Disintegration at the Syntax-Semantics Interface in Prodromal Alzheimer's Disease: New Evidence from Complex Sentence Anaphora in Amnestic Mild Cognitive Impairment (aMCI)

Although diverse language deficits have been widely observed in prodromal Alzheimer's disease (AD), the underlying nature of such deficits and their explanation remains opaque. Consequently, both clinical applications and brain-language models are not well-defined. In this paper we report results from two experiments which test language production in a group of individuals with amnestic Mild Cognitive Impairment (aMCI) in contrast to healthy aging and healthy young. The experiments apply factorial designs informed by linguistic analysis to test two forms of complex sentences involving anaphora (relations between pronouns and their antecedents). Results show that aMCI individuals differentiate forms of anaphora depending on sentence structure, with selective impairment of sentences which involve construal with reference to context (anaphoric coreference). We argue that aMCI individuals maintain core structural knowledge while evidencing deficiency in syntax-semantics integration, thus locating the source of the deficit in the language-thought interface of the Language Faculty.

Impairment of delayed recall as a predictor of amnestic mild cognitive impairment development in normal older adults: a 7-year of longitudinal cohort study in Shanghai

BACKGROUND

Amnestic mild cognitive impairment (aMCI) is considered a prodromal phase of Alzheimer's disease (AD). However, little is known about the neuropsychological characteristic at pre-MCI stage. This study aimed to investigate which neuropsychological tests could significantly predict aMCI from a seven-year longitudinal cohort study.

METHODS

The present study included 123 individuals with baseline cognitive normal (NC) diagnosis and a 7-year follow-up visit. All the subjects were from the China Longitudinal Aging Study (CLAS) study. Participants were divided into two groups, non-converter and converter based on whether progression to aMCI at follow-up. All participants underwent standardized comprehensive neuropsychological tests, including the mini-mental state examination (MMSE), Montreal Cognitive Assessment (MoCA), auditory verbal learning test (AVLT), the digital span test, the verbal fluency test, the visual recognition test, the WAIS picture completion task, and WAIS block design. Logistic regression analysis was used to evaluate the predictive power of baseline cognitive performance for the transformation of amnestic mild cognitive impairment. Receiver operating characteristic (ROC) curve was used to test the most sensitive test for distinguishing different groups.

RESULTS

Between the non-converter group and converter group, there were significant differences in the baseline scores of AVLT-delayed recall (AVLT-DR) (8.70 ± 3.61 vs. 6.81 ± 2.96, p = 0.001) and WAIS block design (29.86 ± 7.07 vs. 26.53 ± 8.29, p = 0.041). After controlling for gender, age, and education level, converter group showed lower baseline AVLT-DR than non-converter group, while no significant difference was found in WAIS block design. Furthermore, converter group had lower AVLT-DR score after controlling for somatic disease. The area under the curve of regression equation model was 0.738 (95%CI:0.635-0.840), with a sensitivity 83.9%, specificity of 63.6%.

CONCLUSIONS

Our results proved the value of delayed recall of AVLT in predicting conversion to aMCI. Early and careful checking of the cognitive function among older people should be emphasized.

Dissociating memory and executive function impairment through temporal features in a word list verbal learning task

The Rey Auditory Verbal Learning Test (RAVLT) is an established verbal learning test commonly used to quantify memory impairments due to Alzheimer's Disease (AD) both at a clinical dementia stage or prodromal stage of mild cognitive impairment (MCI). Focal memory impairment-as quantified e.g. by the RAVLT-at an MCI stage is referred to as amnestic MCI (aMCI) and is often regarded as the cognitive phenotype of prodromal AD. However, recent findings suggest that not only learning and memory but also other cognitive domains, especially executive functions (EF) and processing speed (PS), influence verbal learning performance. This research investigates whether additional temporal features extracted from audio recordings from a participant's RAVLT response can better dissociate memory and EF in such tasks and eventually help to better describe MCI subtypes. 675 age-matched participants from the H70 Swedish birth cohort were included in this analysis; 68 participants were classified as MCI (33 aMCI and 35 due to executive impairment). RAVLT performances were recorded and temporal features extracted. Novel temporal features were correlated with established neuropsychological tests measuring EF and PS. Lastly, the downstream diagnostic potential of temporal features was estimated using group differences and a machine learning (ML) classification scenario. Temporal features correlated moderately with measures of EF and PS. Performance of an ML classifier could be improved by adding temporal features to traditional counts. We conclude that RAVLT temporal features are in general related to EF and that they might be capable of dissociating memory and EF in a word list learning task.

