Effects of estrogen on spatial navigation and memory

RATIONALE

Animal studies suggest that the so-called "female" hormone estrogen enhances spatial navigation and memory. This contradicts the observation that males generally out-perform females in spatial navigation and tasks involving spatial memory. A closer look at the vast number of studies actually reveals that performance differences are not so clear.

OBJECTIVES

To help clarify the unclear performance differences between men and women and the role of estrogen, we attempted to isolate organizational from activational effects of estrogen on spatial navigation and memory.

METHODS

In a double-blind, placebo-controlled study, we tested the effects of orally administered estradiol valerate (E2V) in healthy, young women in their low-hormone menstrual cycle phase, compared to healthy, young men. Participants performed several first-person, environmentally rich, 3-D computer games inspired by spatial navigation and memory paradigms in animal research.

RESULTS

We found navigation behavior suggesting that sex effects dominated any E2 effects with men performing better with allocentric strategies and women with egocentric strategies. Increased E2 levels did not lead to general improvements in spatial ability in either sex but to behavioral changes reflecting navigation flexibility.

CONCLUSION

Estrogen-driven differences in spatial cognition might be better characterized on a spectrum of navigation flexibility rather than by categorical performance measures or skills.

Common and specific activations supporting optic flow processing and navigation as revealed by a meta-analysis of neuroimaging studies

Optic flow provides useful information in service of spatial navigation. However, whether brain networks supporting these two functions overlap is still unclear. Here we used Activation Likelihood Estimation (ALE) to assess the correspondence between brain correlates of optic flow processing and spatial navigation and their specific neural activations. Since computational and connectivity evidence suggests that visual input from optic flow provides information mainly during egocentric navigation, we further tested the correspondence between brain correlates of optic flow processing and that of both egocentric and allocentric navigation. Optic flow processing shared activation with egocentric (but not allocentric) navigation in the anterior precuneus, suggesting its role in providing information about self-motion, as derived from the analysis of optic flow, in service of egocentric navigation. We further documented that optic flow perception and navigation are partially segregated into two functional and anatomical networks, i.e., the dorsal and the ventromedial networks. Present results point to a dynamic interplay between the dorsal and ventral visual pathways aimed at coordinating visually guided navigation in the environment.

Comparing episodic memory outcomes from walking augmented reality and stationary virtual reality encoding experiences

Episodic Memory (EM) is the neurocognitive capacity to consciously recollect personally experienced events in specific spatio-temporal contexts. Although the relevance of spatial and temporal information is widely acknowledged in the EM literature, it remains unclear whether and how EM performance and organisation is modulated by self-motion, and by motor- and visually- salient environmental features (EFs) of the encoding environment. This study examines whether and how EM is modulated by locomotion and the EFs encountered in a controlled lifelike learning route within a large-scale building. Twenty-eight healthy participants took part in a museum-tour encoding task implemented in walking Augmented Reality (AR) and stationary Virtual Reality (VR) conditions. EM performance and organisation were assessed immediately and 48-hours after trials using a Remember/Familiar recognition paradigm. Results showed a significant positive modulation effect of locomotion on distinctive EM aspects. Findings highlighted a significant performance enhancement effect of stairway-adjacent locations compared to dead-end and mid-route stimuli-presentation locations. The results of this study may serve as design criteria to facilitate neurocognitive rehabilitative interventions of EM. The underlying technological framework developed for this study represents a novel and ecologically sound method for evaluating EM processes in lifelike situations, allowing researchers a naturalistic perspective into the complex nature of EM.

Neonatal GABAergic transmission primes vestibular gating of output for adult spatial navigation

GABAergic interneurons are poised with the capacity to shape circuit output via inhibitory gating. How early in the development of medial vestibular nucleus (MVN) are GABAergic neurons recruited for feedforward shaping of outputs to higher centers for spatial navigation? The role of early GABAergic transmission in assembling vestibular circuits for spatial navigation was explored by neonatal perturbation. Immunohistochemistry and confocal imaging were utilized to reveal the expression of parvalbumin (PV)-expressing MVN neurons and their perineuronal nets. Whole-cell patch-clamp recording, coupled with optogenetics, was conducted in vitro to examine the synaptic function of MVN circuitry. Chemogenetic targeting strategy was also employed in vivo to manipulate neuronal activity during navigational tests. We found in rats a neonatal critical period before postnatal day (P) 8 in which competitive antagonization of GABAergic transmission in the MVN retarded maturation of inhibitory neurotransmission, as evidenced by deranged developmental trajectory for excitation/inhibition ratio and an extended period of critical period-like plasticity in GABAergic transmission. Despite increased number of PV-expressing GABAergic interneurons in the MVN, optogenetic-coupled patch-clamp recording indicated null-recruitment of these neurons in tuning outputs along the ascending vestibular pathway. Such perturbation not only offset output dynamics of ascending MVN output neurons, but was further accompanied by impaired vestibular-dependent navigation in adulthood. The same perturbations were however non-consequential when applied after P8. Results highlight neonatal GABAergic transmission as key to establishing feedforward output dynamics to higher brain centers for spatial cognition and navigation.

Fixation-related potentials during mobile map assisted navigation in the real world: The effect of landmark visualization style

An often-proposed enhancement for mobile maps to aid assisted navigation is the presentation of landmark information, yet understanding of the manner in which they should be displayed is limited. In this study, we investigated whether the visualization of landmarks as 3D map symbols with either an abstract or realistic style influenced the subsequent processing of those landmarks during route navigation. We utilized a real-world mobile electroencephalography approach to this question by combining several tools developed to overcome the challenges typically encountered in real-world neuroscience research. We coregistered eye-movement and EEG recordings from 45 participants as they navigated through a real-world environment using a mobile map. Analyses of fixation event-related potentials revealed that the amplitude of the parietal P200 component was enhanced when participants fixated landmarks in the real world that were visualized on the mobile map in a realistic style, and that frontal P200 latencies were prolonged for landmarks depicted in either a realistic or abstract style compared with features of the environment that were not presented on the map, but only for the male participants. In contrast, we did not observe any significant effects of landmark visualization style on visual P1-N1 peaks or the parietal late positive component. Overall, the findings indicate that the cognitive matching process between landmarks seen in the environment and those previously seen on a map is facilitated by more realistic map display, while low-level perceptual processing of landmarks and recall of associated information are unaffected by map visualization style.

Choosing the best way: how wild common marmosets travel to efficiently exploit resources

While foraging, animals have to find potential food sites, remember these sites, and plan the best navigation route. To deal with problems associated with foraging for multiple and patchy resources, primates may employ heuristic strategies to improve foraging success. Until now, no study has attempted to investigate experimentally the use of such strategies by a primate in a context involving foraging in large-scale space. Thus, we carried out an experimental field study that aimed to test if wild common marmosets (Callithrix jacchus) employ heuristic strategies to efficiently navigate through multiple feeding sites distributed in a large-scale space. In our experiment, we arranged four feeding platforms in a trapezoid configuration with up to 60 possible routes and observe marmosets' decisions under two experimental conditions. In experimental condition I, all platforms contained the same amount of food; in experimental condition II, the platforms had different amounts of food. According to the number and arrangement of the platforms, we tested two heuristic strategies: the Nearest Neighbor Rule and the Gravity Rule. Our results revealed that wild common marmosets prefer to use routes consistent with a heuristic strategy more than expected by chance, regardless of food distribution. The findings also demonstrate that common marmosets seem to integrate different factors such as distance and quantity of food across multiple sites distributed over a large-scale space, employing a combination of heuristic strategies to select the most efficient routes available. In summary, our findings confirm our expectations and provide important insights into the spatial cognition of these small neotropical primates.

