Changes In Mild Cognitive Impairment Research Articles

Prediction of longitudinal clinical status changes in mild cognitive impairment by network structural covariance

AbstractBackgroundMild cognitive impairment (MCI) is the transitional zone between normal aging and Alzheimer’s dementia (AD), representing a group of subjects with higher risk of conversion to AD (Petersen, 2010). However, as accumulating evidence shows that there are a non‐negligible number of MCI subjects who revert to be cognitive normal (CN), additional measures are needed for better characterizations on the MCI groups (Petersen, 2014). Thus, the purpose of this study is to explore the structural covariance (SC) feature of subjects with different longitudinal clinical status changes.MethodParticipants were from the Beijing Aging Brain Rejuvenation Initiative (BABRI), with two clinical cognitive assessments and the baseline high‐resolution structural MRI data. And four groups were defined, the stable CN (sCN, n = 99), CN progressing to MCI (pCN, n = 23), stable MCI (sMCI, n = 29), and MCI reverting to CN (rMCI, n = 33), and the mean age and follow‐ups interval for CN and MCI subjects were 64.74 and 66.63, 2.46 and 1.45 years, respectively. And the seed‐based multivariate method (Alexander‐Bloch, 2013) was applied to identify the SC of default‐mode network (scDN), frontoparietal network (scFN) and hippocampal network (scHN), of which the covariance scores were calculated. To obtain the SC templates of three networks, 69 sCN were randomly selected, and the rest 30 sCN, with the other three groups, were included in establishing prediction model of clinical status changes based on network SC scores, by using the support vector machine method and leave‐one‐out cross‐validation. Moreover, baseline cognition was also added in the model.ResultFor classification between sCN and sMCI, the scHN score presented the highest accuracy (area under curve (AUC) = 0.89), and it was the scDN score showing the best performance in classifying sMCI and rMCI (AUC = 0.82), with the scFN score outperforming others in distinguishing pCN from sCN (AUC = 0.68). And when baseline cognition was also included, prediction accuracies of clinical changes were improved (AUC = 0.84 for sMCI vs. rMCI, AUC = 0.83 for sCN vs. pCN).ConclusionTaking together, our findings indicated the potential of network structural covariance in classifying MCI subjects with different risk of conversion.

High-dimensional brain-wide functional connectivity mapping in magnetoencephalography

BackgroundBrain functional connectivity (FC) analyses based on magneto/electroencephalography (M/EEG) signals have yet to exploit the intrinsic high-dimensional information. Typically, these analyses are constrained to regions of interest to avoid the curse of dimensionality, with the latter leading to conservative hypothesis testing. New methodWe removed such constraint by estimating high-dimensional source-based M/EEG-FC using cluster-permutation statistic (CPS) and demonstrated the feasibility of this approach by identifying resting-state changes in mild cognitive impairment (MCI), a prodromal stage of Alzheimer’s disease. Particularly, we proposed a unified framework for CPS analysis together with a novel neighbourhood measure to estimate more compact and neurophysiological plausible neural communication. As clusters could more confidently reveal interregional communication, we proposed and tested a cluster-strength index to demonstrate other advantages of CPS analysis. ResultsWe found clusters of increased communication or hypersynchronization in MCI compared to healthy controls in delta (1−4 Hz) and higher-theta (6−8 Hz) bands oscillations. These mainly consisted of interactions between occipitofrontal and occipitotemporal regions in the left hemisphere, which may be critically affected in the early stages of Alzheimer’s disease. ConclusionsOur approach could be important to create high-resolution FC maps from neuroimaging studies in general, allowing the multimodal analysis of neural communication across multiple spatial scales. Particularly, FC clusters more robustly represent the interregional communication by identifying dense bundles of connections that are less sensitive to inter-individual anatomical and functional variability. Overall, this approach could help to better understand neural information processing in healthy and disease conditions as needed for developing biomarker research.