In the Hands of Hypnos: Associations between Sleep, Cognitive Performance and Financial Capacity in aMCI and Mild AD

Objective  The aim of this monocentric observational study is to assess whether sleep disorders can predict financial capacity in single-and multiple-domain aMCI (amnestic Mild Cognitive Impairment), mild Alzheimer's Disease (AD), and healthy controls. Methods  Older participants from Northern Greece were examined with several neuropsychological tests, including Mini-Mental State Examination (MMSE), Geriatric Depression Scale (GDS-15), and the Legal Capacity for Property Law Transactions Assessment Scale (LCPLTAS). Sleep duration and quality were based on caregiver/family members' reports in the Sleep Disorders Inventory (SDI). Results  These preliminary findings coming from 147 participants indicate for the first time that apart from MMSE, complex cognitive functions, such as financial capacity may be also directly linked to the frequency of sleep-disturbed behaviours as indicated by SDI frequency questions, both in aMCI and mild AD. Discussion  An urgency for further investigation of the neglected sleep factor should be added in financial capacity assessment protocols.

Altered functional coupling between the cerebellum and cerebrum in patients with amnestic mild cognitive impairment

Cognitive processing relies on the functional coupling between the cerebrum and cerebellum. However, it remains unclear how the 2 collaborate in amnestic mild cognitive impairment (aMCI) patients. With functional magnetic resonance imaging techniques, we compared cerebrocerebellar functional connectivity during the resting state (rsFC) between the aMCI and healthy control (HC) groups. Additionally, we distinguished coupling between functionally corresponding and noncorresponding areas across the cerebrum and cerebellum. The results demonstrated decreased rsFC between both functionally corresponding and noncorresponding areas, suggesting distributed deficits of cerebrocerebellar connections in aMCI patients. Increased rsFC was also observed, which were between functionally noncorresponding areas. Moreover, the increased rsFC was positively correlated with attentional scores in the aMCI group, and this effect was absent in the HC group, supporting that there exists a compensatory mechanism in patients. The current study contributes to illustrating how the cerebellum adjusts its coupling with the cerebrum in individuals with cognitive impairment.

Brain Volumes and Metacognitive Deficits in Knowledge of Self, Task and Strategies in Mathematics: A Preliminary Pilot One-Year Longitudinal Study in aMCI Patients Compared to Healthy Controls

Metacognitive knowledge has been little investigated in aMCI patients. The aim of this study is to examine whether there are specific deficits in knowledge of self, task and strategies in mathematical cognition, due its importance for everyday functioning, mainly due to its importance for financial capacity in old age. A total of 24 patients with a diagnosis of aMCI and one-to-one 24 matched individuals (similar age, education and gender) were examined at three time points in a year with a number of neuropsychological tests and a slightly modified version of the Metacognitive Knowledge in Mathematics Questionnaire (MKMQ). We analyzed longitudinal MRI data regarding various brain areas for the aMCI patients. Results indicated that the aMCI group differed in all MKMQ subscale scores at the three time points compared to healthy controls. Correlations were found only for metacognitive avoidance strategies and left and right amygdala volumes at baseline, while after twelve months correlations were found for avoidance and right and left parahippocampal volumes. These preliminary results highlight the role of specific brain regions that could be used as indices in clinical practice for the detection of metacognitive knowledge deficits that are found in aMCI.

Corrigendum: A two-year longitudinal study of retinal vascular impairment in patients with amnestic mild cognitive impairment

[This corrects the article DOI: 10.3389/fnagi.2022.993621.].

