Categorical spatial memory in patients with mild cognitive impairment and Alzheimer dementia: positional versus object-location recall

Prion protein pathology in Ubiquilin 2 models of ALS

Mutations in UBQLN2 cause ALS and frontotemporal dementia (FTD). The pathological signature in UBQLN2 cases is deposition of highly unusual types of inclusions in the brain and spinal cord that stain positive for UBQLN2. However, what role these inclusions play in pathogenesis remains unclear. Here we show cellular prion protein (PrPC) is found in UBQLN2 inclusions in both mouse and human neuronal induced pluripotent (IPSC) models of UBQLN2 mutations, evidenced by the presence of aggregated forms of PrPC with UBQLN2 inclusions. Turnover studies indicated that the P497H UBQLN2 mutation slows PrPC protein degradation and leads to mislocalization of PrPC in the cytoplasm. Immunoprecipitation studies indicated UBQLN2 and PrPC bind together in a complex. The abnormalities in PrPC caused by UBQLN2 mutations may be relevant in disease pathogenesis.

The impact of stimulus configuration on visual short-term memory decline in normal aging and mild cognitive impairment

INTRODUCTION

When we memorize simultaneous items, we not only store information about specific items and/or their locations but also how items are related to each other. Such relational information can be parsed into spatial (spatial configuration) and identity (object configuration) components. Both these configurations are found to support performance during a visual short-term memory (VSTM) task in young adults. How the VSTM performance of older adults is influenced by object/spatial configuration is less understood, which this study investigated.

METHODS

Twenty-nine young adults, 29 normally aging older adults, and 20 older adults with mild cognitive impairment (MCI) completed two yes-no memory-recognition experiments for four simultaneously presented items (2.5 s). Test display items were presented either at the same locations as the memory items (Experiment 1) or were globally shifted (Experiment 2). One of the test display items (target) was highlighted with a square box; participants indicated whether this item was shown in the preceding memory display. Both experiments comprised four conditions where nontarget items changed as follows: (i) nontarget items remained the same; (ii) nontarget items were replaced by new items; (iii) nontarget items switched locations; (iv) nontarget items were replaced by square boxes.

RESULTS

Performance (% correct) in both older groups was significantly reduced than young adults in both experiments and each condition. For the MCI adults, significantly reduced performance (vs. normal older adults) was found only for Experiment 1.

CONCLUSION

VSTM for simultaneous items declines significantly in normal aging; the decline is not influenced differently by spatial/object configuration change. The ability of VSTM to differentiate MCI from normal cognitive aging is apparent only where the spatial configuration of stimuli is retained at original locations. Findings are discussed in terms of the reduced ability to inhibit irrelevant items and location priming (by repetition) deficits.

Melatonin reduces β-amyloid accumulation and improves short-term memory in streptozotocin-induced sporadic Alzheimer's disease model

Melatonin is a hormone secreted by the pineal gland, it can be associated with circadian rhythms, aging and neuroprotection. Melatonin levels are decreased in sporadic Alzheimer's disease (sAD) patients, which suggests a relationship between the melatonergic system and sAD. Melatonin may reduce inflammation, oxidative stress, TAU protein hyperphosphorylation, and the formation of β-amyloid (Aβ) aggregates. Therefore, the objective of this work was to investigate the impact of treatment with 10 mg/kg of melatonin (i.p) in the animal model of sAD induced by the intracerebroventricular (ICV) infusion of 3 mg/kg of streptozotocin (STZ). ICV-STZ causes changes in the brain of rats similar to those found in patients with sAD. These changes include; progressive memory decline, the formation of neurofibrillary tangles, senile plaques, disturbances in glucose metabolism, insulin resistance and even reactive astrogliosis characterized by the upregulation of glucose levels and glial fibrillary acidic protein (GFAP). The results show that ICV-STZ caused short-term spatial memory impairment in rats after 30 days of STZ infusion without locomotor impairment which was evaluated on day 27 post-injury. Furthermore, we observed that a prolonged 30-day treatment with melatonin can improve the cognitive impairment of animals in the Y-maze test, but not in the object location test. Finally, we demonstrated that animals receiving ICV-STZ have high levels of Aβ and GFAP in the hippocampus and that treatment with melatonin reduces Aβ levels but does not reduce GFAP levels, concluding that melatonin may be useful to control the progression of amyloid pathology in the brain.

Overexpression of UCP4 in astrocytic mitochondria prevents multilevel dysfunctions in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is becoming increasingly prevalent worldwide. It represents one of the greatest medical challenges as no pharmacologic treatments are available to prevent disease progression. Astrocytes play crucial functions within neuronal circuits by providing metabolic and functional support, regulating interstitial solute composition, and modulating synaptic transmission. In addition to these physiological functions, growing evidence points to an essential role of astrocytes in neurodegenerative diseases like AD. Early-stage AD is associated with hypometabolism and oxidative stress. Contrary to neurons that are vulnerable to oxidative stress, astrocytes are particularly resistant to mitochondrial dysfunction and are therefore more resilient cells. In our study, we leveraged astrocytic mitochondrial uncoupling and examined neuronal function in the 3xTg AD mouse model. We overexpressed the mitochondrial uncoupling protein 4 (UCP4), which has been shown to improve neuronal survival in vitro. We found that this treatment efficiently prevented alterations of hippocampal metabolite levels observed in AD mice, along with hippocampal atrophy and reduction of basal dendrite arborization of subicular neurons. This approach also averted aberrant neuronal excitability observed in AD subicular neurons and preserved episodic-like memory in AD mice assessed in a spatial recognition task. These findings show that targeting astrocytes and their mitochondria is an effective strategy to prevent the decline of neurons facing AD-related stress at the early stages of the disease.

