What do we know about aging and spatial cognition? Reviews and perspectives

Studying Individual Differences in Spatial Cognition Through Differential Item Functioning Analysis

Background: In the field of spatial cognition, the study of individual differences represents a typical research topic. Gender and age have been prominently investigated. A promising statistical technique used to identify the different responses to items in relation to different group memberships is the Differential Item Functioning Analysis (DIF). The aim of the present study was to investigate the DIF of the Landmark positioning on a Map (LPM) task, across age groups (young and elderly) and gender, in a sample of 400 healthy human participants. Methods: LPM is a hometown map completion test based on well-known and familiar landmarks used to assess allocentric mental representations. DIF was assessed on LPM items two times: on categorical (i.e., positions) and coordinate (i.e., distances) scores, separately. Results: When positions and distances were difficult to assess with respect to the intended reference point, the probability to endorse the items seemed to get worse for the elderly compared to the younger participants. Instead other features of landmarks (high pleasantness, restorativeness) seemed to improve the elderly performance. A gender-related improvement of probability to endorse distance estimation of some landmarks, favoring women, emerged, probably associated with their repeated experiences with those landmarks. Overall, the complexity of the task seemed to have a differential impact on young and elderly people while gender-oriented activities and places seemed to have a differential impact on men and women. Conclusions: For the first time DIF was applied to a spatial mental representation task, based on the schematic sketch maps of the participants. The application of DIF to the study of individual differences in spatial cognition should become a systematic routine to early detect differential items, improving knowledge, as well as experimental control, on individual differences.

Rationale and Design of the PAIRED Trial: Partnered Dance Aerobic Exercise as a Neuroprotective, Motor, and Cognitive Intervention in Parkinson's Disease

Parkinson's disease (PD), an intractable condition impairing motor and cognitive function, is imperfectly treated by drugs and surgery. Two priority issues for many people with PD are OFF-time and cognitive impairment. Even under best medical management, three-fourths of people with PD experience “OFF-time” related to medication-related motor fluctuations, which severely impacts both quality of life and cognition. Cognitive deficits are found even in newly diagnosed people with PD and are often intractable. Our data suggest that partnered dance aerobic exercise (PDAE) reduces OFF-time on the Movement Disorders Society Unified Parkinson Disease Rating Scale-IV (MDS-UPDRS-IV) and ameliorates other disease features, which motivate the PAIRED trial. PDAE provides AE during an improvisational, cognitively engaging rehabilitative physical activity. Although exercise benefits motor and cognitive symptoms and may be neuroprotective for PD, studies using robust biomarkers of neuroprotection in humans are rare. We propose to perform a randomized, controlled trial in individuals with diagnosed mild–moderate PD to compare the efficacy of PDAE vs. walking aerobic exercise (WALK) for OFF-time, cognition, and neuroprotection. We will assess neuroprotection with neuromelanin-sensitive MRI (NM-MRI) and iron-sensitive (R2^*) MRI sequences to quantify neuromelanin loss and iron accumulation in substantia nigra pars compacta (SNc). We will use these biomarkers, neuromelanin loss, and iron accumulation, as tools to chart the course of neurodegeneration in patients with PD who have undergone long-term (16 months) intervention. We will randomly assign 102 individuals with mild–moderate PD to 16 months of PDAE or WALK. The 16-month intervention period will consist of Training (3 months of biweekly sessions) and Maintenance (13 months of weekly sessions) phases. We will assess participants at baseline, 3 months (immediately post-Training), and 16 months (immediately post-Maintenance) for OFF-time and behaviorally and physiologically measured cognition. We will acquire NM-MRI and R2^* imaging data at baseline and 16 months to assess neuroprotection. We will (1) examine effects of Training and Maintenance phases of PDAE vs. WALK on OFF-time, (2) compare PDAE vs. WALK at 3 and 16 months on behavioral and functional MRI (fMRI) measures of spatial cognition, and (3) compare PDAE vs. WALK for effects on rates of neurodegeneration.

Differences in Encoding Strategy as a Potential Explanation for Age-Related Decline in Place Recognition Ability

The ability to recognise places is known to deteriorate with advancing age. In this study, we investigated the contribution of age-related changes in spatial encoding strategies to declining place recognition ability. We recorded eye movements while younger and older adults completed a place recognition task first described by Muffato et al. (2019). Participants first learned places, which were defined by an array of four objects, and then decided whether the next place they were shown was the same or different to the one they learned. Places could be shown from the same spatial perspective as during learning or from a shifted perspective (30° or 60°). Places that were different to those during learning were changed either by substituting an object in the place with a novel object or by swapping the locations of two objects. We replicated the findings of Muffato et al. (2019) showing that sensitivity to detect changes in a place declined with advancing age and declined when the spatial perspective was shifted. Additionally, older adults were particularly impaired on trials in which object locations were swapped; however, they were not differentially affected by perspective changes compared to younger adults. During place encoding, older adults produced more fixations and saccades, shorter fixation durations, and spent less time looking at objects compared to younger adults. Further, we present an analysis of gaze chaining, designed to capture spatio-temporal aspects of gaze behaviour. The chaining measure was a significant predictor of place recognition performance. We found significant differences between age groups on the chaining measure and argue that these differences in gaze behaviour are indicative of differences in encoding strategy between age groups. In summary, we report a direct replication of Muffato et al. (2019) and provide evidence for age-related differences in spatial encoding strategies, which are related to place recognition performance.

Use of an Indoor Navigation System by Sighted and Blind Travelers

This article first reviews the pros and cons of current accessible indoor navigation systems and then describes a study using commercial smart devices to navigate routes through a complex building. Our interest was in comparing performance when using real-time narrative descriptions (system-aided condition) vs. a memory-based condition where the same narrative information was only provided to users from the route's origin. We tested two groups of blind and visually impaired (BVI) users, including people above and below 60 years of age, as well as a third sighted control group. Evaluating older BVI participants is important, as the majority of vision loss is age-related, yet navigation performance using access technology is rarely studied with this demographic. Behavioral results demonstrated that access to real-time (system-aided) information led to better navigation accuracy and greater confidence by blind users compared to the information-matched memory condition. Performance for blind participants over 60 years old was nearly identical with their younger peers—an important outcome supporting the efficacy of using navigational technologies by this fast-growing population. Route completion accuracy and requests for assistance did not reliably differ between blind and sighted participants when using the system, suggesting that access to narrative route information led to functionally equivalent navigation behavior, irrespective of visual status. Survey results revealed strong user support for real-time information and provided important guidance for future interface refinements.