Translating spatial navigation evaluation from experimental to clinical settings: The virtual environments navigation assessment (VIENNA)

Spatial navigation abilities are frequently impaired in neurological disorders and they also decline with normal aging. Researchers and clinicians therefore need valid and easy-to-use spatial navigation assessment tools to study the impact of different neuropathologies and prevent relevant cognitive impairments from going undetected. However, current experimental paradigms rarely address which cognitive processes they recruit, often have resource-intensive setups, and usually require active navigation, e.g., using a joystick or keyboard, thus confounding cognitive performance with fine motor skills. Yet, for clinical feasibility, time-efficient paradigms are needed that are informative and easy to administer in participants with limited technical experience and diverging impairments. Here, we introduce the virtual environments navigation assessment (VIENNA), a virtual adaptation of a brief, standardized, and intuitive spatial navigation paradigm ( https://osf.io/kp4c5/ ). VIENNA is designed to assess spatial navigation without episodic memory demands, requires no interface device, and takes about 16 min to complete. We evaluated VIENNA in 79 healthy middle-aged to older participants (50-85 years) and provide evidence for its feasibility and construct validity. Tests of visuospatial and executive functions, but not episodic memory or selective attention, were identified as cognitive correlates of VIENNA, even when controlling for participant age and overall cognitive performance. Furthermore, VIENNA scores correlated with subjective navigation ability and age, but not with depressiveness, cognitive complaints, or education. The straightforward administration of VIENNA allows for its integration into routine neuropsychological assessments and enables differentiated evaluation of spatial navigation performance in patients with motor impairments and episodic memory deficits.

[Spatial navigation method based on the entorhinal-hippocampal-prefrontal information transmission circuit of rat's brain]

Physiological studies have revealed that rats perform spatial localization relying on grid cells and place cells in the entorhinal-hippocampal CA3 structure. The dynamic connection between the entorhinal-hippocampal structure and the prefrontal cortex is crucial for navigation. Based on these findings, this paper proposes a spatial navigation method based on the entorhinal-hippocampal-prefrontal information transmission circuit of the rat's brain, with the aim of endowing the mobile robot with strong spatial navigation capability. Using the hippocampal CA3-prefrontal spatial navigation model as a foundation, this paper constructed a dynamic self-organizing model with the hippocampal CA1 place cells as the basic unit to optimize the navigation path. The path information was then fed back to the impulse neural network via hippocampal CA3 place cells and prefrontal cortex action neurons, improving the convergence speed of the model and helping to establish long-term memory of navigation habits. To verify the validity of the method, two-dimensional simulation experiments and three-dimensional simulation robot experiments were designed in this paper. The experimental results showed that the method presented in this paper not only surpassed other algorithms in terms of navigation efficiency and convergence speed, but also exhibited good adaptability to dynamic navigation tasks. Furthermore, our method can be effectively applied to mobile robots.

Impoverished details with preserved gist in remote and recent spatial memory following hippocampal and fornix lesions

INTRODUCTION

Cognitive Map Theory predicts that the hippocampus (HPC) plays a specialized, time-invariant role in supporting allocentric spatial memory, while Standard Consolidation Theory makes the competing prediction that the HPC plays a time-limited role, with more remote memories gaining independence of HPC function. These theories, however, are largely informed by the results of laboratory-based tests that are unlikely to simulate the demands of representing real-world environments in humans. Validation of these theories is further limited by an overall focus on spatial memory of newly encountered environments and on individuals with extensive lesions to the HPC and to surrounding medial temporal lobe (MTL) regions. The current study incorporates naturalistic tests of spatial memory based on recently and remotely encountered environments navigated by individuals with lesions to the HPC/MTL or that are limited to the HPC's major output, the fornix.

METHODS

Four participants with bilateral HPC/MTL and/or fornix lesions drew sketch maps of recently and remotely experienced neighbourhoods and houses. Tests of the appearance, distances, and routes between landmarks from the same real-world environments were also administered. Performance on the tasks was compared to that of control participants closely matched in terms of exposure to the same neighbourhoods and home environments as well as to actual maps.

RESULTS

The performance of individuals with fornix/MTL lesions was found to be largely comparable to that of controls on objective tests of spatial memory, other than one case who was impaired on remote and recent conditions for several tasks. The nature of deficits in recent and remote spatial memory were further revealed on house floorplan drawings, which contained spatial distortions, room/structure transpositions, and omissions, and on neighbourhood sketch maps, which were intact in terms of overall layout but sparse in details such as landmarks.

CONCLUSION

Lab-based tests of spatial memory of newly learned environments are unlikely to fully capture patterns of spared and impaired representations of real-world environments (e.g., peripheral features, configurations). Naturalistic tasks, including generative drawing tasks, indicate that contrary to Cognitive Map Theory, neither HPC nor MTL are critical for allocentric gross representations of large-scale environments. Conversely, the HPC appears critical for representing detailed spatial information of local naturalistic environments and environmental objects regardless of the age of the memory, contrary to Standard Consolidation Theory.

The neural correlates of memory integration in value-based decision-making during human spatial navigation

In daily life, we often make decisions based on relative value of the options, and we often derive these values from segmenting or integrating the outcomes of past episodes in memory. The neural correlates involved in value-based decision-making have been extensively studied in the literature, but few studies have investigated this topic in decisions that require segmenting or integrating episodic memory from related sources, and even fewer studies examine it in the context of spatial navigation. Building on the computational models from our previous studies, the current study investigates the neural substrates involved in decisions that require people either segment or integrate wayfinding outcomes involving different goals, across virtual spatial navigation tasks with differing demands. We find that when decisions require computation of spatial distances for navigation options, but also evaluation of one's prior spatial navigation ability with the task, the estimated value of navigational choices (EV) modulates neural activity in the dorsomedial prefrontal (dmPFC) cortex and ventrolateral prefrontal (vlFPC) cortex. However, superior parietal cortex tracked EV when decision-making tasks only require spatial distance memory but not evaluation of spatial navigation ability. Our findings reveal divergent neural substrates of memory integration in value-based decision-making under different spatial processing demands.

Reduced overnight memory consolidation and associated alterations in sleep spindles and slow oscillations in early Alzheimer's disease

Spatial navigation critically underlies hippocampal-entorhinal circuit function that is early affected in Alzheimer's disease (AD). There is growing evidence that AD pathophysiology dynamically interacts with the sleep/wake cycle impairing hippocampal memory. To elucidate sleep-dependent consolidation in a cohort of symptomatic AD patients (n = 12, 71.25 ± 2.16 years), we tested hippocampal place learning by means of a virtual reality task and verbal memory by a word-pair association task before and after a night of sleep. Our results show an impaired overnight memory retention in AD compared with controls in the verbal task, together with a significant reduction of sleep spindle activity (i.e., lower amplitude of fast sleep spindles, p = 0.016) and increased duration of the slow oscillation (SO; p = 0.019). Higher spindle density, faster down-to-upstate transitions within SOs, and the time delay between SOs and nested spindles predicted better memory performance in healthy controls but not in AD patients. Our results show that mnemonic processing and memory consolidation in AD is slightly impaired as reflected by dysfunctional oscillatory dynamics and spindle-SO coupling during NonREM sleep. In this translational study based on experimental paradigms in animals and extending previous work in healthy aging and preclinical disease stages, our results in symptomatic AD further deepen the understanding of the memory decline within a bidirectional relationship of sleep and AD pathology.

The grid-cell normative model: Unifying 'principles'

A normative model for the emergence of entorhinal grid cells in the brain's navigational system has been proposed (Sorscher et al., 2023. Neuron 111, 121-137). Using computational modeling of place-to-grid cell interactions, the authors characterized the fundamental nature of grid cells through information processing. However, the normative model does not consider certain discoveries that complement or contradict the conditions for such emergence. By briefly reviewing current evidence, we draw some implications on the interplay between place cell replay sequences and intrinsic grid cell oscillations related to the hippocampal-entorhinal navigation system that can extend the normative model.

