Allothetic orientation and sequential ordering of places is impaired in early stages of Alzheimer's disease: corresponding results in real space tests and computer tests

Serum levels of neurotensin, pannexin-1, and sestrin-2 and the correlations with sleep quality or/and cognitive function in the patients with chronic insomnia disorder

Objectives

To examine serum concentrations of neurotensin, pannexin-1 and sestrin-2, and their correlations with subjective and objective sleep quality and cognitive function in the patients with chronic insomnia disorder (CID).

Methods

Sixty-five CID patients were enrolled continuously and fifty-six good sleepers in the same period were served as healthy controls (HCs). Serum levels of neurotensin, pannexin-1 and sestrin-2 were measured by enzyme-linked immunosorbent assays. Sleep quality was assessed with the Pittsburgh Sleep Quality Index (PSQI) and polysomnography, and mood was evaluated by 17-item Hamilton Depression Rating Scale. General cognitive function was assessed with the Chinese-Beijing Version of Montreal Cognitive Assessment and spatial memory was evaluated by Blue Velvet Arena Test (BVAT).

Results

Relative to the HCs, the CID sufferers had higher levels of neurotensin (t=5.210, p<0.001) and pannexin-1 (Z=-4.169, p<0.001), and lower level of sestrin-2 (Z=-2.438, p=0.015). In terms of objective sleep measures, pannexin-1 was positively associated with total sleep time (r=0.562, p=0.002) and sleep efficiency (r=0.588, p=0.001), and negatively with wake time after sleep onset (r=-0.590, p=0.001) and wake time (r=-0.590, p=0.001); sestrin-2 was positively associated with percentage of rapid eye movement sleep (r=0.442, p=0.016) and negatively with non-rapid eye movement sleep stage 2 in the percentage (r=-0.394, p=0.034). Adjusted for sex, age and HAMD, pannexin-1 was still associated with the above objective sleep measures, but sestrin-2 was only negatively with wake time (r=-0.446, p=0.022). However, these biomarkers showed no significant correlations with subjective sleep quality (PSQI score). Serum concentrations of neurotensin and pannexin-1 were positively associated with the mean erroneous distance in the BVAT. Adjusted for sex, age and depression, neurotensin was negatively associated with MoCA score (r=-0.257, p=0.044), pannexin-1 was positively associated with the mean erroneous distance in the BVAT (r=0.270, p=0.033).

Conclusions

The CID patients had increased neurotensin and pannexin-1 and decreased sestrin-2 in the serum levels, indicating neuron dysfunction, which could be related to poor sleep quality and cognitive dysfunction measured objectively.

Histone deacetylase inhibitor RG2833 has therapeutic potential for Alzheimer's disease in females

Nearly two-thirds of patients with Alzheimer's are women. Identifying therapeutics specific for women is critical to lowering their elevated risk for developing this major cause of adult dementia. Moreover, targeting epigenetic processes that regulate multiple cellular pathways is advantageous given Alzheimer's multifactorial nature. Histone acetylation is an epigenetic process heavily involved in memory consolidation. Its disruption is linked to Alzheimer's. Through our computational studies, we predicted that the investigational drug RG2833 (N-[6-(2-aminoanilino)-6-oxohexyl]-4-methylbenzamide) has repurposing potential for Alzheimer's. RG2833 is a histone deacetylase HDAC1/3 inhibitor that is orally bioavailable and permeates the blood-brain-barrier. We investigated the RG2833 therapeutic potential in TgF344-AD rats, which are a model of Alzheimer's that exhibits age-dependent progression, thus mimicking this aspect of Alzheimer's patients that is difficult to establish in animal models. We investigated the RG2833 effects on cognitive performance, gene expression, and AD-like pathology in 11-month TgF344-AD female and male rats. A total of 89 rats were used: wild type n = 45 (17 females, 28 males), and TgF344-AD n = 44 (24 females, 20 males)] across multiple cohorts. No obvious toxicity was detected in the TgF344-AD rats up to 6 months of RG2833-treatment starting at 5 months of age administering the drug in rodent chow at ∼30mg/kg of body weight. We started treatment early in the course of pathology when therapeutic intervention is predicted to be more effective than in later stages of the disease. The drug-treatment significantly mitigated hippocampal-dependent spatial memory deficits in 11-month TgF344-AD females but not in males, compared to wild type littermates. This female sex-specific drug effect has not been previously reported. RG2833-treatment failed to ameliorate amyloid beta accumulation and microgliosis in female and male TgF344-AD rats. However, RNAseq analysis of hippocampal tissue from TgF344-AD rats showed that drug-treatment in females upregulated the expression of immediate early genes, such as Arc, Egr1 and c-Fos, and other genes involved in synaptic plasticity and memory consolidation. Remarkably, out of 17,168 genes analyzed for each sex, no significant changes in gene expression were detected in males at P < 0.05, false discovery rate < 0.05, and fold-change ≥ 1.5. Our data suggest that histone modifying therapeutics such as RG2833 improve cognitive behavior by modulating the expression of immediate early, neuroprotective and synaptic plasticity genes. Our preclinical study supports that RG2833 has therapeutic potential specifically for female Alzheimer's patients. RG2833 evaluations using other AD-related models is necessary to confirm our findings.

Induction of spatial anxiety in a virtual navigation environment

Spatial anxiety (i.e., feelings of apprehension and fear about navigating everyday environments) can adversely impact people's ability to reach desired locations and explore unfamiliar places. Prior research has either assessed spatial anxiety as an individual-difference variable or measured it as an outcome, but there are currently no experimental inductions to investigate its causal effects. To address this lacuna, we developed a novel protocol for inducing spatial anxiety within a virtual environment. Participants first learnt a route using directional arrows. Next, we removed the directional arrows and randomly assigned participants to navigate either the same route (n = 22; control condition) or a variation of this route in which we surreptitiously introduced unfamiliar paths and landmarks (n = 22; spatial-anxiety condition). The manipulation successfully induced transient (i.e., state-level) spatial anxiety and task stress but did not significantly reduce task enjoyment. Our findings lay the foundation for an experimental paradigm that will facilitate future work on the causal effects of spatial anxiety in navigational contexts. The experimental task is freely available via the Open Science Framework ( https://osf.io/uq4v7/ ).

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Neuroprotective Effects of a Multi-Herbal Extract on Axonal and Synaptic Disruption in Vitro and Cognitive Impairment in Vivo

Background

Alzheimer's disease (AD) is a multifactorial disorder characterized by cognitive decline. Current available therapeutics for AD have limited clinical benefit. Therefore, preventive therapies for interrupting the development of AD are critically needed. Molecules targeting multifunction to interact with various pathlogical components have been considered to improve the therapeutic efficiency of AD. In particular, herbal medicines with multiplicity of actions produce cognitive benefits on AD. Bugu-M is a multi-herbal extract composed of Ganoderma lucidum (Antler form), Nelumbo nucifera Gaertn., Ziziphus jujuba Mill., and Dimocarpus longan, with the ability of its various components to confer resilience to cognitive deficits.

Objective

To evaluate the potential of Bugu-M on amyloid-β (Aβ) toxicity and its in vitro mechanisms and on in vivo cognitive function.