A-02 Comparing Rate of Change in MoCA and MMSE Scores Over Time in an MCI and AD sample

Abstract Objective The Montreal Cognitive Assessment (MoCA) and Mini-Mental Status Exam (MMSE) are used for tracking cognitive change in mild cognitive impairment (MCI) and Alzheimer’s disease (AD), despite limited empirical support for this purpose. This study compared longitudinal change in MMSE and MoCA scores to investigate their applicability for tracking cognitive change. Method Inclusion criteria were: diagnosis of MCI or AD (CDR global = .5) by consensus conference, administration of the MoCA and MMSE across ≥3 visits, and no reversion to normal (n = 59; Mage = 70.81; Meducation = 14.97; 56% male; 76.3% Caucasian; 80% MCI at baseline). Testing sessions occurred ~ 12 months apart (M = 12.59, SD = 3.43, range 5–28 months). Change in MMSE and MoCA scores was modeled using multilevel regression. A 95% bootstrap confidence interval (BCI) for the slopes of both tests was computed and used to evaluate whether the tests measured significantly different change. Results Controlling for age and education, the MoCA demonstrated significantly more change over time (95% BCI [−0.06, −0.02]; MoCA Visit 1 M = 24.00, Visit 4 M = 21.88) than the MMSE (95% BCI [−0.03, 0.01]; MMSE Visit 1 M = 27.83, Visit 4 M = 27.50). MoCA scores significantly declined over the study period (but did not exceed the reliable change index), while MMSE scores did not. Conclusions The MMSE did not show significant change over time, while the MoCA did in this heavily MCI sample. Although statistically significant, clinical significance of change in the MoCA is unclear. Increasing MoCA use calls for additional research to understand what constitutes a clinically significant change and whether it is appropriate for tracking cognitive trajectories.

Amyloid and cerebrovascular burden divergently influence brain functional network changes over time.

To examine the effects of baseline Alzheimer disease and cerebrovascular disease markers on longitudinal default mode network (DMN) and executive control network (ECN) functional connectivity (FC) changes in mild cognitive impairment (MCI). We studied 30 patients with amnestic MCI (aMCI) and 55 patients with subcortical vascular MCI (svMCI) with baseline Pittsburgh Compound B (PiB)-PET scans and longitudinal MRI scans. Participants were followed up clinically with annual MRI for up to 4 years (aMCI: 26 with 2 timepoints, 4 with 3 timepoints; svMCI: 13 with 2 timepoints, 16 with 3 timepoints, 26 with 4 timepoints). β-Amyloid (Aβ) burden was associated with longitudinal DMN FC declines, while cerebrovascular burden was associated with longitudinal ECN FC changes. When patients were divided into PiB+ and PiB- groups, PiB+ patients showed longitudinal DMN FC declines, while patients with svMCI showed longitudinal ECN FC increases. Direct comparisons between the 2 groups without mixed pathology (aMCI PiB+ and svMCI PiB-) recapitulated this divergent pattern: aMCI PiB+ patients showed steeper longitudinal DMN FC declines, while svMCI PiB- patients showed steeper longitudinal ECN FC increases. Finally, using baseline PiB uptake and lacune numbers as continuous variables, baseline PiB uptake showed inverse U-shape associations with longitudinal DMN FC changes in both MCI subtypes, while baseline lacune numbers showed mainly inverse U-shape relationships with longitudinal ECN FC changes in patients with svMCI. Our findings underscore the divergent effects of Aβ and cerebrovascular burden on longitudinal FC changes in the DMN and ECN in the predementia stage, which reflect the underlying pathology and may be used to track early changes in Alzheimer disease and cerebrovascular disease.

Mild Cognitive Impairment and Decline in Resting State Functional Connectivity after Total Knee Arthroplasty with General Anesthesia.

