Impaired visual recognition memory predicts Alzheimer's disease in amnestic mild cognitive impairment

Structural, static, and dynamic functional MRI predictors for conversion from mild cognitive impairment to Alzheimer's disease: Inter-cohort validation of Shanghai Memory Study and ADNI

Mild cognitive impairment (MCI) is a critical prodromal stage of Alzheimer's disease (AD), and the mechanism underlying the conversion is not fully explored. Construction and inter-cohort validation of imaging biomarkers for predicting MCI conversion is of great challenge at present, due to lack of longitudinal cohorts and poor reproducibility of various study-specific imaging indices. We proposed a novel framework for inter-cohort MCI conversion prediction, involving comparison of structural, static, and dynamic functional brain features from structural magnetic resonance imaging (sMRI) and resting-state functional MRI (fMRI) between MCI converters (MCI_C) and non-converters (MCI_NC), and support vector machine for construction of prediction models. A total of 218 MCI patients with 3-year follow-up outcome were selected from two independent cohorts: Shanghai Memory Study cohort for internal cross-validation, and Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort for external validation. In comparison with MCI_NC, MCI_C were mainly characterized by atrophy, regional hyperactivity and inter-network hypo-connectivity, and dynamic alterations characterized by regional and connectional instability, involving medial temporal lobe (MTL), posterior parietal cortex (PPC), and occipital cortex. All imaging-based prediction models achieved an area under the curve (AUC) > 0.7 in both cohorts, with the multi-modality MRI models as the best with excellent performances of AUC > 0.85. Notably, the combination of static and dynamic fMRI resulted in overall better performance as relative to static or dynamic fMRI solely, supporting the contribution of dynamic features. This inter-cohort validation study provides a new insight into the mechanisms of MCI conversion involving brain dynamics, and paves a way for clinical use of structural and functional MRI biomarkers in future.

Face Name Associative Memory Exam and biomarker status in the ARMADA study: Advancing reliable measurement in Alzheimer's disease and cognitive aging

The Face Name Associative Memory Exam (FNAME) was introduced into the NIH Toolbox as part of the ARMADA study and establishes normative data for diverse participants, ages 64 to 85+, and proposes cutoff scores between biomarker positive versus negative (+/-) groups. The FNAME was administered to 257 participants across the clinical spectrum with 122 having amyloid biomarkers. Linear regression explored the association between demographics and FNAME and between amyloid (+/-) groups. Receiver operating characteristic curves (ROC) identified performance thresholds that best discriminated between biomarker (+/-) individuals. Lower FNAME scores occurred in males, older ages, Black/African Americans, Hispanics, and biomarker-positive participants. ROC analyses demonstrated acceptable accuracy (0.73 to 0.77) but only when combined with clinical status. The diagnostic discrimination of amyloid positivity was acceptable but not excellent, suggesting the FNAME may be a better screening indicator of clinical status rather than amyloid deposition in cognitively normal individuals. Normative data are provided.

Targeting the function of the transentorhinal cortex to identify early cognitive markers of Alzheimer's disease

Initial neuropathology of early Alzheimer's disease accumulates in the transentorhinal cortex. We review empirical data suggesting that tasks assessing cognitive functions supported by the transenthorinal cortex are impaired as early as the preclinical stages of Alzheimer's disease. These tasks span across various domains, including episodic memory, semantic memory, language, and perception. We propose that all tasks sensitive to Alzheimer-related transentorhinal neuropathology commonly rely on representations of entities supporting the processing and discrimination of items having perceptually and conceptually overlapping features. In the future, we suggest a screening tool that is sensitive and specific to very early Alzheimer's disease to probe memory and perceptual discrimination of highly similar entities.

Jacob-induced transcriptional inactivation of CREB promotes Aβ-induced synapse loss in Alzheimer's disease

Synaptic dysfunction caused by soluble β-amyloid peptide (Aβ) is a hallmark of early-stage Alzheimer's disease (AD), and is tightly linked to cognitive decline. By yet unknown mechanisms, Aβ suppresses the transcriptional activity of cAMP-responsive element-binding protein (CREB), a master regulator of cell survival and plasticity-related gene expression. Here, we report that Aβ elicits nucleocytoplasmic trafficking of Jacob, a protein that connects a NMDA-receptor-derived signalosome to CREB, in AD patient brains and mouse hippocampal neurons. Aβ-regulated trafficking of Jacob induces transcriptional inactivation of CREB leading to impairment and loss of synapses in mouse models of AD. The small chemical compound Nitarsone selectively hinders the assembly of a Jacob/LIM-only 4 (LMO4)/ Protein phosphatase 1 (PP1) signalosome and thereby restores CREB transcriptional activity. Nitarsone prevents impairment of synaptic plasticity as well as cognitive decline in mouse models of AD. Collectively, the data suggest targeting Jacob protein-induced CREB shutoff as a therapeutic avenue against early synaptic dysfunction in AD.

Development of a simple screening tool for determining cognitive status in Alzheimer's disease

Cognitive screening is often a first step to document cognitive status of patients suspected having Alzheimer's disease (AD). Unfortunately, screening neuropsychological tests are often insensitivity in the detection. The goal of this study was to develop a simple and sensitive screening neuropsychological test to facilitate early detection of AD. This study recruited 761 elderly individuals suspected of having AD and presenting various cognitive statuses (mean age: 77.69 ± 8.45 years; proportion of females: 65%; cognitively unimpaired, CU, n = 133; mild cognitive impairment, MCI, n = 231; dementia of Alzheimer's type, DAT, n = 397). This study developed a novel screening neuropsychological test incorporating assessments of the core memory deficits typical of early AD and an interview on memory function with an informant. The proposed History-based Artificial Intelligence-Show Chwan Assessment of Cognition (HAI-SAC) was assessed in terms of psychometric properties, test time, and discriminative ability. The results were compared with those obtained using other common screening tests, including Cognitive Abilities Screening Instrument (CASI), Montreal Cognitive Assessment (MoCA), and an extracted Mini-Mental State Examination score from CASI. HAI-SAC demonstrated acceptable internal consistency. Factor analysis revealed two factors: memory (semantic and contextual) and cognition-related information from informants. The assessment performance of HAI-SAC was strongly correlated with that of the common screening neuropsychological tests addressed in this study. HAI-SAC outperformed the other tests in differentiating CU individuals from patients with MCI (sensitivity: 0.87; specificity: 0.58; area under the curve [AUC]: 0.78) or DAT (sensitivity: 0.99; specificity: 0.89; AUC: 0.98). Performance of HAI-SAC on differentiating MCI from DAT was on par with performances of other tests (sensitivity: 0.78; specificity: 0.84; AUC: 0.87), while the test time was less than one quarter that of CASI and half that of MoCA. HAI-SAC is psychometrically sound, cost-effective, and sensitive in discriminating the cognitive status of AD.

Targeted Suppression of Lipoprotein Receptor LSR in Astrocytes Leads to Olfactory and Memory Deficits in Mice

Perturbations of cholesterol metabolism have been linked to neurodegenerative diseases. Glia–neuron crosstalk is essential to achieve a tight regulation of brain cholesterol trafficking. Adequate cholesterol supply from glia via apolipoprotein E-containing lipoproteins ensures neuronal development and function. The lipolysis-stimulated lipoprotein receptor (LSR), plays an important role in brain cholesterol homeostasis. Aged heterozygote Lsr+/− mice show altered brain cholesterol distribution and increased susceptibility to amyloid stress. Since LSR expression is higher in astroglia as compared to neurons, we sought to determine if astroglial LSR deficiency could lead to cognitive defects similar to those of Alzheimer’s disease (AD). Cre recombinase was activated in adult Glast-CreERT/lsrfl/fl mice by tamoxifen to induce astroglial Lsr deletion. Behavioral phenotyping of young and old astroglial Lsr KO animals revealed hyperactivity during the nocturnal period, deficits in olfactory function affecting social memory and causing possible apathy, as well as visual memory and short-term working memory problems, and deficits similar to those reported in neurodegenerative diseases, such as AD. Furthermore, GFAP staining revealed astroglial activation in the olfactory bulb. Therefore, astroglial LSR is important for working, spatial, and social memory related to sensory input, and represents a novel pathway for the study of brain aging and neurodegeneration.