Choice between decision-making strategies in human route-following

To follow a prescribed route, we must decide which way to turn at intersections. To do so, we can memorize either the serial order of directions or the associations between spatial cues and directions ("at the drug store, turn left"). Here, we investigate which of these two strategies is used if both are available. In Task S, all intersections looked exactly alike, and participants therefore had to use the serial order strategy to decide which way their route continued. In Task SA, each intersection displayed a unique spatial cue, and participants therefore could use either strategy. In Task A, each intersection displayed a unique cue, but the serial order of cues varied between trips, and participants therefore had to use the associative cue strategy. We found that route-following accuracy increased from trip to trip, was higher on routes with 12 rather than 18 intersections, and was higher on Task SA than on the other two tasks, both with 12 and with 18 intersections. Furthermore, participants on Task SA acquired substantial knowledge about the serial order of directions as well as about cue-direction associations, both with 12 and with 18 intersections. From this we conclude that, when both strategies were available, participants did not pick the better one but rather used both. This represents dual encoding, a phenomenon previously described for more elementary memory tasks. We further conclude that dual encoding may be implemented even if the memory load is not very high (i.e., even with only 12 intersections).

A virtual reality paradigm with dynamic scene stimuli for use in memory research

Episodic memory may essentially be memory for one's place within a temporally unfolding scene from a first-person perspective. Given this, pervasively used static stimuli may only capture one small part of episodic memory. A promising approach for advancing the study of episodic memory is immersing participants within varying scenes from a first-person perspective. We present a pool of distinct scene stimuli for use in virtual environments and a paradigm that is implementable across varying levels of immersion on multiple virtual reality (VR) platforms and adaptable to studying various aspects of scene and episodic memory. In our task, participants are placed within a series of virtual environments from a first-person perspective and guided through a virtual tour of scenes during a study phase and a test phase. In the test phase, some scenes share a spatial layout with studied scenes; others are completely novel. In three experiments with varying degrees of immersion, we measure scene recall, scene familiarity-detection during recall failure, the subjective experience of déjà vu, the ability to predict the next turn on a tour, the subjective sense of being able to predict the next turn on a tour, and the factors that influence memory search and the inclination to generate candidate recollective information. The level of first-person immersion mattered to multiple facets of episodic memory. The paradigm presents a useful means of advancing mechanistic understanding of how memory operates in realistic dynamic scene environments, including in combination with cognitive neuroscience methods such as functional magnetic resonance imaging and electrophysiology.

Are there sex differences in spatial reference memory in the Morris water maze? A large-sample experimental study

Sex differences have been found in allocentric spatial learning and memory tasks, with the literature indicating that males outperform females, although this issue is still controversial. This study aimed to explore the behavior of male and female rats during the habituation and learning of a spatial memory task performed in the Morris Water Maze (MWM). The study included a large sample of 89 males and 85 females. We found that females searched slightly faster than males during habituation with a visible platform. During learning, both male and female rats decreased the latency and distance traveled to find the hidden platform over the days, with males outperforming females in the distance traveled. Females swam faster but did not find the platform earlier, suggesting a less directed navigational strategy. Both sexes increased time spent in the target zone over the days, with no sex differences. Although females swam more in the periphery during the first days of the task, both sexes decreased the time spent in this area. Finally, only males increased swimming in the pool's center over the days, spending more time than females in this area across the entire training. In conclusion, we need to register several variables in the MWM and analyze path strategies to obtain more robust results concerning sex differences. Research on spatial learning should include both sexes to achieve a more equitable, representative, and translational science.

A map of spatial navigation for neuroscience

Spatial navigation has received much attention from neuroscientists, leading to the identification of key brain areas and the discovery of numerous spatially selective cells. Despite this progress, our understanding of how the pieces fit together to drive behavior is generally lacking. We argue that this is partly caused by insufficient communication between behavioral and neuroscientific researchers. This has led the latter to under-appreciate the relevance and complexity of spatial behavior, and to focus too narrowly on characterizing neural representations of space-disconnected from the computations these representations are meant to enable. We therefore propose a taxonomy of navigation processes in mammals that can serve as a common framework for structuring and facilitating interdisciplinary research in the field. Using the taxonomy as a guide, we review behavioral and neural studies of spatial navigation. In doing so, we validate the taxonomy and showcase its usefulness in identifying potential issues with common experimental approaches, designing experiments that adequately target particular behaviors, correctly interpreting neural activity, and pointing to new avenues of research.

Spatial orientation: A relationship with inferential memory

Two branches of the scientific literature have dominated our understanding of hippocampal function. One focuses on the support this structure offers to declarative memory, while the other views the hippocampus as a part of a system dedicated to spatial navigation. These two different visions can be reconciled in relational theory, which suggests that the hippocampus processes all kinds of associations and sequences of events. According to this, processing would be similar to a route calculation based on associations of spatial information acquired during navigation and the associative relationship established between memories without spatial content. In this paper, we present a behavioral study of healthy individuals to explore the performance of inferential memory tasks and spatial orientation tasks in a virtual environment. Inferential memory and spatial orientation task performances were positively correlated. However, after controlling for a non-inferential memory task, only the correlation between allocentric spatial orientation and inferential memory remained significant. These results provide support for the similarity between the two cognitive functions, lending credence to the relational theory of the hippocampus. Additionally, our behavioral findings are in line with the cognitive map theory, which suggests a potential association between the hippocampus and allocentric spatial representations.

Spatial navigation is associated with subcortical alterations and progression risk in subjective cognitive decline

BACKGROUND

Subjective cognitive decline (SCD) may serve as a symptomatic indicator for preclinical Alzheimer's disease; however, SCD is a heterogeneous entity regarding clinical progression. We aimed to investigate whether spatial navigation could reveal subcortical structural alterations and the risk of progression to objective cognitive impairment in SCD individuals.

METHODS

One hundred and eighty participants were enrolled: those with SCD (n = 80), normal controls (NCs, n = 77), and mild cognitive impairment (MCI, n = 23). SCD participants were further divided into the SCD-good (G-SCD, n = 40) group and the SCD-bad (B-SCD, n = 40) group according to their spatial navigation performance. Volumes of subcortical structures were calculated and compared among the four groups, including basal forebrain, thalamus, caudate, putamen, pallidum, hippocampus, amygdala, and accumbens. Topological properties of the subcortical structural covariance network were also calculated. With an interval of 1.5 years ± 12 months of follow-up, the progression rate to MCI was compared between the G-SCD and B-SCD groups.

RESULTS

Volumes of the basal forebrain, the right hippocampus, and their respective subfields differed significantly among the four groups (p < 0.05, false discovery rate corrected). The B-SCD group showed lower volumes in the basal forebrain than the G-SCD group, especially in the Ch4p and Ch4a-i subfields. Furthermore, the structural covariance network of the basal forebrain and right hippocampal subfields showed that the B-SCD group had a larger Lambda than the G-SCD group, which suggested weakened network integration in the B-SCD group. At follow-up, the B-SCD group had a significantly higher conversion rate to MCI than the G-SCD group.

CONCLUSION

Compared to SCD participants with good spatial navigation performance, SCD participants with bad performance showed lower volumes in the basal forebrain, a reorganized structural covariance network of subcortical nuclei, and an increased risk of progression to MCI. Our findings indicated that spatial navigation may have great potential to identify SCD subjects at higher risk of clinical progression, which may contribute to making more precise clinical decisions for SCD individuals who seek medical help.

