Navigation Mechanism Research Articles

Wizualizacja nawigacji w serwisach typu discovery

Next generation Integrated Library Systems (NGILS) also known as discovery and delivery systems or search and discovery systems, are claimed to be significant innovation in information searching field as well as its visualisation methods. One of the explanation is extended retrieval scope including e-documents in data bases and repositories. Navigation systems have a significant meaning in properly functionality of NGILS. Navigation provide ways to achievement of users’ goals. Main aim of the article is a comparative analysis of navigation systems in selected NGILS: VuFind (open source), Primo ExLibris, Summon ProQuest, Encore Innovative Interfaces, ProlibIntegro, Virtua/Chamo. The visualisation layer of NGILS navigation mechanisms was also discussed. Optimal visualisation of interfaces and navigation assist users in making decision process, and in link selection.

Experimental investigations on permanent magnet based wheel mechanism for safe navigation of climbing robot

This paper presents excremental studies on permanent magnet based wheel mechanism for safe navigation of climbing robot on ferrous wall surface structures. Three types of wheel mechanism (Wheel 1, Wheel 2 and Wheel 3) are manufactured and compared for their working performance experimentally for climbing robot locomotion trials. The Wheel 1 mechanism with MS hub is very compact, simple in design with easy assemble/dissemble features, and having less manufacturing cost. However, the adhesion force of the prototype wheel is comparable with already reported permanent magnet based adhesion mechanism. Wheel 1 design is further improved by developing Wheel 2 and 3 versions by changing hub material from mild steel to Aluminum. These wheel mechanisms are light in weight and more powerful to achieve maximum adhesion force i.e., 210 N and 251 N with and without rubber grip, respectively, at only 200 gm wheel weight as compared to previously reported permanent magnetic adhesion mechanism. Thus, more payload carrying capacity climbing robot can be developed using these developed mechanisms for field trials of climbing robot. A comprehensive experimental study on the influence of rubber grip thickness, air gap, wheel tilt angle and test surface thickness variation on adhesion force of these developed wheel mechanisms have been reported. The influence of both static and kinetic coefficient of friction (COF) for vertical surface locomotion of climbing robot has also been investigated. These developed wheel mechanisms have been further demonstrated using a four-wheel differential drive prototype-climbing robot for safe navigation testing first on a 2-D framed plane wall structure and next on a 3-D framed wall structure. It is found from the laboratory trials that based on these wheel mechanisms, the climbing robot can safely navigate remotely on even surface for these chosen structures.

Review of Wheeled Mobile Robots’ Navigation Problems and Application Prospects in Agriculture

Robot navigation in the environment with obstacles is still a challenging problem. In this paper, the navigation problems with wheeled mobile robots (WMRs) are reviewed, the navigation mechanism of WMRs is analyzed in detail, the methods of solving the sub problems such as mapping, localization and path planning which all both related to robot navigation are summarized and the advantages and disadvantages of the existing methods are expounded. Especially in the agricultural field, the precise navigation of robots in the complex agricultural environment is the prerequisite for the completion of various tasks. This paper is aimed at the special complexity of the agricultural environment, prospected the application of the solution to the navigation problem of WMRs in agricultural engineering, put forward the research direction to solve the problems of precise navigation in agricultural environments.

Non-migratory monarch butterflies, Danaus plexippus (L.), retain developmental plasticity and a navigational mechanism associated with migration

Monarch butterflies are best known from their migratory North American range, although many resident, year-round breeding populations are established throughout the world. Here, we evaluate two non-exclusive hypotheses for the loss of migration in resident monarch populations: (1) absence of cues that trigger migration; and (2) loss of sensory, neural or physiological systems required for migration. To evaluate the first hypothesis, we exposed resident monarchs from Queensland, Australia to decreasing larval photoperiod and observed reproductive development in resulting females to assess their propensity to show reduced reproductive development, a precursor for long-distance migration. To address the second hypothesis, we measured antennal circadian clock gene expression, a crucial element of the monarch's ability to orientate directionally, in a resident and a migratory population. We found that Australian resident monarchs show reduced reproductive development in response to decreasing photoperiod, consistent with the 'loss of cues' hypothesis. We found no differences in antennal clock gene expression between migratory and resident populations, inconsistent with the 'loss of mechanism' hypothesis. Together, these data indicate that even after hundreds of generations of non-migration, monarchs retain two crucial elements of their migratory repertoire: developmental plasticity associated with decreasing photoperiod and antennal circadian rhythms necessary for directional orientation.