Senescence Markers in Peripheral Blood Mononuclear Cells in Amnestic Mild Cognitive Impairment and Alzheimer's Disease

Recent studies suggest that cellular senescence plays a role in Alzheimer’s Disease (AD) pathogenesis. We hypothesize that cellular senescence markers might be tracked in the peripheral tissues of AD patients. Senescence hallmarks, including altered metabolism, cell-cycle arrest, DNA damage response (DDR) and senescence secretory associated phenotype (SASP), were measured in peripheral blood mononuclear cells (PBMCs) of healthy controls (HC), amnestic mild cognitive impairment (aMCI) and AD patients. Senescence-associated βeta-galactosidase (SA-β-Gal) activity, G0-G1 phase cell-cycle arrest, p16 and p53 were analyzed by flow cytometry, while IL-6 and IL-8 mRNA were analyzed by qPCR, and phosphorylated H2A histone family member X (γH2AX) was analyzed by immunofluorescence. Senescent cells in the brain tissue were determined with lipofuscin staining. An increase in the number of senescent cells was observed in the frontal cortex and hippocampus of advanced AD patients. PBMCs of aMCI patients, but not in AD, showed increased SA-β-Gal compared with HCs. aMCI PBMCs also had increased IL-6 and IL8 mRNA expression and number of cells arrested at G0-G1, which were absent in AD. Instead, AD PBMCs had significantly increased p16 and p53 expression and decreased γH2Ax activity compared with HC. This study reports that several markers of cellular senescence can be measured in PBMCs of aMCI and AD patients.

Liberating older adults from the bonds of vascular risk factors: What is their impact on financial capacity in amnestic mild cognitive impairment?

BACKGROUND

There is a pressing need to clarify whether vascular risk factors (VRFs) are related to the heterogeneous cognitive performance found in mild cognitive impairment (MCI) and whether the number of VRFs relates to financial capacity impairment in patients with amnestic MCI (aMCI).

METHODS

A total of 112 participants were divided into three groups: patients with single-domain aMCI, patients with multiple-domain aMCI, and healthy controls (HCs), while taking into consideration whether participants had a diagnosis of one VRF or disease, or more than one VRF or disease. Patients with aMCI with VRFs (one and more than one VRF) and HCs did not differ significantly in age, education, and sex. Mini-Mental State Examination, 15-item Geriatric Depression Scale, and Legal Capacity for Property Law Transactions Assessment Scale (LCPLTAS) were administered to all groups.

RESULTS

Diagnosis (P <0.001) and VRFs (P = 0.006) showed significant main effects on LCPLTAS but no interaction (P = 0.654). Patients with aMCI with high vascular burden were more frequently of the multiple-domain subtype, whereas patients with no vascular burden were more frequently of the single-domain subtype. A larger vascular burden is correlated with lower LCPLTAS scores.

DISCUSSION

Vascular burden plays an important role in the heterogeneity of aMCI by impairing financial capacity.

Diagnosis of Amnesic Mild Cognitive Impairment Using MGS-WBC and VGBN-LM Algorithms

Computer-aided diagnosis (CAD) has undergone rapid development with the advent of advanced neuroimaging and machine learning methods. Nevertheless, how to extract discriminative features from the limited and high-dimensional data is not ideal, especially for amnesic mild cognitive impairment (aMCI) data based on resting-state functional magnetic resonance imaging (rs-fMRI). Furthermore, a robust and reliable system for aMCI detection is conducive to timely detecting and screening subjects at a high risk of Alzheimer's disease (AD). In this scenario, we first develop the mask generation strategy based on within-class and between-class criterion (MGS-WBC), which primarily aims at reducing data redundancy and excavating multiscale features of the brain. Concurrently, vector generation for brain networks based on Laplacian matrix (VGBN-LM) is presented to obtain the global features of the functional network. Finally, all multiscale features are fused to further improve the diagnostic performance of aMCI. Typical classifiers for small data learning, such as naive Bayesian (NB), linear discriminant analysis (LDA), logistic regression (LR), and support vector machines (SVMs), are adopted to evaluate the diagnostic performance of aMCI. This study helps to reveal discriminative neuroimaging features, and outperforms the state-of-the-art methods, providing new insights for the intelligent construction of CAD system of aMCI.

The diagnosis of amnestic mild cognitive impairment by combining the characteristics of brain functional network and support vector machine classifier

BACKGROUND

Amnestic mild cognitive impairment (aMCI) is an essential stage of early detection and potential intervention for Alzheimer's disease (AD). Patients with aMCI exhibit partially abnormal functional brain connectivity and it is suggested that these features may represent a new diagnostic marker of early AD.