Research shows that older adults can have a decline in three key resting state networks (default mode network, central executive network, and salience network) after total knee arthroplasty and that patients' pre-surgery brain and cognitive integrity predicts decline. First, to assess resting state network connectivity decline from the perspective of nodal connectivity changes in a larger older adult surgery sample. Second, to compare pre-post functional connectivity changes in mild cognitive impairment (MCI) versus non-MCI. Surgery (n = 69) and non-surgery (n = 65) peers completed a comprehensive preoperative neuropsychological evaluation and pre- and acute (within 48 hours) post-surgery/pseudo-surgery functional brain magnetic resonance imaging scan. MCI was classified within both (MCI surgery, n = 13; MCI non-surgery, n = 10). Using standard coordinates, we defined default mode network, salience network, central executive network, and the visual network (serving as a control network). The functional connectivity of these networks and brain areas (nodes) that make up these networks were examined for pre-post-surgery changes through paired samples t-test and ANOVA. There was a decline in RSN connectivity after surgery (p < 0.05) only in the three cognitive networks (not the visual network). The default mode and salience network showed nodal connectivity changes (p < 0.01). MCI surgery had greater functional connectivity decline in DMN and SN. Non-surgery participants showed no significant functional connectivity change. Surgery with general anesthesia selectively alters functional connectivity in major cognitive resting state networks particularly in DMN and SN. Participants with MCI appear more vulnerable to these functional changes.

Mild Cognitive Impairment changes Natural Reading in Parkinson’s Disease (P2.8-028)

Mild Cognitive Impairment changes Natural Reading in Parkinson’s Disease (P2.8-028)

Exploring Structural and Functional Brain Changes in Mild Cognitive Impairment: A Whole Brain ALE Meta-Analysis for Multimodal MRI.

Unraveling novel biomarkers for mild cognitive impairment (MCI) was highlighted in the prevention and modification of Alzheimer's disease (AD). Inconsistent results for comparison between MCI patients and healthy controls (HC) were obtained from previous neuroimaging studies. An activation likelihood estimation (ALE) meta-analysis was made for multimodal neuroimaging in MCI. After initial research and step-by-step exclusions procedures, n = 101 articles (MCI, n = 2681; HC, n = 2941, respectively) were included in the study. It detected MCI related gray matter atrophy in the bilateral medial temporal lobe and white matter abnormality in the left posterior cingulate, parahippocampal gyrus, thalamus, caudate, and bilateral precuneus. It revealed MCI-related decreased resting-state activity in the left superior temporal gyrus, right posterior cingulate/precuneus, and uncus and hyperactivation in the inferior parietal lobule and superior parietal lobule compared to HC. Task-related functional neuroimaging studies indicated MCI-related hypoactivation in the left inferior parietal lobule, right posterior cingulate, and bilateral precuneus and hyperactivation in the left middle frontal gyrus, superior parietal lobule, insula, superior temporal gyrus, and right inferior frontal gyrus. Via this ALE meta-analysis, we obtained these key regions suffering from different kinds of deficits in MCI. These regional abnormalities in MRI studies might serve as biomarkers for early diagnosis of MCI.

Serum levels of proteins involved in amyloid-β clearance are related to cognitive decline and neuroimaging changes in mild cognitive impairment

IntroductionAmyloid-β (Aβ) clearance is important for damage prevention in Alzheimer's disease. We investigated the utility of Aβ clearance proteins as biomarkers for mild cognitive impairment (MCI). MethodsSerum apolipoprotein (apo) A-I, compliment protein C3 (C3), transthyretin, and cholesterol levels were measured in 273 subjects, and we analyzed the relationship between these levels and brain atrophy and cerebral blood flow in 63 clinically diagnosed mild cognitive impairment, Alzheimer's disease, and nondemented disease control subjects. ResultsApoA-I and transthyretin levels and the active form of C3:native form of C3 ratio achieved an area under the curve of 0.89 (sensitivity: 83%, specificity: 90%) for detecting late mild cognitive impairment. Atrophy was associated with decreased apoA-I and high-density lipoprotein levels. Subjects with reduced cerebral blood flow had lower levels of native form of C3, apoA-I, high-density lipoprotein, and total cholesterol. Low native form of C3 and high active form of C3 levels were found in the hippocampi of patients with Alzheimer's disease. DiscussionAβ clearance proteins in the serum are potential biomarkers for mild cognitive impairment evaluation.