Age-related differences in visual encoding and response strategies contribute to spatial memory deficits

Successful navigation requires memorising and recognising the locations of objects across different perspectives. Although these abilities rely on hippocampal functioning, which is susceptible to degeneration in older adults, little is known about the effects of ageing on encoding and response strategies that are used to recognise spatial configurations. To investigate this, we asked young and older participants to encode the locations of objects in a virtual room shown as a picture on a computer screen. Participants were then shown a second picture of the same room taken from the same (0°) or a different perspective (45° or 135°) and had to judge whether the objects occupied the same or different locations. Overall, older adults had greater difficulty with the task than younger adults although the introduction of a perspective shift between encoding and testing impaired performance in both age groups. Diffusion modelling revealed that older adults adopted a more conservative response strategy, while the analysis of gaze patterns showed an age-related shift in visual-encoding strategies with older adults attending to more information when memorising the positions of objects in space. Overall, results suggest that ageing is associated with declines in spatial processing abilities, with older individuals shifting towards a more conservative decision style and relying more on encoding target object positions using room-based cues compared to younger adults, who focus more on encoding the spatial relationships among object clusters.

Design, synthesis and biological evaluation of triazole-oxadiazole conjugates for the management of cognitive dysfunction

Acetylcholinesterase has been a promising target for the development of putative therapeutics against cognitive decline. The deleterious effect of oxidative stress on the learning and memory paradigms of an individual has also been well documented. In view of this, the present study demonstrates the design, synthesis and pharmacological evaluation of triazole-oxadiazole conjugates. Eighteen novel hybrids (6-23) have been synthesised by employing suitable synthetic procedures and characterized by various spectral and elemental techniques. Further these synthesised compounds were evaluated against behavioural alterations using step down passive avoidance and escape learning protocol at a dose of 0.5 mg/kg with reference to the standard, donepezil. All the synthesised compounds were evaluated for their in vitro acetylcholinesterase (AChE) inhibition at five different concentrations using mice brain homogenate as the source of the enzyme. Biochemical estimation of markers of oxidative stress (lipid peroxidation, superoxide dismutase, glutathione and catalase) has also been carried out to assess the role of synthesised molecules on the oxidative damage induced by scopolamine. The compounds 13, 17 and 23 displayed appreciable activity towards acetylcholinesterase inhibition. These compounds also decreased scopolamine induced oxidative stress, thus serving as promising leads for the amelioration of oxidative stress induced cognitive decline. The molecular docking study performed to predict the binding mode of the compounds also suggested that these compounds bind appreciably to the amino acids present in the active site of the recombinant human acetylcholinesterase (rhAChE). The results indicated that these compounds could be further traversed as inhibitors of AChE and oxidative stress for the treatment of cognitive dysfunction.

Are age-related deficits in route learning related to control of visual attention?

Typically aged adults show reduced ability to learn a route compared to younger adults. In this experiment, we investigate the role of visual attention through eye-tracking and engagement of attentional resources in age-related route learning deficits. Participants were shown a route through a realistic virtual environment before being tested on their route knowledge. Younger and older adults were compared on their gaze behaviour during route learning and on their reaction time to a secondary probe task as a measure of attentional engagement. Behavioural results show a performance deficit in route knowledge for older adults compared to younger adults, which is consistent with previous research. We replicated previous findings showing that reaction times to the secondary probe task were longer at decision points than non-decision points, indicating stronger attentional engagement at navigationally relevant locations. However, we found no differences in attentional engagement and no differences for a range of gaze measures between age groups. We conclude that age-related changes in route learning ability are not reflected in changes in control of visual attention or regulation of attentional engagement.

Age-related prefrontal cortex activation in associative memory: An fNIRS pilot study

Older adults typically perform more poorly than younger adults in free recall memory tests. This age-related deficit has been linked to decline of brain activation and brain prefrontal lateralization, which may be the result of compensatory mechanisms. In the present pilot study, we investigated the effect of age on prefrontal cortex (PFC) activation during performance of a task that requires memory associations (temporal vs. spatial clustering), using functional Near-Infrared Spectroscopy (fNIRS). Ten younger adults, ten cognitively high-performing older individuals, and ten low-performing older individuals completed a free recall task, where either a temporal or spatial strategy (but not both simultaneously) could be employed to retrieve groups of same-category stimuli, whilst changes in PFC hemodynamics were recorded by means of a 12-channel fNIRS system. The results suggest PFC activation, and right lateralization specific to younger adults. Moreover, age did not affect use of memory organization, given that temporal clustering was preferred over spatial clustering in all groups. These findings are in line with previous literature on the aging brain and on temporal organization of memory. Our results also suggest that the PFC may be specifically involved in memory for temporal associations. Future research may consider whether age-related deficits in temporal organization may be an early sign of PFC pathology and possible neurodegeneration.

Psychometric Tests and Spatial Navigation: Data From the Baltimore Longitudinal Study of Aging

Spatial cognition is the process by which individuals interact with their spatial environment. Spatial cognition encompasses the specific skills of spatial memory, spatial orientation, and spatial navigation. Prior studies have shown an association between psychometric tests of spatial ability and self-reported or virtual measures of spatial navigation. In this study, we examined whether psychometric spatial cognitive tests predict performance on a dynamic spatial navigation task that involves movement through an environment. We recruited 151 community-dwelling adult participants [mean (SD) age 69.7 (13.6), range 24.6–93.2] from the Baltimore Longitudinal Study of Aging (BLSA). Spatial navigation ability was assessed using the triangle completion task (TCT), and two quantities, the angle and distance of deviation, were computed. Visuospatial cognitive ability was assessed primarily using the Card Rotations Test. Additional tests of executive function, memory, and attention were also administered. In multiple linear regression analyses adjusting for age, sex, race, and education, cognitive tests of visuospatial ability, executive function, and perceptual motor speed and integration were significantly associated with spatial navigation, as determined by performance on the TCT. These findings suggest that dynamic spatial navigation ability is related to spatial memory, executive function, and motor processing speed.

Cognitive Impairment in Old Age

Abstract. A decline in cognitive functioning is part of physiological aging. Accelerated cognitive decline is frequently linked to pathological changes, mostly due to Alzheimer’s Disease (AD), but is present also in Mild Cognitive Impairment (MCI) which is a predictor of transition to dementia. This review aims to summarize possible preventive biological and psychological treatments in different stages of lifespan to avoid more rapid cognitive decline and prevent pathological aging. Psychophysiological approaches aim to prevent brain damage and inflammation, two factors playing probably a major role in middle and old age. Interventions on working memory and imagery, using “cognitive reserve,” are beneficial for tolerating neuropathological age-related changes. Some controversial results are outlined, suggesting explanations for the inconsistency of findings. Although clear evidence from interventional studies is lacking, it seems that multi-domain interventions should be recommended to avoid or delay cognitive decline.