A Lack of Practice Effects on Memory Tasks Predicts Conversion to Alzheimer Disease in Patients With Amnestic Mild Cognitive Impairment

The aim of the current study was to test the accuracy of practice effects, that is, improvement in test performance due to repeated neuropsychological evaluations, in identifying patients with amnestic mild cognitive impairment (a-MCI) at greater risk of conversion to Alzheimer disease (AD). For this purpose, we conducted a longitudinal study of 54 patients diagnosed with a-MCI at the first assessment and followed-up for 4 years. During this time, 18 patients converted to AD. Baseline and 6- to 12-month follow-up performances on a large set of neuropsychological tests were analyzed to determine their diagnostic ability to predict later conversion to dementia. Results demonstrate that a lack of practice effects on episodic memory tests is an accurate prognostic indicator of late conversion to AD in a-MCI patients. In fact, even though the performance of both groups was substantially comparable at the baseline evaluation, stable a-MCI patients greatly improved their memory performance at retest after 6 to 12 months; instead, scores of converter a-MCI remained stable or decreased passing from baseline to follow-up. Standardized z-change scores on memory tasks, which were computed as a reliable measure of performance change, classified group membership with very good overall accuracy, which was higher than the classification of converter and stable a-MCIs provided by baseline or follow-up scores. We hypothesize that the lack of practice effects on memory tasks mirrors the early involvement of medial temporal lobe areas in converter a-MCI that are fundamental for the consolidation of new memory traces.

Changes in visual memory in mild cognitive impairment: a longitudinal study with CANTAB

BACKGROUND

Mild cognitive impairment (MCI), as a stage in the cognitive continuum between normal ageing and dementia, is mainly characterized by memory impairment. The aims of this study were to examine CANTAB measures of temporal changes of visual memory in MCI and to evaluate the usefulness of the baseline scores for predicting changes in cognitive status.

METHODS

The study included 201 participants aged over 50 years with subjective cognitive complaints. Visual memory was assessed with four CANTAB tests [paired associates learning (PAL), delayed matching to sample (DMS), pattern recognition memory (PRM) and spatial span (SSP)] administered at baseline and on two further occasions, with a follow-up interval of 18-24 months. Participants were divided into three groups according to the change in their cognitive status: participants with subjective cognitive complaints who remained stable, MCI participants who remained stable (MCI-Stable) and MCI participants whose cognitive deterioration continued (MCI-Worsened). Linear mixed models were used to model longitudinal changes, with evaluation time as a fixed variable, and multinomial regression models were used to predict changes in cognitive status.

RESULTS

Isolated significant effects were obtained for age and group with all CANTAB tests used. Interactions between evaluation time and group were identified in the PAL and DMS tests, indicating different temporal patterns depending on the changes in cognitive status. Regression models also indicated that CANTAB scores were good predictors of changes in cognitive status.

CONCLUSIONS

Decline in visual memory measured by PAL and DMS tests can successfully distinguish different types of MCI, and considered together PAL, DMS, PRM and SSP can predict changes in cognitive status.

Machine Learning for the Prediction of Amyloid Positivity in Amnestic Mild Cognitive Impairment

BACKGROUND

Amyloid-β (Aβ) evaluation in amnestic mild cognitive impairment (aMCI) patients is important for predicting conversion to Alzheimer's disease. However, Aβ evaluation through Aβ positron emission tomography (PET) is limited due to high cost and safety issues.

OBJECTIVE

We therefore aimed to develop and validate prediction models of Aβ positivity for aMCI using optimal interpretable machine learning (ML) approaches utilizing multimodal markers.

METHODS

We recruited 529 aMCI patients from multiple centers who underwent Aβ PET. We trained ML algorithms using a training cohort (324 aMCI from Samsung medical center) with two-phase modelling: model 1 included age, gender, education, diabetes, hypertension, apolipoprotein E genotype, and neuropsychological test scores; model 2 included the same variables as model 1 with additional MRI features. We used four-fold cross-validation during the modelling and evaluated the models on an external validation cohort (187 aMCI from the other centers).

RESULTS

Model 1 showed good accuracy (area under the receiver operating characteristic curve [AUROC] 0.837) in cross-validation, and fair accuracy (AUROC 0.765) in external validation. Model 2 led to improvement in the prediction performance with good accuracy (AUROC 0.892) in cross validation compared to model 1. Apolipoprotein E genotype, delayed recall task scores, and interaction between cortical thickness in the temporal region and hippocampal volume were the most important predictors of Aβ positivity.

CONCLUSION

Our results suggest that ML models are effective in predicting Aβ positivity at the individual level and could help the biomarker-guided diagnosis of prodromal AD.

Characteristics of Individuals Who Converted to Dementia during a 5-Year Follow-Up

INTRODUCTION

Early diagnosis of dementia is important; however, the diagnostic criteria for the preclinical stage of dementia, including biomarkers and pathophysiological markers, are not suitable for application in patients in real-world clinical settings. One potential noninvasive method to predict the risk of dementia conversion is the neuropsychological test. Therefore, in this study, we examined the results of various assessments, such as comprehensive neuropsychological tests, and the daily function of participants who were evaluated periodically for 5 years.

METHODS

All participants were outpatients or inpatients with subjective cognitive complaints, who visited a local university hospital for neuropsychiatric evaluation, between January 2011 and January 2019. Of a total of 1,652 subjects who underwent initial screening during this period, 107 were nondemented individuals. These participants underwent periodic comprehensive cognitive tests for up to 5 years. Survival and factors affecting dementia conversion were analyzed using the time-dependent Cox regression analysis. Assessment items included demographic information, including age, sex, and education; 5 cognitive domains of a comprehensive neuropsychological test including memory, language, attention, visuospatial functions, and frontal (executive) function; Barthel's activities of daily living; the mini-mental state examination findings; and clinical dementia rating (CDR) scores.

RESULTS

This study included 61 participants (21 women and 40 men) who developed dementia during the study period. Verification of the cognitive variables affecting dementia conversion revealed that better memory was associated with a lower risk of conversion (hazard ratio [HR] = 0.614, p = 0.005) and higher attention was associated with a higher risk of conversion (HR = 1.602, p = 0.023). In the analysis of the subscales of the CDR, a higher community affairs score (i.e., less social activities) was associated with a higher risk of conversion (HR = 10.814, p = 0.028).

CONCLUSION

Individuals with prominent memory decline or problems with social activities should be carefully observed for dementia conversion. Cognitive intervention techniques for cognitive stimulation, such as social and leisure activities, as well as cognitive training need to be actively used for patients in whom dementia is a concern.

Association between composite scores of domain-specific cognitive functions and regional patterns of atrophy and functional connectivity in the Alzheimer's disease spectrum

BACKGROUND

Cognitive decline has been found to be associated with gray matter atrophy and disruption of functional neural networks in Alzheimer's disease (AD) in structural and functional imaging (fMRI) studies. Most previous studies have used single test scores of cognitive performance among monocentric cohorts. However, cognitive domain composite scores could be more reliable than single test scores due to the reduction of measurement error. Adopting a multicentric resting state fMRI (rs-fMRI) and cognitive domain approach, we provide a comprehensive description of the structural and functional correlates of the key cognitive domains of AD.

