learning and memory tasks after they navigated a virtual maze that contained: (a) critical landmarks that were located at decision points (i.e., intersections) and (b) non-critical landmarks that were located at non-decision points (i.e., the sides of the route). Participants were given a recognition memory test for critical and non-critical landmarks and also given a landmark-direction associative learning task. Compared to younger adults, older adults committed more navigation errors during route learning and were poorer at associating the correct heading directions with both critical and non-critical landmarks. Notably, older adults exhibited a landmark-direction associative memory deficit at decision points; this was the first finding to show that an associative memory deficit exist among older adults in a navigational context for landmarks that are pertinent for reaching a goal, and suggest that older adults may expend more cognitive resources on the encoding of landmark/object features than on the binding of landmark and directional information. This study is also the first to show that older adults did not have a tendency to process non-critical landmarks, which were regarded as distractors/irrelevant cues for specifying the directions to reach the goal, to an equivalent or larger extent than younger adults. We explain this finding in view of the low number of non-critical cues in our virtual maze (relative to a real-world urban environment) that might not have evoked older adults’ usual tendency toward processing or encoding distractors. We explain the age differences in navigational and cognitive performance with regards to functional and structural changes in the hippocampus and parahippocampus, and recommend further investigations into the functional connectivity between the prefrontal cortex and hippocampus for a better understanding of the landmark-direction associative learning among the elderly. Finally, it is hoped that the current behavioral findings will facilitate efforts to identify the neural markers of Alzheimer’s disease, a disease that commonly involves navigational deficits.

Not all memories are the same: Situational context influences spatial recall within one's city of residency.

Reference frames in spatial memory encoding have been examined intensively in recent years. However, their importance for recall has received considerably less attention. In the present study, passersby used tags to arrange a configuration map of prominent city center landmarks. It has been shown that such configurational knowledge is memorized within a north-up reference frame. However, participants adjusted their maps according to their body orientations. For example, when participants faced south, the maps were likely to face south-up. Participants also constructed maps along their location perspective-that is, the self-target direction. If, for instance, they were east of the represented area, their maps were oriented west-up. If the location perspective and body orientation were in opposite directions (i.e., if participants faced away from the city center), participants relied on location perspective. The results indicate that reference frames in spatial recall depend on the current situation rather than on the organization in long-term memory. These results cannot be explained by activation spread within a view graph, which had been used to explain similar results in the recall of city plazas. However, the results are consistent with forming and transforming a spatial image of nonvisible city locations from the current location. Furthermore, prior research has almost exclusively focused on body- and environment-based reference frames. The strong influence of location perspective in an everyday navigational context indicates that such a reference frame should be considered more often when examining human spatial cognition.

Human Factors Analysis Using Wearable Sensors in the Context of Cognitive and Emotional Arousal

Quantitative investigations on stress conditions in evaluation scenarios have so far mainly been conducted in static scenarios, such as, in desktop studies. Studies involving the mobility of participants are rather rare, in particular, considering substantial comparison between different stress conditions. Recently, data and eye tracking glasses have shifted the attention on future applications classes that would require wearable devices delivering multisensory, including psychophysiological, data in various everyday contexts, requiring information about the psychological status of the user. These settings need to investigate stress conditions in different mobile settings, querying which parameters would provide discriminative features for stress indication. A study with 20 participants was conducted in a shopping and a navigation context, involving participants – being equipped with portable psychophysiological sensors and eye tracking glasses - in memory and orientation tasks, respectively, for the inducing of cognitive and emotional arousal. From the results we conclude that the specific context and the cause of arousal lead to different reactions of the psychophysiological system as well as in the eye movement behavior. Depending on the context and the stress condition under investigation, different arousal, and consequently, stress classifiers as well as attention models should be applied.