Association Between Motor Subtype and Visuospatial and Executive Function in Mild-Moderate Parkinson Disease

OBJECTIVE

To compare participants with Parkinson disease (PD) motor subtypes, postural instability and gait difficulty (PIGD) (n=46) and tremor dominant (TD) (n=28), in cognitive and motor-cognitive assessments with the purpose of identifying associations between subtype and visuospatial, whole-body spatial, inhibition and/or switching, and planning and/or organizational aspects of cognitive and motor-cognitive function.

DESIGN

Retrospective cohort study. Fisher exact test was used for categorical variables, while 2-sample independent t tests were used to analyze continuous variables.

SETTING

Assessments took place at Emory University.

PARTICIPANTS

Participants (N=72) were 40 years and older, had a clinical diagnosis of PD, exhibited 3 of the 4 cardinal signs of PD, had shown benefit from antiparkinsonian medications, and were in Hoehn and Yahr stages I-IV. Participants could walk 3 m or more with or without assistance.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Balance and mobility tests included Fullerton Advanced Balance Scale and the time needed to turn 360 degrees. Cognitive assessments included Montreal Cognitive Assessment, Brooks Spatial Memory Task, Color-Word Interference Test, Tower of London, Trail Making Test, Corsi Blocks, Serial 3s Subtraction, and Body Position Spatial Task. Motor-cognitive function measures included Four Square Step Test and Timed Up and Go.

RESULTS

Participants with PIGD performed lower than those with TD symptoms on mental status (P=.005), spatial memory (P=.027), executive function (P=.0001-.034), and visuospatial ability (P=.048).

CONCLUSIONS

Findings suggest that PIGD subtype is linked to greater deficits in spatial cognition, attentional flexibility and organizational planning, and whole-body spatial memory domains. These findings support the need for more personalized approaches to clinically managing PD.

Inhibition of glycogen synthase kinase 3β improves cognitive function in aged mice by upregulating claudin presences in cerebral endothelial cells

Glycogen synthase kinase-3β (GSK-3β), a serine/threonine protein kinase, is widely distributed in mammalian brains. Since GSK-3β plays a vital role in the development of neurodegenerative disorders, the present study was designed to investigate the role of GSK-3β in the blood-brain barrier (BBB) permeability in aged mice. Morris water maze test was used to examine mouse cognitive function. BBB permeability was examined by the leakage of fluorescence signals of low-molecular weight dextran. GSK-3β inhibitor, 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8), was administrated in aged mice and in cultured mouse brain microvascular endothelial cells (bEnd.3). Compared with young mice, aged mice had increased leftover signals of dextran in the hippocampus and a lower score in the maze test, suggesting that aged mice have abnormal leakage of BBB and cognitive dysfunction. The protein expression of Toll-like receptor 4 (TLR4) was increased, whereas the protein expressions of junction proteins (claudin1 and claudin5) were reduced in endothelial cells of BBB in aged mice. Phosphorylated level of serine 9, an inhibitory residue in GSK-3β protein, was decreased. TDZD-8 treatment downregulated TLR4 protein expression, upregulated claudin1 and claudin5 protein expressions, and significantly improved cognitive function in aged mice. In bEnd.3 cells, TDZD-8 treatment reduced TLR4 expression and increased claudin5 expression in cells stimulated with lipopolysaccharides. In conclusion, the inhibition of GSK-3β activity downregulates aging-induced TLR4 expression and restores the BBB integrity, resulting in the improvement of cognitive function in aged mice.

How age relates to spatial navigation performance: Functional and methodological considerations

Aging effects have often been reported for spatial navigation performance. Moreover, navigation performance is thought to be an early marker of pathological aging. Yet, the cognitive complexity of navigation and large individual variation in healthy population make it difficult to pinpoint the precise aging mechanisms involved. We performed a systematic literature review with specific attention to functional dissociation between the tasks used and methodological characteristics. The literature search resulted in 39 articles in which age comparisons were made for large-scale navigation measures. Outcomes were categorized into the domains of landmark, location (egocentric and allocentric), and path knowledge (route and survey). Results indicate that clear functional dissociation exists between these navigation knowledge domains. Aging effects are found for path knowledge most convincingly, while landmark and egocentric location knowledge are frequently omitted in assessment. The participant samples reported often neglect adult, middle aged participants, while this group could be highly informative to the aging process as well. Moreover, having a clear image of age-related performance across the lifespan could be a valuable addition towards the early detection of pathological aging through navigation performance.

Large-scale assessment of human navigation ability across the lifespan

Navigation ability is particularly sensitive to aging. Evidence of aging patterns is largely restricted to comparing young adults and elderly and limited in the variety of navigation tasks used. Therefore, we designed a novel task battery to assess navigation ability in a very large, representative sample (N = 11,887, 8–100 years). The main aim was to measure navigation ability across the lifespan in a brief, yet comprehensive manner. Tasks included landmark knowledge, egocentric and allocentric location knowledge, and path knowledge for a route and survey perspective. Additionally, factors that potentially contribute to navigation ability were considered; gender, spatial experience and spatial anxiety. Increase in performance with age in children was found for allocentric location knowledge and for route-based path knowledge. Age related decline was found for all five tasks, each with clearly discernible aging patterns, substantiated the claim that each task distinctively contributes to the assessment of navigation ability. This study provides an in depth examination of navigation ability across dissociable functional domains and describes cognitive changes across the lifespan. The outcome supports the use of this task battery for brief assessment of navigation for experimental and clinical purposes.

The differential effect of normal and pathological aging on egocentric and allocentric spatial memory in navigational and reaching space

BACKGROUND

Topographical disorientation (TD) refers to a particular condition which determines the loss of spatial orientation, both in new and familiar environments. TD and spatial memory impairments occur relatively early as effect of cognitive decline in aging, even in prodromal stages of dementia, namely mild cognitive impairment (MCI).

AIMS

(a) To show that components linked to the recall of familiar spatial knowledge are relatively spared with respect to the learning of unfamiliar ones in normal aging, while they are not in MCI, and (b) to investigate gender differences for their impact on egocentric and allocentric frames of reference.

METHOD

Forty young participants (YC), 40 healthy elderly participants (HE), 40 elderly participants with subjective memory complaints (SMC), and 40 elderly with probable MCI were administered with egocentric and allocentric familiar tasks, based on the map of their hometown, and with egocentric and allocentric unfamiliar tasks, based on new material to be learned. A series of general linear models were used to analyze data.

