The Aging Navigational System

Navigating space and the developing mind

In this article, we review the extensive and complex fabric of literature concerning the ontogenesis of spatial representations from earliest childhood to the elderly, including normal and abnormal aging (dementia and Alzheimer's disease). We also revisit fundamental concepts of the neuronal representations of space, egocentric vs. allocentric reference frames, and path integration. We highlight a thread of contradictions in spatial cognition from infant cognition to the first breakthrough at around the age of four. The contradictions reemerge in the literature on age-related decline in spatial cognition. We argue that these contradictions derive from the incorrect assumption that path integration is exclusively associated with allocentric frames of references, hence, signatures of path integration are often taken as evidence for allocentric perspective-taking. We posit that several contradictions in the literature can be resolved by acknowledging that path integration is agnostic to the type of reference frame and can be implemented in both egocentric and allocentric frames of reference. By freeing the frames of reference from path integration, we arrive at a developmental trajectory consistent across cognitive development studies, enabling us to ask questions that may dissolve the obscurity of this topic. The new model also sheds light on the very early stage of spatial cognition.

Longitudinal evaluation of open field and string-pulling behaviors in mice

Spontaneous behaviors involve collections of highly organized movement sequences produced on a specific spatial scale. For example, mice exhibit organized movement while establishing a home base in the open field (ambulatory scale) and bimanual coordination while string-pulling (manipulatory scale). Disruptions in the organization of spontaneous behaviors, including home base establishment and string-pulling, have been observed in mouse models of neurological disorders. The influence of age on the organization of these behaviors is yet to be determined. The current study evaluated longitudinal changes in the organization of mouse open field movement under completely dark conditions and string-pulling movement at multiple timepoints from 10 to 20 months of age. Topographic and kinematic characteristics of movement were used to investigate age-related changes in ambulatory (i.e., home base stability) and manipulatory (i.e., reaching consistency) scale movement organization. In the open field, general locomotion and home base measures remained stable. However, changes in heading and movement scaling varied with age. In contrast, string-pulling performance varied in measures of accuracy and kinematics, with general improvements observed with age. These results suggest minimal age-related decline in the organization of spontaneous behaviors. As mouse models are commonly used to model progressive diseases in humans, it is important to consider the translatability of aging. This work provides a foundation to characterize the effect of age and compounding variables (e.g., sleep fragmentation, exercise) on spontaneous behaviors.

A cognitive-motor framework for spatial navigation in aging and early-stage Alzheimer's disease

Spatial navigation is essential for wellbeing and independence and shows significant declines as part of age-related neurodegenerative disorders, such as Alzheimer's disease. Navigation is also one of the earliest behaviors impacted by this devastating disease. Neurobiological models of aging and spatial navigation have focused primarily on the cognitive factors that account for impaired navigation abilities during the course of healthy aging and early stages of preclinical and prodromal Alzheimer's disease. The contributions of physical factors that are essential to planning and executing movements during successful navigation, such as gait and dynamic balance, are often overlooked despite also being vulnerable to early stages of neurodegenerative disease. We review emerging evidence that spatial navigation and functional mobility each draw on highly overlapping sensory systems, cognitive processes, and brain structures that are susceptible to healthy and pathological aging processes. Based on this evidence, we provide an alternative to models that have focused primarily on spatial navigation as a higher order cognitive function dependent on brain areas such as the hippocampus and entorhinal cortex. Instead, we argue that spatial navigation may offer an ecologically valid cognitive-motor phenotype of age-related cognitive dysfunction. We propose that dual cognitive-motor deficits in spatial navigation may arise from early changes in neuromodulatory and peripheral sensory systems that precede changes in regions such as the entorhinal cortex.

Virtual Reality and Serious Videogame-Based Instruments for Assessing Spatial Navigation in Alzheimer's Disease: A Systematic Review of Psychometric Properties

Over the past decade, research using virtual reality and serious game-based instruments for assessing spatial navigation and spatial memory in at-risk and AD populations has risen. We systematically reviewed the literature since 2012 to identify and evaluate the methodological quality and risk of bias in the analyses of the psychometric properties of VRSG-based instruments. The search was conducted primarily in July-December 2022 and updated in November 2023 in eight major databases. The quality of instrument development and study design were analyzed in all studies. Measurement properties were defined and analyzed according to COSMIN guidelines. A total of 1078 unique records were screened, and following selection criteria, thirty-seven studies were analyzed. From these studies, 30 instruments were identified. Construct and criterion validity were the most reported measurement properties, while structural validity and internal consistency evidence were the least reported. Nineteen studies were deemed very good in construct validity, whereas 11 studies reporting diagnostic accuracy were deemed very good in quality. Limitations regarding theoretical framework and research design requirements were found in most of the studies. VRSG-based instruments are valuable additions to the current diagnostic toolkit for AD. Further research is required to establish the psychometric performance and clinical utility of VRSG-based instruments, particularly the instrument development, content validity, and diagnostic accuracy for preclinical AD screening scenarios. This review provides a straightforward synthesis of the state of the art of VRSG-based instruments and suggests future directions for research.

How spatial-cue reliability affects navigational performance in young and older adults

Navigational abilities decline with age, but the cognitive underpinnings of this cognitive decline remain partially understood. Navigation is guided by landmarks and self-motion cues, that we address when estimating our location. These sources of spatial information are often associated with noise and uncertainty, thus posing a challenge during navigation. To overcome this challenge, humans and other species rely on navigational cues according to their reliability: reliable cues are highly weighted and therefore strongly influence our spatial behavior, compared to less reliable ones. We hypothesize that older adults do not efficiently weigh spatial cues, and accordingly, the reliability levels of navigational cues may not modulate their spatial behavior, as with younger adults. To test this, younger and older adults performed a virtual navigational task, subject to modified reliability of landmarks and self-motion cues. The findings revealed that while increased reliability of spatial cues improved navigational performance across both age groups, older adults exhibited diminished sensitivity to changes in landmark reliability. The findings demonstrate a cognitive mechanism that could lead to impaired navigation abilities in older adults.

The effects of moderate prenatal alcohol exposure on performance in object and spatial discrimination tasks by adult male rats

Exposure to alcohol during pregnancy produces Fetal Alcohol Spectrum Disorders, which in its most severe form is characterized by physical dysmorphology and neurobehavioral alterations. Moderate prenatal alcohol exposure (mPAE) is known to produce deficits in discrimination of spatial locations in adulthood. However, the impact of mPAE on higher-order sensory representations, such as discrimination of perceptually similar stimuli, is currently unknown. In the present study, we tested the hypothesis that mPAE would disrupt performance on hippocampal-sensitive tasks that require discrimination between perceptually similar objects or discrimination between spatial locations in a radial arm maze. Here we report that male mPAE rats exhibited intact performance on three types of object discrimination tasks: one in which rats discriminated between distinct toy objects, a second in which discrimination was made between distinct and similar LEGO objects, and a mnemonic similarity task in which rats discriminated between randomly presented LEGO objects that varied in similarity with a learned object. Although adult male mPAE rats performed similarly to control rats on all three object discrimination tasks, they showed deficits when tested in a radial arm maze spatial discrimination task. Specifically, male mPAE rats expressed a significantly higher number of working memory errors (returns to previously visited arms) and were more likely to use non-spatial strategies during training. Together, the findings of the present study support the conclusion that mPAE produces specific deficits in the online processing of spatial information and executing spatial navigation strategies, but spares the ability to discriminate between perceptually similar stimuli.

