Fronto-temporal-lobe atrophy in early-stage Alzheimer's disease identified using an improved detection methodology

Structural degeneration of the nucleus basalis of Meynert in mild cognitive impairment and Alzheimer's disease - Evidence from an MRI-based meta-analysis

Recent models of Alzheimer's disease (AD) suggest that neuropathological changes of the medial temporal lobe, especially entorhinal cortex, are preceded by degenerations of the cholinergic Nucleus basalis of Meynert (NbM). Evidence from imaging studies in humans, however, is limited. Therefore, we performed an activation-likelihood estimation meta-analysis on whole brain voxel-based morphometry (VBM) MRI data from 54 experiments and 2581 subjects in total. It revealed, compared to healthy older controls, reduced gray matter in the bilateral NbM in AD, but only limited evidence for such an effect in patients with mild cognitive impairment (MCI), which typically precedes AD. Both patient groups showed less gray matter in the amygdala and hippocampus, with hints towards more pronounced amygdala effects in AD. We discuss our findings in the context of studies that highlight the importance of the cholinergic basal forebrain in learning and memory throughout the lifespan, and conclude that they are partly compatible with pathological staging models suggesting initial and pronounced structural degenerations within the NbM in the progression of AD.

Novel insights into the relationship between cerebellum and dementia: A narrative review as a toolkit for clinicians

The role of the cerebellum in neurodegenerative disorders that target cognitive functions has been a subject of increasing interest over the past years. However, a review focused on making clinicians more aware of the role of the cerebellum in dementia is still missing. This narrative review explores the possible factors explaining the involvement of the cerebellum in different kinds of dementia by providing more insights on how this structure can be relevant in clinical practice. It emerged that, despite overlapping in specific areas, structural cerebellar alterations in dementia show a certain degree of disease-specificity. Furthermore, the relevance of cerebellar changes in dementia is corroborated by correlations observed between their topography and cognitive symptomatology, as well as by its previously ignored involvement of the cerebellum in early stages of dementia. Despite needing further investigations, these findings could become a useful diagnostic aid for clinicians that should not be overlooked, in particular for those individuals who do not show distinct and manifest brain or neuropsychological alterations, but that still make clinicians suspect the presence of a neurocognitive disease.

Differential insular cortex sub-regional atrophy in neurodegenerative diseases: a systematic review and meta-analysis

The insular cortex is proposed to function as a central brain hub characterized by wide-spread connections and diverse functional roles. As a result, its centrality in the brain confers high metabolic demands predisposing it to dysfunction in disease. However, the functional profile and vulnerability to degeneration varies across the insular sub-regions. The aim of this systematic review and meta-analysis is to summarize and quantitatively analyze the relationship between insular cortex sub-regional atrophy, studied by voxel based morphometry, with cognitive and neuropsychiatric deficits in frontotemporal dementia (FTD), Alzheimer’s disease (AD), Parkinson’s disease (PD), and dementia with Lewy bodies (DLB). We systematically searched through Pubmed and Embase and identified 519 studies that fit our criteria. A total of 41 studies (n = 2261 subjects) fulfilled the inclusion criteria for the meta-analysis. The peak insular coordinates were pooled and analyzed using Anatomic Likelihood Estimation. Our results showed greater left anterior insular cortex atrophy in FTD whereas the right anterior dorsal insular cortex showed larger clusters of atrophy in AD and PD/DLB. Yet contrast analyses did not reveal significant differences between disease groups. Functional analysis showed that left anterior insular cortex atrophy is associated with speech, emotion, and affective-cognitive deficits, and right dorsal atrophy with perception and cognitive deficits. In conclusion, insular sub-regional atrophy, particularly the anterior dorsal region, may contribute to cognitive and neuropsychiatric deficits in neurodegeneration. Our results support anterior insular cortex vulnerability and convey the differential involvement of the insular sub-regions in functional deficits in neurodegenerative diseases.