METHOD

We analyzed MRI, rs-fMRI and cognitive domain score data of 490 participants from an interim baseline release of the multicenter DELCODE study cohort, including 54 people with AD, 86 with Mild Cognitive Impairment (MCI), 175 with Subjective Cognitive Decline (SCD), and 175 Healthy Controls (HC) in the AD-spectrum. Resulting cognitive domain composite scores (executive, visuo-spatial, memory, working memory and language) from the DELCODE neuropsychological battery (DELCODE-NP), were previously derived using confirmatory factor analysis. Statistical analyses examined the differences between diagnostic groups, and the association of composite scores with regional atrophy and network-specific functional connectivity among the patient subgroup of SCD, MCI and AD.

RESULT

Cognitive performance, atrophy patterns and functional connectivity significantly differed between diagnostic groups in the AD-spectrum. Regional gray matter atrophy was positively associated with visuospatial and other cognitive impairments among the patient subgroup in the AD-spectrum. Except for the visual network, patterns of network-specific resting-state functional connectivity were positively associated with distinct cognitive impairments among the patient subgroup in the AD-spectrum.

CONCLUSION

Consistent associations between cognitive domain scores and both regional atrophy and network-specific functional connectivity (except for the visual network), support the utility of a multicentric and cognitive domain approach towards explicating the relationship between imaging markers and cognition in the AD-spectrum.

A Pilot Study Comparing Effects of Bifrontal Versus Bitemporal Transcranial Direct Current Stimulation in Mild Cognitive Impairment and Mild Alzheimer Disease

OBJECTIVE

While transcranial direct current stimulation (tDCS) can enhance aspects of memory in patients with mild cognitive impairment (MCI) and Alzheimer disease (AD), there has been wide variability in both the placement of tDCS electrodes and treatment response. This study compared the effects of bifrontal (anodal stimulation over the dorsolateral prefrontal cortices), bitemporal (anodal stimulation over the temporal cortices), and sham tDCS on cognitive performance in MCI and AD.

METHODS

Seventeen patients diagnosed with MCI or mild AD received 3 sessions of anodal tDCS (bifrontal, bitemporal, 2 mA for 20 minutes; and sham) in random order. Sessions were separated by 1 week. The Alzheimer's Disease Assessment Scale-Cognitive Word Recognition Task, Alzheimer's Disease Assessment Scale-Cognitive Word Recall Task, 2-back, and Montreal Cognitive Assessment were used to assess cognition.

RESULTS

There was a significant effect of stimulation condition on 2-back accuracy (F2,28 = 5.28 P = 0.01, ηp = 0.27), with greater improvements following bitemporal tDCS compared with both bifrontal and sham stimulations. There were no significant changes on other outcome measures following any stimulation. Adverse effects from stimulation were mild and temporary.

CONCLUSIONS

These findings demonstrate that improvements in specific memory tasks can be safely achieved after a single session of bitemporal tDCS in MCI and mild AD patients.

A Meta-Analysis of Semantic Memory in Mild Cognitive Impairment

Accumulating evidence over the past decade suggests that semantic deficits represent a consistent feature of Mild Cognitive Impairment (MCI). A meta-analysis was performed to examine if semantic deficits are consistently found in patients with MCI. Studies meeting all inclusion criteria were selected for the current meta-analysis. An effect size and a weight were calculated for each study. A random effect model was performed to assess the overall difference in semantic performances between MCI patients and healthy subjects. 22 studies (476 healthy participants, 476 MCI patients, mean Mini Mental Status Examination of the MCI patients: 27.05 ± 0.58) were included in the meta-analysis. Results indicate that MCI patients systematically performed significantly worse than healthy matched controls in terms of overall semantic performance (mean effect size of 1.02; 95% CI [0.80; 1.24]). Semantic deficits are a key feature of MCI. Semantic tests should be incorporated in routine clinical assessments.

Neuropsychological predictors of cognitive deterioration in non-demented individuals

Introduction: Previous studies performed neuropsychological tests in non-demented patients, especially those with mild cognitive impairment (MCI), to predict dementia. Few recent studies reported that subjective cognitive decline (SCD) itself predicts dementia conversion. We evaluated certain characteristics and neuropsychological tests to predict cognitive deterioration in non-demented individuals.Methods: This study included 106 participants with subjective cognitive complaints (SCCs) classified as non-demented (90 MCI and 16 SCD). Data were collected at baseline and follow-up, wherein participants completed a comprehensive neuropsychological assessment to assess their cognitive and daily functions.Results: During the follow-up of all participants, 52 converted to dementia, while 54 did not. There were significant differences in age and education years, as well as language, memory, frontal lobe function, and Barthel's Activities of Daily Living Index between the groups. Correlation analysis showed a significant correlation between the deterioration of the Clinical Dementia Rating scores and baseline language, memory, and frontal lobe function scores.Conclusion(s): SCDs consistently worrying about their SCCs and those identified with SCD by their caregivers were prone to cognitive function deterioration over time. Changes in language, memory, and frontal lobe function in neurocognitive tests were significantly different between the dementia converters and non dementia converters group. Particularly, SCD and MCI individuals with significantly poor initial executive function and memory abilities should be closely monitored for future cognitive decline.

Visual versus Verbal Working Memory in Statistically Determined Patients with Mild Cognitive Impairment: On behalf of the Consortium for Clinical and Epidemiological Neuropsychological Data Analysis (CENDA)

OBJECTIVE

Previous research in mild cognitive impairment (MCI) suggests that visual episodic memory impairment may emerge before analogous verbal episodic memory impairment. The current study examined working memory (WM) test performance in MCI to assess whether patients present with greater visual versus verbal WM impairment. WM performance was also assessed in relation to hippocampal occupancy (HO), a ratio of hippocampal volume to ventricular dilation adjusted for demographic variables and intracranial volume.

METHODS

Jak et al. (2009) (The American Journal of Geriatric Psychiatry, 17, 368-375) and Edmonds, Delano-Wood, Galasko, Salmon, & Bondi (2015) (Journal of Alzheimer's Disease, 47(1), 231-242) criteria classify patients into four groups: little to no cognitive impairment (non-MCI); subtle cognitive impairment (SCI); amnestic MCI (aMCI); and a combined mixed/dysexecutive MCI (mixed/dys MCI). WM was assessed using co-normed Wechsler Adult Intelligence Scale-IV (WAIS-IV) Digit Span Backwards and Wechsler Memory Scale-IV (WMS-IV) Symbol Span Z-scores.

RESULTS

Between-group analyses found worse WMS-IV Symbol Span and WAIS-IV Digit Span Backwards performance for mixed/dys MCI compared to non-MCI patients. Within-group analyses found no differences for non-MCI patients; however, all other groups scored lower on WMS-IV Symbol Span than WAIS-IV Digit Span Backwards. Regression analysis with HO as the dependent variable was statistically significant for WMS-IV Symbol Span performance. WAIS-IV Digit Span Backwards performance failed to reach statistical significance.

CONCLUSIONS

Worse WMS-IV Symbol Span performance was observed in patient groups with measurable neuropsychological impairment and better WMS-IV Symbol Span performance was associated with higher HO ratios. These results suggest that visual WM may be particularly sensitive to emergent illness compared to analogous verbal WM tests.

A Nomogram for Predicting Amyloid PET Positivity in Amnestic Mild Cognitive Impairment

BACKGROUND

Most clinical trials focus on amyloid-β positive (Aβ+) amnestic mild cognitive impairment (aMCI), but screening failures are high because only a half of patients with aMCI are positive on Aβ PET. Therefore, it becomes necessary for clinicians to predict which patients will have Aβ biomarker.

OBJECTIVE

We aimed to compare clinical factors, neuropsychological (NP) profiles, and apolipoprotein E (APOE) genotype between Aβ+ aMCI and Aβ-aMCI and to develop a clinically useful prediction model of Aβ positivity on PET (PET-Aβ+) in aMCI using a nomogram.

METHODS

We recruited 523 aMCI patients who underwent Aβ PET imaging in a nation-wide multicenter cohort. The results of NP measures were divided into following subgroups: 1) Stage (Early and Late-stage), 2) Modality (Visual, Verbal, and Both), 3) Recognition failure, and 4) Multiplicity (Single and Multiple). A nomogram for PET-Aβ+ in aMCI patients was constructed using a logistic regression model.

