Hippocampus and entorhinal cortex in frontotemporal dementia and Alzheimer's disease: a morphometric MRI study

Cholinesterase inhibitor use in amyloid PET-negative mild cognitive impairment and cognitive changes

BACKGROUND

Cholinesterase inhibitors (ChEIs) are prescribed for Alzheimer's disease (AD) and sometimes for mild cognitive impairment (MCI) without knowing underlying pathologies and its effect on cognition. We investigated the frequency of ChEI prescriptions in amyloid-negative MCI and their association with cognitive changes in the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort.

METHODS

We included participants with amyloid positron emission tomography (PET)-negative MCI from the ADNI. We analyzed the associations of ChEI use with cognitive changes, brain volume, and cerebrospinal fluid (CSF) total tau (t-tau), hyperphosphorylated tau181 (p-tau181), and p-tau181/t-tau ratio.

RESULTS

ChEIs were prescribed in 27.4% of amyloid PET-negative MCI and were associated with faster cognitive decline, reduced baseline hippocampal volume and entorhinal cortical thickness, and a longitudinal decrease in the frontal lobe cortical thickness.

CONCLUSIONS

The association between ChEI use and accelerated cognitive decline may stem from underlying pathologies involving reduced hippocampal volume, entorhinal cortical thickness and faster frontal lobe atrophy. We suggest that ChEI use in amyloid PET-negative MCI patients might need further consideration, and studies investigating the causality between ChEI use and cognitive decline are warranted in the future.

The use of an anterior-posterior atrophy index to distinguish Alzheimer's disease from frontotemporal disorders: an automated volumetric MRI Study

BACKGROUND

Alzheimer's disease (AD) and frontotemporal dementia (FTD) require different treatments. Since clinical presentation can be nuanced, imaging biomarkers aid in diagnosis. Automated software such as Neuroreader (NR) provides volumetric imaging data, and indices between anterior and posterior brain areas have proven useful in distinguishing dementia subtypes in research cohorts. Existing indices are complex and require further validation in clinical settings.

PURPOSE

To provide initial validation for a simplified anterior-posterior index (API) from NR in distinguishing FTD and AD in a clinical cohort.

MATERIAL AND METHODS

A retrospective chart review was completed. We derived a simplified API: API = (logVA/VP-μ)/σ where V A is weighted volume of frontal and temporal lobes and V P of parietal and occipital lobes. μ and σ are the mean and standard deviation of logVA/VP computed for AD participants. Receiver operating characteristic (ROC) curves and regression analyses assessed the efficacy of the API versus brain areas in predicting diagnosis of AD versus FTD.

RESULTS

A total of 39 participants with FTD and 78 participants with AD were included. The API had an excellent performance in distinguishing AD from FTD with an area under the ROC curve of 0.82 and a positive association with diagnostic classification on logistic regression analysis (B = 1.491, P < 0.001).

CONCLUSION

The API successfully distinguished AD and FTD with excellent performance. The results provide preliminary validation of the API in a clinical setting.

Effect of Treatment of the Cholinergic Precursor Choline Alphoscerate in Mild Cognitive Dysfunction: A Randomized Controlled Trial

Background and Objectives: The focus on mild cognitive dysfunction in adults is of great interest, given the risk of worsening and conversion to dementia. Cognitive dysfunctions are characterized by a decrease in the weight and volume of the brain, due to cortical atrophy, with a widening of the grooves and flattening of the convolutions. Brain atrophy that mainly involves the hippocampus is related to the progression of cognitive impairment and the conversion from mild cognitive dysfunction to dementia. Currently, there is no treatment for MCI. Results from a trial on Alzheimer's disease (ASCOMALVA trial) suggest that a sustained cholinergic challenge can slow the progression of brain atrophy typical of Alzheimer's disease associated with vascular damage. This study intends to evaluate the efficacy of choline alphoscerate in patients with mild cognitive impairment (MCI) and associated vascular damage, in stabilizing and/or slowing brain atrophy typical of adult-onset cognitive dysfunction, and in improving and/or slowing the progression of cognitive and behavioral symptoms associated with MCI. Materials and Methods: This randomized controlled trial will recruit 60 patients that will be evaluated and randomized in a 1:1 ratio to receive choline alphoscerate (1200 mg/day) or placebo, for 12 months. Analyses will be carried out using SPSS vesion No 26 the Statistician in charge of this study, with the statistical significance level chosen as 0.05. Discussion: This trial may provide evidence about the efficacy of treatment with the cholinergic precursor choline alphoscerate in patients with mild cognitive dysfunction. The results of this study will be published in peer-reviewed journals. Registration: EudraCT number: 2020-000576-38.