Differential vulnerability of the cerebellum in healthy ageing and Alzheimer's disease

Recent findings challenge the prior notion that the cerebellum remains unaffected by Alzheimer's disease (AD). Yet, it is unclear whether AD exacerbates age-related cerebellar grey matter decline or engages distinct structural and functional territories. We performed a meta-analysis of cerebellar grey matter loss in normal ageing and AD. We mapped voxels with structural decline onto established brain networks, functional parcellations, and along gradients that govern the functional organisation of the cerebellum. Importantly, these gradients track continuous changes in cerebellar specialisation providing a more nuanced measure of the functional profile of regions vulnerable to ageing and AD. Gradient 1 progresses from motor to cognitive territories; Gradient 2 isolates attentional processing; Gradient 3 captures lateralisation differences in cognitive functions. We identified bilateral and right-lateralised posterior cerebellar atrophy in ageing and AD, respectively. Age- and AD-related structural decline only showed partial spatial overlap in right lobule VI/Crus I. Despite the seemingly distinct patterns of AD- and age-related atrophy, the functional profiles of these regions were similar. Both participate in the same macroscale networks (default mode, frontoparietal, attention), support executive functions and language processing, and did not exhibit a difference in relative positions along Gradients 1 or 2. However, Gradient 3 values were significantly different in ageing vs. AD, suggesting that the roles of left and right atrophied cerebellar regions exhibit subtle functional differences despite their membership in similar macroscale networks. These findings provide an unprecedented characterisation of structural and functional differences and similarities in cerebellar grey matter loss between normal ageing and AD.

Fear acquisition and extinction in elderly patients with depression

BACKGROUND

Depression in elderly patients is common and characterized by anxiety symptoms and cognitive impairment. To our knowledge, no studies have yet investigated the process of fear extinction in these patients. We investigated fear extinction with a paradigm consisting of habituation, acquisition and extinction.

METHODS

We included three age matched (mean age: 75.7 years) groups: Late Life Depression (LLD, n = 33), Mild Cognitive Impairment (MCI, n = 39), healthy controls (HC, n = 39). All participants were diagnosed with a standardized procedure including clinical examination, CERAD cognitive test battery, as well as magnetic resonance imaging. Participants underwent a fear conditioning paradigm consisting of habituation, acquisition, and extinction. During acquisition, a neutral face (conditioned stimulus, CS+) was paired with an electrical unconditioned stimulus, whereas another face (safety stimulus, CS-) was unpaired. Conditioned responses were measured by US-expectancy and valence ratings.

RESULTS

Compared to HC, both patient groups showed a significantly lower, differential (CS+ vs. CS-) fear acquisition across all measurements. Patients with cognitive impairment showed a significantly slower extinction, which is characterized by higher US-expectancy and reduced positive valence for CS+. Fear extinction was significantly less differential (CS+ vs. CS-) in patients with LLD.

LIMITATIONS

Due to the cross-sectional design we cannot distinguish whether the observed differences in fear extinction are state or trait markers in the LLD patients.

CONCLUSIONS

In this study, we demonstrate that fear extinction is impaired in elderly patients with depression. These results can have influence on treatment strategies.

Cerebellar Grey Matter Volume in Older Persons Is Associated with Worse Cognitive Functioning

The cerebellum is increasingly recognised for its role in modulation of cognition, behaviour, and affect. The present study examined the relation between structural cerebellar damage (grey matter volume (GMV), white matter hyperintensities (WMHs), lacunar infarcts (LIs) and microbleeds (MBs)) and measures of cognitive, psychological (i.e. symptoms of depression and apathy) and general daily functioning in a population of community-dwelling older persons with mild cognitive deficits, but without dementia. In 194 participants of the Discontinuation of Antihypertensive Treatment in Elderly People (DANTE) Study Leiden, the association between cerebellar GMV, WMHs, LIs and MBs and measures of cognitive, psychological and general daily functioning was analysed with linear regression analysis, adjusted for age, sex, education and cerebral volume. Cerebellar GMV was associated with the overall cognition score (standardised beta 0.20 [95% CI, 0.06-0.33]). Specifically, posterior cerebellar GMV was associated with executive function (standardised beta 0.18 [95% CI, 0.03-0.16]). No relation was found between vascular pathology and cognition. Also, no consistent associations were found on the cerebellar GMV and vascular pathology measures and psychological and general daily functioning. In this population of community-dwelling elderly, less posterior cerebellar GMV but not vascular pathology was associated with worse cognitive function, specifically with poorer executive function. No relation was found between cerebellar pathology and psychological and general daily functioning.