Validation of Spatial Orientation Screening questionnaire for use in memory clinic patients

BACKGROUND

Spatial orientation is required for independent mobility in society. Deficits in spatial orientation can be an early symptom of Alzheimer's disease and other dementias, and there is a need for brief assessment tools to identify impairments.

OBJECTIVE

The aim of this study was to evaluate the construct and known-group validity of our newly developed Spatial Orientation Screening (SOS) questionnaire.

METHODS

We included 132 patients with subjective cognitive decline (n = 16), mild cognitive impairment (n = 32), or all-cause dementia (n = 84) from a memory clinic and a reference group of cognitively unimpaired older adults (n = 108). The patients and their next-of-kin answered the self- and proxy-rated versions of the 4-item SOS (0-8 points) and the 10-item Questionnaire of Everyday Navigational Ability (QuENA, 0-30 points). The patients also performed the Floor Maze Test (FMT) for performance-based spatial abilities.

RESULTS

Mean ages (SD) of the patient and reference groups were 68.6 (±7.6) years and 73.7 (±6.7) years, respectively. Construct validity between self-rated versions of the SOS and QuENA was satisfactory with rs = 0.66, between the proxy-rated versions rs = 0.61, and between the proxy-reported SOS and FMT rs = 0.49 (all p < 0.001). Known-group validity was also acceptable, with significantly higher median (IQR) SOS self-reported scores in patients 1.0 (2.0) compared to the reference group 0.2 (0.5) points, (p < 0.001). Informants reported more severe impairments compared to the patients' self-reports on both SOS and QuENA (both p < 0.001).

CONCLUSIONS

The SOS had satisfactory validity for use as a screening instrument for assessment of spatial orientation in memory clinic patients.

Predicting real-world navigation performance from a virtual navigation task in older adults

Virtual reality environments presented on tablets and smartphones offer a novel way of measuring navigation skill and predicting real-world navigation problems. The extent to which such virtual tests are effective at predicting navigation in older populations remains unclear. We compared the performance of 20 older participants (54-74 years old) in wayfinding tasks in a real-world environment in London, UK, and in similar tasks designed in a mobile app-based test of navigation (Sea Hero Quest). In a previous study with young participants (18-35 years old), we were able to predict navigation performance in real-world tasks in London and Paris using this mobile app. We find that for the older cohort, virtual navigation performance predicts real-world performance for medium difficulty, but not for the easy or difficult environments. Overall, our study supports the utility of using digital tests of spatial cognition in older age groups, while carefully adapting the task difficulty to the population.

AMPA Receptors in Synaptic Plasticity, Memory Function, and Brain Diseases

Tetrameric AMPA-type ionotropic glutamate receptors are primary transducers of fast excitatory synaptic transmission in the central nervous system, and their properties and abundance at the synaptic surface are crucial determinants of synaptic efficacy in neuronal communication across the brain. The induction of long-term potentiation (LTP) leads to the insertion of GluA1-containing AMPA receptors at the synaptic surface, whereas during long-term depression (LTD), these receptors are internalized into the cytoplasm of the spine. Disruptions in the trafficking of AMPA receptors to and from the synaptic surface attenuate both forms of synaptic plasticity. Homeostatic scaling up and scaling down, which are additional types of plasticity similar to LTP and LTD, are also regulated by the insertion and removal of GluA1-containing AMPA receptors from the synaptic surface. The trafficking of AMPA receptors is an intricate process assisted by various proteins. Furthermore, AMPA receptors are critical for the formation and consolidation of various types of memory, and alterations in their function are intimately associated with cognitive dysfunction in aging and several neurological and psychiatric diseases. In this review, we will provide an overview of the current understanding of how AMPA receptors regulate various forms of synaptic plasticity, their contribution to memory functions, and their role in aging and brain diseases.

The Neurobiology of Learning and Memory in Rodent Models of Fetal Alcohol Spectrum Disorders

Exposure to ethanol during gestation can lead to the onset of Fetal Alcohol Spectrum Disorders, which describes a range of neurodevelopmental and behavioral dysfunctions that include impairments in learning and memory and can have serious repercussions for scholastic performance during adolescence. The neurobiological basis of learning and memory dysfunction in Fetal Alcohol Spectrum Disorders has been frequently linked to the hippocampal formation, which is due in part to the fact that some hippocampal neurons, called place cells, fire action potentials correlated with an animal's spatial location as well as other features of memory episodes. The goal of this chapter is to provide an overview of research investigating developmental alcohol exposure in rodent models and the impact on learning and memory, hippocampal circuitry, and neural representations of learning and memory. We conclude by highlighting areas in which more concentrated behavioral and neurobiological study is needed to expand and develop rodent models of memory dysfunction in Fetal Alcohol Spectrum Disorders.

Perceptual learning and neural correlates of virtual navigation in subjective cognitive decline: A pilot study

Spatial navigation deficits in age-related diseases involve brain changes affecting spatial memory and verbal cognition. Studies in blind and blindfolded individuals show that multisensory training can induce neuroplasticity through visual cortex recruitment. This proof-of-concept study introduces a digital navigation training protocol, integrating egocentric and allocentric strategies with multisensory stimulation and visual masking to enhance spatial cognition and brain connectivity in 17 individuals (mean age 57.2 years) with subjective cognitive decline. Results indicate improved spatial memory performance correlated with recruitment of the visual area 6-thalamic pathway and enhanced connectivity between memory, executive frontal areas, and default mode network (DMN) regions. Additionally, increased connectivity between allocentric and egocentric navigation areas via the retrosplenial complex (RSC) hub was observed. These findings suggest that this training has the potential to induce perceptual learning and neuroplasticity through key functional connectivity hubs, offering potential widespread cognitive benefits by enhancing critical brain network functions.

The effects of moderate prenatal alcohol exposure on performance in hippocampal-sensitive spatial memory and anxiety tasks by adult male and female rat offspring

Moderate prenatal alcohol exposure (mPAE) results in structural alterations to the hippocampus. Previous studies have reported impairments in hippocampal-sensitive tasks, but have not compared performance between male and female animals. In the present study, performance in hippocampal-sensitive spatial memory and anxiety behavior tests were compared across adult male and female saccharin (SACC) control mPAE Long-Evans rat offspring. Two tests of spatial memory were conducted that were aimed at assessing memory for recently acquired spatial information: A delayed spatial alternation task using an M-shaped maze and a delayed match-to-place task in the Morris water task. In both tasks, rats in SACC and mPAE groups showed similar learning and retention of a spatial location even after a 2-h interval between encoding and retention. A separate group of adult male and female SACC and mPAE rat offspring were tested for anxiety-like behaviors in the elevated plus-maze paradigm. In this test, both male and female mPAE rats exhibited a significantly greater amount of time and a greater number of head dips in the open arms, while locomotion and open arm entries did not differ between groups. The results suggest that mPAE produces a reduction in anxiety-like behaviors in both male and female rats in the elevated plus-maze.