Methods

We illustrated the effect of Bugu-M on Aβ_25-35-evoked toxicity as well as its possible mechanisms to diminish the pathogenesis of AD in rat cortical neurons. For cognitive function studies, 2-month-old female 3×Tg-AD mice were administered 400 mg/kg Bugu-M for 30 days. Behavioral tests were performed to assess the efficacy of Bugu-M on cognitive impairment.

Results

In primary cortical neuronal cultures, Bugu-M mitigated Aβ-evoked toxicity by reducing cytoskeletal aberrations and axonal disruption, restoring presynaptic and postsynaptic protein expression, suppressing mitochondrial damage and apoptotic signaling, and reserving neurogenic and neurotrophic factors. Importantly, 30-day administration of Bugu-M effectively prevented development of cognitive impairment in 3-month-old female 3×Tg-AD mice.

Conclusion

Bugu-M might be beneficial in delaying the progression of AD, and thus warrants consideration for its preventive potential for AD.

Digital Intervention For The Management Of Alzheimer's Disease

Alzheimer's disease (AD) is a progressive, multifactorial, chronic, neurodegenerative disease with high prevalence and limited therapeutic options, making it a global health crisis. Being the most common cause of dementia, AD erodes the cognitive, functional, and social abilities of the individual and causes escalating medical and psychosocial needs. As yet, this disorder has no cure and current treatment options are palliative in nature. There is an urgent need for novel therapy to address this pressing challenge. Digital therapeutics (Dtx) is one such novel therapy that is gaining popularity globally. Dtx provides evidence based therapeutic interventions driven by internet and software, employing tools such as mobile devices, computers, videogames, apps, sensors, virtual reality aiding in the prevention, management, and treatment of ailments like neurological abnormalities and chronic diseases. Dtx acts as a supportive tool for the optimization of patient care, individualized treatment and improved health outcomes. Dtx uses visual, sound and other non-invasive approaches for instance-consistent therapy, reminiscence therapy, computerised cognitive training, semantic and phonological assistance devices, wearables and computer-assisted rehabilitation environment to find applications in Alzheimer's disease for improving memory, cognition, functional abilities and managing motor symptom. A few of the Dtx-based tools employed in AD include "Memory Matters", "AlzSense", "Alzheimer Assistant", "smart robotic dog", "Immersive virtual reality (iVR)" and the most current gamma stimulation. The purpose of this review is to summarize the current trends in digital health in AD and explore the benefits, challenges, and impediments of using Dtx as an adjunctive therapy for the management of AD.

VR for Cognition and Memory

This chapter will provide a review of research into human cognition through the lens of VR-based paradigms for studying memory. Emphasis is placed on why VR increases the ecological validity of memory research and the implications of such enhancements.

Spatial orientation, postural control and the vestibular system in healthy elderly and Alzheimer's dementia

Background

While extensive research has been advancing our understanding of the spatial and postural decline in healthy elderly (HE) and Alzheimer's disease (AD), much less is known about how the vestibular system contributes to the spatial and postural processing in these two populations. This is especially relevant during turning movements in the dark, such as while walking in our garden or at home at night, where the vestibular signal becomes central. As the prevention of falls and disorientation are of serious concern for the medical service, more vestibular-driven knowledge is necessary to decrease the burden for HE and AD patients with vestibular disabilities.

Overview of the article

The review briefly presents the current "non-vestibular based" knowledge (i.e. knowledge based on research that does not mention the "vestibular system" as a contributor or does not investigate its effects) about spatial navigation and postural control during normal healthy ageing and AD pathology. Then, it concentrates on the critical sense of the vestibular system and explores the current expertise about the aspects of spatial orientation and postural control from a vestibular system point of view. The norm is set by first looking at how healthy elderly change with age with respect to their vestibular-guided navigation and balance, followed by the AD patients and the difficulties they experience in maintaining their balance or during navigation.

Conclusion

Vestibular spatial and vestibular postural deficits present a considerable disadvantage and are felt not only on a physical but also on a psychological level by all those affected. Still, there is a clear need for more (central) vestibular-driven spatial and postural knowledge in healthy and pathological ageing, which can better facilitate our understanding of the aetiology of these dysfunctions. A possible change can start with the more frequent implementation of the "vestibular system examination/rehabilitation/therapy" in the clinic, which can then lead to an improvement of future prognostication and disease outcome for the patients.

Vestibular dysfunction is an important contributor to the aging of visuospatial ability in older adults–Data from a computerized test system

Background

A convergence of research supports a key role of the vestibular system in visuospatial ability. However, visuospatial ability may decline with age. This work aims to elucidate the important contribution of vestibular function to visuospatial ability in old adults through a computerized test system.

Methods

Patients with a clinical history of recurrent vertigo and at least failed one vestibular test were included in this cross-sectional study. Healthy controls of three age groups: older, middle-aged, and young adults were also involved. Visuospatial cognitive outcomes including spatial memory, spatial navigation, and mental rotation of all the groups were recorded. Comparing the performance of the visuospatial abilities between patients and age-matched controls as well as within the controls.

Results

A total of 158 individuals were enrolled. Results showed that patients performed worse than the age-matched controls, with the differences in the forward span (p &lt; 0.001), the time of the maze 8 × 8 (p = 0.009), and the time of the maze 12 × 12 (p = 0.032) being significant. For the differences in visuospatial cognitive outcomes within the controls, the younger group had a significantly better performance than the other groups. The older group and the middle-aged group had comparable performances during all the tests.

Conclusions

Older patients with vestibular dysfunction had more difficulties during visuospatial tasks than age-matched controls, especially in spatial memory and spatial navigation. Within the controls, younger adults did much better than other age groups, while older adults behaved similarly to middle-aged adults. It is a valuable attempt to computerize the administration of tests for visuospatial ability.

Application of virtual reality for dementia management

Age is recognized as the major factors of dementia, especially in for Alzheimer’s disease (AD). Given to the aged population, the increased number of demented population has been receiving a great impact in our society. Unfortunately, so far, no cured medicines have been demonstrated to provide effective treatment in AD. The combination of pharmacological and non-pharmacological interventions has been proposed to manage dementia with potential benefits especially in decreasing caregiver’s burden and behavior, as well as psychological problems of demented patients. Recently, giving to the glorious development in digital technologies, the virtual reality, one of the non-pharmacological interventions has been used extensively in dementia managements for its strengths which can be adapted in accordance with the heterogeneous needs from demented patients and their caregivers. However, various study designs and other reasons made these results difficult to be interpreted. In this review our goal is to provide a better understanding for these points.