RESULTS

No group differences were found on egocentric task based on familiar information. MCI performed worse than the other groups on allocentric tasks based on familiar information (YC = HE = SMC > MCI). Significant differences emerged between groups on egocentric and allocentric tasks based on unfamiliar spatial information (YC > HE = SMC > MCI). A gender difference was found, favoring men on allocentric unfamiliar task.

CONCLUSION

Familiarity of spatial memory traces can represent a protective factor for retrospective components of TD in normal aging. Conversely, using newly learned information for assessment may lead to overestimating TD severity.

Older Adults Show Less Flexible Spatial Cue Use When Navigating in a Virtual Reality Environment Compared With Younger Adults

Daily life requires accurate navigation, and thus better understanding of aging on navigational abilities is critical. Importantly, the use of spatial properties by older and younger adults remains unclear. During this study, younger and older human adults were presented with a virtual environment in which they had to navigate a series of hallways. The hallways provided 2 general types of spatial information: geometric, which included distance and directional turns along a learned route, and featural, which included landmarks situated along the route. To investigate how participants used these different cue types, geometric and/or landmark information was manipulated during testing trials. Data from 40 younger (20 women) and 40 older (20 women) adults were analyzed. Our findings suggest that (1) both younger and older adults relied mostly on landmarks to find their way, and (2) younger adults were better able to adapt to spatial changes to the environment compared with older adults.

Does it still fit? - Adapting affordance judgments to altered body properties in young and older adults

Actor-related affordance judgments are decisions about potential actions that arise from environmental as well as bodily and cognitive conditions. The system can be challenged by sudden changes to otherwise rather stable actor references e.g. due to accidental bodily injuries or due to brain damage and resulting motor and cognitive constraints. The current study investigated adaptation to suddenly artificially altered body properties and its reversibility in healthy young versus older adults. Participants were asked to judge whether they would be able to fit their hand through a given horizontal opening (Aperture Task). Body alterations were induced by equipping participants with one hand splint for 24 hours that enlarged the hand in width and height. Participants were tested before and directly after putting the splint on as well as after a habituation period of 24 hours. To assess reversibility, participants were tested again directly after removing the splint and one day later. Judgment accuracy values and detection theory measures were reported. Both, young and older adults judged more conservatively when body properties were altered compared to initial judgments for normal body properties. Especially older adults showed major difficulties in such quick adaptation. Older adults' judgment accuracy as well as perceptual sensitivity were significantly lowered when body properties were suddenly altered. Importantly, lowered judgment performance occurred for both, the splinted as well as the non-splinted hand in older adults. Only after 24 hours of habituation, older adults tended to regain initial performance levels showing adaptive behavior to the altered condition. Removing the hand splint for one day was sufficient to reverse these adaptive effects. Our study results suggest that aging slows down adaptation to sudden bodily alterations affecting actor-related affordance judgments. We propose that these altered processes may go along with uncertainty and a heightened concern about potential consequences of misjudgments. Clearly, future studies are needed to further elucidate the underlying processes of adaptation in affordance judgments. These may reveal major implications for the aging society and its associated problems with an increased risk of falling or stroke related bodily constraints.

The orientation of young and older adults' mental representations of their home town with familiar and new landmarks

Familiarity with an environment produces refined mental representations in adults of all ages, but it is not clear whether these representations tend to have a north-up orientation and whether familiarity facilitates the learning of new spatial information, especially in ageing. Thirty-two young and 32 older adults studied a map of their home town that included familiar and new fictitious landmarks, then performed pointing tasks, some aligned with the cardinal points south-north (SN), and others counter-aligned, north-south (NS). A measure of visuo-spatial working memory (VSWM) and a questionnaire on pleasure in exploring were also administered. The results showed that performance was better when pointing SN than NS (alignment effect), whereas pointing performance for familiar landmarks was similar for SN and NS alignments (no alignment effect). No interaction involving age was found. VSWM emerged as a significant predictor of pointing performance. Spatial mental representations of familiar environments are elaborate and flexible as regards familiar landmarks, in both young and older adults; and a familiar layout does not seem to enhance older adults' spatial memory as regards new landmarks.

Age-Related Differences in Functional and Structural Connectivity in the Spatial Navigation Brain Network

Spatial navigation involves multiple cognitive processes including multisensory integration, visuospatial coding, memory, and decision-making. These functions are mediated by the interplay of cerebral structures that can be broadly separated into a posterior network (subserving visual and spatial processing) and an anterior network (dedicated to memory and navigation planning). Within these networks, areas such as the hippocampus (HC) are known to be affected by aging and to be associated with cognitive decline and navigation impairments. However, age-related changes in brain connectivity within the spatial navigation network remain to be investigated. For this purpose, we performed a neuroimaging study combining functional and structural connectivity analyses between cerebral regions involved in spatial navigation. Nineteen young (μ = 27 years, σ = 4.3; 10 F) and 22 older (μ = 73 years, σ = 4.1; 10 F) participants were examined in this study. Our analyses focused on the parahippocampal place area (PPA), the retrosplenial cortex (RSC), the occipital place area (OPA), and the projections into the visual cortex of central and peripheral visual fields, delineated from independent functional localizers. In addition, we segmented the HC and the medial prefrontal cortex (mPFC) from anatomical images. Our results show an age-related decrease in functional connectivity between low-visual areas and the HC, associated with an increase in functional connectivity between OPA and PPA in older participants compared to young subjects. Concerning the structural connectivity, we found age-related differences in white matter integrity within the navigation brain network, with the exception of the OPA. The OPA is known to be involved in egocentric navigation, as opposed to allocentric strategies which are more related to the hippocampal region. The increase in functional connectivity between the OPA and PPA may thus reflect a compensatory mechanism for the age-related alterations around the HC, favoring the use of the preserved structural network mediating egocentric navigation. Overall, these findings on age-related differences of functional and structural connectivity may help to elucidate the cerebral bases of spatial navigation deficits in healthy and pathological aging.

Age-related preference for geometric spatial cues during real-world navigation

Ageing effects on spatial navigation are characterized mainly in terms of impaired allocentric strategies. However, an alternative hypothesis is that navigation difficulties in aged people are associated with deficits in processing and encoding spatial cues. We tested this hypothesis by studying how geometry and landmark cues control navigation in young and older adults in a real, ecological environment. Recordings of body and gaze dynamics revealed a preference for geometry-based navigation in older adults, and for landmark-based navigation in younger ones. While cue processing was associated with specific fixation patterns, advanced age manifested itself in a longer reorientation time, reflecting an unbalanced exploration-exploitation trade-off in scanning policies. Moreover, a battery of tests revealed a specific cognitive deficit in older adults with geometric preference. These results suggest that allocentric strategy deficits in ageing can result from difficulties related to landmark coding, and predict recovery of allocentric strategies in geometrically polarized environments.