Do total hippocampus and hippocampal subfield volumes relate to navigation ability? A call towards methodological consistency

Despite the need for successful navigation, humans vary greatly in their ability to navigate, and these individual differences may relate to variation in brain structure. While prior research provides support for a correlation between hippocampal volume and navigation ability in both navigation experts and in older individuals, this relationship is under scrutiny for healthy, young adults. We assessed 99 healthy young adults' ability to navigate in a virtual, desktop maze and correlated their performance with total hippocampal gray matter volume. For a subset of these individuals, we further segmented the medial temporal lobe-including regions of the hippocampus-into anatomically-distinct subregions to uniquely examine the association between volumes of hippocampal subfields and navigation. Given the need to distinguish between similar-looking maze hallways and partially overlapping routes, young adults with stronger pattern separation ability may perform better in this task. Thus, we theorized that successful navigation would positively correlate with hippocampal CA3 and dentate gyrus (DG) subfield volumes due to these regions' role in pattern separation. CA1 and entorhinal cortex (ERC) are both associated with rodent spatial memory, too, suggesting a possible relationship between their volumes and navigation performance. Consistent with our hypotheses, we observed a positive relationship between volumes of hippocampal subfields and wayfinding accuracy, while ERC and parahippocampal cortex volumes correlated with navigation efficiency. However, when analyzing total hippocampal volume, a nuanced interpretation is warranted. We found evidence of Simpson's Paradox, where total hippocampal volume and navigation accuracy displayed no correlation in males, a negative correlation in females, yet a positive correlation when considering the full sample of males and females combined. Furthermore, no significant relationship was observed between total hippocampal volume and path efficiency. Given these findings, we urge caution in interpreting the results because these associations differ by analysis techniques (including voxel-based morphometry), after sex stratification, and with anterior and posterior hippocampal subdivisions. Overall, this study enhances our understanding of the relationship between brain volume and navigation ability for young adults but also emphasizes the need for methodological consistency across studies with respect to boundary definitions, neuroimaging techniques, statistical methods, and factors that give rise to individual differences.

Age differences in spatial memory are mitigated during naturalistic navigation

Spatial navigation deficits are often observed among older adults on tasks that require navigating virtual reality (VR) environments on a computer screen. We investigated whether these age differences are attenuated when tested in more naturalistic and ambulatory virtual environments. In Experiment 1, young and older adults navigated a variant of the Morris Water Maze task in each of two VR conditions: a desktop VR condition which required using a mouse and keyboard to navigate, and an ambulatory VR condition which permitted unrestricted locomotion. In Experiment 2, we examined whether age- and VR-related differences in spatial performance were affected by the inclusion of additional spatial cues. In both experiments, older adults navigated to target locations less precisely than younger individuals in the desktop condition. Age differences were significantly attenuated, however, when tested in the ambulatory VR environment. These findings underscore the importance of developing naturalistic assessments of spatial memory and navigation.

Environmental enrichment in middle age rats improves spatial and object memory discrimination deficits

Changes in memory performance are one of the main symptoms of normal aging. The storage of similar experiences as different memories (ie. behavioral pattern separation), becomes less efficient as aging progresses. Studies have focused on hippocampus dependent spatial memories and their role in the aging related deficits in behavioral pattern separation (BPS) by targeting high similarity interference conditions. However, parahippocampal cortices such as the perirhinal cortex are also particularly vulnerable to aging. Middle age is thought to be the stage where mild mnemonic deficits begin to emerge. Therefore, a better understanding of the timing of the spatial and object domain memory impairment could shed light over how plasticity changes in the parahipocampal-hippocampal system affects mnemonic function in early aging. In the present work, we compared the performance of young and middle-aged rats in both spatial (spontaneous location recognition) and non-spatial (spontaneous object recognition) behavioral pattern separation tasks to understand the comparative progression of these deficits from early stages of aging. Moreover, we explored the impact of environmental enrichment (EE) as an intervention with important translational value. Although a bulk of studies have examined the contribution of EE for preventing age related memory decline in diverse cognitive domains, there is limited knowledge of how this intervention could specifically impact on BPS function in middle-aged animals. Here we evaluate the effects of EE as modulator of BPS, and its ability to revert the deficits caused by normal aging at early stages. We reveal a domain-dependent impairment in behavioral pattern separation in middle-aged rats, with spatial memories affected independently of the similarity of the experiences and object memories only affected when the stimuli are similar, an effect that could be linked to the higher interference seen in this group. Moreover, we found that EE significantly enhanced behavioral performance in middle-aged rats in the spatial and object domain, and this improvement is specific of the high similarity load condition. In conclusion, these results suggest that memory is differentially affected by aging in the object and spatial domains, but that BPS function is responsive to an EE intervention in a multidomain manner.

Identifying older adults at risk for dementia based on smartphone data obtained during a wayfinding task in the real world

Alzheimer's disease (AD), as the most common form of dementia and leading cause for disability and death in old age, represents a major burden to healthcare systems worldwide. For the development of disease-modifying interventions and treatments, the detection of cognitive changes at the earliest disease stages is crucial. Recent advancements in mobile consumer technologies provide new opportunities to collect multi-dimensional data in real-life settings to identify and monitor at-risk individuals. Based on evidence showing that deficits in spatial navigation are a common hallmark of dementia, we assessed whether a memory clinic sample of patients with subjective cognitive decline (SCD) who still scored normally on neuropsychological assessments show differences in smartphone-assisted wayfinding behavior compared with cognitively healthy older and younger adults. Guided by a mobile application, participants had to find locations along a short route on the medical campus of the Magdeburg university. We show that performance measures that were extracted from GPS and user input data distinguish between the groups. In particular, the number of orientation stops was predictive of the SCD status in older participants. Our data suggest that subtle cognitive changes in patients with SCD, whose risk to develop dementia in the future is elevated, can be inferred from smartphone data, collected during a brief wayfinding task in the real world.

Spatial updating of gaze position in younger and older adults - A path integration-like process in eye movements

Path integration (PI) is a navigation process that allows an organism to update its current location in reference to a starting point. PI can involve updating self-position continuously with respect to the starting point (continuous updating) or creating a map representation of the route which is then used to compute the homing vector (configural updating). One of the brain areas involved in PI, the entorhinal cortex, is modulated similarly by whole-body and eye movements, suggesting that if PI updates self-position, an analogous process may be used to update gaze position, and may undergo age-related changes. Here, we created an eyetracking version of a PI task in which younger and older participants followed routes with their eyes as guided by visual onsets; at the end of each route, participants were cued to return to the starting point or another enroute location. When only memory for the starting location was required for successful task performance, younger and older adults were generally not influenced by the number of locations, indicative of continuous updating. However, when participants could be cued to any enroute location, thereby requiring memory for the entire route, processing times increased, accuracy decreased, and overt revisits to enroute locations increased with the number of locations in a route, indicative of configural updating. Older participants showed evidence for similar updating strategies as younger participants, but they were less accurate and made more overt revisits to mid-route locations. These findings suggest that spatial updating mechanisms are generalizable across effector systems.

Spatial navigation questionnaires as a supportive diagnostic tool in early Alzheimer's disease

Impaired spatial navigation is early marker of Alzheimer's disease (AD). We examined ability of self- and informant-reported navigation questionnaires to discriminate between clinically and biomarker-defined participants, and associations of questionnaires with navigation performance, regional brain atrophy, AD biomarkers, and biomarker status. 262 participants (cognitively normal, with subjective cognitive decline, amnestic mild cognitive impairment [aMCI], and mild dementia) and their informants completed three navigation questionnaires. Navigation performance, magnetic resonance imaging volume/thickness of AD-related brain regions, and AD biomarkers were measured. Informant-reported questionnaires distinguished between cognitively normal and impaired participants, and amyloid-β positive and negative aMCI. Lower scores were associated with worse navigation performance, greater atrophy in AD-related brain regions, and amyloid-β status. Self-reported questionnaire scores did not distinguish between the groups and were weakly associated with navigation performance. Other associations were not significant. Informant-reported navigation questionnaires may be a screening tool for early AD reflecting atrophy of AD-related brain regions and AD pathology.