Peg Forest Rehabilitation - A novel spatial navigation based cognitive rehabilitation paradigm for experimental neurotrauma

Traumatic brain injury (TBI) results from mechanical forces applied to the head. Ensuing cascades of complex pathophysiology transition the injury event into a disease process. The enduring constellation of emotional, somatic, and cognitive impairments degrade quality of life for the millions of TBI survivors suffering from long-term neurological symptoms. Rehabilitation strategies have reported mixed results, as most have not focused on specific symptomatology or explored cellular processes. The current experiments evaluated a novel cognitive rehabilitation paradigm for brain-injured and uninjured rats. The arena is a plastic floor with a cartesian grid of holes for plastic dowels to create new environments with the rearrangement of threaded pegs. Rats received either two weeks of Peg Forest rehabilitation (PFR) or open field exposure starting at 7 days post-injury; or one week starting at either day 7 or 14 post-injury; or served as caged controls. Cognitive performance was assessed on a battery of novel object tasks at 28 days post-injury. The results revealed that two weeks of PFR was required to prevent the onset of cognitive impairments, while one week of PFR was insufficient regardless of when rehabilitation was initiated after injury. Further assessment of the task showed that novel daily arrangements of the environment were required to impart the cognitive performance benefits, as exposure to a static arrangement of pegs for PFR each day did not improve cognitive performance. The results indicate that PFR prevents the onset of cognitive disorders following acquired a mild to moderate brain injury, and potentially other neurological conditions.

Exploration patterns shape cognitive map learning

Spontaneous, volitional spatial exploration is crucial for building up a cognitive map of the environment. However, decades of research have primarily measured the fidelity of cognitive maps after discrete, controlled learning episodes. We know little about how cognitive maps are formed during naturalistic free exploration. Here, we investigated whether exploration trajectories predicted cognitive map accuracy, and how these patterns were shaped by environmental structure. In two experiments, participants freely explored a previously unfamiliar virtual environment. We related their exploration trajectories to a measure of how long they spent in areas with high global environmental connectivity (integration, as assessed by space syntax). In both experiments, we found that participants who spent more time on paths that offered opportunities for integration formed more accurate cognitive maps. Interestingly, we found no support for our pre-registered hypothesis that self-reported trait differences in navigation ability would mediate this relationship. Our findings suggest that exploration patterns predict cognitive map accuracy, even for people who self-report low ability, and highlight the importance of considering both environmental structure and individual variability in formal theory- and model-building.

Long-lasting spatial memory deficits and impaired hippocampal plasticity following unilateral vestibular loss

Unilateral vestibular loss (UVL) induces a characteristic vestibular syndrome composed of various posturo-locomotor, oculomotor, vegetative and perceptivo-cognitive symptoms. Functional deficits are progressively recovered over time during vestibular compensation, that is supported by the expression of multiscale plasticity mechanisms. While the dynamic of post-UVL posturo-locomotor and oculomotor deficits is well characterized, the expression over time of the cognitive deficits, and in particular spatial memory deficits, is still debated. In this study we aimed at investigating spatial memory deficits and their recovery in a rat model of unilateral vestibular neurectomy (UVN), using a wide spectrum of behavioral tasks. In parallel, we analyzed markers of hippocampal plasticity involved in learning and memory. Our results indicate the UVN affects all domains of spatial memory, from working memory to reference memory and object-in-place recognition. These deficits are associated with long-lasting impaired plasticity in the ipsilesional hippocampus. These results highlight the crucial role of symmetrical vestibular information in spatial memory and contribute to a better understanding of the cognitive disorders observed in vestibular patients.

Investigating medical students' satisfaction towards video-based learning versus face-to-face lectures: a Jordanian tertiary teaching hospital experience

PURPOSE

We aimed to evaluate the disparity between video-based learning and lecture-based learning on Jordanian medical students' satisfaction.

METHODS

We conducted this cross-sectional study using a web-based questionnaire adapted from Student Evaluation of Educational Quality survey. Using convenience sampling, medical students studying at the University of Jordan and Jordan University Hospital were recruited. Participants in either clinical or basic-science years that have completed the entire survey were included in the final analysis.

RESULTS

We surveyed a total 487 participants among which male to female ratio was 1.19:1. Participants perceived greater benefit in terms of learning, instructor enthusiasm, content organization, breadth of teaching, and quality and number of assignments when using video-based learning (all p&lt;0.01). In contrast, face-to-face learning was associated with significantly higher benefits in terms of group interactions (p&lt;0.01) and capacity for rapport building (p&lt;0.01). There was no significant difference in perceived examination performance between the two learning modalities (p=0.11).

CONCLUSION

Video-based learning is the preferred learning modality among Jordanian medical students. Despite its dominance across multiple domains, it should be implemented as an adjunct to traditional classroom teaching for it is vital in the development of good communication skills and building rapport in medical students.

Sequential order spatial memory in male rats: Characteristics and impact of medial prefrontal cortex and hippocampus disruption

Remembering an experience entails linking what happened, where the event transpired, and when it occurred. Most rodent hippocampal studies involve tests of spatial memory, but fewer investigate temporal and sequential order memory. Here we provide a demonstration of rats learning an aversive sequential order task using a radial arm water maze. Male rats learned a fixed sequence of up to seven spatial locations, with each decision session separated by a temporal delay. Rats relied on visuospatial cues and the number of times they had entered the maze for a given day in order to successfully perform the task. Behavioral patterns during asymptotic performance showed similarities to the serial-position effect, especially with regards to faster first choice latency. Rats at asymptotic performance were implanted with bilateral cannula in medial prefrontal cortex, dorsal, and ventral hippocampus. After re-training, we injected muscimol to temporarily disrupt targeted brain regions. While control rats made prospective errors, rats with mPFC muscimol exhibited more retrospective errors. Rats with hippocampal muscimol no longer exhibited a prospective bias and were at chance levels in their error choices. Taken together, our results suggest disruption of mPFC, but not the hippocampus, produced an error choice bias during an aversive sequential order spatial processing task.

Sex and Season Affect Cortical Volumes in Free-Living Western Fence Lizards, Sceloporus occidentalis

The hippocampus plays an important role in spatial navigation and spatial learning across a variety of vertebrate species. Sex and seasonal differences in space use and behavior are known to affect hippocampal volume. Similarly, territoriality and differences in home range size are known to affect the volume of the reptile hippocampal homologues, the medial and dorsal cortices (MC, DC). However, studies have almost exclusively investigated males and little is known about sex or seasonal differences in MC and/or DC volumes in lizards. Here, we are the first to simultaneously examine sex and seasonal differences in MC and DC volumes in a wild lizard population. In Sceloporus occidentalis, males display territorial behaviors that are more pronounced during the breeding season. Given this sex difference in behavioral ecology, we expected males to have larger MC and/or DC volumes than females and for this difference to be most pronounced during the breeding season when territorial behavior is increased. Male and female S. occidentalis were captured from the wild during the breeding season and the post-breeding season and were sacrificed within 2 days of capture. Brains were collected and processed for histology. Cresyl-violet-stained sections were used to quantify brain region volumes. In these lizards, breeding females had larger DC volumes than breeding males and nonbreeding females. There was no sex or seasonal difference in MC volumes. Differences in spatial navigation in these lizards may involve aspects of spatial memory related to breeding other than territoriality that affect plasticity of the DC. This study highlights the importance of investigating sex differences and including females in studies of spatial ecology and neuroplasticity.

Virtual Reality for Spatial Navigation

Immersive virtual reality (VR) allows its users to experience physical space in a non-physical world. It has developed into a powerful research tool to investigate the neural basis of human spatial navigation as an embodied experience. The task of wayfinding can be carried out by using a wide range of strategies, leading to the recruitment of various sensory modalities and brain areas in real-life scenarios. While traditional desktop-based VR setups primarily focus on vision-based navigation, immersive VR setups, especially mobile variants, can efficiently account for motor processes that constitute locomotion in the physical world, such as head-turning and walking. When used in combination with mobile neuroimaging methods, immersive VR affords a natural mode of locomotion and high immersion in experimental settings, designing an embodied spatial experience. This in turn facilitates ecologically valid investigation of the neural underpinnings of spatial navigation.