Memory Decline and Behavioral Inflexibility in Aged Mice Are Correlated With Dysregulation of Protein Synthesis Capacity

Understanding the molecular mechanisms underlying age-associated cognitive impairments will not only contribute to our general knowledge about "aging" biology, but also provide insights for more effective strategies to prevent and improve the quality of life for both normal aging and pathological aging such as Alzheimer's disease (AD). Here we first assessed and compared the performance of cognition and synaptic plasticity in young (3-5-month old) and aged c57BL/6J mice (19-21 months old). Findings from behavioral tests demonstrated that old mice, compared to young mice, displayed impairments in spatial learning/memory, working memory, and behavioral flexibility. Further, synaptic electrophysiology experiments on hippocampal slices revealed that the early form of long-term potentiation (LTP, a synaptic model for memory formation) was inhibited in old mice. At the molecular level, biochemical assays on the hippocampus showed dysregulation of signaling pathways controlling protein synthesis capacity including: up-regulation of AKT-mTORC1-p70S6K signaling, which is associated with translation of terminal oligopyrimidine (TOP) class of mRNAs that encode translational machinery; hyper-phosphorylation of mRNA translational elongation factor 2 (eEF2) and its upstream regulator AMP-activated protein kinase (AMPK), indicating repression of general protein synthesis. Moreover, young and old mice exhibited similar brain levels of translational initiation factor 2α (eIF2α) phosphorylation, which is known to be increased in AD and linked to the disease pathophysiology. Thus, our data provide evidence at the molecular level to highlight the similarity and difference between normal and pathological aging, which may contribute to future studies on diagnostic/prognostic biomarkers for aging-related dementia syndromes.

Effects of Different Dietary Protocols on General Activity and Frailty of Male Wistar Rats During Aging

Dietary restriction (DR) is an important experimental paradigm for lifespan and healthspan extension, but its specific contribution regarding the type, onset, and duration are still debatable. This study was designed to examine the impact of different dietary protocols by assessing the behavioral changes during aging. We exposed male Wistar rats of various age to ad libitum (AL) or DR (60 per cent of AL daily intake) feeding regimens with different onsets. The impact of DR on locomotor activity, memory, and learning was examined in 12-, 18-, and 24-month-old treated animals and controls using open field and Y-maze tests. We have also evaluated the effects of different DR's through the quantification of animal frailty, using behavioral data to create the frailty score. Our results indicated that DR improves general animal activity and spatial memory and decreases frailty with the effect being highly dependent on DR duration and onset. Notably, life-long restriction started at young age had the most profound effect. In contrast, shorter duration and later onset of restricted diet had significantly lower or no impact on animal's behavior and frailty. This study signifies the importance of DR starting point and duration as critical determinants of DR effects on healthspan.

Trajectories of Physiological Brain Aging and Related Factors in People Aged from 20 to over-80

BACKGROUND/OBJECTIVE

In this study, we investigated a long-term trajectory of brain aging (from the 20 s to over-80) in cognitively normal (CN) individuals. We further determined whether differences in sex, education years, and apolipoprotein E ε 4 status affect age-related cortical thinning.

METHODS

A total of 2,944 CN individuals who underwent high-resolution (3.0-Tesla) magnetic resonance imaging were included in this study. Cortical thickness was measured using a surface-based method. Multiple linear regression analyses were performed to evaluate age-related cortical thinning and related factors.

RESULTS

Compared to those in their 20 s/30 s, participants in their 40 s showed thinning primarily in the medial and lateral frontal and inferior parietal regions, and cortical thinning occurred across most of the cortices with increasing age. Notably, the precuneus, inferior temporal and lateral occipital regions were relatively spared until later in life. Male and lower education years were associated with greater cortical thinning with distinct regional specificity.

CONCLUSION

Our findings provide an important clue to understanding the mechanism of age-related cognitive decline and new strategies for preventing the acceleration of pathological brain aging.

The influence of personality traits and facets on visuo-spatial task performance and self-assessed visuo-spatial inclinations in young and older adults

Aims

Personality traits are suggested to influence adults’ cognitive performance, but little is known about their association with visuo-spatial competence, in terms of those visuo-spatial abilities and inclinations crucial to remaining autonomous, especially with aging. This study newly investigated whether, and to what extent, major traits and narrower facets of personality influence young and older adults’ performance in the so-called objective visuo-spatial abilities (mental rotation and visuo-spatial working memory [VSWM]), and self-assessed visuo-spatial inclinations (pleasure and anxiety in exploring places).

Method

Seventy young adults (18–35 years old) and 70 older adults (65–75 years old) completed the Big-Five questionnaire, objective rotation and VSWM tasks, and spatial self-assessments on pleasure and anxiety in exploring places.

Results

Hierarchical regression models confirmed that age negatively predicted the variance in objective visuo-spatial tasks, but not in self-assessed visuo-spatial inclinations, while only the latter were slightly influenced by gender (in favor of men). Further, both objective visuo-spatial abilities (albeit modestly) and self-assessed visuo-spatial inclinations were predicted by higher Conscientiousness. The latter were also predicted by higher Emotional Stability. Finally, a better objective visuo-spatial performance was explained (again modestly) by lower Dynamism and Politeness, and higher Emotion Control, while higher Perseverance, Emotion Control and Cooperativeness explained a moderate part of the variance in the positive self-assessed visuo-spatial inclinations.

Conclusions

Our findings indicate that, beyond age and gender, some personality traits and facets predict self-assessed visuo-spatial inclinations to a larger extent than objective visuo-spatial performance. These results are discussed within the spatial cognition and aging framework.

A bedside application-based assessment of spatial orientation and memory: approaches and lessons learned

Spatial orientation and memory deficits are an often overlooked and potentially powerful early marker for pathological cognitive decline. Pen-and-paper tests for spatial abilities often do not coincide with actual navigational performance due to differences in spatial perspective and scale. Mobile devices are becoming increasingly useful in a clinical setting, for patient monitoring, clinical decision-making, and information management. The same devices have positional information that may be useful for a scale appropriate point-of-care test for spatial ability. We created a test for spatial orientation and memory based on pointing within a single room using the sensors in mobile phone. The test consisted of a baseline pointing condition to which all other conditions were compared, a spatial memory condition with eyes-closed, and two body rotation conditions (real or mental) where spatial updating were assessed. We examined the effectiveness of the sensors from a mobile phone for measuring pointing errors in these conditions in a sample of healthy young individuals. We found that the sensors reliably produced appropriate azimuth and elevation pointing angles for all of the 15 targets presented across multiple participants and days. Within-subject variability was below 6° elevation and 10° azimuth for the control condition. The pointing error and variability increased with task difficulty and correlated with self-report tests of spatial ability. The lessons learned from the first tests are discussed as well as the outlook of this application as a scientific and clinical bedside device. Finally, the next version of the application is introduced as an open source application for further development.