Less spatial exploration is associated with poorer spatial memory in midlife adults

Introduction

Despite its importance for navigation, very little is known about how the normal aging process affects spatial exploration behavior. We aimed to investigate: (1) how spatial exploration behavior may be altered early in the aging process, (2) the relationship between exploration behavior and subsequent spatial memory, and (3) whether exploration behavior can classify participants according to age.

Methods

Fifty healthy young (aged 18-28) and 87 healthy midlife adults (aged 43-61) freely explored a desktop virtual maze, learning the locations of nine target objects. Various exploration behaviors (object visits, distance traveled, turns made, etc.) were measured. In the test phase, participants navigated from one target object to another without feedback, and their wayfinding success (% correct trials) was measured.

Results

In the exploration phase, midlife adults exhibited less exploration overall compared to young adults, and prioritized learning target object locations over maze layout. In the test phase, midlife adults exhibited less wayfinding success when compared to the young adults. Furthermore, following principal components analysis (PCA), regression analyses indicated that both exploration quantity and quality components were associated with wayfinding success in the midlife group, but not the young adults. Finally, we could classify participants according to age with similar accuracy using either their exploration behavior or wayfinding success scores.

Discussion

Our results aid in the understanding of how aging impacts spatial exploration, and encourages future investigations into how pathological aging may affect spatial exploration behavior.

Effects of older age on visual and self-motion sensory cue integration in navigation

Older adults demonstrate impairments in navigation that cannot be explained by general cognitive and motor declines. Previous work has shown that older adults may combine sensory cues during navigation differently than younger adults, though this work has largely been done in dark environments where sensory integration may differ from full-cue environments. Here, we test whether aging adults optimally combine cues from two sensory systems critical for navigation: vision (landmarks) and body-based self-motion cues. Participants completed a homing (triangle completion) task using immersive virtual reality to offer the ability to navigate in a well-lit environment including visibility of the ground plane. An optimal model, based on principles of maximum-likelihood estimation, predicts that precision in homing should increase with multisensory information in a manner consistent with each individual sensory cue's perceived reliability (measured by variability). We found that well-aging adults (with normal or corrected-to-normal sensory acuity and active lifestyles) were more variable and less accurate than younger adults during navigation. Both older and younger adults relied more on their visual systems than a maximum likelihood estimation model would suggest. Overall, younger adults' visual weighting matched the model's predictions whereas older adults showed sub-optimal sensory weighting. In addition, high inter-individual differences were seen in both younger and older adults. These results suggest that older adults do not optimally weight each sensory system when combined during navigation, and that older adults may benefit from interventions that help them recalibrate the combination of visual and self-motion cues for navigation.

Spatial Coding Dysfunction and Network Instability in the Aging Medial Entorhinal Cortex

Across species, spatial memory declines with age, possibly reflecting altered hippocampal and medial entorhinal cortex (MEC) function. However, the integrity of cellular and network-level spatial coding in aged MEC is unknown. Here, we leveraged in vivo electrophysiology to assess MEC function in young, middle-aged, and aged mice navigating virtual environments. In aged grid cells, we observed impaired stabilization of context-specific spatial firing, correlated with spatial memory deficits. Additionally, aged grid networks shifted firing patterns often but with poor alignment to context changes. Aged spatial firing was also unstable in an unchanging environment. In these same mice, we identified 458 genes differentially expressed with age in MEC, 61 of which had expression correlated with spatial firing stability. These genes were enriched among interneurons and related to synaptic transmission. Together, these findings identify coordinated transcriptomic, cellular, and network changes in MEC implicated in impaired spatial memory in aging.

Age dependent path integration deficit in 5xFAD mice

Alzheimer's disease (AD) is a severe neurodegenerative disorder and the most common form of dementia in elderly individuals, characterized by memory deficits, cognitive decline, and neuropathology. The identification of preclinical markers for AD remains elusive. We employed an ultrasound-evoked spatial memory assay to investigate path integration (PI) in wild type C57BL/6 J and 5xFAD mice. We observed significant recruitment of the mammillary bodies (MB) and subiculum (Sub) - core regions of the Papez circuit during PI, as indicated by increased expression of the immediate early gene c-Fos in C57BL/6 J mice. In 5xFAD mice, amyloid-beta (Aβ) vulnerability in the MB and Sub was evident at 3-months of age, preceding widespread pathology at 5-months of age. In parallel, we detected significant behavioral deficits in PI in the 5XFAD mice at 5- but not 3-months of age. Sex based analysis revealed a more profound deficit in males compared to females at 5-months of age. Our data suggest PI may be as an early indicator of AD, potentially associated with dysfunction within the Papez circuit.

Biological aging of two innate behaviors of Drosophila melanogaster: Escape climbing versus courtship learning and memory

Motor and cognitive aging can severely affect life quality of elderly people and burden health care systems. In search for diagnostic behavioral biomarkers, it has been suggested that walking speed can predict forms of cognitive decline, but in humans, it remains challenging to separate the effects of biological aging and lifestyle. We examined a possible association of motor and cognitive decline in Drosophila, a genetic model organism of healthy aging. Long term courtship memory is present in young male flies but absent already during mid life (4-8 weeks). By contrast, courtship learning index and short term memory (STM) are surprisingly robust and remain stable through mid (4-8 weeks) and healthy late life (>8 weeks), until courtship performance collapses suddenly at ~4.5 days prior to death. By contrast, climbing speed declines gradually during late life (>8 weeks). The collapse of courtship performance and short term memory close to the end of life occur later and progress with a different time course than the gradual late life decline in climbing speed. Thus, during healthy aging in male Drosophila, climbing and courtship motor behaviors decline differentially. Moreover, cognitive and motor performances decline at different time courses. Differential behavioral decline during aging may indicate different underlying causes, or alternatively, a common cause but different thresholds for defects in different behaviors.

Large-scale coupling of prefrontal activity patterns as a mechanism for cognitive control in health and disease: evidence from rodent models

Cognitive control of behavior is crucial for well-being, as allows subject to adapt to changing environments in a goal-directed way. Changes in cognitive control of behavior is observed during cognitive decline in elderly and in pathological mental conditions. Therefore, the recovery of cognitive control may provide a reliable preventive and therapeutic strategy. However, its neural basis is not completely understood. Cognitive control is supported by the prefrontal cortex, structure that integrates relevant information for the appropriate organization of behavior. At neurophysiological level, it is suggested that cognitive control is supported by local and large-scale synchronization of oscillatory activity patterns and neural spiking activity between the prefrontal cortex and distributed neural networks. In this review, we focus mainly on rodent models approaching the neuronal origin of these prefrontal patterns, and the cognitive and behavioral relevance of its coordination with distributed brain systems. We also examine the relationship between cognitive control and neural activity patterns in the prefrontal cortex, and its role in normal cognitive decline and pathological mental conditions. Finally, based on these body of evidence, we propose a common mechanism that may underlie the impaired cognitive control of behavior.