RESULTS

PET-Aβ+ had significant associations with NP profiles for several items, including high Clinical Dementia Rating Scale Sum of Boxes score (OR 1.47, p = 0.013) and impaired memory modality (impaired both visual and verbal memories compared with visual only, OR 3.25, p = 0.001). Also, presence of APOEɛ4 (OR 4.14, p < 0.001) was associated with PET-Aβ+. These predictors were applied to develop the nomogram, which showed good prediction performance (C-statistics = 0.79). Its prediction performances were 0.77/0.74 in internal/external validation.

CONCLUSIONS

The nomogram consisting of NP profiles, especially memory domain, and APOEɛ4 genotype may provide a useful predictive model of PET-Aβ+ in patients with aMCI.

Visual memory tests enhance the identification of amnestic MCI cases at greater risk of Alzheimer's disease

OBJECTIVES

To investigate whether amnestic mild cognitive impairment (aMCI) identified with visual memory tests conveys an increased risk of Alzheimer's disease (risk-AD) and if the risk-AD differs from that associated with aMCI based on verbal memory tests.

PARTICIPANTS

4,771 participants aged 70.76 (SD = 6.74, 45.4% females) from five community-based studies, each a member of the international COSMIC consortium and from a different country, were classified as having normal cognition (NC) or one of visual, verbal, or combined (visual and verbal) aMCI using international criteria and followed for an average of 2.48 years. Hazard ratios (HR) and individual patient data (IPD) meta-analysis analyzed the risk-AD with age, sex, education, single/multiple domain aMCI, and Mini-Mental State Examination (MMSE) scores as covariates.

RESULTS

All aMCI groups (n = 760) had a greater risk-AD than NC (n = 4,011; HR range = 3.66 - 9.25). The risk-AD was not different between visual (n = 208, 17 converters) and verbal aMCI (n = 449, 29 converters, HR = 1.70, 95%CI: 0.88, 3.27, p = 0.111). Combined aMCI (n = 103, 12 converters, HR = 2.34, 95%CI: 1.13, 4.84, p = 0.023) had a higher risk-AD than verbal aMCI. Age and MMSE scores were related to the risk-AD. The IPD meta-analyses replicated these results, though with slightly lower HR estimates (HR range = 3.68, 7.43) for aMCI vs. NC.

CONCLUSIONS

Although verbal aMCI was most common, a significant proportion of participants had visual-only or combined visual and verbal aMCI. Compared with verbal aMCI, the risk-AD was the same for visual aMCI and higher for combined aMCI. Our results highlight the importance of including both verbal and visual memory tests in neuropsychological assessments to more reliably identify aMCI.

Visual and Verbal Serial List Learning in Patients with Statistically-Determined Mild Cognitive Impairment

Background and Objective

Prior research with patients with mild cognitive impairment (MCI) suggests that visual versus verbal episodic memory test performance may be more sensitive to emergent illness. However, little research has examined visual versus verbal episodic memory performance as related to MCI subtypes.

Research Design and Methods

Patients were diagnosed with non-MCI, amnestic MCI (aMCI), and combined mixed/dysexecutive MCI (mixed/dys MCI). Visual and verbal episodic memory were assessed with the Brief Visuospatial Memory Test-Revised (BVMT-R) and the 12-word Philadelphia (repeatable) Verbal Learning Test (P[r]VLT), respectively.

Results

BVMT-R and P(r)VLT scores yielded similar between-group patterns of performance. Non-MCI patients scored better than other groups on all parameters. aMCI and mixed/dys MCI did not differ on immediate or delayed free recall. Both delayed BVMT-R and P(r)VLT recognition test performance dissociated all three groups. Logistic regression analyses found that BVMT-R delayed free recall and delayed recognition scores correctly classified more patients with MCI (75.40%) than analogous P(r)VLT scores (66.20%). Visual versus verbal memory within-group analyses found no differences among non-MCI patients; P(r)VLT immediate free recall was worse among aMCI patients, but BVMT-R immediate free recall and delayed recognition were worse among mixed/dys MCI patients.

Discussion and Implications

Between-group analyses found convergent patterns of performance such that both tests identified elements of amnesia. However, logistic and within-group analyses found differing performance patterns suggesting that impaired visual episodic memory performance may be specific to emergent illness in mixed/dys MCI. Complementary but divergent neurocognitive networks may underlie visual versus verbal episodic memory performance in some patients with MCI.

Data-driven prognostic features of cognitive trajectories in patients with amnestic mild cognitive impairments

BACKGROUND

Although amnestic mild cognitive impairment (aMCI) is generally considered to be a prodromal stage of Alzheimer's disease, patients with aMCI show heterogeneous patterns of progression. Moreover, there are few studies investigating data-driven cognitive trajectory in aMCI. We therefore classified patients with aMCI based on their cognitive trajectory, measured by clinical dementia rating sum of boxes (CDR-SOB). Then, we compared the clinical and neuroimaging features among groups classified by cognitive trajectory.

METHODS

We retrospectively recruited 278 patients with aMCI who underwent three or more timepoints of neuropsychological testing. They also had magnetic resonance imaging (MRI) including structured three-dimensional volume images. Cortical thickness was measured using surface-based methods. We performed trajectory analyses to classify our aMCI patients according to their progression and investigate their cognitive trajectory using CDR-SOB.

RESULTS

Trajectory analyses showed that patients with aMCI were divided into three groups: stable (61.8%), slow decliner (31.7%), and fast decliner (6.5%). Changes throughout a mean follow-up duration of 3.7 years in the CDR-SOB for the subgroups of stable/slow/fast decliners were 1.3-, 6.4-, and 12-point increases, respectively. Decliners were older and carried apolipoprotein E4 (APOE4) genotypes more frequently than stable patients. Compared with the stable group, decliners showed a higher frequency of aMCI patients with both visual and verbal memory dysfunction, late stage aMCI, and multiple domain dysfunction. In addition, compared with the stable group, the slow decliners showed cortical thinning predominantly in bilateral parietotemporal areas, while the fast decliners showed cortical thinning predominantly in bilateral frontotemporal areas. Both decliner groups showed worse cognitive function in attention, language, visuospatial, memory, and frontal/executive domains than the stable group.

CONCLUSIONS

Our data-driven trajectory analysis provides new insights into heterogeneous cognitive trajectories of aMCI and further suggests that baseline clinical and neuroimaging profiles might predict aMCI patients with poor prognosis.

Differential Outcomes Training Ameliorates Visual Memory Impairments in Patients With Alzheimer's Disease: A Pilot Study

It is well known that Alzheimer's disease (AD), the most common form of dementia, is associated with deficits in cognitive processes including visual memory impairments. One technique that might be used to ameliorate these impairments is the differential outcomes procedure (DOP) that involves associating each to-be-remembered stimulus with a specific outcome. Objective: Previous research has demonstrated that the DOP can be used to reduce or eliminate the learning and memory deficits associated with animal models of amnesia and dementia. Furthermore, this procedure has been shown to improve delayed facial recognition in healthy older adults as well as in patients diagnosed with AD. The main aim of the present study is twofold: to extend these findings to other types of visual stimulus and to investigate the effect of the DOP in memory retention in AD patients. Method: Ten patients diagnosed with AD and 10 healthy controls participated in this study. The experiment included two phases. In the first one, they had to perform a delayed matching-to-sample task. In the second phase, participants performed a recognition memory task, designed to assess long-term retention, 1 h and 1 week after the training. Results: Participants showed a better memory-based performance as well as a higher long-term retention of the information when trained under the differential outcomes condition, relative to the non-differential outcomes condition. Conclusions: The DOP seems to be an effective, easy-to-implement, technique to enhance visual memory in AD patients.