NEW METHOD

In this paper, we constructed two brain network models, a phase synchronization index (PSI) undirected network and a directed transfer function (DTF) directed network, to evaluate the cognitive function in patients with aMCI. We then built SVM classification models using the network clustering coefficient, global efficiency and average node degree as features to distinguish between aMCI patients and controls.

RESULTS

Our results reveal a classification accuracy and AUC of 66.6 ± 1.7% and 0.7475 and 80.0 ± 2.2% and 0.7825, respectively, for the two network models (PSI and DTF). As the directed network model performed better than the undirected model, we introduced an improved graph theory feature, efficiency density, which resulted in an increased classification accuracy and AUC value 86.6 ± 2.6% and 0.8295, respectively.

COMPARISON WITH EXISTING METHODS

The analysis of network models and the directionality of information flow is suitable for analysis of nonlinear EEG signals for assessment of the functional state of the brain. Compared with traditional network features, our proposed improved features more comprehensively evaluate transmission efficiency and density of the brain.

CONCLUSION

In this study, we demonstrate that an improved efficiency density feature is helpful for enhancing classification the accuracy of aMCI. Moreover, directed brain network models exhibit better classification for aMCI diagnosis than undirected networks.

Discriminant Validity of the WAIS-R Digit Symbol Substitution Test in Subjective Cognitive Decline, Mild Cognitive Impairment (Amnestic Subtype) and Alzheimer's Disease Dementia (ADD) in Greece

Objective: The aim of the current study was to estimate the discriminant potential and validity of the Digit Symbol Substitution Test (DSST) of the WAIS-R in the Greek elderly population meeting criteria for subjective cognitive decline (SCD), mild cognitive impairment (aMCI; amnestic subtype), or Alzheimer’s disease dementia (ADD). Method: Four hundred eighty-eight community-dwelling older adults, visitors of the Day Center of Alzheimer Hellas, participated in the study. Two hundred forty-three of them met the criteria for ADD, one hundred eighty-two for aMCI and sixty-three for SCD. Results: Path analysis indicated that the DSST score is affected by age group, educational level, and diagnostic category, but is not affected by gender. The ROC curve analysis showed that the DSST sum score could perfectly differentiate SCD from ADD patients, whereas test’s discriminant potential between aMCI and dementia ADD’s subtype was satisfactory. However, DSST was unable to separate the SCD from the aMCI group. Conclusion: It appears that the DSST is unable to separate the SCD from aMCI population. Therefore, the test in question may be insensitive to incipient cognitive decline. On the contrary, the discriminant potential of the DSST as regards SCD and ADD is excellent, while discrimination between aMCI and ADD is good.

Late-life sleep duration associated with amnestic mild cognitive impairment

OBJECTIVE

To examine the association between sleep duration in different stages of life and amnestic mild cognitive impairment (aMCI).

DESIGN, SETTING, AND PARTICIPANTS

A total of 2472 healthy elderly and 505 patients with aMCI in China were included in this study. The study analyzed the association between aMCI and sleep duration in different stages of life.

MEASUREMENTS

We compared sleep duration in different stages of life and analyzed the association between Montreal Cognitive Assessment scores and sleep duration by curve estimation. Logistic regression was used to evaluate the association between aMCI and sleep duration.

RESULTS

In the analysis, there were no results proving that sleep duration in youth (P = 0.719, sleep duration < 10 hours; P = 0.999, sleep duration ≥ 10 hours) or midlife (P = 0.898, sleep duration < 9 hours; P = 0.504, sleep duration ≥ 9 hours) had a significant association with aMCI. In the group sleeping less than 7 hours in late life, each hour more of sleep duration was associated with approximately 0.80 of the original risk of aMCI (P = 0.011, odds ratio = 0.80, 95% confidence interval = 0.68-0.95).

CONCLUSIONS

Among the elderly sleeping less than 7 hours, there is a decreased risk of aMCI for every additional hour of sleep.

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.

Sex differences in cortisol and memory following acute social stress in amnestic mild cognitive impairment

OBJECTIVE

Older adults with amnestic mild cognitive impairment (aMCI) develop Alzheimer's type dementia approximately 10 times faster annually than the normal population. Adrenal hormones are associated with aging and cognition. We investigated the relationship between acute stress, cortisol, and memory function in aMCI with an exploratory analysis of sex.