Disrupted Time-Dependent and Functional Connectivity Brain Network in Alzheimer's Disease: A Resting-State fMRI Study Based on Visibility Graph

Background:

Alzheimer's Disease (AD) is a progressive neurodegenerative disease with insidious onset, which is difficult to be reversed and cured. Therefore, discovering more precise biological information from neuroimaging biomarkers is crucial for accurate and automatic detection of AD.

Methods:

We innovatively used a Visibility Graph (VG) to construct the time-dependent brain networks as well as functional connectivity network to investigate the underlying dynamics of AD brain based on functional magnetic resonance imaging. There were 32 AD patients and 29 Normal Controls (NCs) from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database. First, the VG method mapped the time series of single brain region into networks. By extracting topological properties of the networks, the most significant features were selected as discriminant features into a supporting vector machine for classification. Furthermore, in order to detect abnormalities of these brain regions in the whole AD brain, functional connectivity among different brain regions was calculated based on the correlation of regional degree sequences.

Results:

According to the topology abnormalities exploration of local complex networks, we found several abnormal brain regions, including left insular, right posterior cingulate gyrus and other cortical regions. The accuracy of characteristics of the brain regions extracted from local complex networks was 88.52%. Association analysis demonstrated that the left inferior opercular part of frontal gyrus, right middle occipital gyrus, right superior parietal gyrus and right precuneus played a tremendous role in AD.

Conclusion:

These results would be helpful in revealing the underlying pathological mechanism of the disease.

Redox proteomics and amyloid β-peptide: insights into Alzheimer disease

Alzheimer disease (AD) is a progressive neurodegenerative disorder associated with aging and characterized pathologically by the presence of senile plaques, neurofibrillary tangles, and neurite and synapse loss. Amyloid beta-peptide (1-42) [Aβ(1-42)], a major component of senile plaques, is neurotoxic and induces oxidative stress in vitro and in vivo. Redox proteomics has been used to identify proteins oxidatively modified by Aβ(1-42) in vitro and in vivo. In this review, we discuss these proteins in the context of those identified to be oxidatively modified in animal models of AD, and human studies including familial AD, pre-clinical AD (PCAD), mild cognitive impairment (MCI), early AD, late AD, Down syndrome (DS), and DS with AD (DS/AD). These redox proteomics studies indicate that Aβ(1-42)-mediated oxidative stress occurs early in AD pathogenesis and results in altered antioxidant and cellular detoxification defenses, decreased energy yielding metabolism and mitochondrial dysfunction, excitotoxicity, loss of synaptic plasticity and cell structure, neuroinflammation, impaired protein folding and degradation, and altered signal transduction. Improved access to biomarker imaging and the identification of lifestyle interventions or treatments to reduce Aβ production could be beneficial in preventing or delaying the progression of AD. This article is part of the special issue "Proteomics".

Multivariate Deep Learning Classification of Alzheimer's Disease Based on Hierarchical Partner Matching Independent Component Analysis

Machine learning and pattern recognition have been widely investigated in order to look for the biomarkers of Alzheimer’s disease (AD). However, most existing methods extract features by seed-based correlation, which not only requires prior information but also ignores the relationship between resting state functional magnetic resonance imaging (rs-fMRI) voxels. In this study, we proposed a deep learning classification framework with multivariate data-driven based feature extraction for automatic diagnosis of AD. Specifically, a three-level hierarchical partner matching independent components analysis (3LHPM-ICA) approach was proposed first in order to address the issues in spatial individual ICA, including the uncertainty of the numbers of components, the randomness of initial values, and the correspondence of ICs of multiple subjects, resulting in stable and reliable ICs which were applied as the intrinsic brain functional connectivity (FC) features. Second, Granger causality (GC) was utilized to infer directional interaction between the ICs that were identified by the 3LHPM-ICA method and extract the effective connectivity features. Finally, a deep learning classification framework was developed to distinguish AD from controls by fusing the functional and effective connectivities. A resting state fMRI dataset containing 34 AD patients and 34 normal controls (NCs) was applied to the multivariate deep learning platform, leading to a classification accuracy of 95.59%, with a sensitivity of 97.06% and a specificity of 94.12% with leave-one-out cross validation (LOOCV). The experimental results demonstrated that the measures of neural connectivities of ICA and GC followed by deep learning classification represented the most powerful methods of distinguishing AD clinical data from NCs, and these aberrant brain connectivities might serve as robust brain biomarkers for AD. This approach also allows for expansion of the methodology to classify other psychiatric disorders.