Task-dependent learning and memory deficits in the TgF344-AD rat model of Alzheimer's disease: three key timepoints through middle-age in females

The TgF344 rat model of Alzheimer's disease (AD) provides a comprehensive neuropathology presentation, with age-dependent development of tau tangles, amyloid-beta (A[Formula: see text]) plaques, neuronal loss, and increased gliosis. The behavioral trajectory of this model, particularly relating to spatial learning and memory, has yet to be fully characterized. The current experiment evaluated spatial working and reference memory performance, as well as several physiological markers of health, at 3 key age points in female TgF344-AD rats: 6-months, 9-months, and 12-months. At 6 months of age, indications of working and reference memory impairments were observed in transgenic (Tg) rats on the water radial-arm maze, a complex task that requires working and reference memory simultaneously; at 12 months old, Tg impairments were observed for two working memory measures on this task. Notably, no impairments were observed at the 9-month timepoint on this maze. For the Morris maze, a measure of spatial reference memory, Tg rats demonstrated significant impairment relative to wildtype (WT) controls at all 3 age-points. Frontal cortex, entorhinal cortex, and dorsal hippocampus were evaluated for A[Formula: see text]1-42 expression via western blot in Tg rats only. Analyses of A[Formula: see text]1-42 expression revealed age-dependent increases in all 3 regions critical to spatial learning and memory. Measures of physiological health, including heart, uterine, and body weights, revealed unique age-specific outcomes for female Tg rats, with the 9-month timepoint identified as critical for further research within the trajectory of AD-like behavior, physiology, and pathology.

Digital Cognitive Biomarker for Mild Cognitive Impairments and Dementia: A Systematic Review

The dementia population is increasing as the world’s population is growing older. The current systematic review aims to identify digital cognitive biomarkers from computerized tests for detecting dementia and its risk state of mild cognitive impairment (MCI), and to evaluate the diagnostic performance of digital cognitive biomarkers. A literature search was performed in three databases, and supplemented by a Google search for names of previously identified computerized tests. Computerized tests were categorized into five types, including memory tests, test batteries, other single/multiple cognitive tests, handwriting/drawing tests, and daily living tasks and serious games. Results showed that 78 studies were eligible. Around 90% of the included studies were rated as high quality based on the Newcastle–Ottawa Scale (NOS). Most of the digital cognitive biomarkers achieved comparable or even better diagnostic performance than traditional paper-and-pencil tests. Moderate to large group differences were consistently observed in cognitive outcomes related to memory and executive functions, as well as some novel outcomes measured by handwriting/drawing tests, daily living tasks, and serious games. These outcomes have the potential to be sensitive digital cognitive biomarkers for MCI and dementia. Therefore, digital cognitive biomarkers can be a sensitive and promising clinical tool for detecting MCI and dementia.

Neuroprotective properties of chrysin on decreases of cell proliferation, immature neurons and neuronal cell survival in the hippocampal dentate gyrus associated with cognition induced by methotrexate

Methotrexate (MTX) is a drug widely used for chemotherapy and can reduce cancer cell production by inhibiting dihydrofolate reductase and decreasing cancer cell growth. MTX has a neurotoxic effect on neural stem and glial cells, leading to memory deficits. Chrysin is a natural flavonoid that contains essential biological activities, such as neuroprotective and cognitive-improving properties. Therefore, the aim of the present study was to investigate the protective effect of chrysin against MTX-induced memory impairments related to hippocampal neurogenesis. Seventy-two male Sprague Dawley rats were divided into six groups: control, MTX, chrysin (10 and 30 mg/kg), and MTX+ chrysin (10 and 30 mg/kg) groups. Chrysin (10 and 30 mg/kg) was administered by oral gavage for 15 days. MTX (75 mg/kg) was administered by intravenous injection on days 8 and 15. Spatial and recognition memories were evaluated using the novel object location (NOL) and novel object recognition (NOR) tests, respectively. Moreover, cell proliferation, neuronal cell survival, and immature neurons in the subgranular zone of the hippocampal dentate gyrus were quantified by Ki-67, bromodeoxyuridine/neuronal nuclear protein (BrdU/NeuN), and doublecortin (DCX) immunohistochemistry staining. The results of the MTX group demonstrated that spatial and recognition memories were both impaired. Furthermore, cell division reduction, neuronal cell survival reduction, and immature neuron decreases were detected in the MTX group and not observed in the co-administration groups. Therefore, these results revealed that chrysin could alleviate memory and neurogenesis impairments in MTX-treated rats.

Short Digital Spatial Memory Test Detects Impairment in Alzheimer's Disease and Mild Cognitive Impairment

BACKGROUND

Impairment in navigation abilities and object location memory are often seen in early-stage Alzheimer's Disease (AD), yet these constructs are not included in standard neuropsychological assessment. We investigated the differential ability of a short digital spatial memory test in mild AD dementia and mild cognitive impairment (MCI).

METHODS

21 patients with AD dementia (66.9 ± 6.9; 47% female), 22 patients with MCI (69.6 ± 8.3; 46% female) and 21 patients with subjective cognitive decline (SCD) (62.2 ± 8.9; 48% female) from the Amsterdam Dementia Cohort performed the Object Location Memory Test (OLMT), consisting of a visual perception and memory trial, and the Virtual Tübingen (VT) test, consisting of a scene recognition, route continuation, route ordering and distance comparison task. The correlations with other cognitive domains were examined.

RESULTS

Patients with mild AD dementia (Z: -2.51 ± 1.15) and MCI (Z: -1.81 ± 0.92) performed worse than participants with SCD (Z: 0.0 ± 1.0) on the OLMT. Scene recognition and route continuation were equally impaired in patients with AD dementia (Z: -1.14 ± 0.73; Z: -1.44 ± 1.13) and MCI (Z: -1.37 ± 1.25; Z: -1.21 ± 1.07). Route ordering was only impaired in patients with MCI (Z: -0.82 ± 0.78). Weak to moderate correlations were found between route continuation and memory (r(64) = 0.40, p < 0.01), and between route ordering and attention (r(64) = 0.33, p < 0.01), but not for the OLMT.

CONCLUSION

A short digital spatial memory test battery was able to detect object location memory and navigation impairment in patients with mild AD dementia and MCI, highlighting the value of incorporating such a test battery in standard neuropsychological assessment.

Ageing- and dementia-friendly design: theory and evidence from cognitive psychology, neuropsychology and environmental psychology can contribute to design guidelines that minimise spatial disorientation

Many older people, both with and without dementia, eventually move from their familiar home environments into unfamiliar surroundings, such as sheltered housing or care homes. Age-related declines in wayfinding skills can make it difficult to learn to navigate in these new, unfamiliar environments. To facilitate the transition to their new accommodation, it is therefore important to develop retirement complexes and care homes specifically designed to reduce the wayfinding difficulties of older people and those with Alzheimer’s disease (AD). Residential complexes that are designed to support spatial orientation and that compensate for impaired navigation abilities would make it easier for people with dementia to adapt to their new living environment. This would improve the independence, quality of life and well-being of residents, and reduce the caregivers’ workload. Based on these premises, this opinion paper considers how evidence from cognitive psychology, neuropsychology and environmental psychology can contribute to ageing- and dementia-friendly design with a view to minimising spatial disorientation. After an introduction of the cognitive mechanisms and processes involved in spatial navigation, and the changes that occur in typical and atypical ageing, research from the field of environmental psychology is considered, highlighting design factors likely to facilitate (or impair) indoor wayfinding in complex buildings. Finally, psychological theories and design knowledge are combined to suggest ageing- and dementia-friendly design guidelines that aim to minimise spatial disorientation by focusing on residual navigation skills.