Reaching the Goal: Superior Navigators in Late Adulthood Provide a Novel Perspective into Successful Cognitive Aging

Normal aging is typically associated with declines in navigation and spatial memory abilities. However, increased interindividual variability in performance across various navigation/spatial memory tasks is also evident with advancing age. In this review paper, we shed the spotlight on those older individuals who exhibit exceptional, sometimes even youth-like navigational/spatial memory abilities. Importantly, we (1) showcase observations from existing studies that demonstrate superior navigation/spatial memory performance in late adulthood, (2) explore possible cognitive correlates and neurophysiological mechanisms underlying these preserved spatial abilities, and (3) discuss the potential link between the superior navigators in late adulthood and SuperAgers (older adults with superior episodic memory). In the closing section, given the lack of studies that directly focus on this subpopulation, we highlight several important directions that future studies could look into to better understand the cognitive characteristics of older superior navigators and the factors enabling such successful cognitive aging.

Navigational roots of spatial and temporal memory structure

Our minds are constantly in transit, from the present to the past to the future, across places we have and have not directly experienced. Nevertheless, memories of our mental time travel are not organized continuously and are adaptively chunked into contexts and episodes. In this paper, I will review evidence that suggests that spatial boundary representations play a critical role in providing structure to both our spatial and temporal memories. I will illustrate the intimate connection between hippocampal spatial mapping and temporal sequencing of episodic memory to propose that high-level cognitive processes like mental time travel and conceptual mapping are rooted in basic navigational mechanisms that we humans and nonhuman animals share. Our neuroscientific understanding of hippocampal function across species may provide new insight into the origins of even the most uniquely human cognitive abilities.

Spatial orientation - a stable marker for vascular cognitive impairment?

Vascular cognitive impairment (VCI) is the second most prevalent form of dementia, but little is known about the early cognitive and neuroimaging markers. Spatial navigation deficits are an emerging marker for Alzheimer's disease (AD), yet less is known about spatial orientation deficits sensitive to VCI. This case report follows up on the first VCI patient identified to have an egocentric orientation deficit. The study aimed to examine the patient's spatial deficits three years on and gain insights from the addition of the patient's MRI brain scan. A battery of spatial navigation tasks were administered following neuropsychological assessment. Results continue to show spatial orientation deficits. Critically, these changes appear stable and are sensitive to novel spatial tests. Whereas conventional screening tools demonstrate patient recovery. MRI DTI analysis indicates a non-significant trend towards loss of structural integrity to the posterior tracts of the longitudinal superior fasciculus (SLF), while the medial temporal lobe, typically implicated in spatial navigation, is unaffected. This finding potentially reflects reduced network connectivity in posterior to anterior white matter tracts co-existing with spatial orientation deficits. Findings have clinical utility and show spatial orientation as a potential sensitive cognitive marker for VCI.

L-DOPA enhances neural direction signals in younger and older adults

Previous studies indicate a role of dopamine in spatial navigation. Although neural representations of direction are an important aspect of spatial cognition, it is not well understood whether dopamine directly affects these representations, or only impacts other aspects of spatial brain function. Moreover, both dopamine and spatial cognition decline sharply during age, raising the question which effect dopamine has on directional signals in the brain of older adults. To investigate these questions, we used a double-blind cross-over L-DOPA/Placebo intervention design in which 43 younger and 37 older adults navigated in a virtual spatial environment while undergoing functional magnetic resonance imaging (fMRI). We studied the effect of L-DOPA, a dopamine precursor, on fMRI activation patterns that encode spatial walking directions that have previously been shown to lose specificity with age. This was done in predefined regions of interest, including the early visual cortex, retrosplenial cortex, and hippocampus. Classification of brain activation patterns associated with different walking directions was improved across all regions following L-DOPA administration, suggesting that dopamine broadly enhances neural representations of direction. No evidence for differences between regions was found. In the hippocampus these results were found in both age groups, while in the retrosplenial cortex they were only observed in younger adults. Taken together, our study provides evidence for a link between dopamine and the specificity of neural responses during spatial navigation. SIGNIFICANCE STATEMENT: The sense of direction is an important aspect of spatial navigation, and neural representations of direction can be found throughout a large network of space-related brain regions. But what influences how well these representations track someone's true direction? Using a double-blind cross-over L-DOPA/Placebo intervention design, we find causal evidence that the neurotransmitter dopamine impacts the fidelity of direction selective neural representations in the human hippocampus and retrosplenial cortex. Interestingly, the effect of L-DOPA was either equally present or even smaller in older adults, despite the well-known age related decline of dopamine. These results provide novel insights into how dopamine shapes the neural representations that underlie spatial navigation.

Spatial ability and anatomy learning performance among dental students

PURPOSE

Spatial perception is an essential skill for professional dentists. The objective of this study was to observe the spatial ability, as well as anatomy module grades, of dental students at a dental education center in Indonesia and relate these to gender and cohort.

METHODS

A cross-sectional study was carried out where dental students in years (cohorts) 1, 2, 4-6 were invited to take the Revised Purdue Spatial Visualization Test (PSVT-R) and the redrawn Vandenberg and Kuse Mental Rotation Test (MRT) in order to assess spatial ability. In addition, the 1st- and 2nd-year dental students carried out gross anatomy assessments. Spatial ability test results were compared using an independent t-test to detect gender differences, one-way analysis of variance to inspect cohort differences, and correlation relative to anatomy module scores.

RESULTS

A total of 326 dental students voluntarily participated. Statistically significant gender differences were found in both spatial ability tests in the overall sample (PSVT-R: p&lt;0.001; MRT: p=0.001). When the 1st- and 2nd-year dental students were pooled, significant gender differences were detected, in which males scored higher than females in both spatial ability tests (PSVT-R: p&lt;0.001; MRT: p=0.003). In anatomy, however, females scored higher than the males (p=0.005). In addition, there were weak to moderate, but significant correlations between spatial ability tests and anatomy scores.

CONCLUSION

This study indicated that spatial ability may not be the only factor predicting the academic performance of dental students. However, dental students with low spatial ability scores may need supplementary educational techniques when learning specific spatial tasks.

Neural Correlates of Spatial Navigation in Primate Hippocampus

The hippocampus has been extensively implicated in spatial navigation in rodents and more recently in bats. Numerous studies have revealed that various kinds of spatial information are encoded across hippocampal regions. In contrast, investigations of spatial behavioral correlates in the primate hippocampus are scarce and have been mostly limited to head-restrained subjects during virtual navigation. However, recent advances made in freely-moving primates suggest marked differences in spatial representations from rodents, albeit some similarities. Here, we review empirical studies examining the neural correlates of spatial navigation in the primate (including human) hippocampus at the levels of local field potentials and single units. The lower frequency theta oscillations are often intermittent. Single neuron responses are highly mixed and task-dependent. We also discuss neuronal selectivity in the eye and head coordinates. Finally, we propose that future studies should focus on investigating both intrinsic and extrinsic population activity and examining spatial coding properties in large-scale hippocampal-neocortical networks across tasks.

A clinical guide to assessment of navigation impairment: Standardized subjective and objective instruments and normative data

OBJECTIVE

Problems with finding one's way around are frequently reported by neurological patients. However, no dedicated standardized tools exist to assess whether such reports indicate navigation impairment or not. We provide a standardized three-step method to assess navigation ability in neurological patients, based on two recently developed diagnostic tools and normative data. The objective of this method is to assess navigation ability in detail, to allow for appropriate rehabilitation training for navigation impairment.

METHOD

A population-based sample of 7150 Dutch individuals (age 18-89) filled out the Wayfinding Questionnaire (WQ), to assess their self-reported navigation ability and level of spatial anxiety. Additionally, the participants completed the Leiden Navigation Test (LNT), a brief digital test consisting of five subtasks, assessing distinct domains of navigation ability. Both the WQ and LNT can be found online, free of charge.