METHOD

Salivary cortisol was sampled diurnally and during two test sessions, one session with the Trier Social Stress Test (TSST), to explore differences in the relationship between cortisol and memory function in age-normal cognition (NA) and aMCI. Participants with aMCI (n = 6 women, 9 men; mean age = 75) or similarly aged NA (n = 9 women, 7 men, mean age = 75) were given tests of episodic, associative, and spatial working memory with a psychosocial stressor (TSST) in the second session.

RESULTS

The aMCI group performed worse on the memory tests than NA as expected, and males with aMCI had elevated cortisol levels on test days. Immediate episodic memory was enhanced by social stress in NA but not in the aMCI group, indicating that stress-induced alterations in memory are different in individuals with aMCI. High cortisol was associated with impaired performance on episodic memory in aMCI males only. Cortisol in Session 1 moderated the relationship with spatial working memory, whereby higher cortisol was associated with worse performance in NA, but better spatial working memory in aMCI. In addition, effects of aMCI on perceived anxiety in response to stress exposure were moderated by stress-induced cortisol in a sex-specific manner.

CONCLUSIONS

We show effects of aMCI on Test Session cortisol levels and effects on perceived anxiety, and stress-induced impairments in memory in males with aMCI in our exploratory sample. Future studies should explore sex as a biological variable as our findings suggest that effects at the confluence of aMCI and stress can be obfuscated without sex as a consideration.

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

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

Increased intrinsic default-mode network activity as a compensatory mechanism in aMCI: a resting-state functional connectivity MRI study

Numerous studies have investigated the differences in the mean functional connectivity (FC) strength between amnestic mild cognitive impairment (aMCI) patients and normal subjects using resting-state functional magnetic resonance imaging. However, whether the mean FC is increased, decreased or unchanged in aMCI patients compared to normal controls remains unclear. Two factors might lead to inconsistent results: the determination of regions of interest and the reliability of the FC.

We explored differences in FC and the degree centrality (Dc) constructed by the bootstrap method, between and within networks (default-mode network (DN), frontoparietal control network (CN), dorsal attention network (AN)), and resulting from a hierarchical-clustering algorithm.

The mean FC within the DN and CN was significantly increased (P < 0.05, uncorrected) in patients. Significant increases (P < 0.05, uncorrected) in the mean FC were found in patients between DN and CN and between DN and AN. Five pairs of FC (false discovery rate corrected) and the Dc of six regions (Bonferroni corrected) displayed a significant increase in patients. Lower cognitive ability was significantly associated with a greater increase in the Dc of the left superior temporal sulcus.

Our results demonstrate that the early dysfunctions in aMCI disease are mainly compensatory impairments.

The Effects of Exposure to Recent Autobiographical Events on Declarative Memory in Amnestic Mild Cognitive Impairment: A Preliminary Pilot Study

BACKGROUND

Individuals with amnestic Mild Cognitive Impairment (aMCI) are at heightened risk of developing Alzheimer's dementia. In recent years, much attention has been given to the search for new interventions to slow down the progression of cognitive decline of these patients. Wearable digital camera devices are one form of new technology that captures images of one's life events, so they constitute a promising method to be used as a means to stimulate recent autobiographical memory.

OBJECTIVE

This preliminary study investigates the ability of a new cognitive intervention based on exposure to recent autobiographical memory captured by wearable cameras to improve episodic memory in patients with aMCI.

METHODS

Seventeen subjects wore a wearable camera while they went about their daily activities. The images captured were converted into eight different 3-minute films containing the most relevant information of each event. The intervention involved eight individualized weekly sessions during which patients were exposed to a different autobiographical event each week. Besides, several specific questions were formulated within each session. Clinical questionnaires assessing cognitive reserve, premorbid intelligence, depression, and anxiety were administered at baseline. Measures of objective episodic memory were applied at baseline and at post-treatment.

RESULTS

Significant improvements were observed at post-treatment in memory measures, and significant associations were found between memory change scores and age and cognitive reserve. Anyway, these associations did not reach statistical significance after adjusting for multiple comparisons.

CONCLUSION

The present study provides preliminary evidence that aMCI patients may benefit from a cognitive intervention program based on re-experiencing recent autobiographical events. However, future studies incorporating a control group will be needed to confirm these preliminary findings.