Sensitivity of restriction spectrum imaging to memory and neuropathology in Alzheimer\u2019s disease

BackgroundDiffusion imaging has demonstrated sensitivity to structural brain changes in Alzheimer’s disease (AD). However, there remains a need for a more complete characterization of microstructural alterations occurring at the earliest disease stages, and how these changes relate to underlying neuropathology. This study evaluated the sensitivity of restriction spectrum imaging (RSI), an advanced diffusion magnetic resonance imaging (MRI) technique, to microstructural brain changes in mild cognitive impairment (MCI) and AD.MethodsMRI and neuropsychological test data were acquired from 31 healthy controls, 12 individuals with MCI, and 13 individuals with mild AD, aged 63–93 years. Cerebrospinal fluid amyloid-β levels were measured in a subset (n = 38) of participants. RSI measures of neurite density (ND) and isotropic free water (IF) were computed in fiber tracts and in hippocampal and entorhinal cortex gray matter, respectively. Analyses evaluated whether these measures predicted memory performance, correlated with amyloid-β levels, and distinguished impaired individuals from controls. For comparison, analyses were repeated with standard diffusion tensor imaging (DTI) metrics of fractional anisotropy (FA) and mean diffusivity.ResultsBoth RSI and DTI measures correlated with episodic memory and disease severity. RSI, but not DTI, measures correlated with amyloid-β42 levels. ND and FA in the arcuate fasciculus and entorhinal cortex IF most strongly predicted recall performance. RSI measures of arcuate fasciculus ND and entorhinal cortex IF best discriminated memory impaired participants from healthy participants.ConclusionsRSI is highly sensitive to microstructural changes in the early stages of AD, and is associated with biochemical markers of AD pathology. Reduced ND in cortical association fibers and increased medial temporal lobe free-water diffusion predicted episodic memory, distinguished cognitively impaired from healthy individuals, and correlated with amyloid-β. Although further research is needed to assess the sensitivity of RSI to preclinical AD and disease progression, these results suggest that RSI may be a promising tool to better understand neuroanatomical changes in AD and their association with neuropathology.

QUALITY ASPECTS OF A NOVEL COGNITIVE-FUNCTIONAL COMPOSITE FOR THE MEASUREMENT OF DISEASE PROGRESSION IN ALZHEIMER’S DISEASE: FEASIBILITY, TEST-RETEST RELIABILITY AND PRACTICE EFFECTS

To improve the detection of clinically relevant changes in mild cognitive impairment (MCI) and mild Alzheimer's disease (AD), we designed a novel composite measure: the Cognitive-Functional Composite (CFC). As a first validation step, we investigated its feasibility, test-retest reliability and potential practice effects. We recruited patients with MCI or mild dementia due to AD (MMSE ≥18) from four memory clinics in The Netherlands and Scotland (n=48). We included cognitively healthy subjects as control group (n=30). The CFC consists of tests that focus on episodic memory (ADAS-Cog Word Recognition, ADAS-Cog Orientation and ADAS-Cog Word Recall), working memory (Digit Span Backwards) and executive functioning (Category Fluency Test, Controlled Oral Word Association Test and Digit Symbol Substitution Test (DSST)), and an everyday functioning questionnaire (Amsterdam Instrumental Activities of Daily Living Questionnaire, A-IADL-Q). At baseline and after 2–3 weeks follow-up, all subjects underwent the cognitive tests whilst their study partners completed the A-IADL-Q. Feasibility was investigated by interviewing subjects after follow-up. We compared baseline and follow-up scores using paired t-tests with Bonferroni correction for multiple testing, and test-retest reliability with intraclass correlation coefficients (ICC) using a two-factor mixed model and type absolute agreement. Additionally, we applied the Bland-Altman method to explore systematic differences that could point towards practice effects. The patient group (40% female, age 69.9 (SD=7.4), MMSE 25.3 (SD=3.3)) was slightly older than the control group (50% female, age 65 (SD=7.1), p=.006). Overall, subjects experienced test content and materials as feasible. For patients, we only found a significant higher score at follow-up (M=2.4, SD=5.4, corrected p=.04) for the DSST, despite a high absolute agreement (ICC=.881, p<.001). The Bland-Altman plot did not show systematic differences (Figure 1). For all subtests, we found moderate to high test-retest reliability in patients (ICCs ranging from .551 to .945). ICCs were substantially lower in controls (ranging from .048 to .650), probably due to ceiling effects.

Exercise Training and Functional Connectivity Changes in Mild Cognitive Impairment and Healthy Elders.