Human hippocampal theta power indicates movement onset and distance travelled

Theta frequency oscillations in the 6- to 10-Hz range dominate the rodent hippocampal local field potential during translational movement, suggesting that theta encodes self-motion. Increases in theta power have also been identified in the human hippocampus during both real and virtual movement but appear as transient bursts in distinct high- and low-frequency bands, and it is not yet clear how these bursts relate to the sustained oscillation observed in rodents. Here, we examine depth electrode recordings from the temporal lobe of 13 presurgical epilepsy patients performing a self-paced spatial memory task in a virtual environment. In contrast to previous studies, we focus on movement-onset periods that incorporate both initial acceleration and an immediately preceding stationary interval associated with prominent theta oscillations in the rodent hippocampal formation. We demonstrate that movement-onset periods are associated with a significant increase in both low (2-5 Hz)- and high (6-9 Hz)-frequency theta power in the human hippocampus. Similar increases in low- and high-frequency theta power are seen across lateral temporal lobe recording sites and persist throughout the remainder of movement in both regions. In addition, we show that movement-related theta power is greater both before and during longer paths, directly implicating human hippocampal theta in the encoding of translational movement. These findings strengthen the connection between studies of theta-band activity in rodents and humans and offer additional insight into the neural mechanisms of spatial navigation.

Long-distance flights and high-risk breeding by nomadic waterbirds on desert salt lakes.

Understanding and conserving mobile species presents complex challenges, especially for animals in stochastic or changing environments. Nomadic waterbirds must locate temporary water in arid biomes where rainfall is highly unpredictable in space and time. To achieve this they need to travel over vast spatial scales and time arrival to exploit pulses in food resources. How they achieve this is an enduring mystery. We investigated these challenges in the colonial-nesting Banded Stilt (Cladorhynchus leucocephalus), a nomadic shorebird of conservation concern. Hitherto, Banded Stilts were hypothesized to have only 1-2 chances to breed during their long lifetime, when flooding rain fills desert salt lakes, triggering mass-hatching of brine shrimp. Over 6 years, we satellite tagged 57 individuals, conducted 21 aerial surveys to detect nesting colonies on 14 Australian desert salt lakes, and analyzed 3 decades of Landsat and MODIS satellite imagery to quantify salt-lake flood frequency and extent. Within days of distant inland rainfall, Banded Stilts flew 1,000-2,000 km to reach flooded salt lakes. On arrival, females laid over half their body weight in eggs. We detected nesting episodes across the species' range at 7 times the frequency reported during the previous 80 years. Nesting colonies of thousands formed following minor floods, yet most were subsequently abandoned when the water rapidly evaporated prior to egg hatching. Satellite imagery revealed twice as many flood events sufficient for breeding-colony initiation as recorded colonies, suggesting that nesting at remote sites has been underdetected. Individuals took risk on uncertain breeding opportunities by responding to frequent minor flood events between infrequent extensive flooding, exemplifying the extreme adaptability and trade-offs of species exploiting unstable environments. The conservation challenges of nest predation by overabundant native gulls and anthropogenic modifications to salt lakes filling frequencies require investigation, as do the physiological and navigational mechanisms that enable such extreme strategies.

Hydronephones: Acoustic receivers on unmanned underwater vehicles

Noun | hy-drone-phone | \hi-drōn-fōn\ : An Instrument for listening to sound, mounted on an unmanned underwater vehicle. Yes, I made that word up—you heard it here first! The acronyms “UUV” (Unmanned Underwater Vehicle) and “AUV” (Autonomous Underwater Vehicle) have been buzzing around the underwater community recently, along with the term “underwater drone,” which gained popularity in the media due to an international incident in December 2016 regarding an ocean glider (a subclass of AUV). Unmanned underwater vehicles are quickly becoming ubiquitous in the world of oceanographic sensing, military operations, and oil and gas exploration. Because sound travels far and fast underwater, it is an enabling mechanism for navigation and communication for these vehicles. “Hydronephones,” specifically ocean gliders, are being used by our underwater acoustics community as receivers for long-range acoustics and marine mammal sensing. Key advantages of these vehicles are that they can be deployed for long durations of time in harsh environments and that they are much more cost-effective than traditional ship-based observational methods. An overview of this exciting technology will be presented along with details of some recent and ongoing “hydronephone” projects in underwater acoustics.