Virtual Morris water maze: opportunities and challenges

The ability to accurately recall locations and navigate our environment relies on multiple cognitive mechanisms. The behavioural and neural correlates of spatial navigation have been repeatedly examined using different types of mazes and tasks with animals. Accurate performances of many of these tasks have proven to depend on specific circuits and brain structures and some have become the standard test of memory in many disease models. With the introduction of virtual reality (VR) to neuroscience research, VR tasks have become a popular method of examining human spatial memory and navigation. However, the types of VR tasks used to examine navigation across laboratories appears to greatly differ, from open arena mazes and virtual towns to driving simulators. Here, we examined over 200 VR navigation papers, and found that the most popular task used is the virtual analogue of the Morris water maze (VWM). Although we highlight the many advantages of using the VWM task, there are also some major difficulties related to the widespread use of this behavioural method. Despite the task's popularity, we demonstrate an inconsistency of use - particularly with respect to the environmental setup and procedures. Using different versions of the virtual water maze makes replication of findings and comparison of results across researchers very difficult. We suggest the need for protocol and design standardisation, alongside other difficulties that need to be addressed, if the virtual water maze is to become the 'gold standard' for human spatial research similar to its animal counterpart.

Basal Forebrain Atrophy Is Associated With Allocentric Navigation Deficits in Subjective Cognitive Decline

Individuals with subjective cognitive decline (SCD) are at higher risk of incipient Alzheimer's disease (AD). Spatial navigation (SN) impairments in AD dementia and mild cognitive impairment patients have been well-documented; however, studies investigating SN deficits in SCD subjects are still lacking. This study aimed to explore whether basal forebrain (BF) and entorhinal cortex (EC) atrophy contribute to spatial disorientation in the SCD stage. In total, 31 SCD subjects and 24 normal controls were enrolled and administered cognitive scales, a 2-dimensional computerized SN test, and structural magnetic resonance imaging (MRI) scanning. We computed the differences in navigation distance errors and volumes of BF subfields, EC, and hippocampus between the SCD and control groups. The correlations between MRI volumetry and navigation distance errors were also calculated. Compared with the controls, the SCD subjects performed worse in both egocentric and allocentric navigation. The SCD group showed volume reductions in the whole BF (p < 0.05, uncorrected) and the Ch4p subfield (p < 0.05, Bonferroni corrected), but comparable EC and hippocampal volumes with the controls. In the SCD cohort, the allocentric errors were negatively correlated with total BF (r = −0.625, p < 0.001), Ch4p (r = −0.625, p < 0.001), total EC (r = −0.423, p = 0.031), and left EC volumes (r = −0.442, p = 0.024), adjusting for age, gender, years of education, total intracranial volume, and hippocampal volume. This study demonstrates that SN deficits and BF atrophy may be promising indicators for the early detection of incipient AD patients. The reduced BF volume, especially in the Ch4p subfield, may serve as a structural basis for allocentric disorientation in SCD subjects independent of hippocampal atrophy. Our findings may have further implications for the preclinical diagnosis and intervention for potential AD patients.

The use of egocentric and allocentric reference frames in static and dynamic conditions in humans

The dissociation between egocentric and allocentric reference frames is well established. Spatial coding relative to oneself has been associated with a brain network distinct from spatial coding using a cognitive map independently of the actual position. These differences were, however, revealed by a variety of tasks from both static conditions, using a series of images, and dynamic conditions, using movements through space. We aimed to clarify how these paradigms correspond to each other concerning the neural correlates of the use of egocentric and allocentric reference frames. We review here studies of allocentric and egocentric judgments used in static two- and three-dimensional tasks and compare their results with the findings from spatial navigation studies. We argue that neural correlates of allocentric coding in static conditions but using complex three-dimensional scenes and involving spatial memory of participants resemble those in spatial navigation studies, while allocentric representations in two-dimensional tasks are connected with other perceptual and attentional processes. In contrast, the brain networks associated with the egocentric reference frame in static two-dimensional and three-dimensional tasks and spatial navigation tasks are, with some limitations, more similar. Our review demonstrates the heterogeneity of experimental designs focused on spatial reference frames. At the same time, it indicates similarities in brain activation during reference frame use despite this heterogeneity.

Reframing spatial frames of reference: What can aging tell us about egocentric and allocentric navigation?

Representations of space in mind are crucial for navigation, facilitating processes such as remembering landmark locations, understanding spatial relationships between objects, and integrating routes. A significant problem, however, is the lack of consensus on how these representations are encoded and stored in memory. Specifically, the nature of egocentric and allocentric frames of reference in human memory is widely debated. Yet, in recent investigations of the spatial domain across the lifespan, these distinctions in mnemonic spatial frames of reference have identified age-related impairments. In this review, we survey the ways in which different terms related to spatial representations in memory have been operationalized in past aging research and suggest a taxonomy to provide a common language for future investigations and theoretical discussion. This article is categorized under: Psychology > Memory Neuroscience > Cognition Psychology > Development and Aging.

Allocentric coordinate spatial representations are impaired in aMCI and Alzheimer's disease patients

Research has reported deficits in egocentric (subject-to-object) and mainly allocentric (object-to-object) spatial representations in the early stages of the Alzheimer's disease (eAD). To identify early cognitive signs of neurodegenerative conversion, several studies have shown alterations in both reference frames, especially the allocentric ones in amnestic-Mild Cognitive Impairment (aMCI) and eAD patients. However, egocentric and allocentric spatial frames of reference are intrinsically connected with coordinate (metric/variant) and categorical (non-metric/invariant) spatial relations. This raises the question of whether allocentric deficit found to detect the conversion from aMCI to dementia is differently affected when combined with categorical or coordinate spatial relations. Here, we compared eAD and aMCI patients to Normal Controls (NC) on the Ego-Allo/Cat-Coor spatial memory task. Participants memorized triads of objects and then were asked to provide right/left (i.e. categorical) and distance based (i.e. coordinate) judgments according to an egocentric or allocentric reference frame. Results showed a selective deficit of coordinate, but not categorical, allocentric judgments in both aMCI and eAD patients as compared to NC group. These results suggest that a sign of the departure from normal/healthy aging towards the AD may be traced in elderly people's inability to represent metric distances among elements in the space.

The Effectiveness of Home-Based Training Software Designed to Influence Strategic Navigation Preferences in Healthy Subjects

One approach to the rehabilitation of navigation impairments is to train the use of compensatory egocentric or allocentric navigation strategies. Yet, it is unknown whether and to what degree training programs can influence strategic navigation preferences. In validating this approach, the key assumption that strategic preference can be changed by using a navigation training was assessed in a group of healthy participants (n = 82). The training program consisted of a psychoeducation session and a software package that included either allocentric or egocentric navigation exercises in virtual environments. Strategic navigation preference, objective and self-reported spatial abilities were assessed in pre- and post-training sessions. Based on their pre-training strategic preference, participants received either the egocentric training (n = 19) or the allocentric training (n = 21) version of the training. These participants engaged in four training sessions over a period of 2-3 weeks. The second group of participants did not use the training software (n = 43) and served as a control group. The results show that 50% of participants that received the egocentric training shifted from an allocentric to and an egocentric strategic preference. The proportion of participants that switched their strategic preference as a result of the allocentric training was identical to this proportion in the control group (19%). The training did not affect objective and self-reported navigation abilities as measured in the pre- and post-training sessions. We conclude that strategic navigation preferences can be influenced by using home-based training in healthy participants. However, using the current approach, only a preference shift from an allocentric to an egocentric navigation strategy could be achieved. The effectiveness of this navigation strategy training should next be assessed in relevant patient populations.