Quantifying memory deficits in amnestic mild cognitive impairment

INTRODUCTION

In the present study, we use the item-specific deficit approach (ISDA), a method for characterizing memory deficits in list-learning, to portray the memory deficits in amnestic mild cognitive impairment (aMCI).

METHODS

We applied the ISDA to compare memory performance of patients with aMCI and healthy controls in encoding, consolidation, and retrieval using the Free and Cued Selective Reminding Test.

RESULTS

The results revealed clear differences in recall performance between patients with aMCI and controls. When analyzing the ISDA deficit indices, the results revealed a prominent encoding deficit, followed by a consolidating deficit. A greater sensitivity for the encoding index confirmed that a difficulty with encoding information plays a major role in explaining the episodic memory deficits experienced by patients with aMCI.

DISCUSSION

The present study applying the ISDA reveals great sensitivity and specificity of the encoding deficit index when identifying aMCI. As aMCI constitutes a risk factor to develop Alzheimer's disease, the current findings also confirm the need to concentrate on encoding deficits as an early diagnostic sign of cognitive decline.

Potential Value of Plasma Amyloid-β, Total Tau, and Neurofilament Light for Identification of Early Alzheimer's Disease

The objective of the study was to explore the potential value of plasma indicators for identifying amnesic mild cognitive impairment (aMCI) and determine whether levels of plasma indicators are related to the performance of cognitive function and brain tissue volumes. In total, 155 participants (68 aMCI patients and 87 health controls) were recruited in the present cross-sectional study. The levels of plasma amyloid-β (Aβ) 40, Aβ42, total tau (t-tau), and neurofilament light (NFL) were measured using an ultrasensitive quantitative method. Machine learning algorithms were performed for establishing an optimal model of identifying aMCI. Compared with healthy controls, Aβ40 and Aβ42 levels were lower and NFL levels were higher in plasma of aMCI patients with an exception of t-tau levels. In aMCI patients, the higher plasma Aβ40 levels were correlated with the impaired episodic memory and negative correlations were observed between plasma t-tau levels and global cognitive function and gray matter (GM) volume. In addition, the higher plasma NFL levels were correlated with reduced hippocampus volume and total GM volume of the left inferior and middle temporal gyrus. An integrated model included clinical features, hippocampus volume, and plasma Aβ42 and NFL and had the highest accuracy for detecting aMCI patients (accuracy, 74.2%). We demonstrated that plasma Aβ40, Aβ42, t-tau, and NFL may be useful to identify aMCI and correlate with cognitive decline and brain atrophy. Among these plasma indicators, Aβ42 and NFL are more valuable as key members of a peripheral biomarker panel to detect aMCI.

Effect of sleep quality on amnestic mild cognitive impairment vulnerable brain regions in cognitively normal elderly individuals

STUDY OBJECTIVES

This study aims to evaluate the extent to which sleep quality impacts amnestic mild cognitive impairment (aMCI)-related brain regions in a cognitively normal cohort of individuals.

METHODS

Seventy-four participants were rigorously evaluated using a battery of cognitive tests and a detailed clinical assessment to verify normal cognitive status. We then screened for sleep quality using the Pittsburgh Sleep Quality Index (PSQI) and depressive symptoms using the Geriatric Depression Scale (GDS). Five subjects were excluded due to mild depression. Overall 38 individuals with mean age 70.7 ± 7 were classified as poor sleepers and 31 with mean age of 69.6 ± 6 years as normal sleepers. Structural MRI and Freesurfer brain parcellation were used to measure aMCI-related brain regions.

RESULTS

Relative to normal sleepers, poor sleepers exhibited significant reductions in cortical and subcortical volumes bilaterally in the hippocampi, as well as in the superior parietal lobules and left amygdala. The effects were strongest in the left superior parietal lobule (p < .015), followed by the hippocampi. Diffuse patterns of cortical thinning were observed in the frontal lobes, but significant effects were concentrated in the right mesial frontal cortex. Lower sleep duration was most correlated with cortical volume and thickness reductions among all subjects.

CONCLUSIONS

Atrophy related to poor sleep quality impacted a number of regions implicated in aMCI and Alzheimer's disease (AD). As such, interventions targeted towards improving sleep quality amongst the elderly may prove an effective tool for modulating the course of aMCI and AD.