Temporal encoding strategies result in boosts to final free recall performance comparable to spatial ones.

The method of loci is a highly effective mnemonic that recruits existing salient memory for spatial locations and uses the information as a scaffold for remembering a list of items (Yates, 1966). One possible account for the effectiveness of the spatial method of loci comes from the perspective that it utilizes evolutionarily preserved mechanisms for spatial navigation within the hippocampus (Maguire et al. in Proceedings of the National Academy of Sciences, 97(8), 4398-4403, 2000; O'Keefe & Nadel, 1978; Rodriguez et al. in Brain Research Bulletin, 57(3), 499-503, 2002). Recently, though, neurons representing temporal information have also been described within the hippocampus (Eichenbaum in Nature Reviews Neuroscience, 15(11), 732-744, 2014; Itskov, Curto, Pastalkova, & Buzsáki in The Journal of Neuroscience, 31(8), 2828-2834, 2011; MacDonald, Lepage, Eden, & Eichenbaum in Neuron, 71(4), 737-749, 2011; Mankin et al. in Proceedings of the National Academy of Sciences, 109(47), 19462-19467, 2012; Meck, Church, & Matell in Behavioral Neuroscience, 127(5), 642, 2013), challenging the primacy of spatial-based functions to hippocampal processing. Given the presence of both spatial and temporal coding mechanisms within the hippocampus, we predicted that primarily temporal encoding strategies might also enhance memory. In two different experiments, we asked participants to learn lists of unrelated nouns using the (spatial) method of loci (i.e., the layout of their home as the organizing feature) or using two novel temporal methods (i.e., autobiographical memories or using the steps to making a sandwich). Participants' final free recall performance showed comparable boosts to the method of loci for both temporal encoding strategies, with all three scaffolding approaches demonstrating performance well above uninstructed free recall. Our findings suggest that primarily temporal representations can be used effectively to boost memory performance, comparable to spatial methods, with some caveats related to the relative ease with which participants appear to master the spatial versus temporal methods.

Mechanisms for maintaining mental maps

Neuroscience When an animal runs around, some hippocampal neurons are selectively active in specific locations called their place fields. A maplike representation created from many such place fields serves as a navigation mechanism. How such hippocampal maps stabilize is still unknown. Roux et al. investigated a discrete form of high-frequency neuronal oscillations called sharp wave ripples. In a spatial learning task, they focally silenced a subpopulation of hippocampal area CA1 neurons during sharp wave ripple events. The place fields of the silenced neurons were altered, and their spatial information content failed to increase. Control place cells, however, largely kept their spatial correlates and showed increased information after learning. Sharp wave ripple–associated neuronal firing is necessary for stabilizing and refining hippocampal place fields. Nat. Neurosci. 20 , 845 (2017).

Sequential neuromodulation of Hebbian plasticity offers mechanism for effective reward-based navigation

Spike timing-dependent plasticity (STDP) is under neuromodulatory control, which is correlated with distinct behavioral states. Previously, we reported that dopamine, a reward signal, broadens the time window for synaptic potentiation and modulates the outcome of hippocampal STDP even when applied after the plasticity induction protocol (Brzosko et al., 2015). Here, we demonstrate that sequential neuromodulation of STDP by acetylcholine and dopamine offers an efficacious model of reward-based navigation. Specifically, our experimental data in mouse hippocampal slices show that acetylcholine biases STDP toward synaptic depression, whilst subsequent application of dopamine converts this depression into potentiation. Incorporating this bidirectional neuromodulation-enabled correlational synaptic learning rule into a computational model yields effective navigation toward changing reward locations, as in natural foraging behavior. Thus, temporally sequenced neuromodulation of STDP enables associations to be made between actions and outcomes and also provides a possible mechanism for aligning the time scales of cellular and behavioral learning.