Strategies used by people with Alzheimer's disease for outdoor wayfinding: A repeated observational study

This study aimed to describe the wayfinding strategies used during outdoor walks by people with Alzheimer's disease. Inspired by an ethnographic approach, observations and conversations during repeated outdoor walks with five people with Alzheimer's disease living in their own homes were conducted. Data were analyzed using qualitative content analysis. The wayfinding strategies the participants described were: (1) landmarks, (2) used their senses, (3) stopped, looked around, and thought, (4) walking the same way or loop and in familiar areas, and (5) only walked in places and on routes where they could see other people and houses. Using wayfinding strategies might help people with Alzheimer's disease to be independent during outdoor walks, and discussing these strategies with relatives and nursing care staff may help finding people with Alzheimer's disease if lost outdoors. Wayfinding during the winter might be facilitated if temporary and changeable objects are avoided in people with Alzheimer's disease's walking route.

Assessment of Memory Impairment in Early Diagnosis of Alzheimer's Disease

Memory impairment has been considered as one of the earliest clinical hallmarks of Alzheimer's disease. This paper summarizes recent progress in the assessment of memory impairment in predementia stages. New promising approaches of memory assessment include evaluation of longitudinal cognitive changes, assessment of long-term memory loss, evaluation of subjective cognitive concerns and testing of other memory modalities, such as spatial memory. In addition, we describe new challenging memory tests based on memory binding paradigms that have been recently developed and are currently being validated.

Effect of age on spatial memory performance in real museum vs. computer simulation

BACKGROUND

Healthy older adults frequently complain on difficulty in recalling the locations of objects of everyday use. Cognitive abilities decline with normal aging; inefficiencies of information processing, as well as deterioration of neuronal structures, may impede the performance of complex cognitive skills such as spatial memory. Extraneous, task-irrelevant cognitive load in real environments is usually high and might interfere with spatial memory abilities of older adults. The purpose of this study was to determine (1) the extent to which older adults maintain their cognitive capacity during a spatial memory task as compared to young adults and (2) whether this capacity is affected by performance of the task in a real environment setting where the cognitive demands are similar to a simulation, but the physical demands (navigating via walking versus via a mouse) vary.

METHODS

In the museum, participants physically moved between display stations to locate hidden tokens performing a task in which an ongoing representation of previous searches had to be remembered. A comparable task was implemented via mouse actions on a computer simulation. Seventeen healthy older (60-80 years) and twenty younger (20-45 years) adults performed both tasks in a counterbalanced order.

RESULTS

The younger group was superior to the older group in terms of success rate and completion time for both conditions. All participants performed better during the simulated task. The delta between the total performance score in the two settings of the older group was significantly larger as compared to the younger group, suggesting a differential impact of setting on the groups.

CONCLUSIONS

Our results highlight the importance and feasibility of experimentation in ecologically relevant settings: differences were found in the way the cognitive performance of older and younger adults was affected by setting. Older adults appear to preserve basic cognitive abilities required for successful performance of object-location memory tasks. However, real museum setting appeared to impose higher demands on the older adults.

Differentiation of mild cognitive impairment using an entorhinal cortex-based test of virtual reality navigation

The entorhinal cortex is one of the first regions to exhibit neurodegeneration in Alzheimer's disease, and as such identification of entorhinal cortex dysfunction may aid detection of the disease in its earliest stages. Extensive evidence demonstrates that the entorhinal cortex is critically implicated in navigation underpinned by the firing of spatially modulated neurons. This study tested the hypothesis that entorhinal-based navigation is impaired in pre-dementia Alzheimer's disease. Forty-five patients with mild cognitive impairment (26 with CSF Alzheimer's disease biomarker data: 12 biomarker-positive and 14 biomarker-negative) and 41 healthy control participants undertook an immersive virtual reality path integration test, as a measure of entorhinal-based navigation. Behavioural performance was correlated with MRI measures of entorhinal cortex volume, and the classification accuracy of the path integration task was compared with a battery of cognitive tests considered sensitive and specific for early Alzheimer's disease. Biomarker-positive patients exhibited larger errors in the navigation task than biomarker-negative patients, whose performance did not significantly differ from controls participants. Path-integration performance correlated with Alzheimer's disease molecular pathology, with levels of CSF amyloid-β and total tau contributing independently to distance error. Path integration errors were negatively correlated with the volumes of the total entorhinal cortex and of its posteromedial subdivision. The path integration task demonstrated higher diagnostic sensitivity and specificity for differentiating biomarker positive versus negative patients (area under the curve = 0.90) than was achieved by the best of the cognitive tests (area under the curve = 0.57). This study demonstrates that an entorhinal cortex-based virtual reality navigation task can differentiate patients with mild cognitive impairment at low and high risk of developing dementia, with classification accuracy superior to reference cognitive tests considered to be highly sensitive to early Alzheimer's disease. This study provides evidence that navigation tasks may aid early diagnosis of Alzheimer's disease, and the basis of this in animal cellular and behavioural studies provides the opportunity to answer the unmet need for translatable outcome measures for comparing treatment effect across preclinical and clinical trial phases of future anti-Alzheimer's drugs.

Hesperidin Alleviates Methotrexate-Induced Memory Deficits via Hippocampal Neurogenesis in Adult Rats

Methotrexate (MTX), a folic acid antagonist, is widely used in cancer treatment. However, treatment with MTX reduces hippocampal neurogenesis, leading to memory deficits. Hesperidin (Hsd) is a flavonoid glycoside that promotes anti-inflammation, acts as an antioxidant, and has neuroprotective properties. Consumption of Hsd enhances learning and memory. In the present study, we investigated the protective effects of Hsd against MTX-induced impairments of memory and neurogenesis; male Sprague Dawley rats were administered with a single dose of MTX (75 mg/kg) by intravenous (i.v.) injection on days 8 and 15 or Hsd (100 mg/kg) by oral gavage for 21 days. Memory was tested using novel object location (NOL) and novel object recognition (NOR) tasks. Immunofluorescence staining of Ki-67, bromodeoxyuridine (BrdU), and doublecortin (DCX) was performed to assess cell proliferation, survival, and immature neurons. The data showed that Hsd and MTX did not disable locomotor ability. The MTX animals exhibited memory deficits in both memory tests. There were significant decreases in the numbers of cell proliferation, survival, and immature neurons in the MTX animals. However, co-administration with MTX and Hsd alleviated memory loss and neurogenesis decline. These results revealed that Hsd could protect against MTX side effects in the animals in this study.

The potential of virtual reality for spatial navigation research across the adult lifespan

Older adults often experience serious problems in spatial navigation, and alterations in underlying brain structures are among the first indicators for a progression to neurodegenerative diseases. Studies investigating the neural mechanisms of spatial navigation and its changes across the adult lifespan are increasingly using virtual reality (VR) paradigms. VR offers major benefits in terms of ecological validity, experimental control and options to track behavioral responses. However, navigation in the real world differs from navigation in VR in several aspects. In addition, the importance of body-based or visual cues for navigation varies between animal species. Incongruences between sensory and motor input in VR might consequently affect their performance to a different degree. After discussing the specifics of using VR in spatial navigation research across species, we outline several challenges when investigating age-related deficits in spatial navigation with the help of VR. In addition, we discuss ways to reduce their impact, together with the possibilities VR offers for improving navigational abilities in older adults.