Dissociable cognitive impairments in two strains of transgenic Alzheimer's disease mice revealed by a battery of object-based tests

Object recognition tasks detect cognitive deficits in transgenic Alzheimer's disease (AD) mouse models. Object recognition, however, is not a unitary process, and there are many uncharacterized facets of object processing with relevance to AD. We therefore systematically evaluated object processing in 5xFAD and 3xTG AD mice to clarify the nature of object recognition-related deficits. Twelve-month-old male and female 5xFAD and 3xTG mice were assessed on tasks for object identity recognition, spatial recognition, and multisensory object perception. Memory and multisensory perceptual impairments were observed, with interesting dissociations between transgenic AD strains and sex that paralleled neuropathological changes. Overreliance on the widespread "object recognition" task threatens to slow discovery of potentially significant and clinically relevant behavioural effects related to this multifaceted cognitive function. The current results support the use of carefully designed object-based test batteries to clarify the relationship between "object recognition" impairments and specific aspects of AD pathology in rodent models.

Enhancement of Visuospatial Working Memory by the Differential Outcomes Procedure in Mild Cognitive Impairment and Alzheimer's Disease

In the present study we investigated the efficacy of the differential outcomes procedure (DOP) to improve visuospatial working memory in patients with Alzheimer’s disease and mild cognitive impairment (MCI). The DOP associates correct responses to the to-be-remember stimulus with unique outcomes. Eleven patients diagnosed with Alzheimer’s disease, 11 participants with MCI, and 17 healthy matched controls performed a spatial delayed memory task under the DOP and a control condition (non-differential outcomes –NOP-). We found that performance (terminal accuracy) was significantly better in the DOP condition relative to the NOP condition in all three groups of participants. AD patients performed worse, and took longer to benefit from the DOP. In line with previous animal and human research, we propose that the DOP activates brain structures and cognitive mechanisms that are less affected by healthy and pathological aging, optimizing in this way the function of the cognitive system.

Dementia-Predicting Cognitive Risk Score and Its Correlation with Cortical Thickness in Parkinson Disease

BACKGROUND

We developed a risk score system to predict risks of developing dementia in individual Parkinson disease (PD) patients using baseline neuropsychological tests.

METHODS

A total of 216 nondemented PD patients underwent a baseline neuropsychological evaluation and were followed up for a mean of 2.7 (±1.1) years. Univariate Cox regression models controlled for age, gender, and education selected neuropsychological tests individually predicting dementia risk. Then, a multivariate Cox regression model combined them into a cognitive risk score system. Cortical areas correlating with cognitive risk score were investigated using a separate MRI data set from 207 nondemented PD patients.

RESULTS

Fifty-two patients (23.9%) developed dementia. The univariate Cox regression analyses identified the confrontational naming and semantic fluency tests, frontal/executive function tests, immediate verbal memory test, and visuospatial function test as predicting dementia risk. The calculated cognitive risk score (range 53-188) predicted future dementia with moderate accuracy (integrated area under the curve = 0.79; 95% CI: 0.73-0.85). A higher cognitive risk score correlated with cortical thinning in the right anteromedial temporal cortex, bilateral posterior cingulate cortex, right anterior cingulate cortex, left parahippocampal gyrus, and right superior frontal cortex in a separate MRI data set.

CONCLUSION

The cognitive risk score system is a useful approach to predict the dementia risk among PD patients.

Resting-State Functional Connectivity Changes Associated with Visuospatial Cognitive Deficits in Patients with Mild Alzheimer Disease

BACKGROUND/AIMS

Alzheimer disease (AD) is a neurodegenerative disorder characterized by progressive disconnection of various brain networks leading to neuropsychological impairment. Pathology in the visual association areas has been documented in presymptomatic AD and therefore we aimed at examining the relationship between brain connectivity and visuospatial (VS) cognitive deficits in early AD.

METHODS

Tests for VS working memory, episodic memory and construction were used to classify patients with AD (n = 48) as having severe VS deficits (n = 12, female = 4) or mild deficits (n = 11, female = 4). Resting-state functional magnetic resonance imaging and structural images were acquired as per the standard protocols. Between-group differences in resting-state functional connectivity (rsFC) were examined by dual regression analysis correcting for age, gender, and total brain volume.

RESULTS

Patients with AD having severe VS deficits exhibited significantly reduced rsFC in bilateral lingual gyri of the visual network compared to patients with mild VS deficits.

CONCLUSION

Reduced rsFC in the visual network in patients with more severe VS deficits may be a functional neuroimaging biomarker reflecting hypoconnectivity of the brain with progressive VS deficits during early AD.

Using Base Rate of Low Scores to Identify Progression from Amnestic Mild Cognitive Impairment to Alzheimer's Disease

OBJECTIVES

To investigate the implications of obtaining one or more low scores on a battery of cognitive tests on diagnosing mild cognitive impairment (MCI).

DESIGN

Observational longitudinal study.

SETTING

Alzheimer's Disease Neuroimaging Initiative.

PARTICIPANTS

Normal controls (NC, n = 280) and participants with MCI (n = 415) according to Petersen criteria were reclassified using the Jak/Bondi criteria and number of impaired tests (NIT) criteria.

MEASUREMENTS

Diagnostic statistics and hazard ratios of progression to Alzheimer's disease (AD) were compared according to diagnostic criteria.

RESULTS

The NIT criteria were a better predictor of progression to AD than the Petersen or Jak/Bondi criteria, with optimal sensitivity, specificity, and positive and negative predictive value.

CONCLUSION

Considering normal variability in cognitive test performance when diagnosing MCI may help identify individuals at greatest risk of progression to AD with greater certainty.

A Method to Train Marmosets in Visual Working Memory Task and Their Performance

Learning and memory processes are similarly organized in humans and monkeys; therefore, monkeys can be ideal models for analyzing human aging processes and neurodegenerative diseases such as Alzheimer's disease. With the development of novel gene modification methods, common marmosets (Callithrix jacchus) have been suggested as an animal model for neurodegenerative diseases. Furthermore, the common marmoset's lifespan is relatively short, which makes it a practical animal model for aging. Working memory deficits are a prominent symptom of both dementia and aging, but no data are currently available for visual working memory in common marmosets. The delayed matching-to-sample task is a powerful tool for evaluating visual working memory in humans and monkeys; therefore, we developed a novel procedure for training common marmosets in such a task. Using visual discrimination and reversal tasks to direct the marmosets' attention to the physical properties of visual stimuli, we successfully trained 11 out of 13 marmosets in the initial stage of the delayed matching-to-sample task and provided the first available data on visual working memory in common marmosets. We found that the marmosets required many trials to initially learn the task (median: 1316 trials), but once the task was learned, the animals needed fewer trials to learn the task with novel stimuli (476 trials or fewer, with the exception of one marmoset). The marmosets could retain visual information for up to 16 s. Our novel training procedure could enable us to use the common marmoset as a useful non-human primate model for studying visual working memory deficits in neurodegenerative diseases and aging.

Muscarinic Receptor-Dependent Long Term Depression in the Perirhinal Cortex and Recognition Memory are Impaired in the rTg4510 Mouse Model of Tauopathy

Neurodegenerative diseases affecting cognitive dysfunction, such as Alzheimer's disease and fronto-temporal dementia, are often associated impairments in the visual recognition memory system. Recent evidence suggests that synaptic plasticity, in particular long term depression (LTD), in the perirhinal cortex (PRh) is a critical cellular mechanism underlying recognition memory. In this study, we have examined novel object recognition and PRh LTD in rTg4510 mice, which transgenically overexpress tau_P301L. We found that 8-9 month old rTg4510 mice had significant deficits in long- but not short-term novel object recognition memory. Furthermore, we also established that PRh slices prepared from rTg4510 mice, unlike those prepared from wildtype littermates, could not support a muscarinic acetylcholine receptor-dependent form of LTD, induced by a 5 Hz stimulation protocol. In contrast, bath application of the muscarinic agonist carbachol induced a form of chemical LTD in both WT and rTg4510 slices. Finally, when rTg4510 slices were preincubated with the acetylcholinesterase inhibitor donepezil, the 5 Hz stimulation protocol was capable of inducing significant levels of LTD. These data suggest that dysfunctional cholinergic innervation of the PRh of rTg4510 mice, results in deficits in synaptic LTD which may contribute to aberrant recognition memory in this rodent model of tauopathy.