Consensus Paper: Cerebellum and Ageing

Given the key roles of the cerebellum in motor, cognitive, and affective operations and given the decline of brain functions with aging, cerebellar circuitry is attracting the attention of the scientific community. The cerebellum plays a key role in timing aspects of both motor and cognitive operations, including for complex tasks such as spatial navigation. Anatomically, the cerebellum is connected with the basal ganglia via disynaptic loops, and it receives inputs from nearly every region in the cerebral cortex. The current leading hypothesis is that the cerebellum builds internal models and facilitates automatic behaviors through multiple interactions with the cerebral cortex, basal ganglia and spinal cord. The cerebellum undergoes structural and functional changes with aging, being involved in mobility frailty and related cognitive impairment as observed in the physio-cognitive decline syndrome (PCDS) affecting older, functionally-preserved adults who show slowness and/or weakness. Reductions in cerebellar volume accompany aging and are at least correlated with cognitive decline. There is a strongly negative correlation between cerebellar volume and age in cross-sectional studies, often mirrored by a reduced performance in motor tasks. Still, predictive motor timing scores remain stable over various age groups despite marked cerebellar atrophy. The cerebello-frontal network could play a significant role in processing speed and impaired cerebellar function due to aging might be compensated by increasing frontal activity to optimize processing speed in the elderly. For cognitive operations, decreased functional connectivity of the default mode network (DMN) is correlated with lower performances. Neuroimaging studies highlight that the cerebellum might be involved in the cognitive decline occurring in Alzheimer's disease (AD), independently of contributions of the cerebral cortex. Grey matter volume loss in AD is distinct from that seen in normal aging, occurring initially in cerebellar posterior lobe regions, and is associated with neuronal, synaptic and beta-amyloid neuropathology. Regarding depression, structural imaging studies have identified a relationship between depressive symptoms and cerebellar gray matter volume. In particular, major depressive disorder (MDD) and higher depressive symptom burden are associated with smaller gray matter volumes in the total cerebellum as well as the posterior cerebellum, vermis, and posterior Crus I. From the genetic/epigenetic standpoint, prominent DNA methylation changes in the cerebellum with aging are both in the form of hypo- and hyper-methylation, and the presumably increased/decreased expression of certain genes might impact on motor coordination. Training influences motor skills and lifelong practice might contribute to structural maintenance of the cerebellum in old age, reducing loss of grey matter volume and therefore contributing to the maintenance of cerebellar reserve. Non-invasive cerebellar stimulation techniques are increasingly being applied to enhance cerebellar functions related to motor, cognitive, and affective operations. They might enhance cerebellar reserve in the elderly. In conclusion, macroscopic and microscopic changes occur in the cerebellum during the lifespan, with changes in structural and functional connectivity with both the cerebral cortex and basal ganglia. With the aging of the population and the impact of aging on quality of life, the panel of experts considers that there is a huge need to clarify how the effects of aging on the cerebellar circuitry modify specific motor, cognitive, and affective operations both in normal subjects and in brain disorders such as AD or MDD, with the goal of preventing symptoms or improving the motor, cognitive, and affective symptoms.

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.

The Impact of Spatial Orientation Changes on Driving Behavior in Healthy Aging

OBJECTIVES

Global cognitive changes in older age affect driving behavior and road safety, but how spatial orientation differences affect driving behaviors is unknown on a population level, despite clear implications for driving policy and evaluation during aging. The present study aimed to establish how spatial navigation changes affect driving behavior and road safety within a large cohort of older adults.

METHODS

Eight hundred and four participants (mean age: 71.05) were recruited for a prospective cohort study. Participants self-reported driving behavior followed by spatial orientation (allocentric and egocentric) testing and a broader online cognitive battery (visuomotor speed, processing speed, executive functioning, spatial working memory, episodic memory, visuospatial functioning).

RESULTS

Spatial orientation performance significantly predicted driving difficulty and frequency. Experiencing more driving difficulty was associated with worse allocentric spatial orientation, processing speed, and source memory performance. Similarly, avoiding challenging driving situations was associated with worse spatial orientation and episodic memory. Allocentric spatial orientation was the only cognitive domain consistently affecting driving behavior in under 70 and over 70 age groups, a common age threshold for driving evaluation in older age.

DISCUSSION

We established for the first time that worse spatial orientation performance predicted increased driving difficulty and avoidance of challenging situations within an older adult cohort. Deficits in spatial orientation emerge as a robust indicator of driving performance in older age, which should be considered in future aging driving assessments, as it has clear relevance for road safety within the aging population.

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.

Getting LOST: A conceptual framework for supporting and enhancing spatial navigation in aging

Spatial navigation is more difficult and effortful for older than younger individuals, a shift which occurs for a variety of neurological, physical, and cognitive reasons associated with aging. Despite a large body of evidence documenting age-related deficits in spatial navigation, comparatively less research addresses how to facilitate more effective navigation behavior for older adults. Since navigation challenges arise for a variety of reasons in old age, a one-size-fits-all solution is unlikely to work. Here, we introduce a framework for the variety of spatial navigation challenges faced in aging, which we call LOST-Location, Orientation, Spatial mapping, and Transit. The LOST framework builds on evidence from the cognitive neuroscience of spatial navigation, which reveals distinct components underpinning human wayfinding. We evaluate research on navigational aids-devices and depictions-which help people find their way around; and we reflect on how navigation aids solve (or fail to solve) specific wayfinding difficulties faced by older adults. In summary, we emphasize a bespoke approach to improving spatial navigation in aging, which focuses on tailoring navigation solutions to specific navigation challenges. Our hope is that by providing precise support to older navigators, navigation opportunities can facilitate independence and exploration, while minimizing the danger of becoming lost. We conclude by delineating critical knowledge gaps in how to improve older adults' spatial navigation capacities that the novel LOST framework could guide to address. This article is categorized under: Psychology > Development and Aging Neuroscience > Cognition Neuroscience > Behavior.

Exploring the Remediation of Behavioral Disturbances of Spatial Cognition in Community-Dwelling Senior Citizens with Mild Cognitive Impairment via Innovative Technological Apparatus (BDSC-MCI Project): Protocol for a Prospective, Multi-Center Observational Study

Spatial navigation (SN) has been reported to be one of the first cognitive domains to be affected in Alzheimer's disease (AD), which occurs as a result of progressive neuropathology involving specific brain areas. Moreover, the epsilon 4 isoform of apolipoprotein-E (APOE-ε4) has been associated with both sporadic and familial late-onset AD, and patients with mild cognitive impairment (MCI) due to AD are more likely to progressively deteriorate. Spatial navigation performance will be examined on a sample of 76 community-dwelling senior citizens (25 healthy controls; 25 individuals with subjective cognitive decline (SCD); and 26 patients with MCI due to AD) via a virtual computer-based task (i.e., the AppleGame) and a naturalistic task (i.e., the Detour Navigation Test-modified version) for which a wearable device with sensors will be used for recording gait data and revealing physiological parameters that may be associated with spatial disorientation. We expect that patients with MCI due to AD and APOE-ε4 carriers will show altered SN performances compared to individuals with SCD and healthy controls in the experimental tasks, and that VR testing may predict ecological performance. Impaired SN performances in people at increased risk of developing AD may inform future cognitive rehabilitation protocols for counteracting spatial disorientation that may occur during elders' traveling to unfamiliar locations. The research protocol has been approved by the Ethics Committee of the Istituto Auxologico Italiano. Findings will be published in peer-reviewed medical journals and discussed in national and international congresses.

Enhancing spatial navigation skills in mild cognitive impairment patients: a usability study of a new version of ANTaging software

Introduction

Mild Cognitive Impairment (MCI) often presents challenges related to spatial navigation and retention of spatial information. Navigating space involves intricate integration of bodily and environmental cues. Spatial memory is dependent on two distinct frame of reference systems for organizing this information: egocentric and allocentric frames of reference. Virtual Reality (VR) has emerged as a promising technology for enhancing spatial navigation skills and spatial memory by facilitating the manipulation of bodily, environmental, and cognitive cues.