Effect of cognitive training on episodic memory retrieval in amnestic mild cognitive impairment patients: study protocol for a clinical randomized controlled trial

BACKGROUND

Mild cognitive impairment (MCI) is a transition state between asymptomatic stage and dementia. Amnestic MCI (aMCI) patients who mainly present with memory deficits are highly likely to progress to Alzheimer's disease (AD). At present, no broadly effective drug therapy is available to prevent the progression from memory deficit to dementia. Cognitive control training, which has transfer effects on multiple cognitive capacities including memory function in healthy old adults, has not yet been applied to aMCI.

METHODS/DESIGN

In this single-center, randomized double-blind placebo-controlled study, 70 aMCI patients will be recruited and randomly assigned to the training and control groups. The intervention is an Internet-based cognitive control training program performed for 30 min daily, five days per week, for 12 consecutive weeks. Neuropsychological assessment and structural and functional magnetic resonance imaging (MRI) will be performed at baseline and outcome. Primary outcomes are changes of episodic memory retrieval function. Secondary outcome measures are neuroplasticity changes measured by functional and structural MRI.

DISCUSSION

In this study, an Internet-based cognitive control training program is adopted to investigate whether cognitive control training can enhance the retrieval of episodic memory in aMCI patients. The combination of multi-modal MRI and neuropsychological tests could have a good sensitivity in evaluating the effects of cognitive control training and could also uncover the underlying neural underpinning.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03133052 . Registered on 21 April 2017.

Changes of gray matter volume and amplitude of low-frequency oscillations in amnestic MCI: An integrative multi-modal MRI study

BACKGROUND

Numerous studies have reported that the amnestic-type mild cognitive impairment (aMCI) patients have impaired brain structural integrity and functional alterations separately.

PURPOSE

To investigate the changes of gray matter and amplitude of low-frequency oscillations in patients with aMCI by combining structural and functional magnetic resonance imaging (fMRI).

MATERIAL AND METHODS

Thirty-four patients with aMCI and 34 controls were recruited. We adopted optimized voxel-based morphometry to detect regions with gray matter volume (GMV) loss induced by aMCI. Then regional differences in amplitude of slow-4 band (0.027-0.073 Hz) oscillations among these regions between patients and healthy controls were examined. Both slow-4 amplitude of low-frequency fluctuations (ALFF) and slow-4 fractional ALFF (fALFF; the relative amplitude that resides in the low frequencies) were employed.

RESULTS

Patients with aMCI demonstrated significant GMV loss in the ventral medial prefrontal cortex (vMPFC), posterior cingulate cortex (PCC), bilateral hippocampus, right superior parietal gyrus, left insula and left middle temporal gyrus (P < 0.01). The patients exhibited significant decreases of slow-4 ALFF in the left hippocampus (P = 0.05) and PCC (P = 0.02), while the decreased slow-4 fALFF was detected in PCC (P = 0.01) and increased slow-4 fALFF in vMPFC (P = 0.03). In PCC, aMCI and controls exhibited significant different GMV-fALFF correlation (P < 0.05), with opposite correlation trend.

CONCLUSION

The correlates between anatomical deficits and functional alterations in aMCI suggest that anatomical and functional deficits are linked to each other. The differences of GMV-fALFF correlations demonstrated altered anatomical-functional relationship in aMCI.

Abnormal changes of multidimensional surface features using multivariate pattern classification in amnestic mild cognitive impairment patients

Previous studies have suggested that amnestic mild cognitive impairment (aMCI) is associated with changes in cortical morphological features, such as cortical thickness, sulcal depth, surface area, gray matter volume, metric distortion, and mean curvature. These features have been proven to have specific neuropathological and genetic underpinnings. However, most studies primarily focused on mass-univariate methods, and cortical features were generally explored in isolation. Here, we used a multivariate method to characterize the complex and subtle structural changing pattern of cortical anatomy in 24 aMCI human participants and 26 normal human controls. Six cortical features were extracted for each participant, and the spatial patterns of brain abnormities in aMCI were identified by high classification weights using a support vector machine method. The classification accuracy in discriminating the two groups was 76% in the left hemisphere and 80% in the right hemisphere when all six cortical features were used. Regions showing high weights were subtle, spatially complex, and predominately located in the left medial temporal lobe and the supramarginal and right inferior parietal lobes. In addition, we also found that the six morphological features had different contributions in discriminating the two groups even for the same region. Our results indicated that the neuroanatomical patterns that discriminated individuals with aMCI from controls were truly multidimensional and had different effects on the morphological features. Furthermore, the regions identified by our method could potentially be useful for clinical diagnosis.