Validation of the Delayed Matching-to-Sample Task 48 (DMS48) in Elderly Chinese

BACKGROUND

Delayed Matching-to-Sample Task 48 (DMS48), a brief tool measuring visual recognition memory, is valid to identify the early stage of Alzheimer's disease (AD) in Caucasians. However, little data is available in Chinese.

OBJECTIVE

To develop norms and optimal cutoff points for the DMS48 in Chinese elders.

METHODS

A cross-sectional study was conducted in seven memory clinics from five cities across China. DMS48 was applied to 369 Chinese aged 50 or older (138 cognitively normal [CN], 112 mild cognitive impairment due to AD (MCI-A), and 119 mild AD dementia). The demographic factors which influence DMS48 scores were investigated and the norms were established considering those factors. Receiver operating characteristic (ROC) analysis was used to determine the optimal cutoff points.

RESULTS

Age was shown to influence DMS48 scores (r = -0.36, p < 0.05), and we presented the age-stratified normative data for the DMS48. The optimal cutoff point is 42/43 for identifying cognitive impairment (MCI-A and AD dementia) against CN (sensitivity 97.80% and specificity 89.13%) and MCI-A against CN (sensitivity 86.60% and specificity 94.20%). A cutoff of 39/40 obtained good sensitivity (100.00%) and specificity (94.90%) in discriminating AD dementia from CN. The age-stratified optimal cutoff points for identifying MCI-A were 43/44 for individuals aged 50 to 59 years old, 42/43 for 60 to 69 years old, 41/42 for 70 to 79 years old, and 40/41 for 80 or older, respectively (sensitivity 84.80% and specificity 95.70%).

CONCLUSION

This study proved that DMS48 is of good validation in screening MCI-A in elderly Chinese.

Longitudinal evaluation of Tau-P301L transgenic mice reveals no cognitive impairments at 17 months of age

Introduction

Tau is a microtubule-associated binding protein implicated in neurodegenerative tauopathies, including frontotemporal dementia (FTD) and Alzheimer's disease (AD). These diseases result in the intracellular accumulation of hyperphosphorylated tau in the form of neurofibrillary tangles, the presence of which is associated with cognitive deficits.

Methods

We conducted a longitudinal behavioral study to provide a profile of the TgTau(P301L)23027 transgenic mouse in multiple cognitive domains across multiple ages. P301L is the tau mutation most frequently observed in patients with frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17) and this mouse model recapitulates the progressive development of glial and neurofibrillary tangles, and associated cerebral atrophy observed in patients. We examined frontal cortex-dependent executive function and attention with the touchscreen 5-choice serial reaction time test (5-CSRTT) and assessed the function of temporal cortical structures using novel object recognition (OR).

Results

Despite using sensitive tasks, there were no apparent changes in executive function, attention, or recognition memory in the transgenic mice from 5 to 17 months of age.

Conclusions

This study represents the first comprehensive longitudinal analysis of cognition in the TgTauP301L mouse model and suggests that this model is not ideal for studying early attention and recognition memory impairments associated with tauopathy. However, spatial and object recognition memory impairments were observed during follow-up assessments when the mice were 18 and 21 months, respectively. These impairments are consistent with previous publications, and with a dementia-like phenotype in these mice when aged.

Extremely long-term memory and familiarity after 12 years

In 2006 Mitchell demonstrated that implicit memory was robust to decay. He showed that the ability to identify fragments of pictures seen 17 years before was significantly higher than for new stimuli. Is this true only for implicit memory? In this study, we tested whether explicit memory was still possible for drawings (n = 144) that had been presented once or three times, two seconds each time on average, approximately 12 years earlier. Surprisingly, our data reveal that our participants were able to recognize pictures above chance level. Preserved memory was mainly observed in the youngest subjects, for stimuli seen three times. Despite the fact that confidence judgments were low, reports suggest that recognition could be based on a strong sense of familiarity. These data extend Mitchell's findings and show that familiarity can also be robust to decay.

Increased Physical Fitness Is Associated with Higher Executive Functioning in People with Dementia

Physical fitness (PF) has been associated with improved cognition in older age, but less is known about its effects on different cognitive domains in individuals diagnosed with dementia. We explored the associations between PF and cognitive performance in 40 healthy elderly and 30 individuals with dementia. Participants completed a battery of standardized cognitive tests (Mini-Mental State Exam, Verbal Fluency, Prospective and Retrospective Memory Questionnaire, Clock Drawing, and California Verbal Learning Test) and were classified into high versus low levels of PF based on their score on the Physical Fitness Questionnaire. Analyses took into account age, gender, education, occupation, head injury, Internet use, brain training, and past levels of exercise and revealed overall benefits of PF, in particular for the people with dementia. Discriminant analysis showed high accuracy of reclassification, with most errors being due to the misclassification of dementia cases as healthy when they had high PF. The first discriminant function accounted for 83% of the variance. Using individual estimates of this function, which reflected global cognitive performance, confirmed the beneficial role of PF in dementia, even when taking into account age, past level of exercise, and the number of years since the dementia diagnosis. Finally, univariate analyses confirmed the differential sensitivity of the cognitive tests, with MMSE and clock drawing showing reliable interaction effects. This work shows that PF is associated with a reduced level of cognitive deterioration expected with dementia, especially in executive functioning and provides empirical support for the cognitive benefits of interventions promoting PF for individuals with dementia.

Cerebral Glucose Metabolism is Associated with Verbal but not Visual Memory Performance in Community-Dwelling Older Adults

Increasing evidence suggests that Alzheimer's disease (AD) sufferers show region-specific reductions in cerebral glucose metabolism, as measured by [18F]-fluoro-2-deoxyglucose positron emission tomography (18F-FDG PET). We investigated preclinical disease stage by cross-sectionally examining the association between global cognition, verbal and visual memory, and 18F-FDG PET standardized uptake value ratio (SUVR) in 43 healthy control individuals, subsequently focusing on differences between subjective memory complainers and non-memory complainers. The 18F-FDG PET regions of interest investigated include the hippocampus, amygdala, posterior cingulate, superior parietal, entorhinal cortices, frontal cortex, temporal cortex, and inferior parietal region. In the cohort as a whole, verbal logical memory immediate recall was positively associated with 18F-FDG PET SUVR in both the left hippocampus and right amygdala. There were no associations observed between global cognition, delayed recall in logical memory, or visual reproduction and 18F-FDG PET SUVR. Following stratification of the cohort into subjective memory complainers and non-complainers, verbal logical memory immediate recall was positively associated with 18F-FDG PET SUVR in the right amygdala in those with subjective memory complaints. There were no significant associations observed in non-memory complainers between 18F-FDG PET SUVR in regions of interest and cognitive performance. We observed subjective memory complaint-specific associations between 18F-FDG PET SUVR and immediate verbal memory performance in our cohort, however found no associations between delayed recall of verbal memory performance or visual memory performance. It is here argued that the neural mechanisms underlying verbal and visual memory performance may in fact differ in their pathways, and the characteristic reduction of 18F-FDG PET SUVR observed in this and previous studies likely reflects the pathophysiological changes in specific brain regions that occur in preclinical AD.