Methods

This usability study was based on a fully within-subjects design in which seven MCI patients underwent two kinds of VR conditions: participants were required to complete the ANTaging demo both in Oculus Rift S (immersive condition) and in Samsung UHD 4K monitor (semi-immersive condition). Participants were seated and they had to use a foot-motion pad to navigate and explore the environment to collect and relocate some objects in the virtual environment. Post-interaction, users provided feedback on their experiences. Additionally, usability, potential side effects, data analysis feasibility, and user preferences with immersive and semi-immersive technologies were assessed through questionnaires.

Results

Results indicated higher usability ratings for the semi-immersive setup, with fewer negative effects reported compared to the immersive counterpart. According to qualitative analyses of the interviews, patients do seem to like both VR apparatuses even though the semi-immersive condition was perceived as the most suitable choice because of the size of the screen. Patients generally found it difficult to remember object locations. Participants expressed the need for more practice with the foot-motion pad, despite an overall positive experience. They generally would like to use this system to improve their memory.

Discussion

Identifying these key aspects was crucial for refining the system before the upcoming clinical trial. This study sheds light on the potential of semi-immersive VR in aiding individuals with MCI, paving the way for enhanced spatial navigation interventions.

Embodied Spatial Navigation Training in Mild Cognitive Impairment: A Proof-of-Concept Trial

Background

Egocentric and allocentric spatial memory impairments affect the navigation abilities of older adults with mild cognitive impairment (MCI). Embodied cognition research hints that specific aids can be implemented into virtual reality (VR) training to enhance spatial memory.

Objective

In this study, we preliminarily tested 'ANTaging', an embodied-based immersive VR training for egocentric and allocentric memory, compared to treatment as usual (TAU) spatial training in MCI.

Methods

MCI patients were recruited for this controlled trial. A cognitive battery was administered at pre-test, after ten sessions of ANTaging or TAU intervention, and at 3-month follow-up (FU). The primary outcomes were spatial cognition tests (Corsi supra-span, CSS; Manikin test, MT). VR egocentric and allocentric performance was also collected.

Results

We found that ANTaging significantly improved MT scores at FU compared to TAU. CSS slightly improved in both groups. Concerning secondary outcomes, auditory-verbal forgetting significantly improved at post-test in the ANTaging but not TAU group and significantly declined at FU in the TAU but not in the ANTaging group. Global cognition significantly improved at FU for TAU and remained stable for ANTaging. Other tests showed no improvement or deterioration. Clinical significance showed that ANTaging is effective for CSS. Virtual egocentric and allocentric memory performance improved across ANTaging sessions.

Conclusions

ANTaging holds the potential to be superior for improving spatial cognition in MCI compared to TAU. Embodied cognition research provides insights for designing effective spatial navigation rehabilitation in aging.

Unraveling the role of miRNAs in the diagnosis, progression, and therapeutic intervention of Alzheimer's disease

Alzheimer's disease (AD) is a multifaceted, advancing neurodegenerative illness that is responsible for most cases of neurological impairment and dementia in the aged population. As the disease progresses, affected individuals may experience cognitive decline, linguistic problems, affective instability, and behavioral changes. The intricate nature of AD reflects the altered molecular mechanisms participating in the affected human brain. MicroRNAs (miRNAs, miR) are essential for the intricate control of gene expression in neurobiology. miRNAs exert their influence by modulating the transcriptome of brain cells, which typically exhibit substantial genetic activity, encompassing gene transcription and mRNA production. Presently, comprehensive studies are being conducted on AD to identify miRNA-based signatures that are indicative of the disease pathophysiology. These findings can contribute to the advancement of our understanding of the mechanisms underlying this disorder and can inform the development of therapeutic interventions based on miRNA and related RNA molecules. Therefore, this comprehensive review provides a detailed holistic analysis of the latest advances discussing the emerging role of miRNAs in the progression of AD and their possible application as potential biomarkers and targets for therapeutic interventions in future studies.

Bodily and Visual-Cognitive Navigation Aids to Enhance Spatial Recall in Mild Cognitive Impairment

Background

Individuals with mild cognitive impairment (MCI) syndrome often report navigation difficulties, accompanied by impairments in egocentric and allocentric spatial memory. However, studies have shown that both bodily (e.g., motor commands, proprioception, vestibular information) and visual-cognitive (e.g., maps, directional arrows, attentional markers) cues can support spatial memory in MCI.

Objective

We aimed to assess navigation cues for innovative spatial training in aging.

Methods

Fifteen MCI patients were recruited for this study. Their egocentric and allocentric memory recall performances were tested through a navigation task with five different virtual reality (VR) assistive encoding navigation procedures (bodily, vision only, interactive allocentric map, reduced executive load, free navigation without cues). Bodily condition consisted of an immersive VR setup to engage self-motion cues, vision only condition consisted of passive navigation without interaction, in the interactive allocentric map condition patients could use a bird-view map, in the reduced executive load condition directional cues and attentional markers were employed, and during free navigation no aid was implemented.

Results

Bodily condition improved spatial memory compared to vision only and free navigation without cues. In addition, the interactive allocentric map was superior to the free navigation without cues. Surprisingly, the reduced executive load was comparable to vison only condition. Moreover, a detrimental impact of free navigation was observed on allocentric memory across testing trials.

Conclusions

These findings challenge the notion of an amodal representation of space in aging, suggesting that spatial maps can be influenced by the modality in which the environment was originally encoded.

A long-term ketogenic diet in young and aged rats has dissociable effects on prelimbic cortex and CA3 ensemble activity

Introduction

Age-related cognitive decline has been linked to distinct patterns of cellular dysfunction in the prelimbic cortex (PL) and the CA3 subregion of the hippocampus. Because higher cognitive functions require both structures, selectively targeting a neurobiological change in one region, at the expense of the other, is not likely to restore normal behavior in older animals. One change with age that both the PL and CA3 share, however, is a reduced ability to utilize glucose, which can produce aberrant neural activity patterns.

Methods

The current study used a ketogenic diet (KD) intervention, which reduces the brain's reliance on glucose, and has been shown to improve cognition, as a metabolic treatment for restoring neural ensemble dynamics in aged rats. Expression of the immediate-early genes Arc and Homer1a were used to quantify the neural ensembles that were active in the home cage prior to behavior, during a working memory/biconditional association task, and a continuous spatial alternation task.

Results

Aged rats on the control diet had increased activity in CA3 and less ensemble overlap in PL between different task conditions than did the young animals. In the PL, the KD was associated with increased activation of neurons in the superficial cortical layers, establishing a clear link between dietary macronutrient content and frontal cortical activity. The KD did not lead to any significant changes in CA3 activity.

Discussion

These observations suggest that the availability of ketone bodies may permit the engagement of compensatory mechanisms in the frontal cortices that produce better cognitive outcomes.

Hippocampal contributions to novel spatial learning are both age-related and age-invariant

Older adults show declines in spatial memory, although the extent of these alterations is not uniform across the healthy older population. Here, we investigate the stability of neural representations for the same and different spatial environments in a sample of younger and older adults using high-resolution functional MRI of the medial temporal lobes. Older adults showed, on average, lower neural pattern similarity for retrieving the same environment and more variable neural patterns compared to young adults. We also found a positive association between spatial distance discrimination and the distinctiveness of neural patterns between environments. Our analyses suggested that one source for this association was the extent of informational connectivity to CA1 from other subfields, which was dependent on age, while another source was the fidelity of signals within CA1 itself, which was independent of age. Together, our findings suggest both age-dependent and independent neural contributions to spatial memory performance.