The Multidisciplinary Approach to Alzheimer's Disease and Dementia. A Narrative Review of Non-Pharmacological Treatment

Background: Alzheimer's disease (AD) and dementia are chronic diseases with progressive deterioration of cognition, function, and behavior leading to severe disability and death. The prevalence of AD and dementia is constantly increasing because of the progressive aging of the population. These conditions represent a considerable challenge to patients, their family and caregivers, and the health system, because of the considerable need for resources allocation. There is no disease modifying intervention for AD and dementia, and the symptomatic pharmacological treatments has limited efficacy and considerable side effects. Non-pharmacological treatment (NPT), which includes a wide range of approaches and techniques, may play a role in the treatment of AD and dementia. Aim: To review, with a narrative approach, current evidence on main NPTs for AD and dementia. Methods: PubMed and the Cochrane database of systematic reviews were searched for studies written in English and published from 2000 to 2018. The bibliography of the main articles was checked to detect other relevant papers. Results: The role of NPT has been largely explored in AD and dementia. The main NPT types, which were reviewed here, include exercise and motor rehabilitation, cognitive rehabilitation, NPT for behavioral and psychological symptoms of dementia, occupational therapy, psychological therapy, complementary and alternative medicine, and new technologies, including information and communication technologies, assistive technology and domotics, virtual reality, gaming, and telemedicine. We also summarized the role of NPT to address caregivers' burden. Conclusions: Although NPT is often applied in the multidisciplinary approach to AD and dementia, supporting evidence for their use is still preliminary. Some studies showed statistically significant effect of NPT on some outcomes, but their clinical significance is uncertain. Well-designed randomized controlled trials with innovative designs are needed to explore the efficacy of NPT in AD and dementia. Further studies are required to offer robust neurobiological grounds for the effect of NPT, and to examine its cost-efficacy profile in patients with dementia.

Thermoregulatory profile of neurodegeneration-induced dementia of the Alzheimer's type using intracerebroventricular streptozotocin in rats

AIM

Here, we have extensively investigated the relationship between thermoregulation and neurodegeneration-induced dementia of the Alzheimer's type using intracerebroventricular injections of streptozotocin (icv-STZ).

METHODS

Male Wistar rats were treated with bilateral injections of icv-STZ, and their thermoregulatory profiles (core body temperature, tail-skin temperature, cold and heat defence responses and thermal place preference) were evaluated. Spatial memory, locomotor activity, social interaction, brain ventricular volume, and Aβ_1-42 and tau protein levels in the brain were analysed to characterize the effects of STZ on the brain and behaviour.

RESULTS

In addition to deficits in spatial memory, reduced social interaction and an increased brain ventricular volume, icv-STZ rats presented a pattern of hyperthermia, as demonstrated by an increased core body temperature. Hyperthermia was due to the activation of both autonomic heat conservation and behavioural cold avoidance, as STZ-treated rats presented tail-cutaneous vasoconstriction and an altered thermal preference. They also showed a distinct cold defence response when exposed to cold.

CONCLUSION

Our data bring evidence that icv-STZ in rats causes hyperthermia, with activation of both autonomic and behavioural thermoregulatory defence responses when challenged at colder temperatures, leading us to hypothesize that they are more efficient in preventing hypothermia. These data are relevant for a better understanding of neurodegenerative disease mechanisms.

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.

Changes in cerebral metabolic activity in men undergoing androgen deprivation therapy for non-metastatic prostate cancer

OBJECTIVE

Androgen deprivation therapy (ADT) is a common treatment option for men with biochemical relapse from prostate cancer. ADT is associated with changes in mood, cognition, and quality of life, and most recently with increased risk for Alzheimer's disease (AD). This study examined changes in brain metabolism using positron emission tomography (PET) in men undergoing intermittent ADT.

METHODS

Nine men with prostate cancer and a rising PSA (biochemical recurrence) without evidence of metastases were treated with intermittent ADT consisting of 9 months of complete androgen blockade achieved with combined leuprolide acetate and flutamide. Patients underwent resting [Fuorine-18] fluorodeoxyglucose PET (18F-FDGPET) at baseline (before treatment) and again after 9 months of ADT.

RESULTS

Whole-brain mapping analysis after 9 months of androgen deprivation compared to pretreatment baseline revealed decreased regional cerebral glucose metabolism in the cerebellum, posterior cingulate, and medial thalamus bilaterally. Associations of brain metabolism with measurements of cognition and mood while on androgen deprivation revealed positive correlations between the posterior cingulate, left inferior parietal lobule (BA40), and left mid temporal gyrus (BA39) and spatial reasoning and a negative correlation between left inferior parietal lobule and verbal memory. Several mood indices were negatively correlated with hypothalamus and brainstem.

CONCLUSION

These findings suggest that complete androgen deprivation may result in changes in regional brain metabolism associated with variation in mood, verbal memory, and spatial performance. Brain regions that were impacted from ADT are similar and overlap with brain regions with metabolic decline found in early AD and diabetes, suggesting possible common mechanisms.

Hypercapnic and Hypoxic Respiratory Response During Wakefulness and Sleep in a Streptozotocin Model of Alzheimer's Disease in Rats

Besides the typical cognitive decline, patients with Alzheimer's disease (AD) develop disorders of the respiratory system, such as sleep apnea, shortness of breath, and arrhythmias. These symptoms are aggravated with the progression of the disease. However, the cause and nature of these disturbances are not well understood. Here, we treated animals with intracerebroventricular streptozotocin (STZ, 2 mg/kg), a drug that has been described to cause Alzheimer-like behavioral and histopathological impairments. We measured ventilation (V̇E), electroencephalography, and electromyography during normocapnia, hypercapnia, and hypoxia in Wistar rats. In addition, we performed western blot analyses for phosphorylated tau, total tau, and amyloid-β (Aβ) peptide in the locus coeruleus (LC), retrotrapezoid nucleus, medullary raphe, pre-Bötzinger/Bötzinger complex, and hippocampus, and evaluated memory and learning acquisition using the Barnes maze. STZ treatment promoted memory and learning deficits and increased the percentage of total wakefulness during normocapnia and hypercapnia due to a reduction in the length of episodes of wakefulness. CO2-drive to breathe during wakefulness was increased by 26% in STZ-treated rats due to an enhanced tidal volume, but no changes in V̇E were observed in room air or hypoxic conditions. The STZ group also showed a 70% increase of Aβ in the LC and no change in tau protein phosphorylation. In addition, no alteration in body temperature was observed. Our findings suggest that AD animals present an increased sensitivity to CO2 during wakefulness, enhanced Aβ in the LC, and sleep disruption.

Using virtual reality to distinguish subjects with multiple- but not single-domain amnestic mild cognitive impairment from normal elderly subjects

AIM

Spatial disorientation is a hallmark of amnestic mild cognitive impairment (aMCI) and Alzheimer's disease. Our aim was to use virtual reality to determine the allocentric and egocentric memory deficits of subjects with single-domain aMCI (aMCIsd) and multiple-domain aMCI (aMCImd). For this purpose, we introduced an advanced virtual reality navigation task (VRNT) to distinguish these deficits in mild Alzheimer's disease (miAD), aMCIsd, and aMCImd.