THE CORRELATION OF SENSE OF LOCATION AND REAL-WORLD NAVIGATION ABILITIES: A PRELIMINARY REPORT

Spatial navigation impairment (SNI) frequently occurs in people with Alzheimer's disease (AD), even in the very early stage of it and when the people with AD still residing in the community. The aim of this study was to predict SNI in a group of people with very mild AD by a device to assess sense of location (SoL). The neuropsychological tests included Mini-mental State Examinaiton (MMSE), Cognitive Abilities Screening Instrument (CASI), and Consortium to Establish a Registry for Alzheimer's Disease (CERAD). The real-world navigation abilities were assessed by the Questionnaire of Everyday Navigational Ability (QuENA). The history of getting lost events was assessed by the QuENA and obtained from reliable family members, based on which the participants were categorized to frequent way losers (WL) and getting lost resistant (GR, never been lost). The participants were instructed to point their current location on a tablet PC at five test points when they were walking along a route of 660 meters (including forward and backward paths). The SoL was determined by the hit rate of location within pre-set linear deviation of distance. Two independent raters scored the performance of each participants on the SoL. 32 AD participants (15 males) completed the study. Among them, 19 were WL (age 75.3±6.8 years, education 7.2±3.4 years, MMSE 20.2±3.5, CASI 71.5±11.7, CDR 0.7±0.3) and 13 GR (age 72.4±8.7 years, education 9.3±3.6 years, MMSE 22.9±5.4, CASI 78.3±13.1, CDR 0.6±0.2). The age, education, MMSE, CASI and CDR showed no difference between the two groups. The total QuENA score was 11.5±7.4 for WL and 7.0±3.5 for GR (p=0.029). The WL showed more linear deviation at the P5 on the backward path (p=0.044), while the other parameters, including SoL, linear deviation, and point-to-start test, showed no difference between the WL and the GR groups. More participants and more subgroups (subtypes or variants) are needed to verify the the role of SoL in SNI in AD. The underlying mechanisms for human spatial navigation are complex. More efforts must be put before the real causes are clearly known.

Memory, not just perception, plays an important role in terrestrial mammalian migration.

One of the key questions regarding the underlying mechanisms of mammalian land migrations is how animals select where to go. Most studies assume perception of resources as the navigational mechanism. The possible role of memory that would allow forecasting conditions at distant locations and times based on information about environmental conditions from previous years has been little studied. We study migrating zebra in Botswana using an individual-based simulation model, where perceptually guided individuals use currently sensed resources at different perceptual ranges, while memory-guided individuals use long-term averages of past resources to forecast future conditions. We compare simulated individuals guided by perception or memory on resource landscapes of remotely sensed vegetation data to trajectories of GPS-tagged zebras. Our results show that memory provides a clear signal that best directs migrants to their destination compared to perception at even the largest perceptual ranges. Zebras modelled with memory arrived two to four times, or up to 100 km, closer to the migration destination than those using perception. We suggest that memory in addition to perception is important for directing ungulate migration. Furthermore, our findings are important for the conservation of migratory mammals, as memory informing direction suggests migration routes could be relatively inflexible.

Dissociable patterns of brain activity for mentalizing about known others: a role for attachment.

The human brain tracks dynamic changes within the social environment, forming and updating representations of individuals in our social milieu. This mechanism of social navigation builds an increasingly complex map of persons with whom we are familiar and form attachments to guide adaptive social behaviors. We examined the neural representation of known others along a continuum of attachment using fMRI. Heterosexual adults (N = 29, 16 females), in romantic relationships for more than 2 years, made trait judgments for a romantic partner, parent, close friend, familiar acquaintance and self-during scanning. Multivariate analysis, partial least squares, was used to identify whole-brain patterns of brain activation associated with trait judgments of known others across a continuum of attachment. Across conditions, trait judgments engaged the default network and lateral prefrontal cortex. Judgments about oneself and a partner were associated with a common activation pattern encompassing anterior and middle cingulate, posterior superior temporal sulcus, as well as anterior insula. Parent and close friend judgments engaged medial and anterior temporal lobe regions. These results provide novel evidence that mentalizing about known familiar others results in differential brain activity. We provide initial evidence that the representation of adult attachment is a distinguishing feature of these differences.

The axonal transport motor kinesin-2 navigates microtubule obstacles via protofilament switching.