Muscimol inactivation of dorsal striatum in young and aged male rats does not affect paired associates learning performance

Improving cognitive health for older adults requires understanding the neurobiology of age-related cognitive decline and the mechanisms underlying preserved cognition in old age. During spatial learning tasks, aged humans and rodents shift navigation preferences in favor of a stimulus-response learning strategy. This has been hypothesized to result from competitive interactions of the caudate nucleus/dorsal striatum (DS) memory system with the hippocampus (HPC)-dependent spatial/allocentric memory system. In support of this hypothesis, a recent study reported that inactivation of the DS in aged rodents rescued HPC-dependent spatial learning on a T-maze (Gardner, Gold, & Korol, 2020). Currently, it is unclear whether a shift from HPC-dependent to DS-dependent behavior also contributes to age-related cognitive decline outside of spatial learning and memory. To test the hypothesis that inactivation of the DS can restore age-related cognitive function outside of spatial behavior, the present study bilaterally inactivated the DS of young (n = 8) and aged (n = 7) rats during visuospatial paired associates learning (PAL). This study found that inactivation of the DS did not alter PAL performance in young or aged rats, but did alter a positive control, DS-dependent spatial navigation task. This observation suggests that elevated DS activity does not play a role in the decline of HPC-dependent PAL performance in aged male rats. Given the persistent tendencies of aged rodents toward DS-dependent learning, it will be worthwhile to explore further the coordination dynamics between the HPC and DS that may contribute to age-related cognitive decline. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Levodopa suppresses grid-like activity and impairs spatial learning in novel environments in healthy young adults

Accumulated evidence from animal studies suggests a role for the neuromodulator dopamine in memory processes, particularly under conditions of novelty or reward. Our understanding of how dopaminergic modulation impacts spatial representations and spatial memory in humans remains limited. Recent evidence suggests age-specific regulation effects of dopamine pharmacology on activity in the medial temporal lobe, a key region for spatial memory. To which degree this modulation affects spatially patterned medial temporal representations remains unclear. We reanalyzed recent data from a pharmacological dopamine challenge during functional brain imaging combined with a virtual object-location memory paradigm to assess the effect of Levodopa, a dopamine precursor, on grid-like activity in the entorhinal cortex. We found that Levodopa impaired grid cell-like representations in a sample of young adults (n = 55, age = 26-35 years) in a novel environment, accompanied by reduced spatial memory performance. We observed no such impairment when Levodopa was delivered to participants who had prior experience with the task. These results are consistent with a role of dopamine in modulating the encoding of novel spatial experiences. Our results suggest that dopamine signaling may play a larger role in shaping ongoing spatial representations than previously thought.

Hippocampal contributions to novel spatial learning are both age-related and age-invariant

Older adults show declines in spatial memory, although the extent of these alterations is not uniform across the healthy older population. Here, we investigate the stability of neural representations for the same and different spatial environments in a sample of younger and older adults using high-resolution functional magnetic resonance imaging (fMRI) of the medial temporal lobe. Older adults showed, on average, lower neural pattern similarity for retrieving the same environment and more variable neural patterns compared to young adults. We also found a positive association between spatial distance discrimination and the distinctiveness of neural patterns between environments. Our analyses suggested that one source for this association was the extent of informational connectivity to CA1 from other subfields, which was dependent on age, while another source was the fidelity of signals within CA1 itself, which was independent of age. Together, our findings suggest both age-dependent and independent neural contributions to spatial memory performance.

Dissociating effects of aging and genetic risk of sporadic Alzheimer's disease on path integration

Path integration is a spatial navigation ability that requires the integration of information derived from self-motion cues and stable landmarks, when available, to return to a previous location. Path integration declines with age and Alzheimer's disease (AD). Here, we sought to separate the effects of age and AD risk on path integration, with and without a landmark. Overall, 279 people participated, aged between 18 and 80 years old. Advanced age impaired the appropriate use of a landmark. Older participants furthermore remembered the location of the goal relative to their starting location and reproduced this initial view without considering that they had moved in the environment. This lack of adaptative behavior was not associated with AD risk. In contrast, participants at genetic risk of AD (apolipoprotein E ε4 carriers) exhibited a pure path integration deficit, corresponding to difficulty in performing path integration in the absence of a landmark. Our results show that advanced-age impacts landmark-supported path integration, and that this age effect is dissociable from the effects of AD risk impacting pure path integration.

Route sequence knowledge supports the formation of cognitive maps

In this study, we examined the extent to which knowledge about the sequence of places encountered during route learning supports the formation of a metric cognitive map. In a between subjects design, participants learned a route until they could navigate it independently without error whilst also learning information about either the identity of places along the route (Recognition Learning condition) or the sequence of places along the route (Sequence Learning condition). In a follow-up Reconstruction of Order Task, we confirmed that participants in the Sequence Learning condition had more accurate route sequence knowledge than those in the Recognition Learning condition, despite requiring the same overall number of trials to learn the route. Participants then completed a Pointing Task to assess the quality of their cognitive map of the environment. Both groups performed above chance level, showing incidental encoding of metric information, but the Sequence Learning group produced significantly lower pointing errors than the Recognition Learning group. Further, we found that route distance between pairs of places was a strong predictor of pointing error in both groups, whilst Euclidean distance between places was a significant, but weak, predictor only for the Sequence Learning condition. The results of this study demonstrate that discrete route sequence knowledge directly supports the formation of metric cognitive maps. We consider how the results are best explained by interactions between striatal route representations and hippocampal metric representations, centered around the sequence of places acting as a scaffold for the encoding of metric information.

Components of navigation ability and their predictors in a community-dwelling sample of older adults

Introduction: Navigation, as a complex skill important for independent living, requires a variety of cognitive processes. Current scales tapping components are lengthy and can be burdensome for older adults. Methods: Community-dwelling older adults (n = 380, age 60-90 years) completed an online survey tapping wayfinding, being lost navigating, and needing help navigating. Participants then completed objective measures of navigation ability and self-reported memory ability. Cronbach's α was calculated for navigation subscales consisting of subsets of the Wayfinding Questionnaire and Santa Barbara Sense of Direction Questionnaire, and an exploratory factor analysis (EFA) was conducted. Regression analyses were used to test whether objective navigation, memory, and demographic information navigation predicted navigation subscale performance. Results: Each of the individual subscales demonstrated high reliability. EFA generated five unique factors: routing, mental mapping, navigation in near vicinities, feeling lost in far vicinities, and needing help in far vicinities. Across regression analyses, memory, gender, and performance on the Spatial Orientation Test were significant predictors. Discussion: Navigation is a multi-faceted construct that can be reliably measured using concise surveys. Further research is necessary to understand the intricacies of aging and navigation.

Navigability of Residential Care Homes From Residents', Family Members', and Staff's Points of View: The Residential Care Home Navigability Scale

BACKGROUND AND OBJECTIVES

Navigational skills display clear signs of decline with increasing age, especially in pathological aging. Therefore, navigability-the extent to which destinations can be reached with reasonable effort and time-should be considered in residential care home design. We aimed to develop a scale assessing environmental features (i.e., indoor visual differentiation, signage, and layout) for navigability in residential care homes: the Residential Care Home Navigability (RCHN) scale. To this end, we examined whether navigability and its factors were associated with a sense of direction within the residential care homes to different degrees for older adult residents, caregivers, and staff. The relationship between navigability and residential satisfaction was also considered.

RESEARCH DESIGN AND METHODS

A sample of 523 participants (230 residents, 126 family caregivers, and 167 staff members) responded to the RCHN, assessed their sense of orientation and general satisfaction, and performed a pointing task.