Effects of a polyphenol-rich grape and blueberry extract (Memophenol™) on cognitive function in older adults with mild cognitive impairment: A randomized, double-blind, placebo-controlled study

Background

Polyphenols are naturally occurring organic compounds found in plants. Research suggests that their intake reduces the risk of cognitive decline and related dementias. Grapes and blueberries are polyphenol-rich foods that have attracted attention for their potential cognitive-enhancing effects.

Purpose

Examine the effects of supplementation with a standardized and patented polyphenol-rich grape and blueberry extract (Memophenol™) on cognitive function in older adults with mild cognitive impairment.

Study design

Two-arm, 6 month, parallel-group, randomized, double-blind, placebo-controlled trial.

Methods

One hundred and forty-three volunteers aged 60 to 80 years with mild cognitive impairment were supplemented with either 150 mg of Memophenol™, twice daily or a placebo. Outcome measures included computer-based cognitive tasks, the Behavior Rating Inventory of Executive Function (BRIEF-A), the Cognitive Failures Questionnaire, and the CASP-19.

Results

Compared to the placebo, Memophenol™ supplementation was associated with greater improvements in the speed of information processing (p = 0.020), visuospatial learning (p = 0.012), and the BRIEF-A global score (p = 0.046). However, there were no other statistically significant between-group differences in the performance of other assessed cognitive tests or self-report questionnaires. Memophenol™ supplementation was well-tolerated with no reports of significant adverse reactions.

Conclusion

The promising results from this trial suggest that 6-months of supplementation with Memophenol™ may improve aspects of cognitive function in adults with mild cognitive impairment. Further research will be important to expand on the current findings and identify the potential mechanisms of action associated with the intake of this polyphenol-rich extract.

The alternate-form reliability study of six variants of the Brief Visual-Spatial Memory Test-Revised and the Hopkins Verbal Learning Test-Revised

Introduction

The revised Hopkins Verbal Learning Test-Revised (HVLT-R) and the Brief Visual-Spatial Memory Test-Revised (BVMT-R) are two widely used test involving verbal and visual learning and memory. In the two tests, six different versions are assembled, respectively, to prevent learning effects. Currently, no researchers have compared the six versions of the two tests. Thus, their usefulness in clinical studies requiring multiple follow-ups is limited. In this work, we confirm the equivalence of six HVLT-R and BVMT-R versions.

Methods

20 people completed all six HVLT-R and BVMT-R versions, while 120 people were randomly assigned to complete one of the six versions of each test. The Intelligence Quotient (IQ) level is measured using the short version of the Wechsler Adult Intelligence test. R4.2.0 is used for statistical analysis. The K-Related sample test (a non-parametric test) is used to observe the differences in test scores among the 20 subjects. The one-way Analysis of Variance (ANOVA) test is utilized to analyze the differences in test scores among the 120 subjects. The scores on different versions are compared using two similar sample tests. The HVLT-R Total Learning, the HVLT-R Delayed Recall, the BVMT-R Total Learning, and the BVMT-R Delayed Recall are indexes for comparison. Version and test scores are used as research factors, while different versions are used as research levels.

Results

The results suggest that HVLT-R and BVMT-R versions 3, 5 and 6 are equally difficult, and relatively easy compared to versions 1, 2 and 4. HVLT-R versions 3, 5, and 6 show good reliability and can be used interchangeably when testing word learning ability or short-term memory; BVMT-R Versions 3, 5, and 6 show acceptable reliability and can be can be used interchangeably.

Discussion

In the study of multiple follow-ups, it is a must to avoid discrepant versions and choose other equivalent versions. The results from this study could be used as a guide for upcoming studies and clinical applications in China.

Assessing mild cognitive impairment using object-location memory in immersive virtual environments

Pathological changes in the medial temporal lobe (MTL) are found in the early stages of Alzheimer's disease (AD) and aging. The earliest pathological accumulation of tau colocalizes with the areas of the MTL involved in object processing as part of a wider anterolateral network. Here, we sought to assess the diagnostic potential of memory for object locations in iVR environments in individuals at high risk of AD dementia (amnestic mild cognitive impairment [aMCI] n = 23) as compared to age-related cognitive decline. Consistent with our primary hypothesis that early AD would be associated with impaired object location, aMCI patients exhibited impaired spatial feature binding. Compared to both older (n = 24) and younger (n = 53) controls, aMCI patients, recalled object locations with significantly less accuracy (p < .001), with a trend toward an impaired identification of the object's correct context (p = .05). Importantly, these findings were not explained by deficits in object recognition (p = .6). These deficits differentiated aMCI from controls with greater accuracy (AUC = 0.89) than the standard neuropsychological tests. Within the aMCI group, 16 had CSF biomarkers indicative of their likely AD status (MCI+ n = 9 vs. MCI- n = 7). MCI+ showed lower accuracy in the object-context association than MCI- (p = .03) suggesting a selective deficit in object-context binding postulated to be associated with anterior-temporal areas. MRI volumetric analysis across healthy older participants and aMCI revealed that test performance positively correlates with lateral entorhinal cortex volumes (p < .05) and hippocampus volumes (p < .01), consistent with their hypothesized role in binding contextual and spatial information with object identity. Our results indicate that tests relying on the anterolateral object processing stream, and in particular requiring successful binding of an object with spatial information, may aid detection of pre-dementia AD due to the underlying early spread of tau pathology.