Neuropsychological Measures that Predict Progression from Mild Cognitive Impairment to Alzheimer's type dementia in Older Adults: a Systematic Review and Meta-Analysis

This study aimed to determine the extent to which cognitive measures can predict progression from mild cognitive impairment (MCI) to Alzheimer’s type dementia (AD), assess the predictive accuracy of different cognitive domain categories, and determine whether accuracy varies as a function of age and length of follow-up. We systematically reviewed and meta-analyzed data from longitudinal studies reporting sensitivity and specificity values for neuropsychological tests to identify individuals with MCI who will develop AD. We searched articles in Medline, Cochrane, EMBASE, PsycINFO, and the Web of Science. Methodological quality was assessed using the STARDem and QUADAS standards. Twenty-eight studies met the eligibility criteria (2365 participants) and reported predictive values from 61 neuropsychological tests with a 31-month mean follow-up. Values were pooled to provide combined accuracy for 14 cognitive domains. Many domains showed very good predictive accuracy with high sensitivity and specificity values (≥ 0.7). Verbal memory measures and many language tests yielded very high predictive accuracy. Other domains (e.g., executive functions, visual memory) showed better specificity than sensitivity. Predictive accuracy was highest when combining memory measures with a small set of other domains or when relying on broad cognitive batteries. Cognitive tests are excellent at predicting MCI individuals who will progress to dementia and should be a critical component of any toolkit intended to identify AD at the pre-dementia stage. Some tasks are remarkable as early indicators, whereas others might be used to suggest imminent progression.

Multistage Grading of Amnestic Mild Cognitive Impairment: The Associated Brain Gray Matter Volume and Cognitive Behavior Characterization

Background and Purpose: It is well known that there is a wide range of different pathological stages related to Alzheimer's disease (AD) among patients with amnestic mild cognitive impairment (aMCI). Further refinement of the stages based on neuropsychological and neuroimaging methods is important for earlier disease detection, as well as for the development and evaluation of disease-modifying interventions.

Materials and Methods: In this cross-sectional study, 125 aMCI patients were classified into declined progressively three stages of mild, moderate and severe, utilizing the extreme groups approach (EGA) based on their memory function. Fifty-two patients, in addition to 24 cognitively normal subjects, were included in further structural MRI analyses. Characteristics of cognitive functions and brain structures across these newly defined stages were explored through general linear models.

Results: Almost all the non-memory cognitive functions showed progressive decline as memory function deteriorated. In addition, medial structures including the right hippocampus, right lingual and left fusiform gyrus, presented with greater gray matter (GM) atrophy during the later stages of aMCI (corrected p < 0.05). Correlations were found between GM volume of the lingual gyrus and processing speed (r = 0.419, p = 0.003) and between the fusiform gyrus and general cognitive function (r = 0.281, p = 0.046). Moreover, both cognitive function and GM volume presented non-linear trajectories over stages of aMCI.

Conclusion: Our study characterized the cognitive profiles along with the degree of episodic memory impairment, and these three stages of aMCI showed non-linear progressive decline in cognitive functions and GM volumes.

Exploring anterograde memory: a volumetric MRI study in patients with mild cognitive impairment

BACKGROUND

The aim of this volumetric study was to explore the neuroanatomical correlates of the Free and Cued Selective Reminding Test (FCSRT) and the Delayed Matching-to-Sample-48 items (DMS-48), two tests widely used in France to assess verbal and visual anterograde memory. We wanted to determine to what extent the two tests rely on the medial temporal lobe, and could therefore be predictive of Alzheimer's disease, in which pathological changes typically start in this region.

METHODS

We analysed data from a cohort of 138 patients with mild cognitive impairment participating in a longitudinal multicentre clinical research study. Verbal memory was assessed using the FCSRT and visual recognition memory was evaluated using the DMS-48. Performances on these two tests were correlated to local grey matter atrophy via structural MRI using voxel-based morphometry.

RESULTS

Our results confirm the existence of a positive correlation between the volume of the medial temporal lobe and the performance on the FCSRT, prominently on the left, and the performance on the DMS-48, on the right, for the whole group of patients (family-wise error, P < 0.05). Interestingly, this region remained implicated only in the subgroup of patients who had deficient scores on the cued recall of the FCSRT, whereas the free recall was associated with prefrontal aspects. For the DMS-48, it was only implicated for the group of patients whose performances declined between the immediate and delayed trial. Conversely, temporo-parietal cortices were implicated when no decline was observed. Within the medial temporal lobe, the parahippocampal gyrus was prominently involved for the FCSRT and the immediate trial of the DMS-48, whereas the hippocampus was solely involved for the delayed trial of the DMS-48.

CONCLUSIONS

The two tests are able to detect an amnestic profile of the medial temporal type, under the condition that the scores remain deficient after the cued recall of the FCSRT or decline on the delayed recognition trial of the DMS-48. Strategic retrieval as well as perceptual/attentional processes, supported by prefrontal and temporo-parietal cortices, were also found to have an impact on the performances. Finally, the implication of the hippocampus appears time dependent, triggered by a longer delay than the parahippocampus, rather than determined by the sense of recollection or the encoding strength associated with the memory trace.

Feature Binding Deficits in Subjective Cognitive Decline and in Mild Cognitive Impairment

BACKGROUND

Feature binding is a sensitive and specific cognitive marker for Alzheimer's disease (AD). Subjective cognitive decline (SCD) and mild cognitive impairment (MCI) are clinical categories associated with an increased risk for AD.

OBJECTIVE

To investigate whether the SCD and MCI group are impaired with regard to feature binding.

METHODS

The feature binding test was administered to memory clinic patients with either SCD (n = 19, mean MMSE: 29.2) or with MCI (n = 23, mean MMSE: 26.5), and to a group of healthy controls (HC, n = 23, mean MMSE: 29.0). Participants were assessed with the CERAD Plus neuropsychological test battery. Cognitive performance of the three groups was compared by ANCOVA with age, gender and education as covariates and planned contrasts.

RESULTS

Groups differed in the binding condition. Planned contrasts showed significant differences in adjusted means between HC and SCD (p = 0.003), as well as between HC and MCI (p <  0.0001).

DISCUSSION

The feature binding task detects subtle cognitive impairments in participants with SCD, who are unimpaired in traditional neuropsychological testing. This corroborates the use of feature binding tests in preclinical AD studies and suggests that specific cognitive deficits can be found in SCD. Future studies incorporating AD biomarkers and longitudinal follow-up are needed to further establish the clinical utility of feature binding.

Clinical and biomarker profiling of prodromal Alzheimer's disease in workpackage 5 of the Innovative Medicines Initiative PharmaCog project: a 'European ADNI study'

BACKGROUND

In the field of Alzheimer's disease (AD), the validation of biomarkers for early AD diagnosis and for use as a surrogate outcome in AD clinical trials is of considerable research interest.

OBJECTIVE

To characterize the clinical profile and genetic, neuroimaging and neurophysiological biomarkers of prodromal AD in amnestic mild cognitive impairment (aMCI) patients enrolled in the IMI WP5 PharmaCog (also referred to as the European ADNI study).

METHODS

A total of 147 aMCI patients were enrolled in 13 European memory clinics. Patients underwent clinical and neuropsychological evaluation, magnetic resonance imaging (MRI), electroencephalography (EEG) and lumbar puncture to assess the levels of amyloid β peptide 1-42 (Aβ42), tau and p-tau, and blood samples were collected. Genetic (APOE), neuroimaging (3T morphometry and diffusion MRI) and EEG (with resting-state and auditory oddball event-related potential (AO-ERP) paradigm) biomarkers were evaluated.

RESULTS

Prodromal AD was found in 55 aMCI patients defined by low Aβ42 in the cerebrospinal fluid (Aβ positive). Compared to the aMCI group with high Aβ42 levels (Aβ negative), Aβ positive patients showed poorer visual (P = 0.001), spatial recognition (P < 0.0005) and working (P = 0.024) memory, as well as a higher frequency of APOE4 (P < 0.0005), lower hippocampal volume (P = 0.04), reduced thickness of the parietal cortex (P < 0.009) and structural connectivity of the corpus callosum (P < 0.05), higher amplitude of delta rhythms at rest (P = 0.03) and lower amplitude of posterior cingulate sources of AO-ERP (P = 0.03).