METHODS

The VRNT performance of 110 subjects, including 20 with miAD, 30 with pure aMCIsd, 30 with pure aMCImd, and 30 cognitively normal controls was compared. Our newly developed VRNT consists of a virtual neighbourhood (allocentric memory) and virtual maze (egocentric memory). Verbal and visuospatial memory impairments were also examined with Rey Auditory-Verbal Learning Test and Rey-Osterrieth Complex Figure Test, respectively.

RESULTS

We found that miAD and aMCImd subjects were impaired in both allocentric and egocentric memory, but aMCIsd subjects performed similarly to the normal controls on both tasks. The miAD, aMCImd, and aMCIsd subjects performed worse on finding the target or required more time in the virtual environment than the aMCImd, aMCIsd, and normal controls, respectively. Our findings indicated the aMCImd and miAD subjects, as well as the aMCIsd subjects, were more impaired in egocentric orientation than allocentric orientation.

CONCLUSION

We concluded that VRNT can distinguish aMCImd subjects, but not aMCIsd subjects, from normal elderly subjects. The VRNT, along with the Rey Auditory-Verbal Learning Test and Rey-Osterrieth Complex Figure Test, can be used as a valid diagnostic tool for properly distinguishing different forms of aMCI.

A second wind for the cholinergic system in Alzheimer's therapy

Notwithstanding tremendous research efforts, the cause of Alzheimer's disease (AD) remains elusive and there is no curative treatment. The cholinergic hypothesis presented 35 years ago was the first major evidence-based hypothesis on the etiology of AD. It proposed that the depletion of brain acetylcholine was a primary cause of cognitive decline in advanced age and AD. It relied on a series of observations obtained in aged animals, elderly, and AD patients that pointed to dysfunctions of cholinergic basal forebrain, similarities between cognitive impairments induced by anticholinergic drugs and those found in advanced age and AD, and beneficial effects of drugs stimulating cholinergic activity. This review revisits these major results to show how this hypothesis provided the drive for the development of anticholinesterase inhibitor-based therapies of AD, the almost exclusively approved treatment in use despite transient and modest efficacy. New ideas for improving cholinergic therapies are also compared and discussed in light of the current revival of the cholinergic hypothesis on the basis of two sets of evidence from new animal models and refined imagery techniques in humans. First, human and animal studies agree in detecting signs of cholinergic dysfunctions much earlier than initially believed. Second, alterations of the cholinergic system are deeply intertwined with its reactive responses, providing the brain with efficient compensatory mechanisms to delay the conversion into AD. Active research in this field should provide new insight into development of multitherapies incorporating cholinergic manipulation, as well as early biomarkers of AD enabling earlier diagnostics. This is of prime importance to counteract a disease that is now recognized to start early in adult life.

Route repetition and route reversal: Effects of age and encoding method

Previous research indicates age-related impairments in learning routes from a start location to a target destination. There is less research on age effects on the ability to reverse a learned path. The method used to learn routes may also influence performance. This study examined how encoding methods influence the ability of younger and older adults to recreate a route in a virtual reality environment in forward and reverse directions. Younger (n = 50) and older (n = 50) adults learned a route either by self-navigation through the virtual environment or through studying a map. At test, participants recreated the route in the forward and reverse directions. Older adults in the map study condition had greater difficulty learning the route in the forward direction compared to younger adults. Older adults who learned the route by self-navigation were less accurate in traversing the route in the reverse compared to forward direction after a delay. In contrast, for older adults who learned via map study there were no significant differences between forward and reverse directions. Results suggest that older adults may not as readily develop and retain a sufficiently flexible representation of the environment during self-navigation to support accurate route reversal. Thus, initially learning a route from a map may be more difficult for older adults, but may ultimately be beneficial in terms of better supporting the ability to return to a start location. (PsycINFO Database Record

Salient Cues and Wayfinding in Alzheimer's Disease within a Virtual Senior Residence

Wayfinding is a problem for persons with Alzheimer's disease (AD), especially in complex environments such as senior residential communities. In this study, persons with AD or mild cognitive impairment (MCI) and a control group of older adults were asked to navigate a virtual reality simulation of a senior residential community. Subjects had to find their way repeatedly over multiple trials for two consecutive days in standard (no extra cues) and salient (colorful, memorable cues placed at key decision points) cue conditions. The results showed that all subjects found their way faster and more effectively in the salient cue condition than in the standard cue condition. Those in the AD/MCI group were significantly more impaired in wayfinding ability compared with those in the control group. Persons with impaired wayfinding ability due to AD and MCI can find their way more effectively in virtual environments enhanced with salient environmental cues.

Scopolamine disrupts place navigation in rats and humans: a translational validation of the Hidden Goal Task in the Morris water maze and a real maze for humans

RATIONALE

Development of new drugs for treatment of Alzheimer's disease (AD) requires valid paradigms for testing their efficacy and sensitive tests validated in translational research.

OBJECTIVES

We present validation of a place-navigation task, a Hidden Goal Task (HGT) based on the Morris water maze (MWM), in comparable animal and human protocols.

METHODS

We used scopolamine to model cognitive dysfunction similar to that seen in AD and donepezil, a symptomatic medication for AD, to assess its potential reversible effect on this scopolamine-induced cognitive dysfunction. We tested the effects of scopolamine and the combination of scopolamine and donepezil on place navigation and compared their effects in human and rat versions of the HGT. Place navigation testing consisted of 4 sessions of HGT performed at baseline, 2, 4, and 8 h after dosing in humans or 1, 2.5, and 5 h in rats.

RESULTS

Scopolamine worsened performance in both animals and humans. In the animal experiment, co-administration of donepezil alleviated the negative effect of scopolamine. In the human experiment, subjects co-administered with scopolamine and donepezil performed similarly to subjects on placebo and scopolamine, indicating a partial ameliorative effect of donepezil.

CONCLUSIONS

In the task based on the MWM, scopolamine impaired place navigation, while co-administration of donepezil alleviated this effect in comparable animal and human protocols. Using scopolamine and donepezil to challenge place navigation testing can be studied concurrently in animals and humans and may be a valid and reliable model for translational research, as well as for preclinical and clinical phases of drug trials.

Spatial Navigation in Preclinical Alzheimer's Disease

Although several previous studies have demonstrated navigational deficits in early-stage symptomatic Alzheimer's disease (AD), navigational abilities in preclinical AD have not been examined. The present investigation examined the effects of preclinical AD and early-stage symptomatic AD on spatial navigation performance. Performance on tasks of wayfinding and route learning in a virtual reality environment were examined. Comparisons were made across the following three groups: Clinically normal without preclinical AD (n = 42), clinically normal with preclinical AD (n = 13), and early-stage symptomatic AD (n = 16) groups. Preclinical AD was defined based on cerebrospinal fluid Aβ42 levels below 500 pg/ml. Preclinical AD was associated with deficits in the use of a wayfinding strategy, but not a route learning strategy. Moreover, post-hoc analyses indicated that wayfinding performance had moderate sensitivity and specificity. Results also confirmed early-stage symptomatic AD-related deficits in the use of both wayfinding and route learning strategies. The results of this study suggest that aspects of spatial navigation may be particularly sensitive at detecting the earliest cognitive deficits of AD.