Patterns of Cerebellar Gray Matter Atrophy Across Alzheimer's Disease Progression

The role of the cerebellum in cognitive function has been broadly investigated in the last decades from an anatomical, clinical, and functional point of view and new evidence points toward a significant contribution of the posterior lobes of the cerebellum in cognition in Alzheimer’s disease (AD). In the present work we used SUIT-VBM (spatially unbiased infratentorial template, voxel-based morphometry) to perform an analysis of the pattern of cerebellar gray matter (GM) atrophy in amnestic mild cognitive impairment (a-MCI) and AD dementia patients compared to healthy subjects (HS), in order to follow the changes of non-motor features of cerebellar degeneration throughout disease progression. This template has been validated to guarantee a significant improvement in voxel-to-voxel alignment of the individual fissures and the deep cerebellar nuclei compared to Montreal Neurological Institute (MNI) whole-brain template. Our analysis shows a progression of cerebellar GM volume changes throughout a continuous spectrum from early to late clinical stages of AD. In particular vermis and paravermian areas of the anterior (I-V) and posterior (VI) lobes are involved since the a-MCI stage, with a later involvement of the hemispheric part of the posterior lobes (VI lobule) and Crus I in AD dementia patients only. These findings support the role of the cerebellum in higher-level functions, and whilst confirming previous data on the involvement of Crus I in AD dementia, provide new evidence of an involvement of the vermis in the early stages of the disease.

The Pathoconnectivity Profile of Alzheimer's Disease: A Morphometric Coalteration Network Analysis

Gray matter alterations are typical features of brain disorders. However, they do not impact on the brain randomly. Indeed, it has been suggested that neuropathological processes can selectively affect certain assemblies of neurons, which typically are at the center of crucial functional networks. Because of their topological centrality, these areas form a core set that is more likely to be affected by neuropathological processes. In order to identify and study the pattern formed by brain alterations in patients’ with Alzheimer’s disease (AD), we devised an innovative meta-analytic method for analyzing voxel-based morphometry data. This methodology enabled us to discover that in AD gray matter alterations do not occur randomly across the brain but, on the contrary, follow identifiable patterns of distribution. This alteration pattern exhibits a network-like structure composed of coaltered areas that can be defined as coatrophy network. Within the coatrophy network of AD, we were able to further identify a core subnetwork of coaltered areas that includes the left hippocampus, left and right amygdalae, right parahippocampal gyrus, and right temporal inferior gyrus. In virtue of their network centrality, these brain areas can be thought of as pathoconnectivity hubs.

Altered Functional Connectivity of the Basal Nucleus of Meynert in Mild Cognitive Impairment: A Resting-State fMRI Study

Background: Cholinergic dysfunction plays an important role in mild cognitive impairment (MCI). The basal nucleus of Meynert (BNM) provides the main source of cortical cholinergic innervation. Previous studies have characterized structural changes of the cholinergic basal forebrain in individuals at risk of developing Alzheimer’s disease (AD). However, whether and how functional connectivity of the BNM (BNM-FC) is altered in MCI remains unknown.

Objective: The aim of this study was to identify alterations in BNM-FC in individuals with MCI as compared to healthy controls (HCs), and to examine the relationship between these alterations with neuropsychological measures in individuals with MCI.