Axonal transport involves kinesin motors trafficking cargo along microtubules that are rich in microtubule-associated proteins (MAPs). Much attention has focused on the behavior of kinesin-1 in the presence of MAPs, which has overshadowed understanding the contribution of other kinesins such as kinesin-2 in axonal transport. We have previously shown that, unlike kinesin-1, kinesin-2 in vitro motility is insensitive to the neuronal MAP Tau. However, the mechanism by which kinesin-2 efficiently navigates Tau on the microtubule surface is unknown. We hypothesized that mammalian kinesin-2 side-steps to adjacent protofilaments to maneuver around MAPs. To test this, we used single-molecule imaging to track the characteristic run length and protofilament switching behavior of kinesin-1 and kinesin-2 motors in the absence and presence of 2 different microtubule obstacles. Under all conditions tested, kinesin-2 switched protofilaments more frequently than kinesin-1. Using computational modeling that recapitulates run length and switching frequencies in the presence of varying roadblock densities, we conclude that kinesin-2 switches protofilaments to navigate around microtubule obstacles. Elucidating the kinesin-2 mechanism of navigation on the crowded microtubule surface provides a refined view of its contribution in facilitating axonal transport.

How do migrating birds find their way?

Bird is one of the most abundant and widespread groups in the world. With many specialized structures, such as plumage, air sacs, and hollow bones, most bird species have got flight ability to adapt various niches. Therefore, bird can migrate between wintering and breeding ground, which is usually a long distance, and it’s called migration. Bird navigation is important in migration and is a complex process, which attracts many scientists to dig in how bird finds its way. Since 1873, Charles Darwin has ever mentioned that bird might take the method of dead reckoning on a long-distance migration like human, but at that time no one made further progress. Until 1950s, Kramer firstly found that Common Starling ( Sturnus vulgaris ) can respond to solar azimuth via mirror test. From then on, many experiments revealed that at least four navigation mechanisms are used in bird migration via more than nine external factors. They are: (i) celestial navigation, celestial clues (e.g. solar azimuth, star position, and polarized light) are used during migration period. (ii) Olfactory navigation, odor distributing in the air forms odorous gradient map or mosaic map which can be detected, or can activate directly certain mechanism to navigate. (iii) Auditory navigation, infrasound (0.05 Hz) produced by mountains and rivers generate sonic gradient map. And (iv) magnetic navigation, geomagnetic field can be detected via magnetic materials or chemical magnetoreception to find correct directions. Although many scientists approve that magnetic navigation may be the main mechanism to orientate and navigate, bird has never taken just one mechanism to migrate. Indeed, many species also use the other three mechanisms to calibrate direction, for example, Savannah Sparrow ( Passerculus sandwichensis ) can use polarized light to calibrate the magnetic compass at both sunrise and sunset. Different external clues correspond to different sense organs, so various brain areas should deal with information from different navigation mechanisms. The hippocampus participates in spatial perception and manages anything about celestial navigation via the tectofugal visual pathway and the thalamofugal visual pathway. The piriform cortex (CPi) is the main area to receive stimulation from olfactory bulb and determines how to migrate after receiving olfactory clues. Nervous systems of magnetic navigation include two parts which are trigeminus system and Cluster N. Despite the controversy whether there are some magnetic materials on bird, many experimental evidences have proved that magnetic materials detecting geomagnetic field involve to Trigeminus system. Cluster N, however, is an active area when bird migrates at night and it has an important role in transferring information from chemical magnetoreception to the hippocampus. As illustrated above, navigation mechanisms can get full information from many clues, and then, different brain areas trade off those and co-operate each other to make an elaborate map. Bird navigation involves the receptors to environment and the response of nervous system, so many issues are still maintained. The exact mechanism will be revealed with the new techniques and model animal applied.

Response properties of place cells in the hippocampus of freely moving pigeons

Place cells are considered to be the basic unit of cognitive maps, which play an important role in spatial cognition for many animals. To investigate the neural mechanisms underlying spatial cognition in birds, we designed four spatial cognitive tasks with or without goals, using pigeons as an animal model. We examined place cells in the hippocampus of 12 pigeons while they performed each task. We measured their spatial response properties and comparatively analyzed place field properties between tasks with and without goals using qualitative and quantitative measures. The results revealed that the reliability of place fields increased when the presence of a goal was clearer, and that place fields were more easily activated in tasks with a goal compared with those with no goal. In addition, we found that place cells in the hippocampus generally possessed multiple place fields, with an average of 2.7 place fields for each place cell. Place fields recorded simultaneously were always located in a similar position, and most exhibited overlapping regions. These results will be helpful for extending our understanding of the mechanisms underlying spatial cognition in different species, and provide a foundation for future studies investigating three-dimensional spatial cognition and navigation mechanisms in pigeons.