RESULTS

Normative data stratified by gender and age are reported for each of the three subscales of the WQ, and for each of the five subtasks of the LNT.

CONCLUSIONS

Based on performance data of a very large population-based sample of participants, navigation performance of neurological patients with specific navigation complaints can be assessed in three steps. First, we recommend to inquire about potential problems concerning navigation. Next, in case of navigation complaints, the extent of potential navigation impairment can first be measured with the WQ. Lastly, if impaired scores are found, the LNT can provide objective verification of the perceived impairment, as well as insight into which navigation domains are affected. Such insight will allow for prediction of the practical consequences of the impairment and can be used for informed and tailored rehabilitation.

Cognitive map formation supported by auditory, haptic, and multimodal information in persons with blindness

For efficient navigation, the brain needs to adequately represent the environment in a cognitive map. In this review, we sought to give an overview of literature about cognitive map formation based on non-visual modalities in persons with blindness (PWBs) and sighted persons. The review is focused on the auditory and haptic modalities, including research that combines multiple modalities and real-world navigation. Furthermore, we addressed implications of route and survey representations. Taking together, PWBs as well as sighted persons can build up cognitive maps based on non-visual modalities, although the accuracy sometime somewhat differs between PWBs and sighted persons. We provide some speculations on how to deploy information from different modalities to support cognitive map formation. Furthermore, PWBs and sighted persons seem to be able to construct route as well as survey representations. PWBs can experience difficulties building up a survey representation, but this is not always the case, and research suggests that they can acquire this ability with sufficient spatial information or training. We discuss possible explanations of these inconsistencies.

The medial pallium and the spatial encoding of geometric and visual cues in the terrestrial toad, Rhinella arenarum

The medial pallium (MP) of amphibians is the homologue of the mammalian hippocampus, and previous research has implicated MP for locating a using the boundary geometry of an environment. MP-lesioned, sham-operated and intact control terrestrial toads, Rhinella arenarum, were trained to locate a goal in a rectangular arena with a visual feature cue placed on one of the short walls. Whereas the sham-operated and intact subjects successfully learned to locate the goal, the MP-lesioned toads showed no evidence of learning. The data support the hypothesis that the amphibian MP is involved when the boundary geometry of an environment is used to locate a goal, which is consistent with evidence from other vertebrate groups. Curious, however, is that the MP lesions also resulted in the toads' inability to locate the goal based on the visual feature cue. This result supports previous research and suggests that, in contrast to the hippocampal homologue of amniotes, the amphibian medial pallium plays a broader role in spatial learning processes.

Self-projection in early childhood: No evidence for a common underpinning of episodic memory, episodic future thinking, theory of mind, and spatial navigation

Buckner and Carroll [Trends in Cognitive Sciences (2007), Vol. 11, pp. 49-57] argued that episodic memory (EM), episodic future thinking (EFT), theory of mind (ToM), and spatial navigation all build on the same mental mechanism-self-projection, that is, the ability to disengage from the immediate present and shift perspective to alternative temporal, mental, or spatial situations. Developmental studies indeed show that all four abilities undergo profound developmental changes around 4 years of age, and there are first indications of developmental interrelations between some of the abilities. However, strong evidence for the self-projection account, namely that all four abilities are interrelated in their emergence during early childhood, is still lacking. To thoroughly investigate the self-projection hypothesis, we tested 151 4-year-old children on 12 different tasks assessing their EM, EFT, ToM, and spatial navigation skills (3 tasks per ability). Structural equation modeling under maximum likelihood estimation was conducted on a final sample of 144 children to evaluate a model with the 12 tasks as indicators and self-projection as the latent factor. The model showed a very good fit to the data. However, the factor loadings, indicating the strength of association between the latent factor and the indicators, were very low-which speaks against the validity of the measurement model. In summary, the results do not support the assumption of a common latent factor underlying the various abilities EM, EFT, ToM, and spatial navigation. Implications of our results for the self-projection account and possible related theoretical and methodological challenges are discussed.

Training the spatially-coded SSVEP BCI on the fly

BACKGROUND

The spatially-coded SSVEP BCI employs the retinotopic map in the human visual pathway to infer the gaze direction of the operator relative to a flicker stimulus inducing steady-state visual evoked potentials (SSVEPs) in the brain. It has been shown that with this method, up to 16 channels can be encoded using only a single flicker stimulus. Another advantage over conventional frequency-coded SSVEP BCIs, in which channels are encoded by different combinations of frequencies and phases, is that the operator does not have to gaze directly at flickering lights. This can reduce visual fatigue and improve user comfort. Whereas the frequency of the SSVEP response is well predictable, which has enabled the development of frequency-coded SSVEP BCIs which do not require training data, the spatial distribution of the SSVEP response over the scalp differs much more between different people. This requires collecting a substantial amount of training data before the spatially-coded BCI could be put into operation.

NEW METHOD

In this study we address this issue by combining the spatially-coded BCI with a feedback channel which the operator uses to flag classification errors, and which allows the system to accumulate valid training data while the BCI is used to solve a spatial navigation task.

RESULTS

Starting from the minimal number of samples required by the classification method, the approach achieved an average accuracy of 69 ± 15 %, corresponding to an ITR of 31 ± 17 bits/min, in solving the task for the first time. This accuracy improved to 87 ± 9 % (ITR: 54 ± 14 bits/min) after completing the task 2 more times. Further we show that participants with a stable SSVEP topography over repeated stimulation enable the BCI to achieve higher accuracies.

COMPARISON WITH EXISTING METHODS

Compared to a similar system with separate training and application phases, the time to achieve the same output is reduced by more than 50 %.

CONCLUSIONS

Evaluating the approach in 17 participants suggests that the performance of the spatially-coded BCI with a minimal set of training samples is sufficient to be operational, and that performance keeps improving in the course of its application.

Largely intact memory for spatial locations during navigation in an individual with dense amnesia

Spatial navigation and event memory (termed episodic memory) are thought to be heavily intertwined, both in terms of their cognitive processes and underlying neural systems. Some theoretical models posit that both memory for places during navigation and episodic memory depend on highly overlapping brain systems. Here, we assessed this relationship by testing navigation in an individual with severe retrograde and anterograde amnesia; the amnesia stemmed from bilateral lesions in the medial temporal lobes from two separate strokes. The individual with amnesia and age-matched controls were tested on their memories for the locations of previously seen objects relative to distal mountain cues in an immersive virtual environment involving free ambulation. All participants were tested from both repeated and novel start locations and when a single distal mountain cue was unknowingly moved to determine if they relied on a single (beacon) cue to a greater extent than the collection of all distal cues. Compared to age-matched controls, the individual with amnesia showed no significant deficits in navigation from either the repeated or novel start points, although both the individual with amnesia and controls performed well above chance at placing objects near their correct locations. The individual with amnesia also relied on a combination of distal cues in a manner comparable to age-matched controls. Despite largely intact memory for locations using distal cues, the individual with amnesia walked longer paths, rotated more, and took longer to complete trials. Our findings suggest that memory for places during navigation and episodic memory may involve partially dissociable brain circuits and that other brain regions outside of the medial temporal lobe partially support some aspects of navigation. At the same time, the fact that the individual with amnesia walked more circuitous paths and had dense amnesia for autobiographic events supports the idea that the hippocampus may be important for binding information as part of a larger role in memory.

Two Immersive Virtual Reality Tasks for the Assessment of Spatial Orientation in Older Adults with and Without Cognitive Impairment: Concurrent Validity, Group Comparison, and Accuracy Results

OBJECTIVE

Spatial disorientation is common in Alzheimer's disease (AD), Mild Cognitive Impairment (MCI), and preclinical individuals with AD biomarkers. However, traditional neuropsychological tests lack ecological validity for the assessment of spatial orientation and to date, there is still no gold standard. The current study aimed to determine the validity and accuracy of two virtual reality tasks for the assessment of spatial orientation.