The challenge of neuropsychological assessment of visual/visuo-spatial memory: A critical, historical review, and lessons for the present and future

A proliferation of tests exists for the assessment of auditory-verbal memory processes. However, from a clinical practice perspective, the situation is less clear when it comes to the ready availability of reliable and valid tests for the evaluation of visual/visuo-spatial memory processes. While, at face value, there appear to be a wide range of available tests of visual/visuo-spatial memory, utilizing different types of materials and assessment strategies, a number of criticisms have been, and arguably should be, leveled at the majority of these tests. The criticisms that have been directed toward what are typically considered to be visual/visuo-spatial memory tests, such as (1) the potential for verbal mediation, (2) over-abstraction of stimuli, (3) the requirement of a drawing response, and (4) the lack of sensitivity to unilateral brain lesions, mean that, in reality, the number of readily available valid tests of visual/visuo-spatial memory is, at best, limited. This article offers a critical, historical review on the existing measures and resources for the neuropsychological assessment of visual/visuo-spatial memory, and it showcases some examples of newer tests that have aimed to overcome the challenges of assessing these important aspects of memory. The article also identifies new trends and examples of how technological advances such as virtual reality may add value to overcome previous obstacles to assessment, thereby offering professionals more reliable, accurate means to evaluate visual/visuo-spatial memory in clinical practice.

Episodic recognition memory based on incidental learning of visual associations is largely preserved compared to recall in amnestic mild cognitive impairment and mild Alzheimer's disease

We investigated preserved episodic recognition memory based on incidental learning of visual associations in Alzheimer's disease (AD). In a cross-sectional design, we analyzed episodic memory score profiles of patients with amnestic mild cognitive impairment (a-MCI) (n = 42) or mild AD (n = 19) who had hippocampal atrophy, and healthy elderly controls (n = 43). The Visual Association Test-Extended served as a measure of episodic memory. Multiple-choice cued recognition was compared with paired associate recall and free recall within groups. Results showed that patients recognized learned material much better compared to when they had to recall material, resulting in large effect sizes (Cohen's d) ranging from 1.3 to 3.5. We conclude that episodic recognition memory based on incidental learning of visual associations is largely preserved when compared to recall in a-MCI and mild AD. This suggests that the episodic memory impairment in AD may be characterized as a retrieval impairment rather than a consolidation impairment, indicating that preserved recognition compared to recall may be compatible with AD being the correct diagnosis. Measuring the episodic memory impairment in AD may benefit from using tests that capture different aspects of memory processes such as incidental learning of visual associations.

Association Between Leptin, Cognition, and Structural Brain Measures Among "Early" Middle-Aged Adults: Results from the Framingham Heart Study Third Generation Cohort

BACKGROUND

There is growing interest in the pathophysiological processes of preclinical Alzheimer's disease (AD), including the potential role of leptin. Human studies have shown that both low and high levels of leptin can be associated with worse neurocognitive outcomes, suggesting this relationship may be moderated by another risk factor.

OBJECTIVE

We examined the association between plasma leptin levels and both neuropsychological test performance and structural neuroimaging and assessed whether body mass index (BMI) is an effect modifier of these associations.

METHODS

Our study sample consisted of 2,223 adults from the Framingham Heart Study Third Generation Cohort (average age = 40 years, 53% women).

RESULTS

Among the entire sample, there was no association between leptin and any of the neuropsychological domain measures or any of the MRI brain volume measures, after adjustment for BMI, APOE4, and other clinical factors. However, we did observe that BMI category was an effect modifier for the association between leptin and verbal memory (p for interaction = 0.03), where higher levels of leptin were associated with better performance among normal weight participants (BMI 18.5-24.9) kg/m2 (beta = 0.12, p = 0.02). No association was observed between leptin level and verbal memory test performance among participants who were overweight or obese.

CONCLUSION

These findings suggest that the association between leptin and cognitive function is moderated by BMI category. Prospective examination of individuals transitioning from middle age to older adulthood will help to clarify the contribution of leptin to AD and other neurodegenerative conditions.

The Location Learning Test-Revised is associated with informant-reported everyday functioning in a sample of community-dwelling older adults

OBJECTIVE

Object location learning and memory may be important for older adults to successfully complete some everyday activities.

METHOD

This cross-sectional, correlational study investigated the ecological relevance of the Location Learning Test-Revised (LLT-R) in 195 community-dwelling, older adults in Western Australia. The LLT-R assesses object location learning and memory for everyday objects over five learning trials and after a 30-min delay. Knowledgeable informants provided structured ratings of participants' activities of daily living and memory symptoms.

RESULTS

A greater number of errors on LLT-R total learning trials were associated with mild problems in activities of daily living (particularly in travel and household domains), but not with memory symptoms. The LLT-R's association with activities of daily living was accompanied by a small-to-medium effect size and was not better explained by demographics, global cognitive functioning, mood, or chronic medical conditions.

CONCLUSIONS

Findings provide some support for the ecological relevance of the LLT-R among older community-dwelling adults and suggest that object location learning may play a role in some everyday functioning problems that accompany typical aging.