Effective interventions are needed to improve brain function in mild cognitive impairment (MCI), an early stage of Alzheimer's disease (AD). The posterior cingulate cortex (PCC)/precuneus is a hub of the default mode network (DMN) and is preferentially vulnerable to disruption of functional connectivity in MCI and AD. We investigated whether 12 weeks of aerobic exercise could enhance functional connectivity of the PCC/precuneus in MCI and healthy elders. Sixteen MCI and 16 healthy elders (age range = 60-88) engaged in a supervised 12-week walking exercise intervention. Functional MRI was acquired at rest; the PCC/precuneus was used as a seed for correlated brain activity maps. A linear mixed effects model revealed a significant interaction in the right parietal lobe: the MCI group showed increased connectivity while the healthy elders showed decreased connectivity. In addition, both groups showed increased connectivity with the left postcentral gyrus. Comparing pre to post intervention changes within each group, the MCI group showed increased connectivity in 10 regions spanning frontal, parietal, temporal and insular lobes, and the cerebellum. Healthy elders did not demonstrate any significant connectivity changes. The observed results show increased functional connectivity of the PCC/precuneus in individuals with MCI after 12 weeks of moderate intensity walking exercise training. The protective effects of exercise training on cognition may be realized through the enhancement of neural recruitment mechanisms, which may possibly increase cognitive reserve. Whether these effects of exercise training may delay further cognitive decline in patients diagnosed with MCI remains to be demonstrated.

Potential neuroimaging biomarkers of pathologic brain changes in Mild Cognitive Impairment and Alzheimer’s disease: a systematic review

BackgroundNeuroimaging-biomarkers of Mild Cognitive Impairment (MCI) allow an early diagnosis in preclinical stages of Alzheimer’s disease (AD). The goal in this paper was to review of biomarkers for Mild Cognitive Impairment (MCI) and Alzheimer’s disease (AD), with emphasis on neuroimaging biomarkers.MethodsA systematic review was conducted from existing literature that draws on markers and evidence for new measurement techniques of neuroimaging in AD, MCI and non-demented subjects. Selection criteria included: 1) age ≥ 60 years; 2) diagnosis of AD according to NIAAA criteria, 3) diagnosis of MCI according to NIAAA criteria with a confirmed progression to AD assessed by clinical follow-up, and 4) acceptable clinical measures of cognitive impairment, disability, quality of life, and global clinical assessments.ResultsSeventy-two articles were included in the review. With the development of new radioligands of neuroimaging, today it is possible to measure different aspects of AD neuropathology, early diagnosis of MCI and AD become probable from preclinical stage of AD to AD dementia and non-AD dementia.ConclusionsThe panel of noninvasive neuroimaging-biomarkers reviewed provides a set methods to measure brain structural and functional pathophysiological changes in vivo, which are closely associated with preclinical AD, MCI and non-AD dementia. The dynamic measures of these imaging biomarkers are used to predict the disease progression in the early stages and improve the assessment of therapeutic efficacy in these diseases in future clinical trials.

ID 326 – Functional connectivity alterations and their relation to pathophysiological changes in mild cognitive impairment

So far many studies have addressed the issue of connectivity changes in mild cognitive impairment (MCI) and Alzheimer’s disease (AD) using different methods, including whole-brain network analyses describing structural and functional topology. In this study we address an association between network topology and brain pathology in MCI. We investigated functional connectivity of MCI subjects ( n = 84) and age-matched healthy controls (HC; n = 32) defined on AAL atlas. In the MCI group we assessed how changes in brain topology correlate with cognitive performance and CSF levels of AD biomarkers in order to shed further light on underlying pathophysiological mechanisms. We used following parameters to describe brain topology: clustering coefficient, path length, node strength, and eigenvector centrality. We found shorter global path length, changes in frontal, occipital and subcortical regions, and more homogeneous hub distribution in MCI as compared to HC. Worse cognitive performance was related to topological changes in mentioned regions. Network properties correlated with CSF biomarkers in frontal and occipital regions. We observed a shift in MCI networks towards random topology with extensive regional changes, parallels can be found in literature. Network results are supported by cognitive results and CSF biomarkers levels, combined bringing unique information to current knowledge of MCI changes.