METHODS

We adapted two spatial orientation tasks to immersive virtual environments: a "survey to route" task in which participants had to transfer information from a map to their body position within a maze [Spatial Orientation in Immersive Virtual Environment Test (SOIVET) Maze], and an allocentric-type, route learning task, with well-established topographic landmarks (SOIVET Route). A total of 19 MCI patients and 29 cognitively healthy older adults aged 61-92 participated in this study. Regular neuropsychological assessments were used for correlation analysis and participant performances were compared between groups. Receiver Operating Characteristic (ROC) curve analysis was performed for accuracy.

RESULTS

The SOIVET Maze correlated with measures of visuoperception, mental rotation, and planning, and was not related to age, educational level, or technology use profile. The SOIVET Route immediate correlated with measures of mental rotation, memory, and visuoconstruction, and was influenced only by education. Both tasks significantly differentiated MCI and control groups, and demonstrated moderate accuracy for the MCI diagnosis.

CONCLUSION

Traditional neuropsychological assessment presents limitations and immersive environments allow for the reproduction of complex cognitive processes. The two immersive virtual reality tasks are valid tools for the assessment of spatial orientation and should be considered for cognitive assessments of older adults.

Progesterone rapidly alters the use of place and response memory during spatial navigation in female rats

17β-Estradiol (E2) and progesterone (P) influence place and response memory in female rats in spatial navigation tasks. Use of these memory systems is associated with the hippocampus and the dorsal striatum, respectively. Injections of E2 result in a well-established bias to use place memory, while much less is understood about the role of P. A total of 120 ovariectomized female rats were tested within a dual-solution T-maze task and treated with either low E2 (n = 24), high E2 (10 μg/kg; n = 24), or high E2 in combination with P (500 μg/kg) at three time points before testing: 15 min (n = 24), 1 h (n = 24), and 4 h (n = 24). Given alone, high E2 biases rats to the use of place memory, but this effect is reversed when P is given 1 h or 4 h before testing. This indicates that P may be playing an inhibitory role in the hippocampus during spatial tasks, which is consistent with past findings. Our findings show that P acts rapidly (within an hour) to affect performance during spatial tasks.

Navigation strategies in patients with vestibular loss tested in a virtual reality T-maze

During navigation, humans mainly rely on egocentric and allocentric spatial strategies, two different frames of reference working together to build a coherent representation of the environment. Spatial memory deficits during navigation have been repeatedly reported in patients with vestibular disorders. However, little is known about how vestibular disorders can change the use of spatial navigation strategies. Here, we used a new reverse T-maze paradigm in virtual reality to explore whether vestibular loss specifically modifies the use of egocentric or allocentric spatial strategies in patients with unilateral (n = 23) and bilateral (n = 23) vestibular loss compared to healthy volunteers (n = 23) matched for age, sex and education level. Results showed that the odds of selecting and using a specific strategy in the T-maze were significantly reduced in both unilateral and bilateral vestibular loss. An exploratory analysis suggests that only right vestibular loss decreased the odds of adopting a spatial strategy, indicating an asymmetry of vestibular functions. When considering patients who used strategies to navigate, we observed that a bilateral vestibular loss reduced the odds to use an allocentric strategy, whereas a unilateral vestibular loss decreased the odds to use an egocentric strategy. Age was significantly associated with an overall lower chance to adopt a navigation strategy and, more specifically, with a decrease in the odds of using an allocentric strategy. We did not observe any sex difference in the ability to select and use a specific navigation strategy. Findings are discussed in light of previous studies on visuo-spatial abilities and studies of vestibulo-hippocampal interactions in peripheral vestibular disorders. We discuss the potential impact of the history of the disease (chronic stage in patients with a bilateral vestibulopathy vs. subacute stage in patients with a unilateral vestibular loss), of hearing impairment and non-specific attentional deficits in patients with vestibular disorders.

Testing landmark-specific effects on route navigation in an ecologically valid setting: a simulated driving study

We used a driving simulator to investigate landmark-based route navigation in young adults. Previous research has examined how proximal and distal landmarks influence route navigation, however, these effects have not been extensively tested in ecologically-relevant settings. We used a virtual town in which participants learned various routes while simultaneously driving. We first examined the effect of four different landmark conditions on navigation performance, such that each driver experienced one of four versions of the town with either proximal landmarks only, distal landmarks only, both proximal and distal landmarks, or no landmarks. Drivers were given real-time navigation directions along a route to a target destination, and were then tested on their ability to navigate to the same destination without directions. We found that the presence of proximal landmarks significantly improved route navigation. We then examined the effect of prior exposure to proximal vs. distal landmarks by testing the same drivers in the same environment they previously encountered, but with the landmarks removed. In this case, we found that prior exposure to distal landmarks significantly improved route navigation. The present results are in line with existing research on route navigation and landmarks, suggesting that these findings can be extended to ecologically-relevant settings.

Future trends in brain aging research: Visuo-cognitive functions at stake during mobility and spatial navigation

Aging leads to a complex pattern of structural and functional changes, gradually affecting sensorimotor, perceptual, and cognitive processes. These multiscale changes can hinder older adults' interaction with their environment, progressively reducing their autonomy in performing tasks relevant to everyday life. Autonomy loss can further be aggravated by the onset and progression of neurodegenerative disorders (e.g., age-related macular degeneration at the sensory input level; and Alzheimer's disease at the cognitive level). In this context, spatial cognition offers a representative case of high-level brain function that involves multimodal sensory processing, postural control, locomotion, spatial orientation, and wayfinding capabilities. Hence, studying spatial behavior and its neural bases can help identify early markers of pathogenic age-related processes. Until now, the neural correlates of spatial cognition have mostly been studied in static conditions thereby disregarding perceptual (other than visual) and motor aspects of natural navigation. In this review, we first demonstrate how visuo-motor integration and the allocation of cognitive resources during locomotion lie at the heart of real-world spatial navigation. Second, we present how technological advances such as immersive virtual reality and mobile neuroimaging solutions can enable researchers to explore the interplay between perception and action. Finally, we argue that the future of brain aging research in spatial navigation demands a widespread shift toward the use of naturalistic, ecologically valid experimental paradigms to address the challenges of mobility and autonomy decline across the lifespan.

Rapid spatial learning in cooperative and non-cooperative cichlids

The number, duration and depth of social relationships that an individual maintains can impact social cognition, but the connection between sociality and other aspects of cognition has hardly been explored. To date, the link between social living and intelligence has been mainly supported by studies on primates, and far fewer tests connecting sociality to cognitive abilities have used other taxa. Here, we present the first comparative study in fishes that examines whether complex social living is associated with better performance on a cognitively demanding spatial task. Using three cooperative, group-living cichlid fish species and three of their non-cooperative, more solitary close relatives, we studied maze learning and employed a new statistical extension for the 'lme4' and 'glmmTMB' packages in R that allows phylogeny to be included as a random effect term. Across trials, the three cooperative and the three non-cooperative species completed the maze faster, made fewer mistakes, and improved their inhibitory control. Although fish improved their performance, we did not detect any differences in the extent of improvement between cooperative and non-cooperative species. Both the cooperative species and the non-cooperative species took similar amounts of time to complete the maze, had comparable numbers of mistakes, and exhibited similar inhibitory control while in the maze. Our results suggest that living and breeding in complex social groups does not necessarily imply enhancement of other forms of cognition nor, more specifically, an enhanced spatial learning capacity.