Hereditary vulnerabilities to post-operative cognitive dysfunction and dementia

In view of multiple prospective investigations reporting an incidence of 10% or greater in elderly patients after cardiac and non-cardiac procedures, it is surprising that no families, twins or even individual cases have been reported with persistent post-operative cognitive dysfunction (POCD) or post-operative dementia (POD) that is otherwise unexplained. As POCD and POD research has shifted in recent years from surgical and anesthetic variables to predictors of intrinsic, patient-specific susceptibility, a number of markers based on DNA sequence variation have been investigated. Nevertheless, no heritable, genomic indices of persistent POCD or post-operative dementia lasting 3 months or longer after surgery have been identified to date. The present manuscript surveys challenges confronting the search for markers of heritable vulnerability to POCD and POD, and proposes steps forward to be taken now, including the addition of surgical and anesthetic descriptors to ongoing longitudinal dementia protocols and randomized clinical trials (RCTs) comprising serial psychometric testing, and a fresh focus on phenotypes and genotypes shared between outliers with "extreme" POCD and POD traits.

The utility of age-specific cut-offs for visual rating of medial temporal atrophy in classifying Alzheimer's disease, MCI and cognitively normal elderly subjects

Background: New research criteria for diagnosing Alzheimer's disease (AD) in the mild cognitive impairment stage (MCI-AD) incorporate biomarkers to assign a level of certainty to the diagnosis. Structural MRI is widely available but greatly under-utilized for assessing atrophy of structures affected in early AD, such as the hippocampus (HP), because the quantification of HP volumes (HP-v) requires special expertise, and normative values have not been established.

Methods: Elderly subjects (n =273) from the Florida ADRC were classified as having no cognitive impairment (cognitively normal, CN), amnestic mild cognitive impairment (aMCI) or AD. Volumes for the hippocampus (HP-v) were measured on structural MRI scans. A validated visual rating system for measuring medial temporal atrophy (VRS-MTA), including hippocampal, entorhinal cortex and perirhinal cortex atrophy was employed. The participants were subdivided into younger (less than or equal to 75 years of age) and older (greater than 75 years of age) subgroups.

Results: Volumetric and VRS-MTA measures were equivalent in predicting classification of CN vs. aMCI for older (area under the receiver operator curves [aROC]: 0.652 vs. 0.723) and younger subjects (aROC: 0.764 vs. 0.736). However, for younger AD subjects, aROC values were significantly higher for VRS-MTA measures (0.920) than for volumetric measures (0.847). Relative to HP-v, VRS-MTA score was significantly more correlated to impairment on a range of memory tests and was more associated with progression of aMCI to AD than HP-v.

Conclusion: Structural MRI with VRS-MTA assessment can serve as a biomarker for supporting the diagnosis of MCI-AD. Age-adjusted VRS-MTA scores are at least as effective as HP-v for distinguishing aMCI and AD from CN and for predicting progression from aMCI to AD. VRS-MTA is convenient for use in the clinic as well as for clinical trials and can readily be incorporated into a standardized radiological report.

Ascending monoaminergic systems alterations in Alzheimer's disease. translating basic science into clinical care

Extensive neuropathological studies have established a compelling link between abnormalities in structure and function of subcortical monoaminergic (MA-ergic) systems and the pathophysiology of Alzheimer's disease (AD). The main cell populations of these systems including the locus coeruleus, the raphe nuclei, and the tuberomamillary nucleus undergo significant degeneration in AD, thereby depriving the hippocampal and cortical neurons from their critical modulatory influence. These studies have been complemented by genome wide association studies linking polymorphisms in key genes involved in the MA-ergic systems and particular behavioral abnormalities in AD. Importantly, several recent studies have shown that improvement of the MA-ergic systems can both restore cognitive function and reduce AD-related pathology in animal models of neurodegeneration. This review aims to explore the link between abnormalities in the MA-ergic systems and AD symptomatology as well as the therapeutic strategies targeting these systems. Furthermore, we will examine possible mechanisms behind basic vulnerability of MA-ergic neurons in AD.