Patient navigation for depressed mothers in Head Start: A pilot study of intervention mechanism

We sought to assess potential mechanisms of action of a patient navigation intervention in Head Start, designed to help depressed mothers engage with mental health care. We employed mixed methods, linking qualitative interviews (n = 21) to a randomized intervention pilot (n = 47). Early in follow-up, navigated mothers had lower mean depressive symptom scores than non-navigated mothers (9.61 vs. 12.95, p = 0.03). These differences attenuated but preceded a greater likelihood of engaging with care among navigated mothers. Navigated mothers reported greater self-esteem (score 21.45 vs. 18.60, p = 0.05) and greater confidence in their ability to self-manage depression (7.65 vs. 5.67, p = 0.01). In qualitative interviews, navigated mothers linked decreased symptom burden to feeling activated; they communicated optimism toward the future and a willingness to work toward symptom improvement by trying something new. Early symptom relief, behavioral activation, self-esteem, self-management, and optimism represent plausible navigation mechanisms of action. These constructs require formal testing.

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.

Change of white matter neuronal integrity associated with spatial navigation impairment in mild cognitive impairment

Objective: To analyze the correlation between white matter integrity and spatial navigation impairment in patients with mild cognitive impairment (MCI). Methods: A total of 27 MCI subjects and 24 healthy controls were enrolled from the Affiliated Drum Tower Hospital of Nanjing University Medical School from May 2015 to February 2016, who underwent 3.0 T MRI scan and 2D-computer version spatial navigation test.DTI preprocessing and tract-based spatial statistics (TBSS) were performed by PANDA.Two sample t-test and partial correlation coefficients were performed to investigate the correlation of white matter impairments and spatial navigation decline. Results: Relative to controls, MCI showed worse egocentric navigation (t=-2.202, P<0.05). Decreased FA in superior longitudinal fasciculus (left t=2.95, right t=2.95, P<0.05), inferior longitudinal fasciculus and inferior fronto-occipital fasciculus (left t=2.66, right t=2.96, P<0.05), corpus callosum (t=2.09, P<0.05), cingulum (left t=2.76, right t=2.41, P<0.05), fornix (t=4.83, P<0.05), and corticospinal tract (left t=2.33, right t=2.26, P<0.05), were found in the MCI subjects.The decreased FA value of superior longitudinal fasciculus (left r=-0.354, right r=-0.347, P<0.05), inferior longitudinal fasciculus (left r=-0.338, right r=-0.336, P<0.05), cingulum (left r=-0.395, right r=-0.370, P<0.05), right corticospinal tract (r=-0.362, P<0.05) and fornix (r=-0.369, P<0.05) were correlated with increased ego average total error.Allo average total error were negative correlated with FA value of superior longitudinal fasciculus (left r=-0.329, right r=-0.350, P<0.05), inferior longitudinal fasciculus (left r=-0.349, right r=-0.378, P<0.05), splenium of corpus callosum (r=-0.364, P<0.05) and cingulum (left r=-0.340, right r=-0.406, P<0.05). Conclusion: This study implicated the potential white matter structural basis of spatial navigation impairment and will have an impact on the further study of the neurobiological mechanisms of human spatial navigation ability.

Vectorial representation of spatial goals in the hippocampus of bats.

To navigate, animals need to represent not only their own position and orientation, but also the location of their goal. Neural representations of an animal's own position and orientation have been extensively studied. However, it is unknown how navigational goals are encoded in the brain. We recorded from hippocampal CA1 neurons of bats flying in complex trajectories toward a spatial goal. We discovered a subpopulation of neurons with angular tuning to the goal direction. Many of these neurons were tuned to an occluded goal, suggesting that goal-direction representation is memory-based. We also found cells that encoded the distance to the goal, often in conjunction with goal direction. The goal-direction and goal-distance signals make up a vectorial representation of spatial goals, suggesting a previously unrecognized neuronal mechanism for goal-directed navigation.