Determining affected memory domains in patients with amnestic mild cognitive impairment using computerized and interactive tests

This study explores different episodic memory domains, namely object, temporal and spatial memory, affected in patients with a clinical diagnosis of single domain amnestic mild cognitive impairment (aMCI). 15 aMCI patients and 25 healthy controls were recruited and tested. Object, spatial, and temporal memory were tested using computerized tasks and again in interactive, real-world tasks. Controls outperformed patients on the object computerized task and showed a trend toward significance for the computerized spatial and temporal tasks, but there was no difference in spatial and temporal memory when using the interactive tasks, indicating the employment of compensatory mechanisms in patients to overcome some of the memory impairments associated with aMCI. These findings highlight that aMCI patients might delay seeking help due to compensatory mechanisms which mask their deficits in real-world situations.

Relationship Between PET-Assessed Amyloid Burden and Visual and Verbal Episodic Memory Performance in Elderly Subjects

BACKGROUND

Studies of elderly subjects using biomarkers that are proxies for Alzheimer's disease (AD) pathology have the potential to document meaningful relationships between cognitive performance and biomarker changes along the AD continuum.

OBJECTIVE

To document cognitive performance differences across distinct AD stages using a categorization based on the presence of PET-assessed amyloid-β (Aβ) burden and neurodegeneration.

METHODS

Patients with mild dementia compatible with AD (n = 38) or amnestic mild cognitive impairment (aMCI; n = 43) and a cognitively unimpaired group (n = 27) underwent PET with Pittsburgh compound-B (PiB) assessing Aβ aggregation (A+) and [18F]FDG-PET assessing neurodegeneration ((N)+). Cognitive performance was assessed with verbal and visual episodic memory tests and the Mini-Mental State Examination.

RESULTS

The A+(N)+ subgroup (n = 32) showed decreased (p < 0.001) cognitive test scores compared to both A+(N)-(n = 18) and A-(N)-(n = 49) subjects, who presented highly similar mean cognitive scores. Despite its modest size (n = 9), the A-(N)+ subgroup showed lower (p < 0.043) verbal memory scores relative to A-(N)-subjects, and trend lower (p = 0.096) scores relative to A+(N)-subjects. Continuous Aβ measures (standard uptake value ratios of PiB uptake) were correlated most significantly with visual memory scores both in the overall sample and when analyses were restricted to dementia or (N)+ subjects, but not in non-dementia or (N)-groups.

CONCLUSION

These results demonstrate that significant Aβ-cognition relationships are highly salient at disease stages involving neurodegeneration. The fact that findings relating Aβ burden to memory performance were detected only at (N)+ stages, together with the similarity of test scores between A+(N)-and A-(N)-subjects, reinforce the view that Aβ-cognition relationships during early AD stages may remain undetectable unless substantially large samples are evaluated.

Age-Related Changes in Instrumental and Basic Activities of Daily Living Impairment in Older Adults with Very Mild Alzheimer's Disease

Background/Aims

Age-related changes in impairments in activities of daily living (ADL) in older adults with very mild Alzheimer's disease (vmAD) have been scarcely explored. We clarified the characteristics of ADL impairment and examined how ADL impairments differed by age in such patients compared with community-dwelling cognitively normal older adults.

Methods

The participants were 107 older adults with vmAD (Mini-Mental State Examination [MMSE] score ≥24), all of whom were first-visit outpatients at the Dementia Clinic of the Department of Neuropsychiatry, Kumamoto University Hospital. The controls were 682 community-dwelling older adults who participated in the 3rd Nakayama Study with MMSE score ≥24. We examined the association of instrumental and basic ADL (IADL and BADL, respectively) independence with the odds of vmAD using multiple logistic regression analysis and determined differences in ADL impairment by age using age- and sex-matched analysis.

Results

Impairments in handling finances (OR 57.08), managing medication (OR 5.13), and dressing (OR 3.35; BADL) were associated with greater odds of vmAD. Among those aged 65 years and above, there were fewer patients with vmAD than healthy controls who could independently handle finances and medication. Among patients with vmAD, the percentages of those who could independently manage shopping, food preparation, and housekeeping only decreased after age 74. Age-related decreases in independence were observed in few BADL items; these, however, were temporary.

Conclusions

Patients with vmAD show significantly decreased IADL independence from early old age.

Centella asiatica attenuates hippocampal mitochondrial dysfunction and improves memory and executive function in β-amyloid overexpressing mice

Centella asiatica is a medicinal plant used to enhance memory. We have previously shown that a water extract of Centella asiatica (CAW) attenuates β-amyloid (Aβ)-induced spatial memory deficits in mice and improves neuronal health. Yet the effect of CAW on other cognitive domains remains unexplored as does its in vivo mechanism of improving Aβ-related cognitive impairment. This study investigates the effects of CAW on learning, memory and executive function as well as mitochondrial function and antioxidant response in the 5xFAD model of Aβ accumulation. Seven month old 5xFAD female mice were treated with CAW (2 mg/mL) in their drinking water for two weeks prior to behavioral testing. Learning, memory and executive function were assessed using the object location memory task (OLM), conditioned fear response (CFR) and odor discrimination reversal learning (ODRL) test. Mitochondrial function was profiled using the Seahorse XF platform in hippocampal mitochondria isolated from these animals and tissue was harvested for assessment of mitochondrial, antioxidant and synaptic proteins. CAW improved performance in all behavioral tests in the 5xFAD but had no effect on WT animals. Hippocampal mitochondrial function was improved and hippocampal and cortical expression of mitochondrial genes was increased in CAW-treated 5xFAD mice. Gene expression of the transcription factor NRF2, as well as its antioxidant target enzymes, was also increased with CAW treatment in both WT and 5xFAD mice. CAW treatment also decreased Aβ-plaque burden in the hippocampus of treated 5xFAD mice but had no effect on plaques in the cortex. These data show that CAW can improve many facets of Aβ-related cognitive impairment in 5xFAD mice. Oral treatment with CAW also attenuates hippocampal mitochondrial dysfunction in these animals. Because mitochondrial dysfunction and oxidative stress accompany cognitive impairment in many pathological conditions beyond Alzheimer's disease, this suggests potentially broad therapeutic utility of CAW.