Method: One-hundred-and-one MCI patients and 103 HCs underwent resting-state functional magnetic resonance imaging (rs-fMRI). Imaging data were processed with SPM8 and CONN software. BNM-FC was examined via correlation in low frequency fMRI signal fluctuations between the BNM and all other brain voxels. Group differences were examined with a covariance analysis with age, gender, education level, mean framewise displacement (FD) and global correlation (GCOR) as nuisance covariates. Pearson’s correlation was conducted to evaluate the relationship between the BNM-FC and clinical assessments.

Result: Compared with HCs, individuals with MCI showed significantly decreased BNM-FC in the left insula extending into claustrum (insula/claustrum). Furthermore, greater decrease in BNM-FC with insula/claustrum was associated with more severe impairment in immediate recall during Auditory Verbal Learning Test (AVLT) in MCI patients.

Conclusion: MCI is associated with changes in BNM-FC to the insula/claustrum in relation to cognitive impairments. These new findings may advance research of the cholinergic bases of cognitive dysfunction during healthy aging and in individuals at risk of developing AD.

Targeting Alzheimer's Disease Neuro-Metabolic Dysfunction with a Small Molecule Nuclear Receptor Agonist (T3D-959) Reverses Disease Pathologies

Background

Alzheimer’s disease (AD) could be regarded as a brain form of diabetes since insulin resistance and deficiency develop early and progress with severity of neurodegeneration. Preserving insulin’s actions in the brain restores function and reduces neurodegeneration. T3D-959 is a dual nuclear receptor agonist currently in a Phase 2a trial in mild-to-moderate AD patients (ClinicalTrials.gov identifier NCT02560753). Herein, we show that T3D-959 improves motor function and reverses neurodegeneration in a sporadic model of AD.

Methods

Long Evans rats were administered intracerebral (i.c.) streptozotocin (STZ) or normal saline (control) and dosed orally with T3D-959 (1.0 mg/kg/day) or saline for 21 or 28 days. Rotarod tests evaluated motor function. Histopathology with image analysis was used to assess neurodegeneration.

Results

T3D-959 significantly improved motor performance, and preserved both cortical and normalized white matter structure in i.c STZ-treated rats. T3D-959 treatments were effective when dosed therapeutically, whether initiated 1 day or 7 days after i.c. STZ.

Conclusion

T3D-959’s targeting neuro-metabolic dysfunctions via agonism of PPAR delta and PPAR gamma nuclear receptors provides potential disease modification in AD.

Removing inter-subject technical variability in magnetic resonance imaging studies

Magnetic resonance imaging (MRI) intensities are acquired in arbitrary units, making scans non-comparable across sites and between subjects. Intensity normalization is a first step for the improvement of comparability of the images across subjects. However, we show that unwanted inter-scan variability associated with imaging site, scanner effect, and other technical artifacts is still present after standard intensity normalization in large multi-site neuroimaging studies. We propose RAVEL (Removal of Artificial Voxel Effect by Linear regression), a tool to remove residual technical variability after intensity normalization. As proposed by SVA and RUV [Leek and Storey, 2007, 2008, Gagnon-Bartsch and Speed, 2012], two batch effect correction tools largely used in genomics, we decompose the voxel intensities of images registered to a template into a biological component and an unwanted variation component. The unwanted variation component is estimated from a control region obtained from the cerebrospinal fluid (CSF), where intensities are known to be unassociated with disease status and other clinical covariates. We perform a singular value decomposition (SVD) of the control voxels to estimate factors of unwanted variation. We then estimate the unwanted factors using linear regression for every voxel of the brain and take the residuals as the RAVEL-corrected intensities. We assess the performance of RAVEL using T1-weighted (T1-w) images from more than 900 subjects with Alzheimer's disease (AD) and mild cognitive impairment (MCI), as well as healthy controls from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. We compare RAVEL to two intensity-normalization-only methods: histogram matching and White Stripe. We show that RAVEL performs best at improving the replicability of the brain regions that are empirically found to be most associated with AD, and that these regions are significantly more present in structures impacted by AD (hippocampus, amygdala, parahippocampal gyrus, enthorinal area, and fornix stria terminals). In addition, we show that the RAVEL-corrected intensities have the best performance in distinguishing between MCI subjects and healthy subjects using the mean hippocampal intensity (AUC=67%), a marked improvement compared to results from intensity normalization alone (AUC=63% and 59% for histogram matching and White Stripe, respectively). RAVEL is promising for many other imaging modalities.