Pauses During Autobiographical Discourse Reflect Episodic Memory Processes in Early Alzheimer's Disease.

There is a large body of research on discourse production in Alzheimer’s disease (AD). Some studies have focused on pause production, revealing that patients make extensive use of pauses during speech. This has been attributed to lexical retrieval difficulties, but pausing may also reflect other forms of cognitive impairment as it increases with cognitive load. The aim of the present study was to analyze autobiographical discourse impairment in AD from a broad perspective, looking at pausing behavior (frequency, duration, and location). Our first objective was to characterize discourse changes in mild cognitive impairment (MCI) due to AD. Our second objective was to determine the cognitive and neuroanatomical correlates of these changes. Fifteen patients with MCI due to AD and 15 matched cognitively normal controls underwent an ecological episodic memory task, a full neuropsychological assessment, and a 3D T1-weighted MRI scans. Autobiographical discourse collected from the ecological episodic memory task was recorded, transcribed, and analyzed, focusing on pausing. Intergroup comparisons showed that although patients did not produce more pauses than controls overall, they did make more between-utterance pauses. The number of these specific pauses was positively correlated with patients’ episodic memory performance. Furthermore, neuroimaging analysis showed that, in the patient group, their use was negatively correlated with frontopolar area (BA 10) grey matter density. This region may therefore play an important role in the planning of autobiographical discourse production. These findings demonstrate that pauses in early AD may reflect a compensatory mechanism for improving mental time travel and memory retrieval.

Role of β-Amyloidosis and Neurodegeneration in Subsequent Imaging Changes in Mild Cognitive Impairment.

To understand how a model of Alzheimer disease pathophysiology based on β-amyloidosis and neurodegeneration predicts the regional anatomic expansion of hypometabolism and atrophy in persons with mild cognitive impairment (MCI). To define the role of β-amyloidosis and neurodegeneration in the subsequent progression of topographic cortical structural and metabolic changes in MCI. Longitudinal, observational study with serial brain imaging conducted from March 28, 2006, to January 6, 2015, using a population-based cohort. A total of 96 participants with MCI (all aged >70 years) with serial imaging biomarkers from the Mayo Clinic Study of Aging or Mayo Alzheimer's Disease Research Center were included. Participants were characterized initially as having elevated or not elevated brain β-amyloidosis (A+ or A-) based on 11C-Pittsburgh compound B positron emission tomography. They were further characterized initially by the presence or absence of neurodegeneration (N+ or N-), where the presence of neurodegeneration was defined by abnormally low hippocampal volume or hypometabolism in an Alzheimer disease-like pattern on 18fluorodeoxyglucose (FDG)-positron emission tomography. Regional FDG standardized uptake value ratio (SUVR) and gray matter volumes in medial temporal, lateral temporal, lateral parietal, and medial parietal regions. In the primary regions of interest (ROI), the A+N+ group (n = 45) had lower FDG SUVR at baseline compared with the A+N- group (n = 17) (all 4 ROIs; P < .001). The A+N+ group also had lower FDG SUVR at baseline (all 4 ROIs; P < .01) compared with the A-N- group (n = 12). The A+N+ group had lower medial temporal gray matter volume at baseline (P < .001) compared with either the A+N- group or A-N- group. The A+N+ group showed large longitudinal declines in FDG SUVR (P < .05 for medial temporal, lateral temporal, and medial parietal regions) and gray matter volumes (P < .05 for medial temporal and lateral temporal regions) compared with the A-N+ group (n = 22). The A+N+ group also showed large longitudinal declines compared with the A-N- group on FDG SUVR (P < .05 for medial temporal and lateral parietal regions) and gray matter volumes (all 4 ROIs; P < .05) compared with the A+N- group. The A-N+ group did not show declines in FDG SUVR or gray matter volume compared with the A+N- or A-N- groups. Persons with MCI who were A+N+ demonstrated volumetric and metabolic worsening in temporal and parietal association areas, consistent with the expectation that the MCI stage in the Alzheimer pathway heralds incipient isocortical involvement. The A-N+ group, those with suspected non-Alzheimer pathophysiology, lacked a distinctive longitudinal volumetric or metabolic profile.