Spatial memory and navigation in ageing: A systematic review of MRI and fMRI studies in healthy participants

AIM

Spatial deficits are widely observed in normal ageing and early Alzheimer's disease. This review systematically examined neuroimaging evidence for structural and functional differences in the hippocampus (HC) associated with non-pathological age-related changes in allocentric spatial abilities.

METHODS

Databases were searched to identify peer-reviewed studies on allocentric spatial processing in normal ageing including MRI or fMRI data. 15 eligible studies were reviewed after applying exclusion criteria and quality assessment.

RESULTS

There was a marked deficit in allocentric spatial processing and trend towards egocentric strategies in older adults when compared to young controls or across the lifespan, associated in the majority of studies with HC volumetric changes, metabolic or microstructural indicators, and underactivity. A few studies reported no significant correlations.

CONCLUSION

Findings confirm literature supporting an age-related allocentric spatial processing deficit and a shift towards egocentric strategies. A majority of studies implicated HC atrophy, microstructural/metabolic alterations or functional changes in age-related allocentric spatial impairment. More sensitive imaging techniques and ecologically valid spatial tasks are needed to detect subtle changes in the HC and brain's navigational network.

Evidence for age-related deficits in object-location binding during place recognition

Deciding whether a place is the same or different than places encountered previously is a common task in daily navigation which requires to develop knowledge about the locations of objects (object-location binding) and to recognize places from different perspectives. These abilities rely on hippocampal functioning which is susceptible to increasing age. Thus, the question of the present study is how they both together impact on place recognition in aging. Forty people aged 20-29, 44 aged 60-69, and 32 aged 70-79 were presented with places consisting of four different objects during the encoding phase. In the test phase, they were then presented with a second place and had to decide whether it was the same or different. Test places were presented from different perspectives (0°, 30°, 60°) and with different object conditions (same, a swap of two objects, a substitution with a novel object). The sensitivity for detecting changes (d') decreased from 20-29 to 60-69 and to 70-79 years old, and with increasing perspective shifts. Importantly, older adults were less sensitive to object swapping than to object substitution, while young participants did not show any difference. Overall, these results suggest specific age-related difficulties in object-location binding in the context of place recognition.

The role of visuo-spatial abilities in environment learning from maps and navigation over the adult lifespan

Visuo-spatial abilities have an important role in environment learning. The aim of the present study was to explore whether these abilities relate to spatial recall after learning an environment from a map or a video, and irrespective of the learner's age (from youth to old age). The study involved 431 participants from 25 to 84 years old, who were assessed for their visuo-spatial working memory, object-based mental rotation, and perspective-taking abilities. Then, they learned environments from a map and a video, and performed pointing, map drawing, and route repetition tasks after learning from each type of input. The resulting path models showed that age related to visuo-spatial abilities and (in some cases) to spatial accuracy, too. After accounting for age, visuo-spatial abilities also related to spatial recall performance, whatever the type of learning input, especially in pointing tasks and, to a lesser degree, in map drawing and route repetition tasks. Overall, the relationship between individual visuo-spatial abilities and environment learning relates to the learning input and the type of task used to assess recall. This relationship was found in a large and diverse sample of participants ranging from youth to old age.

Predictors of Performance in Real and Virtual Scenarios across Age

BACKGROUND

Virtual reality applications to assist older adult with cognitive and functional decline are fast growing. However, such technological developments face limitations such as due to limited constructs and ecological validity. This study was aimed at investigating age-related changes in functional abilities and their associated cognitive underpinnings during task performance in virtual and real environments.

METHOD

Twenty-two younger adults (university students) and 22 older adults (aged 58-74) performed a multiple errands task twice, once in the "Discoveries" section of the National Museum of Scotland and once in the same room as a virtual environment. Accuracy and distance traveled were measured in both groups. Cognitive and daily living abilities were recorded in older adults using standard and novel questionnaires.

RESULTS

The testing environment had a significant effect on how efficient individuals performed the task. Older and younger adults' performance was alike but older adults relied on more cognitive resources. Older adults struggled in the virtual but not in the real environment. Younger but not older adults could transfer knowledge between environments.

CONCLUSION

The use of technology to assist frail older adults and those affected by dementia is growing rapidly. For these novel tools to be theoretically valid, they need to incorporate knowledge of the challenges they pose to these vulnerable groups. Here we present evidence of such challenges and their cognitive underpinnings. This theory may be considered by future applications aimed at enhancing functional abilities in these populations.

Using Sensory Wearable Devices to Navigate the City: Effectiveness and User Experience in Older Pedestrians

Preserving older pedestrians’ navigation skills in urban environments is a challenge for maintaining their quality of life. However, the maps that are usually used by older pedestrians might be unsuitable to their specificities and the existing digital aids do not consider older people’s perceptual and cognitive declines or user experience. This study presents a rich description of the navigation experience of older pedestrians either with a visual (augmented reality glasses), auditory (bone conduction headphones), or a visual and haptic (smartwatch) wearable device adapted to age-related declines. These wearable devices are compared to the navigation aid older people usually use when navigating the city (their own digital or paper map). The study, with 18 participants, measured the navigation performance and captured detailed descriptions of the users’ experience using interviews. We highlight three main phenomena which impact the quality of the user experience with the four aids: (1) the shifts in attention over time, (2) the understanding of the situation over time, and (3) the emergence of affective and aesthetic feelings over time. These findings add a new understanding of the specificities of navigation experience by older people and are discussed in terms of design recommendations for navigation devices.

Does it fit? - Trainability of affordance judgments in young and older adults

Will I fit into the overcrowded subway? Advanced aging can change our abilities associated with accurately judging the fit between perceived environmental properties and our own actual physical capabilities (affordance judgments). Two experimental studies examined the effects of aging and trainability in affordance judgments. Participants were asked to decide whether their hand fits into a given opening (Aperture Task). We used a detection theory approach to evaluate different judgment characteristics. Study 1 demonstrated that older (N = 39) compared to younger adults (N = 39) produced rather conservative judgments, but did not differ in perceptual sensitivity. Distributions of Hit and False-Alarm rates, as well as risk-perception statements (DOSPERT questionnaire), indicated a heightened concern about potential consequences of misjudgments in older adults. In Study 2, 20 younger and 22 older adults were trained by actually trying to fit their hand into each presented opening. Training included acoustic, haptic and visual feedback. Compared to pre-training, both groups demonstrated significant increases in accuracy when assessed post-training and after a one-week follow-up. While younger adults improved in perceptual sensitivity in post-training as well as in follow-up, the older group adjusted their tendency towards less conservative judgments in both following sessions. Our results are consistent with affordance models that propose a complex and dynamic interplay of different neural processes involved in this skill. Future studies are needed to further elucidate that interplay and the trainability of affordance judgments.