CONCLUSION

These results suggest that, in aMCI patients, prodromal AD is characterized by a distinctive cognitive profile and genetic, neuroimaging and neurophysiological biomarkers. Longitudinal assessment will help to identify the role of these biomarkers in AD progression.

Profile of memory impairment as a prognostic marker in amnestic mild cognitive impairment

We aimed to evaluate whether recognition memory can be used to identify patients with amnestic mild cognitive impairment (aMCI) at greater risk for converting to dementia. We recruited 2172 aMCI patients. They were divided into two groups: aMCI with impaired recall but normal recognition (aMCI-IRNR) vs aMCI with impaired recall and impaired recognition (aMCI-IRIR). We compared demographic findings and neuropsychological performance and illustrated the difference in converting to dementia between the two groups. Study subjects consisted of 1022 (47.0%) patients with aMCI-IRNR and 1150 (53.0%) patients with aMCI-IRIR. In most neuropsychological tests except for digit span forward, patients with aMCI-IRIR were more impaired than patients with aMCI-IRNR even after adjustment of their age and sex. Cox analysis adjusting age and gender revealed that the risk of dementia conversion was higher in patients with aMCI-IRIR than in patients with aMCI-IRNR [hazard ratio (HR)=1.400, 95% CI 1.009-1.943; P=0.044]. This study showed that recognition memory can be used to identify patients with amnestic mild cognitive impairment (aMCI) at greater risk for converting to dementia.

Early neuropsychological detection of Alzheimer's disease

Lifestyle modification offers a promising way of preventing or delaying Alzheimer's disease (AD). In particular, nutritional interventions can contribute to decrease the risk of dementia. The efficacy of such interventions should be assessed in individuals thought to be prone to AD. It is therefore necessary to identify markers that may help detecting AD as early as possible. This review will focus on subtle neuropsychological changes that may already exist in the predementia phase, and that could point to individuals at risk of dementia. Episodic memory decline appears consistently as the earliest sign of incipient typical AD. An episodic memory test that ensures deep encoding of information and assesses retrieval with free as well as cued recall appears as a useful tool to detect patients at an early stage of AD. Beyond the memory domain, category verbal fluency has been shown to decline early and to predict progression to AD. Moreover, in line with current diagnosis criteria for prodromal AD, combining neuropsychological scores and neuroimaging data allows a better discrimination of future AD patients than neuroimaging or neuropsychological data alone. Altogether, the detection of cognitive changes that are predictive of the typical form of probable AD already in the predementia stage points to at risk people who are the best target for therapeutic interventions, such as nutrition or physical exercise counseling or dietary interventions.

Non-invasive brain stimulation of the right inferior frontal gyrus may improve attention in early Alzheimer's disease: a pilot study

INTRODUCTION

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive tool for modulating cortical activity.

OBJECTIVES

In this pilot study, we evaluated the effects of high frequency rTMS applied over the right inferior frontal gyrus (IFG) on cognitive functions in patients with amnestic mild cognitive impairment (MCI) or incipient dementia due to Alzheimer's disease (AD).

METHODS

Ten patients (6 men; 4 women, mean age of 72 ± 8 years; MMSE 23 ± 3.56) were enrolled in a randomized, placebo-controlled study with a crossover design. All participants received 2 sessions of 10 Hz rTMS over the non-dominant right hemisphere in random order: IFG (active stimulation site) and vertex (control stimulation site). Intensities were adjusted to 90% of resting motor threshold. A total of 2250 pulses were applied in a session. The Trail Making Test (TMT), the Stroop test, and the complex visual scene encoding task (CVSET) were administered before and immediately after each session. The Wilcoxon paired test was used for data analysis.

RESULTS

Stimulation applied over the IFG induced improvement in the TMT parts A (p = 0.037) and B (p = 0.049). No significant changes were found in the Stroop test or the CVSET after the IFG stimulation. We observed no significant cognitive aftereffects of rTMS applied over the vertex.

CONCLUSIONS

High frequency rTMS of the right IFG induced significant improvement of attention and psychomotor speed in patients with MCI/mild dementia due to AD. This pilot study is part of a more complex protocol and ongoing research.

Associative memory and its cerebral correlates in Alzheimer׳s disease: evidence for distinct deficits of relational and conjunctive memory

This study investigated the impact of Alzheimer׳s disease (AD) on conjunctive and relational binding in episodic memory. Mild AD patients and controls had to remember item-color associations by imagining color either as a contextual association (relational memory) or as a feature of the item to be encoded (conjunctive memory). Patients׳ performance in each condition was correlated with cerebral metabolism measured by FDG-PET. The results showed that AD patients had an impaired capacity to remember item-color associations, with deficits in both relational and conjunctive memory. However, performance in the two kinds of associative memory varied independently across patients. Partial Least Square analyses revealed that poor conjunctive memory was related to hypometabolism in an anterior temporal-posterior fusiform brain network, whereas relational memory correlated with metabolism in regions of the default mode network. These findings support the hypothesis of distinct neural systems specialized in different types of associative memory and point to heterogeneous profiles of memory alteration in Alzheimer׳s disease as a function of damage to the respective neural networks.

Cued recall measure predicts the progression of gray matter atrophy in patients with amnesic mild cognitive impairment

Amnesic mild cognitive impairment (aMCI) is a heterogeneous syndrome that could be subdivided into distinct neuropsychological variants. To investigate relationships between the neuropsychological profile of memory impairment at baseline and the neuroimaging pattern of grey matter (GM) loss over 18 months, we performed a prospective volumetric brain study on 31 aMCI patients and 29 matched controls. All subjects were tested at baseline using a standardized neuropsychological battery, which included the Free and Cued Selective Recall Reminding Test (FCSRT) for the assessment of verbal declarative memory. Over 18 months, patients with impaired free recall but normal total recall (high index of cueing) on the FCSRT developed subcortical and frontal GM loss, while patients with impaired free and total recall (low index of cueing) developed GM atrophy within the left anterior and lateral temporal lobe. In summary, cued recall deficits are associated with a progression of atrophy that closely parallels the spatiotemporal distribution of neurofibrillary degeneration in early Alzheimer's disease (AD), indicating possible AD pathological changes.

Recognition memory in amnestic-mild cognitive impairment: insights from event-related potentials

Episodic memory loss is the hallmark cognitive dysfunction associated with Alzheimer’s disease (AD). Amnestic mild cognitive impairment (a-MCI) frequently represents a transitional stage between normal aging and early AD. A better understanding of the qualitative features of memory loss in a-MCI may have important implications for predicting those most likely to harbor AD-related pathology and for disease monitoring. Dual process models of memory argue that recognition memory is subserved by the dissociable processes of recollection and familiarity. Work studying recognition memory in a-MCI from this perspective has been controversial, particularly with regard to the integrity of familiarity. Event-related potentials (ERPs) offer an alternative means for assessing these functions without the associated assumptions of behavioral estimation methods. ERPs were recorded while a-MCI patients and cognitively normal (CN) age-matched adults performed a recognition memory task. When retrieval success was measured (hits versus correct rejections) in which performance was matched by group, a-MCI patients displayed similar neural correlates to that of the CN group, including modulation of the FN400 and the late positive complex (LPC) which are thought to index familiarity and recollection, respectively. Alternatively, when the integrity of these components was measured based on retrieval attempts (studied versus unstudied items), a-MCI patients displayed a reduced FN400 and LPC. Furthermore, modulation of the FN400 correlated with a behavioral estimate of familiarity and the LPC with a behavioral estimate of recollection obtained in a separate experiment in the same individuals, consistent with the proposed mappings of these indices. These results support a global decline of recognition memory in a-MCI, which suggests that the memory loss of prodromal AD may be qualitatively distinct from normal aging.