Bayesian decision theory and navigation

Spatial navigation is a complex cognitive activity that depends on perception, action, memory, reasoning, and problem-solving. Effective navigation depends on the ability to combine information from multiple spatial cues to estimate one's position and the locations of goals. Spatial cues include landmarks, and other visible features of the environment, and body-based cues generated by self-motion (vestibular, proprioceptive, and efferent information). A number of projects have investigated the extent to which visual cues and body-based cues are combined optimally according to statistical principles. Possible limitations of these investigations are that they have not accounted for navigators' prior experiences with or assumptions about the task environment and have not tested complete decision models. We examine cue combination in spatial navigation from a Bayesian perspective and present the fundamental principles of Bayesian decision theory. We show that a complete Bayesian decision model with an explicit loss function can explain a discrepancy between optimal cue weights and empirical cues weights observed by (Chen et al. Cognitive Psychology, 95, 105-144, 2017) and that the use of informative priors to represent cue bias can explain the incongruity between heading variability and heading direction observed by (Zhao and Warren 2015b, Psychological Science, 26[6], 915-924). We also discuss (Petzschner and Glasauer's , Journal of Neuroscience, 31(47), 17220-17229, 2011) use of priors to explain biases in estimates of linear displacements during visual path integration. We conclude that Bayesian decision theory offers a productive theoretical framework for investigating human spatial navigation and believe that it will lead to a deeper understanding of navigational behaviors.

Hippocampal acidity and volume are differentially associated with spatial navigation in older adults

The hippocampus is negatively affected by aging and is critical for spatial navigation. While there is evidence that wayfinding navigation tasks are especially sensitive to preclinical hippocampal deterioration, these studies have primarily used volumetric hippocampal imaging without considering microstructural properties or anatomical variation within the hippocampus. T1ρ is an MRI measure sensitive to regional pH, with longer relaxation rates reflecting acidosis as a marker of metabolic dysfunction and neuropathological burden. For the first time, we investigate how measures of wayfinding including landmark location learning and delayed memory in cognitively normal older adults (N = 84) relate to both hippocampal volume and T1ρ in the anterior and posterior hippocampus. Regression analyses revealed hippocampal volume was bilaterally related to learning, while right lateralized T1ρ was related to delayed landmark location memory and bilateral T1ρ was related to the delayed use of a cognitive map. Overall, results suggest hippocampal volume and T1ρ relaxation rate tap into distinct mechanisms involved in preclinical cognitive decline as assessed by wayfinding navigation, and laterality influenced these relationships more than the anterior-posterior longitudinal axis of the hippocampus.

Using your nose to find your way: Ethological comparisons between human and non-human species

Olfaction is arguably the least valued among our sensory systems, and its significance for human behavior is often neglected. Spatial navigation represents no exception to the rule: humans are often characterized as purely visual navigators, a view that undermines the contribution of olfactory cues. Accordingly, research investigating whether and how humans use olfaction to navigate space is rare. In comparison, research on olfactory navigation in non-human species is abundant, and identifies behavioral strategies along with neural mechanisms characterizing the use of olfactory cues during spatial tasks. Using an ethological approach, our review draws from studies on olfactory navigation across species to describe the adaptation of strategies under the influence of selective pressure. Mammals interact with spatial environments by abstracting multisensory information into cognitive maps. We thus argue that olfactory cues, alongside inputs from other sensory modalities, play a crucial role in spatial navigation for mammalian species, including humans; that is, odors constitute one of the many building blocks in the formation of cognitive maps.

Overcoming navigational challenges: A novel approach to the study and assessment of topographical orientation

Several studies investigating environmental navigation require participants to navigate in virtual environments, in which the proprioceptive and vestibular components present during real environmental navigation are lost. Here, we aimed to provide a novel computerized ecological navigational battery, investigating whether the absence of proprioceptive and vestibular inputs yields a representation of the navigational space comparable to that acquired ecologically. In Study 1, 38 participants underwent two sets of tasks, one performed in a laboratory-based setting (LBS) and the other in an ecological environment (EE), with both including evaluation of route, landmark, and survey knowledge and a landmark ordering task. All tasks, except the route task, significantly correlated between EE and LBS. In LBS, performance in the landmark ordering task was predicted by that in the survey task, but not by those in the route and landmark tasks. Results of Study 1 were replicated in Study 2, in which 44 participants completed a modified and shorter online version of LBS tests. Reliability of the online LBS tests was also tested and showed a moderate-to-high internal consistency. Overall, results show that the conditions in which tasks are performed affect the acquisition of route knowledge, likely due to the lack of proprioceptive and vestibular information in LBS. However, LBS tasks presented here provide a standard battery of tests that can overcome the replicability problems encountered by ecological navigation tests, while taking into consideration all the complexities of navigational processes in terms of the use of landmark, route, and survey strategies.

Navigation using global or local reference frames in rats with medial and lateral entorhinal cortex lesions

The medial (MEC) and the lateral (LEC) regions of the entorhinal cortex send a major input to the hippocampus and have been proposed to play a foremost role in combining spatial and non-spatial attributes of episodic memory. In addition, it has been recently suggested that the MEC is involved in the processing of information in a global reference frame and the LEC in the processing of information in a local reference frame. Whether these putative functions could be generalized to navigation contexts has not been established yet. To address this hypothesis, rats with MEC or LEC NMDA-induced lesions were trained in two versions of a navigation task in the water maze, a global cue condition in which they had to use distal room cues and a local cue condition in which they had to use 3 objects placed in the pool. In the global cue condition, MEC-lesioned rats exhibited slower acquisition and were not able to precisely locate the submerged platform during the probe trial. In contrast LEC-lesioned rats exhibited control-like performance. In the local cue condition, navigational abilities were spared in both lesion groups. In addition when the 3 different objects were replaced by 3 identical objects, all groups maintained their navigation accuracy suggesting that the identity of objects is not crucial for place navigation. Overall, the results indicate that the MEC is necessary for place navigation using a global reference frame. In contrast, navigation using a local reference frame does not require the LEC nor the MEC.

Human spatial navigation: Neural representations of spatial scales and reference frames obtained from an ALE meta-analysis

Humans use different spatial reference frames (allocentric or egocentric) to navigate successfully toward their destination in different spatial scale spaces (environmental or vista). However, it remains unclear how the brain represents different spatial scales and different spatial reference frames. Thus, we conducted an activation likelihood estimation (ALE) meta-analysis of 47 fMRI articles involving human spatial navigation. We found that both the environmental and vista spaces activated the parahippocampal place area (PPA), retrosplenial complex (RSC), and occipital place area in the right hemisphere. The environmental space showed stronger activation than the vista space in the occipital and frontal regions. No brain region exhibited stronger activation for the vista than the environmental space. The allocentric and egocentric reference frames activated the bilateral PPA and right RSC. The allocentric frame showed more stronger activations than the egocentric frame in the right culmen, left middle frontal gyrus, and precuneus. No brain region displayed stronger activation for the egocentric than the allocentric navigation. Our findings suggest that navigation in different spatial scale spaces can evoke specific and common brain regions, and that the brain regions representing spatial reference frames are not absolutely separated.

Vestibular cues improve landmark-based route navigation: A simulated driving study

It is well established that humans use self-motion and landmark cues to successfully navigate their environment. Existing research has demonstrated a critical role of the vestibular system in supporting navigation across many species. However, less is known about how vestibular cues interact with landmarks to promote successful navigation in humans. In the present study, we used a motion simulator to manipulate the presence or absence of vestibular cues during a virtual navigation task. Participants learned routes to a target destination in three different landmark blocks in a virtual town: one with proximal landmarks, one with distal landmarks, and one with no landmarks present. Afterwards, they were tested on their ability to retrace the route and find the target destination. We observed a significant interaction between vestibular cues and proximal landmarks, demonstrating that the potential for vestibular cues to improve route navigation is dependent on landmarks that are present in the environment. In particular, vestibular cues significantly improved route navigation when proximal landmarks were present, but this was not significant when distal landmarks or no landmarks were present. Overall, our results indicate that landmarks play an important role in the successful incorporation of vestibular cues to human spatial navigation.