Time-of-Day and Age Impact on Memory in Elevated Plus-Maze Test in Rats

The purpose of the present study was to establish the effect of daytime and aging on memory in rats in the Elevated Plus-Maze (EPM) test. Young (2-months) and aged (18-months) male Wistar rats were exposed to the EPM test, at the beginning, mid-time or at the end of the light period. On the acquisition trial, the animals were placed individually at the end of one of the open arms of the EPM and the latency to enter in the enclosed arms was registered (cut-off time 60 s). The test was repeated 24 h later on. A longer latency period to reach the enclosed arm indicated poor retention compared to significantly shorter latencies. There were no significant differences between groups on the acquisition trial. In all tested periods, the latency time on the 24 h retention trial was significantly shorter in the young rats compared to the old ones. Furthermore, in the early and mid-time period of the light period, the young rats showed significantly decreased transfer latency (TL) time on the 24 h retention trial in comparison with the acquisition trial. In the aged rats, the TL time on the 24 h retention trial was significantly longer at the end of the light period, in comparison to the two other testing periods. In conclusion, aging significantly affects memory and the more critical period for memory process in both young and old animals, particularly at the end of the light period of the circadian cycle.

The Body Position Spatial Task, a Test of Whole-Body Spatial Cognition: Comparison Between Adults With and Without Parkinson Disease

BACKGROUND

The Body Position Spatial Task (BPST) is a novel measure of whole-body spatial cognition involving multidirectional steps and turns. Individuals with Parkinson disease (PD) are affected by motor and cognitive impairments, particularly in spatial function, which is important for mental imagery and navigation. Performance on the BPST may inform understanding of motor-cognitive and spatial cognitive function of individuals with PD.

OBJECTIVES

We conducted this study to determine feasibility and validity of the BPST with standard, validated, and reliable measures of spatial cognition and motor-cognitive integration and to compare BPST performance in adults with and without PD.

METHODS

A total of 91 individuals with mild-moderate PD and 112 neurotypical (NT) adults of similar age were recruited for the study to complete the BPST and other measures of mobility and cognition. Correlations were used to determine construct and concurrent validity of BPST with valid measures of spatial cognition and motor-cognitive integration. Performance was compared between PD and NT adults using independent t-tests.

RESULTS

BPST was feasible to administer. Analyses show evidence of construct validity for spatial cognition and for motor-cognitive integration. Concurrent validity was demonstrated with other tests of mobility and cognition. Relationships were stronger and more significant for individuals with PD than for NT individuals. BPST performance was not significantly different between groups.

CONCLUSION

Tests that integrate cognitive challenge in mobility contexts are necessary to assess the health of spatial cognitive and motor-cognitive integration. The BPST is a feasible and valid test of whole-body spatial cognition and motor-cognitive integration in individuals with PD.

Inhibition and decision-processing speed are associated with performance on dynamic posturography in older adults

Changes in cognition due to age have been associated with falls and reduced standing postural control. Sensory integration is one component of postural control that may be influenced by certain aspects of cognitive functioning. This study investigated associations between measures of cognitive function and sensory integration capabilities for healthy young and older adults. Dynamic posturography was performed using the Equitest Sensory Organization Test (SOT) protocol to evaluate sensory integration during standing using sway-referencing of the platform and/or visual scene to alter somatosensory and visual inputs. The Equilibrium Score was used as a measure of sway. Cognitive testing examined aspects of cognitive function that have been associated with falls in older adults. A correlational analysis investigated associations between the cognitive measures and postural sway during the altered sensory conditions of the SOT. For older subjects only, slower decision-processing speed was associated with increased sway during SOT conditions whenever somatosensation was altered. Reduced perceptual inhibition was associated with increased sway whenever somatosensation was intact, and particularly when vision was altered in the presence of somatosensation. Visuospatial construct ability was associated with sway only when the eyes were closed during altered somatosensation. Task-switching was associated with sway only when vision and somatosensation were intact. With increased age, deficits in decision speed and inhibition appear associated with the sensory integration crucial for balance maintenance. Associations are modulated by the availability of somatosensation and vision. These associations define situations and individual differences in aspects of cognition that may relate to situational loss of balance in older adults.

Spatial reorientation decline in aging: the combination of geometry and landmarks

OBJECTIVES

The study is focused on the assessment of reorientation skills in a sample of community-dwelling elderly people, manipulating landmarks and geometric (layout) information.

METHOD

A neuropsychological assessment was administered to 286 elderly participants, divided into six groups (healthy controls, HC; four subgroups of participants with mild cognitive impairment, MCI; participants with probable dementia, Prob_D) and tested with the Virtual Reorientation Test (VReoT). VReoT manipulated different spatial cues: geometry and landmarks (proximal and distal).

RESULT

Compared with HC, participants with MCI and Prob_D showed to be impaired in tasks involving geometry, landmarks and a combination of them. Both single and multiple domain impairment in MCI had an impact on reorientation performance. Moreover, VReoT was marginally able to discriminate between amnesic and non-amnesic MCI. The occurrence of getting lost events seemed to be associated to learning of geometric information.

CONCLUSION

The associative strength between landmark and target plays an important role in affecting spatial orientation performance of cognitively impaired participants. Geometry significantly supports landmark information and becomes helpful with the increase of cognitive impairment which is linked to a decrement in landmark encoding. VReoT seems to represent a reliable evaluation supplement for spatial orientation deficits in prodromal stages of dementia.