RESULTS

Results confirmed the RCHN scale's 3-level factor structure, good reliability, and validity. A subjective sense of direction, but not pointing task performance, was associated with navigability and its factors. In particular, visual differentiation is positively associated with a sense of direction regardless of group, whereas signage and layout contributed to a better experience of a sense of direction, especially among older residents. Navigability was not related to residents' satisfaction.

DISCUSSION AND IMPLICATIONS

Navigability supports perceived orientation in residential care homes, especially for older residents. Moreover, the RCHN is a reliable tool for the assessment of RCHN, with important implications for minimizing spatial disorientation through environmental interventions.

Age differences in spatial memory are mitigated during naturalistic navigation

Spatial navigation deficits in older adults are well documented. These findings are often based on experimental paradigms that require using a joystick or keyboard to navigate a virtual desktop environment. In the present study, we investigated whether age differences in spatial memory are attenuated when tested in a more naturalistic and ambulatory virtual environment. In Experiment 1, cognitively normal young and older adults navigated a virtual variant of the Morris Water Maze task in each of two virtual reality (VR) conditions: a desktop VR condition which required using a mouse and keyboard to navigate and an immersive and ambulatory VR condition which permitted unrestricted locomotion. In Experiment 2, we examined whether age- and VR-related differences in spatial performance were affected by the inclusion of additional spatial cues in an independent sample of young and older adults. In both experiments, older adults navigated to target locations less precisely than did younger individuals in the desktop condition, replicating numerous prior studies. These age differences were significantly attenuated, however, when tested in the fully immersive and ambulatory environment. These findings underscore the importance of developing naturalistic and ecologically valid measures of spatial memory and navigation, especially when performing cross-sectional studies of cognitive aging.

Navigating the Maze: Caregivers Perception on Design Elements to Improve Wayfinding for Older Adults With Dementia in Long-Term Care Facilities

AIM

The main purpose of this research is to understand the wayfinding experience of older adults with dementia in long-term care facilities and identifying environmental design elements that support older adults' spatial abilities.

BACKGROUND

Wayfinding problems are the earliest symptoms of dementia, and older adults with cognitive impairment are more likely to get lost in the community and consequences cause psychological responses such as insecurity, agitation, and falling in their environment.

METHOD

The research used data collected from 30 caregivers of two long-term care facilities in the Midwest through a survey and interview on their perceptions of wayfinding design elements.

RESULTS

The research findings highlighted on caregivers' perception on wayfinding experience of older adults with dementia. The findings show a significant difference between importance and satisfaction on floor pattern and visibility in the facilities. Study indicated that glass partitions in the middle of the hall and corridor can create visual obstruction for older adults and barrier for staff as well to keep visual track on them. The qualitative study revealed that different colored doors for individual patient room in a memory care enhance older adults' wayfinding abilities. In addition, in case of multisensory stimuli, noise and smell can improve their wayfinding abilities as well.

CONCLUSION

The conclusion of the study highlights the importance of understanding the design elements that can be effective in creating a safer environment for older adults with dementia.

Real-World Navigation With Application: Characteristics of Gaze Behavior and Associated Factors in Older Adults

Background and Objectives

Advancing age might impair real-world navigation ability. The use of mobile devices by older adults has grown rapidly in recent years. Navigation applications (apps) in mobile devices may facilitate the freedom of outings for older adults. Our aim is to investigate age-related differences in real-world app-based navigation walking in terms of accuracy, efficiency, and gaze behavior; and to explore clinical factors associated with navigation walking in older adults.

Research Design and Methods

A total of 20 community-dwelling older adults and 16 young adults completed a route navigation task using a navigation app while recording their gaze behavior. Outcomes were compared in both groups and a general linear regression was used to explore clinical factors associated with app-based navigation walk in older adults.

Results

Compared with young participants, older participants had more stops and root errors and less fixation time, smaller amplitude of saccades. Additionally, older adults were more likely to glance at their smartphones while app-based navigation walking. Furthermore, gait speed and the following assessment scores were significantly associated with navigation walking in older adults: Mini-Mental State Examination, Life-Space Assessment, and the short version of the Mobile Device Proficiency Questionnaire.

Discussion and Implications

For app-based navigation walks, differences in accuracy and gaze behavior were found to exist with age. Additionally, efficient real-world navigation walks in older adults require the extent of life space and proficiency with mobile devices, along with walking speed and cognitive function. It is possible that age-related functional decline, such as the visual field and shifting attention between mobile devices and the real world, may have influenced the results. The study also suggests the need to understand the level of proficiency with mobile devices so that older adults can continue to go out freely. These findings give the basis for providing older adults with appropriate navigation assistance.

Acute stress impairs visual path integration

Acute stress exerts substantial effects on episodic memory, which are often mediated by glucocorticoids, the end-product of the hypothalamic-pituitary-adrenal axis. Surprisingly little is known, however, about the influence of acute stress on human spatial navigation. One specific navigational strategy is path integration, which is linked to the medial entorhinal cortex, a region harboring glucocorticoid receptors and thus susceptible for stress effects. Here, we investigated effects of acute stress on path integration performance using a virtual homing task. We divided a sample of healthy young male participants into a stress group (nstress = 32) and a control group (ncontrol = 34). The stress group underwent the socially evaluated cold-pressor test, while the control group underwent a non-stressful control procedure. Stress induction was confirmed via physiological and subjective markers, including an increase of salivary cortisol concentrations. We applied linear mixed models to investigate the effect of acute stress on path integration depending on task difficulty and the presence or absence of spatial cues. These analyses revealed that stress impaired path integration especially in trials with high difficulty and led to greater decline of performance upon removal of spatial cues. Stress-induced deficits were strongly related to impaired distance estimation, and to a lesser extent to compromised rotation estimation. These behavioral findings are in accordance with the hypothesis that acute stress impairs path integration processes, potentially by affecting the entorhinal grid cell system. More generally, the current data suggests acute stress to impair cognitive functions mediated by medial temporal lobe regions outside the hippocampus.

MSK1 is required for the beneficial synaptic and cognitive effects of enriched experience across the lifespan

Positive experiences, such as social interaction, cognitive training and physical exercise, have been shown to ameliorate some of the harms to cognition associated with ageing. Animal models of positive interventions, commonly known as environmental enrichment, strongly influence neuronal morphology and synaptic function and enhance cognitive performance. While the profound structural and functional benefits of enrichment have been appreciated for decades, little is known as to how the environment influences neurons to respond and adapt to these positive sensory experiences. We show that adult and aged male wild-type mice that underwent a 10-week environmental enrichment protocol demonstrated improved performance in a variety of behavioural tasks, including those testing spatial working and spatial reference memory, and an enhancement in hippocampal LTP. Aged animals in particular benefitted from enrichment, performing spatial memory tasks at levels similar to healthy adult mice. Many of these benefits, including in gene expression, were absent in mice with a mutation in an enzyme, MSK1, which is activated by BDNF, a growth factor implicated in rodent and human cognition. We conclude that enrichment is beneficial across the lifespan and that MSK1 is required for the full extent of these experience-induced improvements of cognitive abilities, synaptic plasticity and gene expression.

Spatial navigation: Alzheimer's pathology disrupts movement-based navigation

All animals use two different strategies to navigate: idiothetic or movement-based navigation, and allothetic or landmark-based navigation. A new study reveals that compromised idiothetic navigation underlies disrupted grid cell coding in an early stage Alzheimer's disease mouse model.