Amyloid burden, cortical thickness, and cognitive function in the Wisconsin Registry for Alzheimer's Prevention

There is a growing interest in understanding how amyloid β (Aβ) accumulation in preclinical Alzheimer's disease relates to brain morphometric measures and cognition. Existing investigations in this area have been primarily conducted in older cognitively normal (CN) individuals. Therefore, not much is known about the associations between Aβ burden, cortical thickness, and cognition in midlife. We examined this question in 109, CN, late to middle-aged adults (mean age = 60.72 ± 5.65 years) from the Wisconsin Registry for Alzheimer's Prevention. They underwent Pittsburgh Compound B (PiB) and anatomical magnetic resonance (MR) imaging, and a comprehensive cognitive examination. Blinded visual rating of the PiB scans was used to classify the participants as Aβ+ or Aβ−. Cortical thickness measurements were derived from the MR images. The Aβ+ group exhibited significant thinning of the entorhinal cortex and accelerated age-associated thinning of the parahippocampal gyrus compared with the Aβ− group. The Aβ+ group also had numerically lower, but nonsignificant, test scores on all cognitive measures, and significantly faster age-associated cognitive decline on measures of Speed & Flexibility, Verbal Ability, and Visuospatial Ability. Our findings suggest that early Aβ aggregation is associated with deleterious changes in brain structure and cognitive function, even in midlife, and that the temporal lag between Aβ deposition and the inception of neurodegenerative/cognitive changes might be narrower than currently thought.

Amyloid β-peptide (1-42)-induced oxidative stress in Alzheimer disease: importance in disease pathogenesis and progression

SIGNIFICANCE

Alzheimer disease (AD) is an age-related neurodegenerative disease. AD is characterized by progressive cognitive impairment. One of the main histopathological hallmarks of AD brain is the presence of senile plaques (SPs) and another is elevated oxidative stress. The main component of SPs is amyloid beta-peptide (Aβ) that is derived from the proteolytic cleavage of amyloid precursor protein.

RECENT ADVANCES

Recent studies are consistent with the notion that methionine present at 35 position of Aβ is critical to Aβ-induced oxidative stress and neurotoxicity. Further, we also discuss the signatures of oxidatively modified brain proteins, identified using redox proteomics approaches, during the progression of AD.

CRITICAL ISSUES

The exact relationships of the specifically oxidatively modified proteins in AD pathogenesis require additional investigation.

FUTURE DIRECTIONS

Further studies are needed to address whether the therapies directed toward brain oxidative stress and oxidatively modified key brain proteins might help delay or prevent the progression of AD.

Amygdala atrophy is prominent in early Alzheimer's disease and relates to symptom severity

Despite numerous studies on the role of medial temporal lobe structures in Alzheimer's disease (AD), the magnitude and clinical significance of amygdala atrophy have been relatively sparsely investigated. In this study, we used magnetic resonance imaging (MRI) to compare the level of amygdala atrophy to that of the hippocampus in very mild and mild AD subjects in two large samples (Sample 1 n=90; Sample 2 n=174). Using a series of linear regression analyses, we investigated whether amygdala atrophy is related to global cognitive functioning (Clinical Dementia Rating Sum of Boxes: CDR-SB; Mini Mental State Examination: MMSE) and neuropsychiatric status. Results indicated that amygdala atrophy was comparable to hippocampal atrophy in both samples. MMSE and CDR-SB were strongly related to amygdala atrophy, with amygdala atrophy predicting MMSE scores as well as hippocampal atrophy, but predicting CDR-SB scores less robustly. Amygdala atrophy was related to aberrant motor behavior, with potential relationships to anxiety and irritability. These results suggest that the magnitude of amygdala atrophy is comparable to that of the hippocampus in the earliest clinical stages of AD, and is related to global illness severity. There also appear to be specific relationships between the level of amygdala atrophy and neuropsychiatric symptoms that deserve further investigation.