Hippocampal place cell dysfunction and the effects of muscarinic M1 receptor agonism in a rat model of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease that disproportionately impacts memory and the hippocampus. However, it is unclear how AD pathology influences the activity of surviving neurons in the hippocampus to contribute to the memory symptoms in AD. One well-understood connection between spatial memory and neuronal activity in healthy brains is the activity of place cells, neurons in the hippocampus that fire preferentially in a specific location of a given environment (the place field of the place cell). In the present study, place cells were recorded from the hippocampus in a recently-developed rat model of AD (Tg-F344 AD) at an age (12-20 months) at which the AD rats showed marked spatial memory deficits. Place cells in the CA2 and CA3 pyramidal regions of the hippocampus in AD rats showed sharply reduced spatial fidelity relative to wild-type (WT) rats. In contrast, spiking activity of place cells recorded in region CA1 in AD rats showed good spatial fidelity that was similar to CA1 place cells in WT rats. Oral administration of the M₁ muscarinic acetylcholine receptor agonist VU0364572 impacted place cell firing rates in CA1 and CA2/3 hippocampal regions, but did not improve the spatial fidelity of CA2/3 hippocampal place cells in AD rats. The results indicated that, to the extent the spatial memory impairment in AD rats was attributable to hippocampal dysfunction, the memory impairment was more attributable to dysfunction in hippocampal regions CA2 and CA3 rather than CA1.

The association of visual memory with hippocampal volume

BACKGROUND

In this study we investigated the role of hippocampal volume (HV) in visual memory.

METHODS

Participants were a subsample of older adults (> = 70 years) from the Einstein Aging Study. Visual performance was measured using the Complex Figure (CF) copy and delayed recall tasks from the Repeatable Battery for the Assessment of Neuropsychological Status. Linear regressions were fitted to study associations between HV and visual tasks.

RESULTS

Participants' (n = 113, mean age = 78.9 years) average scores on the CF copy and delayed recall were 17.4 and 11.6, respectively. CF delayed recall was associated with total (β = .031, p = 0.001) and left (β = 0.031, p = 0.001) and right HVs (β = 0.24, p = 0.012). CF delayed recall remained significantly associated with left HV even after we also included right HV (β = 0.27, p = 0.025) and the CF copy task (β = 0.30, p = 0.009) in the model. CF copy did not show any significant associations with HV.

CONCLUSION

Our results suggest that left HV contributes in retrieval of visual memory in older adults.

Changes of EEG Spectra and Functional Connectivity during an Object-Location Memory Task in Alzheimer's Disease

Object-location memory is particularly fragile and specifically impaired in Alzheimer’s disease (AD) patients. Electroencephalogram (EEG) was utilized to objectively measure memory impairment for memory formation correlates of EEG oscillatory activities. We aimed to construct an object-location memory paradigm and explore EEG signs of it. Two groups of 20 probable mild AD patients and 19 healthy older adults were included in a cross-sectional analysis. All subjects took an object-location memory task. EEG recordings performed during object-location memory tasks were compared between the two groups in the two EEG parameters (spectral parameters and phase synchronization). The memory performance of AD patients was worse than that of healthy elderly adults The power of object-location memory of the AD group was significantly higher than the NC group (healthy elderly adults) in the alpha band in the encoding session, and alpha and theta bands in the retrieval session. The channels-pairs the phase lag index value of object-location memory in the AD group was clearly higher than the NC group in the delta, theta, and alpha bands in encoding sessions and delta and theta bands in retrieval sessions. The results provide support for the hypothesis that the AD patients may use compensation mechanisms to remember the items and episode.

Understanding the world of dementia. How do people with dementia experience the world?

BACKGROUND

There is growing awareness that the subjective experience of people with dementia is important for understanding behavior and improving quality of life. This paper reviews and reflects on the currently available theories on subjective experience in dementia and it explores the possibility of a knowledge gap on the influence of neurological deficits on experience in late stage dementia.

METHODS

A literature review on current commonly used theories on experience in dementia was supplemented with a systematic review in PubMed and Psychinfo. For the systematic review, the terms used were Perception and Dementia and Behavior; and Awareness and Dementia and Long term care.

RESULTS

Current models emphasize the psychosocial factors that influence subjective experience, but the consequences of neurological deficits are not elaborated upon. The systematic literature search on the neuropsychological functioning in dementia resulted in 631 papers, of which 94 were selected for review. The current knowledge is limited to the early stages of Alzheimer's disease. Next to memory impairments, perception of the direct environment, interpretation of the environment, and inhibition of own responses to the environment seem to be altered in people with dementia.

CONCLUSIONS

Without knowledge on how perception, interpretation and the ability for response control are altered, the behavior of people with dementia can easily be misinterpreted. Research into neuropsychological functioning of people in more severe stages and different forms of dementia is needed to be able to develop a model that is truly biopsychosocial. The proposed model can be used in such research as a starting point for developing tests and theories.