Allocentric Spatial Memory Testing Predicts Conversion from Mild Cognitive Impairment to Dementia: An Initial Proof-of-Concept Study

The hippocampus is one of the first regions to exhibit neurodegeneration in Alzheimer's disease (AD), and knowledge of its role in allocentric spatial memory may therefore aid early diagnosis of AD. The 4 Mountains Test (4MT) is a short and easily administered test of spatial memory based on the cognitive map theory of hippocampal function as derived from rodent single cell and behavioral studies. The 4MT has been shown in previous cross-sectional studies to be sensitive and specific for mild cognitive impairment (MCI) due to AD. This report describes the initial results of a longitudinal study testing the hypothesis that allocentric spatial memory is predictive of conversion from MCI to dementia. Fifteen patients with MCI underwent baseline testing on the 4MT in addition to CSF amyloid/tau biomarker studies, volumetric MRI and neuropsychological assessment including the Rey Auditory Verbal Learning Test (RAVLT) and Trail Making Test "B" (TMT-B). At 24 months, 9/15 patients had converted to AD dementia. The 4MT predicted conversion to AD with 93% accuracy (Cohen's d = 2.52). The predictive accuracies of the comparator measures were as follows: CSF tau/β-amyloid_1-42 ratio 92% (d = 1.81), RAVLT 64% (d = 0.41), TMT-B 78% (d = 1.56), and hippocampal volume 77% (d = 0.65). CSF tau levels were strongly negatively correlated with 4MT scores (r = -0.71). This proof-of-concept study provides initial support for the hypothesis that allocentric spatial memory testing is a predictive cognitive marker of hippocampal neurodegeneration in pre-dementia AD. The 4MT is a brief, non-invasive, straightforward spatial memory test and is therefore ideally suited for use in routine clinical diagnostic practice. This is of particular importance given the current unmet need for simple accurate diagnostic tests for early AD and the ongoing development of potential disease-modifying therapeutic agents, which may be more efficacious when given earlier in the disease course. By applying a test based on studies of hippocampal function in rodents to patient populations, this work represents the first step in the development of translatable biomarkers of hippocampal involvement in early AD for use in both animal models and human subjects.

Effect of Probiotics on Central Nervous System Functions in Animals and Humans: A Systematic Review

To systematically review the effects of probiotics on central nervous system function in animals and humans, to summarize effective interventions (species of probiotic, dose, duration), and to analyze the possibility of translating preclinical studies. Literature searches were conducted in Pubmed, Medline, Embase, and the Cochrane Library. Only randomized controlled trials were included. In total, 38 studies were included: 25 in animals and 15 in humans (2 studies were conducted in both). Most studies used Bifidobacterium (eg, B. longum, B. breve, and B. infantis) and Lactobacillus (eg, L. helveticus, and L. rhamnosus), with doses between 10⁹ and 10¹⁰ colony-forming units for 2 weeks in animals and 4 weeks in humans. These probiotics showed efficacy in improving psychiatric disorder-related behaviors including anxiety, depression, autism spectrum disorder (ASD), obsessive-compulsive disorder, and memory abilities, including spatial and non-spatial memory. Because many of the basic science studies showed some efficacy of probiotics on central nervous system function, this background may guide and promote further preclinical and clinical studies. Translating animal studies to human studies has obvious limitations but also suggests possibilities. Here, we provide several suggestions for the translation of animal studies. More experimental designs with both behavioral and neuroimaging measures in healthy volunteers and patients are needed in the future.

Introducing a new age-and-cognition-sensitive measurement for assessing spatial orientation using a landmark-less virtual reality navigational task

Age-related impairments during spatial navigation have been widely reported in egocentric and allocentric paradigms. However, the effect of age on more specific navigational components such as the ability to drive or update directional information has not received enough attention. In this study we investigated the effect of age on spatial updating of a visual target after a series of whole-body rotations and transitions using a novel landmark-less virtual reality (VR) environment. Moreover, a significant number of previous studies focused on measures susceptible to a general decline in motor skills such as the spent time navigating, the distance traversed. The current paper proposes a new compound spatial measure to assess navigational performance, examines its reliability and compares its power with those of the measures of duration and traversed distance in predicting participants' age and cognitive groups assessed by Montreal Cognitive Assessment (MoCA) scores. Using data from 319 adults (20-83 years), our results confirm the reliability, the age sensitivity, and the cognitive validity of the designed spatial measure as well as its superiority to the measures of duration and traversed distance in predicting age and MoCA score. In addition, the results show the significant effect of age cognitive status on spatial updating.

Real-space path integration is impaired in Alzheimer's disease and mild cognitive impairment

INTRODUCTION

Path integration (PI) is an important component of spatial navigation that integrates self-motion cues to allow the subject to return to a starting point. PI depends on the structures affected early in the course of Alzheimer's disease (AD) such as the medial temporal lobe and the parietal cortex.

OBJECTIVES

To assess whether PI is impaired in patients with mild AD and amnestic mild cognitive impairment (aMCI) and to investigate the role of the hippocampus, entorhinal and inferior parietal cortex in this association.

METHODS

27 patients with aMCI, 14 with mild AD and 18 controls completed eight trials of Arena Path Integration Task. The task required subjects with a mask covering their eyes to follow an enclosed triangle pathway through two previously seen places: start-place1-place2-start. Brains were scanned at 1.5T MRI and respective volumes and thicknesses were derived using FreeSurfer algorithm.

RESULTS

Controlling for age, education, gender and Mini-Mental State Examination score the aMCI and AD subjects were impaired in PI accuracy on the pathway endpoint (p=0.042 and p=0.013) compared to controls. Hippocampal volume and thickness of entorhinal and parietal cortices explained separately 36-45% of the differences in PI accuracy between controls and aMCI and 28-31% of the differences between controls and AD subjects.

CONCLUSIONS

PI is affected in aMCI and AD, possibly as a function of neurodegeneration in the medial temporal lobe structures and the parietal cortex. PI assessment (as a part of spatial navigation testing) may be useful for identification of patients with incipient AD.

Wayfinding in ageing and Alzheimer's disease within a virtual senior residence: study protocol

AIM

To report a study protocol that examines the impact of adding salient cues in a virtual reality simulation of a senior residential building on wayfinding for older adults with and without Alzheimer's disease.

BACKGROUND

An early symptom of Alzheimer's disease is the inability to find one's way (wayfinding). Senior residential environments are especially difficult for wayfinding. Salient cues may be able to help persons with Alzheimer's disease find their way more effectively so they can maintain independence.

DESIGN

A repeated measures, within and between subjects design.

METHODS

This study was funded by the National Institutes of Health (August 2012). Older adults (N = 40) with normal cognition and older adults with early stage Alzheimer's disease/mild cognitive impairment (N = 40) will try to find their way to a location repeatedly in a virtual reality simulation of senior residence. There are two environments: standard (no cues) and salient (multiple cues). Outcome measures include how often and how quickly participants find the target location in each cue condition.

CONCLUSION

The results of this study have the potential to provide evidence for ways to make the environment more supportive for wayfinding for older adults with Alzheimer's disease. This study is registered at Trialmatch.alz.org (Identifier 260425-5).