Lipid peroxidation and neurodegenerative disease

Lipid peroxidation is a complex process involving the interaction of oxygen-derived free radicals with polyunsaturated fatty acids, resulting in a variety of highly reactive electrophilic aldehydes. Since 1975, lipid peroxidation has been extensively studied in a variety of organisms. As neurodegenerative diseases became better understood, research establishing a link between this form of oxidative damage, neurodegeneration, and disease has provided a wealth of knowledge to the scientific community. With the advent of proteomics in 1995, the identification of biomarkers for neurodegenerative disorders became of paramount importance to better understand disease pathogenesis and develop potential therapeutic strategies. This review focuses on the relationship between lipid peroxidation and neurodegenerative diseases. It also demonstrates how findings in current research support the common themes of altered energy metabolism and mitochondrial dysfunction in neurodegenerative disorders.

ACE I/D polymorphism affects cognitive function and gray-matter volume in amnestic mild cognitive impairment

To characterize the correlates of cognitive function, serum concentrations of angiotensin converting enzyme (ACE) and brain structure with the ACE insertion or deletion (I/D) polymorphism were analyzed in subjects with amnestic-mild cognitive impairment (aMCI). A group of 48 subjects meeting criteria for aMCI and 36 age-matched control subjects were assessed using a comprehensive battery of standardized neuropsychological tests and magnetic resonance imaging (MRI). The ACE gene's I/D polymorphism was analyzed by means of PCR, and serum ACE concentrations were measured using ultraviolet spectrophotometry. Genotype effects on neuropsychological domains and MRI gray matter volume (GMV) measurements (optimized voxel-based morphometry) were examined using general linear models. The D carriers among the aMCI subjects performed significantly worse on AVLT-delayed recall compared to the I homozygous group. The D carriers had higher serum ACE concentrations than did the I homozygous carriers, though this difference only reached statistical significance in the aMCI group. Compared with the I homozygous carriers, in the aMCI group, D carriers showed smaller GMV of the bilateral middle frontal gyrus, right cuneus, right precentral gyrus, right medial frontal gyrus, right superior frontal gyrus, and left postcentral gyrus. However, there was no significant difference in GMV between I homozygous and D carriers in the normal control group. The study suggests that ACE genotype has considerable effect on the cognitive performance of aMCI subjects, particularly episodic memory, serum activity of ACE, and the structure of specified brain regions. The ACE D allele may be a genetic risk factor for greater atrophy of gray matter in aMCI.

Redox proteomic analysis of carbonylated brain proteins in mild cognitive impairment and early Alzheimer's disease

Previous studies indicated increased levels of protein oxidation in brain from subjects with Alzheimer's disease (AD), raising the question of whether oxidative damage is a late effect of neurodegeneration or precedes and contributes to the pathogenesis of AD. Hence, in the present study we used a parallel proteomic approach to identify oxidatively modified proteins in inferior parietal lobule (IPL) from subjects with mild cognitive impairment (MCI) and early stage-AD (EAD). By comparing to age-matched controls, we reasoned that such analysis could help in understanding potential mechanisms involved in upstream processes in AD pathogenesis. We have identified four proteins that showed elevated levels of protein carbonyls: carbonic anhydrase II (CA II), heat shock protein 70 (Hsp70), mitogen-activated protein kinase I (MAPKI), and syntaxin binding protein I (SBP1) in MCI IPL. In EAD IPL we identified three proteins: phosphoglycerate mutase 1 (PM1), glial fibrillary acidic protein, and fructose bisphospate aldolase C (FBA-C). Our results imply that some of the common targets of protein carbonylation correlated with AD neuropathology and suggest a possible involvement of protein modifications in the AD progression.

Alzheimer's disease and implicit memory

Specific neuropsychiatric disorders, such as Alzheimer's disease (AD) affect some forms of memory while leaving others relatively intact. In this review, we investigate particularities of the relationship between explicit and implicit memories in AD. It was found that implicit memory is preserved in AD, irrespective of the task used; in other words, there was not interference from explicit memory. In addition, it was verified that is possible through implicit memory compensatory strategies such as, activities of daily living (ADL) to compensate for the explicit memory deficits. In this sense, cognitive rehabilitation (CR) demonstrates reasonable results in the process of compensation of explicit memory deficits. Concluding, the decline in explicit memory suggests that both systems are functionally independent even if the other is compromised. We expect that when explicit memory system is not involved in competition with the implicit system, the final effect of learning is better, because all of the implicit memory capacity is engaged in learning and not in competition with the explicit system.