Verbal and non-verbal memory and hippocampal volumes in a memory clinic population

Introduction

Better characterization of the relationship between episodic memory and hippocampal volumes is crucial in early detection of neurodegenerative disease. We examined these relationships in a memory clinic population.

Methods

Participants (n = 226) underwent structural magnetic resonance imaging and tests of verbal (Hopkins Verbal Learning Test-Revised, HVLT-R) and non-verbal (Brief Visuospatial Memory Test-Revised, BVMT-R) memory. Correlational analyses were performed, and analyses on clinical subgroups (i.e., amnestic Mild Cognitive Impairment, non-amnestic Mild Cognitive Impairment, probable Alzheimer’s disease, intact memory) were conducted.

Results

Positive associations were identified between bilateral hippocampal volumes and both memory measures, and BVMT-R learning slope was more strongly positively associated with hippocampal volumes than HVLT-R learning slope. Amnestic Mild Cognitive Impairment (aMCI) participants showed specific positive associations between BVMT-R performance and hippocampal volumes bilaterally. Additionally, analyses of the aMCI group showed trend-level evidence of material-specific lateralization, such that retention of verbal information was positively associated with left hippocampal volume, whereas learning curve and retention of non-verbal information was positively associated with right hippocampal volume.

Conclusions

Findings support the link between episodic memory and hippocampal volumes in a memory clinic population. Non-verbal memory measures also may have higher diagnostic value, particularly in individuals at elevated risk for Alzheimer’s disease.

Spatial navigation in elderly healthy subjects, amnestic and non amnestic MCI patients

INTRODUCTION

Mild cognitive impairment (MCI) is considered an early stage of cognitive impairment. Therefore, it is important to identify early cognitive markers of MCI conversion to dementia and topographical disorientation (TD) may help differentiate normal aging from MCI and prodromal Alzheimer's disease (AD). Our aim was to propose a new instrument in elderly healthy subjects and MCI patients of amnestic (aMCI) and non-amnestic (naMCI) type.

METHOD

We observed 18 healthy subjects and 18 MCI patients (9 aMCI and 9 naMCI). All participants were submitted to a neuropsychological battery and to a new experimental small-scale spatial navigation test reproducing an ideal city.

RESULTS

a-MCI patients performed worse in learning a new route, in replacing landmarks in the city and in drawing a map of the city. Na-MCI patients' performance was not different from that observed in healthy subjects, except for a longer time span in Route Forward learning. MCI and healthy samples showed different correlations between experimental subtests and neuropsychological tests.

CONCLUSIONS

Our task seems to be sensitive in pointing out differences in spatial abilities of MCI subtypes, especially with regard to the following subtests: learning a new route, retrieving a landmark's place and building a map of the environment. In comparison with more complex tests, these results allow us to consider the new tool as useful to evaluate spatial navigation in healthy elderly subjects and MCI patients.

Entorhinal cortical defects in Tg2576 mice are present as early as 2-4 months of age

The entorhinal cortex (EC) is one of the first brain areas to display neuropathology in Alzheimer's disease. A mouse model which simulates amyloid-β (Aβ) neuropathology, the Tg2576 mouse, was used to address these early changes. Here, we show EC abnormalities occur in 2- to 4-month-old Tg2576 mice, an age before Aβ deposition and where previous studies suggest that there are few behavioral impairments. First we show, using a sandwich enzyme-linked immunosorbent assay, that soluble human Aβ40 and Aβ42 are detectable in the EC of 2-month-old Tg2576 mice before Aβ deposition. We then demonstrate that 2- to 4-month-old Tg2576 mice are impaired at object placement, an EC-dependent cognitive task. Next, we show that defects in neuronal nuclear antigen expression and myelin uptake occur in the superficial layers of the EC in 2- to 4-month-old Tg2576 mice. In slices from Tg2576 mice that contained the EC, there were repetitive field potentials evoked by a single stimulus to the underlying white matter, and a greater response to reduced extracellular magnesium ([Mg(2+)]o), suggesting increased excitability. However, deep layer neurons in Tg2576 mice had longer latencies to antidromic activation than wild type mice. The results show changes in the EC at early ages and suggest that altered excitability occurs before extensive plaque pathology.

PDE9A inhibition rescues amyloid beta-induced deficits in synaptic plasticity and cognition

The cyclic nucleotide cGMP is an important intracellular messenger for synaptic plasticity and memory function in rodents. Therefore, inhibition of cGMP degrading phosphodiesterases, like PDE9A, has gained interest as potential target for treatment of cognition deficits in indications like Alzheimer's disease (AD). In fact, PDE9A inhibition results in increased hippocampal long-term potentiation and exhibits procognitive effects in rodents. To date, however, no evidence has been published linking PDE9A inhibition to the pathologic hallmarks of AD such as amyloid beta (Aβ) deposition. Therefore, we investigated the role of PDE9A inhibition in an AD relevant context by testing its effects on Aβ-related deficits in synaptic plasticity and cognition. The PDE9A inhibitor BAY 73-6691 was found to restore long-term potentiation impaired by Aβ42 oligomers. Furthermore, we demonstrated that BAY 73-6691 enhanced cGMP levels in the hippocampus of APP transgenic tg2576 mice and improved memory performance of these mice. Altogether, our results support the hypothesis that inhibition of PDE9A could be a beneficial approach for the treatment of memory impairment in AD patients.