Not another computerized cognitive test: Aspects of responding to a weekly online health questionnaire are sensitive to identifying early cognitive change in mild cognitive impairment

Not another computerized cognitive test: Aspects of responding to a weekly online health questionnaire are sensitive to identifying early cognitive change in mild cognitive impairment

Detection of Alzheimer Disease Using Grow Cut Method and Brain Volume Estimation

뇌에서 신경세포의 손상은 치매환자의 대부분의 병명이다. MRI 연구 기반 3차원 화소는 뇌크기의 축소가 AD 치매의 전과정인 MCI에서 아트로픽 변화를 보여주는 것으로 설명한다. 수많은 연구중에서 의학전문가는 뇌의 구조적 수축에 의한 신경 손상을 양적으로 측정하는 MRI 영상을 사용한다. 게다가, 어떤 특정 구조의 아트로피는 뇌 전반적인 크기에 있어 줄어든 것과 직접적인 관계가 있다. 이 논문은 알츠하이머 병의 조기 진단을 하기 위하여 MRI 영상으로 뇌전체의 크기를 세분화하는 새로운 알고리듬에 관한 것이다. 연구 과정은 건강 관리와 AD 환자의 두 분류를 생성하며 수행한다. 뇌 MRI 영상의 세션화를 사용한 뇌 크기를 추정한다. 최종적으로 이 논문은 MRI 영상으로 뇌의 크기를 정확하게 추출하는 grow cut 방법의 개선점을 이용한다. 제안된 방법은 단순하며 실험적 결과는 우수한 것으로 보여진다.

Neural Correlates of Spatial Navigation Changes in Mild Cognitive Impairment and Alzheimer’s Disease

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

EEG network connectivity changes in mild cognitive impairment — Preliminary results

Resting state EEGs were compared between patients with amnestic subtype of mild cognitive impairment (aMCI) and matched elderly controls at two times over a one year period. The study aimed at investigating the role of functional connectivity between and within different brain regions in relation to the progression of cognitive deficit in MCI. The EEG was recorded in two sessions during eyes closed and eyes open resting conditions. Functional brain connectivity was investigated based on the measurement of phase synchronization in different frequency bands. Delta and theta synchronization characteristics indicated decreased level of local and large-scale connectivity in the patients within the frontal, between the frontal and temporal, and frontal and parietal brain areas which was more pronounced 1year later. As a consequence of opening the eyes connectivity in the alpha1 band within the parietal lobe decreased compared to the eyes closed condition but only in the control group. The lack of alpha1 band reactivity following eye opening could reliably differentiate patients from controls. Our preliminary results support the notion that the functional disconnection between distant brain areas is a characteristic feature of MCI, and may prove to be predictive in terms of the progression of this condition.

CSF contamination contributes to apparent microstructural alterations in mild cognitive impairment

Diffusion MRI is used widely to probe microstructural alterations in neurological and psychiatric disease. However, ageing and neurodegeneration are also associated with atrophy, which leads to artefacts through partial volume effects due to cerebrospinal-fluid contamination (CSFC). The aim of this study was to explore the influence of CSFC on apparent microstructural changes in mild cognitive impairment (MCI) at several spatial levels: individually reconstructed tracts; at the level of a whole white matter skeleton (tract-based spatial statistics); and histograms derived from all white matter. 25 individuals with MCI and 20 matched controls underwent diffusion MRI. We corrected for CSFC using a post-acquisition voxel-by-voxel approach of free-water elimination. Tracts varied in their susceptibility to CSFC. The apparent pattern of tract involvement in disease shifted when correction was applied. Both spurious group differences, driven by CSFC, and masking of true differences were observed. Tract-based spatial statistics were found to be robust across much of the skeleton but with some localised CSFC effects. Diffusivity measures were affected disproportionately in MCI, and group differences in fornix microstructure were exaggerated. Group differences in white matter histogram measures were also partly driven by CSFC. For diffusivity measures, up to two thirds of observed group differences were due to CSFC. Our results demonstrate that CSFC has an impact on quantitative differences between MCI and controls. Furthermore, it affects the apparent spatial pattern of white matter involvement. Free-water elimination provides a step towards disentangling intrinsic and volumetric alterations in individuals prone to atrophy.