The neural basis of visuospatial perception in Alzheimer's disease and healthy elderly comparison subjects: an fMRI study

The neural basis of visuospatial deficits in Alzheimer's disease is unclear. We wished to investigate the neural basis of visuospatial perception in patients with Alzheimer's disease compared with healthy elderly comparison subjects using functional magnetic resonance imaging (fMRI). Twelve patients with AD and thirteen elderly comparison subjects were investigated. The patients were recruited from the local clinic and comparison subjects were from spouses and community. All participants underwent fMRI whilst viewing visuospatial stimuli and structural MRI, and findings were analysed using voxel-based morphometry. The comparison group activated V5, superior parietal lobe, parieto-occipital cortex and premotor cortices. The AD group demonstrated hypoactivation in the above regions and instead showed greater activation in inferior parietal lobule and activated additional areas. There was no structural atrophy above and beyond that found globally in patients in the identified regions of BOLD activation. To our knowledge, this is the first study to explore the neuroanatomy of perception of depth and motion in Alzheimer's disease. These specific functional deficits in AD provide evidence for an underlying patho-physiological basis for the clinically important symptom of visuospatial disorientation in patients with AD.

Impairment in emotion recognition abilities in patients with mild cognitive impairment, early and moderate Alzheimer disease compared with healthy comparison subjects

OBJECTIVE

To investigate emotion discrimination abilities in healthy comparison subjects, patients with mild cognitive impairment (MCI), early and moderate Alzheimer disease (AD).

DESIGN

Prospective study design.

SETTING

Outpatient memory clinic, Department of Psychiatry, Innsbruck, Austria.

METHODS

One hundred forty-one subjects older than 60 years were included in the study. Thirty-five subjects were classified as healthy comparison subjects, 51 subjects as MCI (21 subjects with amnestic MCI single domain, 31 subjects with amnestic MCI multiple domain), 32 subjects with early AD and 23 subjects with moderate AD.

MEASUREMENTS

All subjects were tested on an extensive neuropsychological test battery including the Penn Emotion Recognition Tests and depression symptoms were assessed additionally.

RESULTS

Healthy subjects and patients with MCI, early and moderate AD differed significantly in the recognition of all emotions and neutral faces combined. When separated by emotion, the authors found significant differences in emotion recognition between the diagnostic groups for happy, sad, fearful, and neutral faces. Compared with comparison subjects, amnestic MCI patients single domain did not differ significantly in their emotion recognition abilities, but amnestic MCI multiple domain patients were already impaired in the recognition of overall emotions, sad, fearful, and neutral faces and the deficits increased with the severity of AD. Depression had a significant influence on the recognition of overall emotion and neutral faces and increased the probability of misinterpreting neutral faces as sad leading to a negative bias.

CONCLUSIONS

Diminished abilities for emotion discrimination are already present in patients with MCI and further decreased with AD progression.

Magnetic resonance imaging findings in Hunter syndrome

Hunter syndrome is a rare genetic lysosomal storage disease that is caused by a deficiency, or absence, of iduronate-2-sulphatase, an enzyme needed to break down specific glycosaminoglycans (GAGs). As a result, GAGs build up in various tissues throughout the body leading to adverse neurological and non-neurological effects. This literature review focuses on the neurological findings. Although few magnetic resonance imaging studies have been conducted, those done have shown that patients with Hunter syndrome generally exhibit brain atrophy, enlarged periventricular spaces and ventriculomegaly. Similar findings have been reported in other mucopolysaccharide disorders. Enzyme replacement therapy is a novel treatment which has had success in treating peripheral disease in mice and humans.

CONCLUSION

Future studies should focus on how structural and chemical signatures in the brain of Hunter patients are altered before and after enzyme replacement therapy, and how those alterations correlate with clinical outcome.