Neural correlates of spatial navigation changes in mild cognitive impairment and Alzheimer's disease

Although the memory impairment is a hallmark of Alzheimer's disease (AD), AD has also been characterized by spatial disorientation, which is present from its early stages. Spatial disorientation in AD manifests itself in getting lost in familiar and unfamiliar places and have been characterized more specifically using spatial navigation tests in both real space and virtual environments as an impairment in multiple spatial abilities, including allocentric and egocentric navigation strategies, visuo-spatial perception, or selection of relevant information for successful navigation. Patients suffering mild cognitive impairment (MCI), who are at a high risk of development of dementia, show impairment in a subset of these abilities, mainly connected with allocentric and egocentric processing. While spatial disorientation in typical AD patients probably reflects neurodegenerative changes in medial and posterior temporal, parietal, and frontal lobes, and retrosplenial cortex, the impairment of spatial navigation in MCI seem to be connected mainly with the medial temporal and also parietal brain changes. In this review, we will summarize the signs of brain disease in most MCI and AD patients showing in various tasks of spatial memory and navigation.

Memantine protects rats treated with intrathecal methotrexate from developing spatial memory deficits

PURPOSE

To test whether memantine can prevent methotrexate-induced cognitive deficits in a preclinical model.

EXPERIMENTAL DESIGN

After noting that methotrexate exposure induces prolonged elevations of the glutamate analog homocysteic acid (HCA) within cerebrospinal fluid, we tested whether intrathecal injection of HCA would produce memory deficits similar to those observed after intrathecal methotrexate. We then tested whether memantine, an antagonist of the N-methyl-d-aspartate (NMDA) subclass of glutamate receptors, could protect animals treated with clinically relevant doses of intrathecal methotrexate against developing memory deficits. Finally, we asked whether memantine affected this pathway beyond inhibiting the NMDA receptor by altering expression of the NMDA receptor or affecting concentrations of HCA or glutamate within the central nervous system.

RESULTS

Four intrathecal doses of methotrexate induced deficits in spatial memory, persisting at least one month following the final injection. Intrathecal HCA was sufficient to reproduce this deficit. Concurrent administration of memantine during the period of methotrexate exposure was protective, decreasing the incidence of methotrexate-induced spatial memory deficits from 56% to 20% (P < 0.05). Memantine neither altered expression of NMDA receptors within the hippocampus nor blunted the methotrexate-induced increases in glutamate or HCA.

CONCLUSIONS

Excitotoxic glutamate analogs including HCA contribute to cognitive deficits observed after intrathecal methotrexate. Memantine, an NMDA receptor antagonist, reduces the incidence of cognitive deficits in rats treated with intrathecal methotrexate, and may therefore benefit patients with cancer receiving similar treatment.

Reorientation deficits are associated with amnestic mild cognitive impairment

BACKGROUND/AIMS

Spatial memory can be impaired in amnestic mild cognitive impairment (aMCI). The present study investigates categorical spatial memory deficits using a virtual navigation-based reorientation task.

METHODS

Twenty-eight amnestic single domain and 23 amnestic multiple domain patients were compared with 53 healthy elderly controls on the performance of the virtual reorientation test (VReoT).

RESULTS

The reorientation performance of participants in both aMCI groups was significantly worse than that of controls suggesting that VReoT detects spatial memory deficits. No significant difference emerged between the 2 groups of patients. A subsequent receiver-operating characteristic analysis showed that a score of 8 had a sensitivity of 80.4% and a specificity of 94.3% (area under the curve = 0.90).

CONCLUSION

The VReoT seemed to be accurate in differentiating patients with aMCI from controls and may represent an evaluation supplement for spatial memory deficits in prodromal stages of Alzheimer's dementia.

Comprehensive neurocognitive endophenotyping strategies for mouse models of genetic disorders

There is a need for refinement of the current behavioral phenotyping methods for mouse models of genetic disorders. The current approach is to perform a behavioral screen using standardized tasks to define a broad phenotype of the model. This phenotype is then compared to what is known concerning the disorder being modeled. The weakness inherent in this approach is twofold: First, the tasks that make up these standard behavioral screens do not model specific behaviors associated with a given genetic mutation but rather phenotypes affected in various genetic disorders; secondly, these behavioral tasks are insufficiently sensitive to identify subtle phenotypes. An alternate phenotyping strategy is to determine the core behavioral phenotypes of the genetic disorder being studied and develop behavioral tasks to evaluate specific hypotheses concerning the behavioral consequences of the genetic mutation. This approach emphasizes direct comparisons between the mouse and human that facilitate the development of neurobehavioral biomarkers or quantitative outcome measures for studies of genetic disorders across species.

Everyday episodic memory in amnestic mild cognitive impairment: a preliminary investigation

BACKGROUND

Decline in episodic memory is one of the hallmark features of Alzheimer's disease (AD) and is also a defining feature of amnestic Mild Cognitive Impairment (MCI), which is posited as a potential prodrome of AD. While deficits in episodic memory are well documented in MCI, the nature of this impairment remains relatively under-researched, particularly for those domains with direct relevance and meaning for the patient's daily life. In order to fully explore the impact of disruption to the episodic memory system on everyday memory in MCI, we examined participants' episodic memory capacity using a battery of experimental tasks with real-world relevance. We investigated episodic acquisition and delayed recall (story-memory), associative memory (face-name pairings), spatial memory (route learning and recall), and memory for everyday mundane events in 16 amnestic MCI and 18 control participants. Furthermore, we followed MCI participants longitudinally to gain preliminary evidence regarding the possible predictive efficacy of these real-world episodic memory tasks for subsequent conversion to AD.