Age differences in spatial memory for mediated environments

Compared with younger adults, older adults have more difficulty with navigation and spatial memory in both familiar and unfamiliar domains. However, the cognitive mechanisms underlying these effects have been little explored. We examined three potential factors: (a) use of and coordination across spatial reference frames, (b) nonspatial cognitive abilities, and (c) the ability to segment a route into effective chunks. In two experiments, healthy young and older adults watched videos of navigation in a novel environment and had to remember the placement of landmarks along the route. Participants completed three spatial memory tasks-a virtual pointing task, a distance estimation task, and sketch map drawing-for each route. The pointing task depends on updating and accessing the updated egocentric reference frame relative to other frames. Map drawing may rely more on environment-centered processing. The distance estimation task could be solved using either frame of reference. Last, participants segmented each route. In a separate session, working memory, processing speed, and verbal memory were assessed. Older adults performed less well on all spatial tasks compared with younger adults; aging had a stronger negative effect on pointing performance. This may point to impairments in older adults' ability to update and coordinate information across reference frames. Performance on all spatial tasks was predicted by nonspatial task performance. Segmentation did not predict spatial memory. These results underline the importance of situating age differences in navigation in the context of basic transformations of spatial reference frames, and also in the context of nonspatial cognitive abilities. (PsycINFO Database Record

Global Determinants of Navigation Ability

Human spatial ability is modulated by a number of factors, including age [1-3] and gender [4, 5]. Although a few studies showed that culture influences cognitive strategies [6-13], the interaction between these factors has never been globally assessed as this requires testing millions of people of all ages across many different countries in the world. Since countries vary in their geographical and cultural properties, we predicted that these variations give rise to an organized spatial distribution of cognition at a planetary-wide scale. To test this hypothesis, we developed a mobile-app-based cognitive task, measuring non-verbal spatial navigation ability in more than 2.5 million people and sampling populations in every nation state. We focused on spatial navigation due to its universal requirement across cultures. Using a clustering approach, we find that navigation ability is clustered into five distinct, yet geographically related, groups of countries. Specifically, the economic wealth of a nation was predictive of the average navigation ability of its inhabitants, and gender inequality was predictive of the size of performance difference between males and females. Thus, cognitive abilities, at least for spatial navigation, are clustered according to economic wealth and gender inequalities globally, which has significant implications for cross-cultural studies and multi-center clinical trials using cognitive testing.

Spatial mental representations: the influence of age on route learning from maps and navigation

Experiencing an environment by navigating in it or reading a map (route and survey views, respectively) is a typical activity of everyday life. Previous research has demonstrated that aging coincides with a decline in spatial learning, but it is unclear whether this depends to some degree on how the learning conditions relate to the method used to assess the recall. The present study aims to shed light on this issue. Forty-six young, 43 young-old and 38 old-old adults learned outdoor environments from a map and a video, then performed sketch map and route repetition tasks. Participants were assessed on their visuo-spatial working memory (VSWM), and reported their self-assessed visuo-spatial inclinations. The results showed that young adults completed the sketch maps more accurately after learning from a map rather than a video. The same was true of the young-old participants (but not of the old-old), though their performance was not as good as the younger group's. The learning condition had no effect on the route repetition task, however, and only age-related differences emerged, with both older groups performing less well than the young adults. After controlling for learning condition and age group, VSWM and participants' reported propensity to explore places predicted their accuracy in both types of spatial task. The overall results, discussed in the light of spatial cognitive and aging models, show that learning condition (combined with recall tasks) and visuo-spatial factors influence spatial representations, even in aging.

Intra-hippocampal D-cycloserine rescues decreased social memory, spatial learning reversal, and synaptophysin levels in aged rats

RATIONALE

Aging is characterized by a decrease in N-methyl-D-aspartate receptors (NMDARs) in the hippocampus, which might be one of the factors involved in the age-dependent cognitive decline. D-Cycloserine (DCS), a partial agonist of the NMDAR glycine recognition site, could improve memory deficits associated to neurodegenerative disorders and cognitive deficits observed in normal aging.

OBJECTIVES AND METHODS

The aim of the present study was to explore whether DCS would reverse age-dependent memory deficits and decreases in NMDA receptor subunits (GluN1, GluN2A, and GluN2B) and the presynaptic protein synaptophysin in Wistar rats. We investigated the effects of pre-training infusions of DCS (10 μg/hemisphere) in the ventral hippocampus on two hippocampal-dependent learning tasks, the social transmission of food preference (STFP), and the Morris water maze (MWM).

RESULTS

The results revealed that infusions of DCS administered before the acquisition sessions rescued deficits in the STFP retention and MWM reversal learning in old rats. DCS also significantly increased the hippocampal levels of synaptophysin in old rats, which correlated with STFP and MWM performance in all tests. Moreover, although the levels of the GluN1 subunit correlated with the MWM acquisition and reversal, DCS did not enhance the expression of such synaptic protein.

CONCLUSIONS

The present behavioral results support the role of DCS as a cognitive enhancer and suggest that enhancing the function of NMDARs and synaptic plasticity in the hippocampus may be related to improvement in social memory and spatial learning reversal in aged animals.

Revisiting Metchnikoff: Age-related alterations in microbiota-gut-brain axis in the mouse

Over the last decade, there has been increased interest in the role of the gut microbiome in health including brain health. This is by no means a new theory; Elie Metchnikoff proposed over a century ago that targeting the gut by consuming lactic acid bacteria such as those in yogurt, could improve or delay the onset of cognitive decline associated with ageing. However, there is limited information characterising the relationship between the behavioural and physiological sequelae of ageing and alterations in the gut microbiome. To this end, we assessed the behavioural, physiological and caecal microbiota profile of aged male mice. Older mice (20-21months old) exhibited deficits in spatial memory and increases in anxiety-like behaviours compared to younger mice (2-3months old). They also exhibited increased gut permeability, which was directly correlated with elevations in peripheral pro-inflammatory cytokines. Furthermore, stress exacerbated the gut permeability of aged mice. Examination of the caecal microbiota revealed significant increases in phylum TM7, family Porphyromonadaceae and genus Odoribacter of aged mice. This represents a shift of aged microbiota towards a profile previously associated with inflammatory disease, particularly gastrointestinal and liver disorders. Furthermore, Porphyromonadaceae, which has also been associated with cognitive decline and affective disorders, was directly correlated with anxiety-like behaviour in aged mice. These changes suggest that changes in the gut microbiota and associated increases in gut permeability and peripheral inflammation may be important mediators of the impairments in behavioural, affective and cognitive functions seen in ageing.

Cognitive and behavioral evaluation of nutritional interventions in rodent models of brain aging and dementia

Evaluation of behavior and cognition in rodent models underpins mechanistic and interventional studies of brain aging and neurodegenerative diseases, especially dementia. Commonly used tests include Morris water maze, Barnes maze, object recognition, fear conditioning, radial arm water maze, and Y maze. Each of these tests reflects some aspects of human memory including episodic memory, recognition memory, semantic memory, spatial memory, and emotional memory. Although most interventional studies in rodent models of dementia have focused on pharmacological agents, there are an increasing number of studies that have evaluated nutritional interventions including caloric restriction, intermittent fasting, and manipulation of macronutrients. Dietary interventions have been shown to influence various cognitive and behavioral tests in rodents indicating that nutrition can influence brain aging and possibly neurodegeneration.