RESULTS

The most discriminating tests at baseline were measures of acquisition, delayed recall, and associative memory, followed by everyday memory, and spatial memory tasks, with MCI patients scoring significantly lower than controls. At follow-up (mean time elapsed: 22.4 months), 6 MCI cases had progressed to clinically probable AD. Exploratory logistic regression analyses revealed that delayed associative memory performance at baseline was a potential predictor of subsequent conversion to AD.

CONCLUSIONS

As a preliminary study, our findings suggest that simple associative memory paradigms with real-world relevance represent an important line of enquiry in future longitudinal studies charting MCI progression over time.

Where did I put that? Patients with amnestic mild cognitive impairment demonstrate widespread reductions in activity during the encoding of ecologically relevant object-location associations

Remembering the location of objects in the environment is both important in everyday life and difficult for patients with amnestic mild cognitive impairment (aMCI), a clinical precursor to Alzheimer's disease. To test the hypothesis that memory impairment for object location in aMCI reflects hippocampal dysfunction, we used an event-related functional magnetic resonance imaging paradigm to compare patients with aMCI and healthy elderly controls (HEC) as they encoded 90 ecologically relevant object-location associations (OLAs). Two additional OLAs, repeated a total of 45 times, served as control stimuli. Memory for these OLAs was assessed following a 1-h delay. The groups were well matched on demographics and brain volumetrics. Behaviorally, HEC remembered significantly more OLAs than did aMCI patients. Activity differences were assessed by contrasting activation for successfully encoded Novel stimuli vs. Repeated stimuli. The HEC demonstrated activity within object-related (ventral visual stream), spatial location-related (dorsal visual stream), and feature binding-related cortical regions (hippocampus and other memory-related regions) as well as in frontal cortex and associated subcortical structures. Activity in most of these regions correlated with memory test performance. Although the aMCI patients demonstrated a similar activation pattern, the HEC showed significantly greater activity within each of these regions. Memory test performance in aMCI patients, in contrast to the HEC, was correlated with activity in regions involved in sensorimotor processing. We conclude that aMCI patients demonstrate widespread cerebral dysfunction, not limited to the hippocampus, and rely on encoding-related mechanisms that differ substantially from healthy individuals.

Neuroanatomic changes and their association with cognitive decline in mild cognitive impairment: a meta-analysis

Mild cognitive impairment (MCI) is an acquired syndrome characterised by cognitive decline not affecting activities of daily living. Using a quantitative meta-analytic approach, we aimed to identify consistent neuroanatomic correlates of MCI and how they are related to cognitive dysfunction. The meta-analysis enrols 22 studies, involving 917 MCI (848 amnestic MCI) patients and 809 healthy controls. Only studies investigating local changes in grey matter and reporting whole-brain results in stereotactic coordinates were included and analysed using the activation likelihood estimation approach. Probabilistic cytoarchitectonic maps were used to compare the localization of the obtained significant effects to histological areas. A correlation between the probability of grey matter changes and cognitive performance of MCI patients was performed. In MCI patients, the meta-analysis revealed three significant clusters of convergent grey matter atrophy, which were mainly situated in the bilateral amygdala and hippocampus, extending to the left medial temporal pole and thalamus, as well as in the bilateral precuneus. A sub-analysis in only amnestic MCI revealed a similar pattern. A voxel-wise analysis revealed a correlation between grey matter reduction and cognitive decline in the right hippocampus and amygdala as well as in the left thalamus. This study provides convergent evidence of a distinct neuroanatomical pattern in MCI. The correlation analysis with cognitive-mnestic decline further highlights the impact of limbic structures and the linkage with data from a functional neuroimaging database provides additional insight into underlying functions. Although different pathologies are underlying MCI, the observed neuroanatomical pattern of structural changes may reflect the common clinical denominator of cognitive impairment.

Landmark recognition in Alzheimer's dementia: spared implicit memory for objects relevant for navigation

Background

In spatial navigation, landmark recognition is crucial. Specifically, memory for objects placed at decision points on a route is relevant. Previous fMRI research in healthy adults showed higher medial-temporal lobe (MTL) activation for objects placed at decision points compared to non-decision points, even at an implicit level. Since there is evidence that implicit learning is intact in amnesic patients, the current study examined memory for objects relevant for navigation in patients with Alzheimer’s dementia (AD).

Methodology/Principal Findings

21 AD patients participated with MTL atrophy assessed on MRI (mean MMSE = 21.2, SD = 4.0), as well as 20 age- and education-matched non-demented controls. All participants watched a 5-min video showing a route through a virtual museum with 20 objects placed at intersections (decision points) and 20 at simple turns (non-decision points). The instruction was to pay attention to the toys (half of the objects) for which they were supposedly tested later. Subsequently, a recognition test followed with the 40 previously presented objects among 40 distracter items (both toys and non-toys). Results showed a better performance for the non-toy objects placed at decision points than non-decision points, both for AD patients and controls.

Conclusion/Significance

Our findings indicate that AD patients with MTL damage have implicit memory for object information relevant for navigation. No decision point effect was found for the attended items. Possibly, focusing attention on the items occurred at the cost of the context information in AD, whereas the controls performed at an optimal level due to intact memory function.