Compositional structural brain signatures capture Alzheimer's genetic risk on brain structure along the disease continuum

INTRODUCTION

Traditional brain imaging genetics studies have primarily focused on how genetic factors influence the volume of specific brain regions, often neglecting the overall complexity of brain architecture and its genetic underpinnings.

METHODS

This study analyzed data from participants across the Alzheimer's disease (AD) continuum from the ALFA and ADNI studies. We exploited compositional data analysis to examine relative brain volumetric variations that (i) differentiate cognitively unimpaired (CU) individuals, defined as amyloid-negative (A-) based on CSF profiling, from those at different AD stages, and (ii) associated with increased genetic susceptibility to AD, assessed using polygenic risk scores.

RESULTS

Distinct brain signatures differentiated CU A-individuals from amyloid-positive MCI and AD. Moreover, disease stage-specific signatures were associated with higher genetic risk of AD.

DISCUSSION

The findings underscore the complex interplay between genetics and disease stages in shaping brain structure, which could inform targeted preventive strategies and interventions in preclinical AD.

Subjective clustering in patients with fronto-temporal dementia

In the behavioral variant of frontotemporal dementia (bvFTD) memory deficits have been traditionally considered as due to difficulties in encoding/retrieval frontal strategies. However, the frontal origin of memory deficits in bvFTD has been questioned and hippocampal dysfunction has been also proposed. Here we analyzed bvFTD patients' proficiency in subjectively organizing memories without an external criterion. Twenty bvFTD patients and 20 healthy individuals were assessed with memory and executive tasks. The ability to subjectively organize memories in the immediate recall of a 15 unrelated word list was measured by calculating the index of subjective clustering (ISC) based on the constancies in response order across the five consecutive free recall trials. Results revealed reduced ISC in bvFTD patients with respect to normal controls. In the bvFTD group, the ISC score correlated with the Corsi span backward score and the number of categories achieved on the Modified Card Sorting Test. The bvFTD patients' reduced ISC and its correlation with executive performance suggest that executive deficits underlie their defective strategic organization of memories. However, as ISC did not predict memory accuracy in these patients, the memory deficit may not be the mere expression of their executive difficulties.

Entorhinal cortex astrocytic atrophy in human frontotemporal dementia

The pathophysiology of Fronto Temporal Dementia (FTD) remains poorly understood, specifically the role of astroglia. Our aim was to explore the hypothesis of astrocytic alterations as a component for FTD pathophysiology. We performed an in-depth tri-dimensional (3-D) anatomical and morphometric study of glial fibrillary acidic protein (GFAP)-positive and glutamine synthetase (GS)-positive astrocytes in the human entorhinal cortex (EC) of FTD patients. The studies at this level in the different types of human dementia are scarce. We observed a prominent astrocyte atrophy of GFAP-positive astrocytes and co-expressing GFAP/GS astrocytes, characterised by a decrease in area and volume, whilst minor changes in GS-positive astrocytes in FTD compared to non-dementia controls (ND) samples. This study evidences the importance of astrocyte atrophy and dysfunction in human EC. We hypothesise that FTD is not only a neuropathological disease, but also a gliopathological disease having a major relevance in the understanding the astrocyte role in FTD pathological processes and development.

Quantitative Electroencephalography Markers for an Accurate Diagnosis of Frontotemporal Dementia: A Spectral Power Ratio Approach

Background and Objectives: Frontotemporal dementia (FTD) is the second most common form of presenile dementia; however, its diagnosis has been poorly investigated. Previous attempts to diagnose FTD using quantitative electroencephalography (qEEG) have yielded inconsistent results in both spectral and functional connectivity analyses. This study aimed to introduce an accurate qEEG marker that could be used to diagnose FTD and other neurological abnormalities. Materials and Methods: We used open-access electroencephalography data from OpenNeuro to investigate the power ratio between the frontal and temporal lobes in the resting state of 23 patients with FTD and 29 healthy controls. Spectral data were extracted using a fast Fourier transform in the delta (0.5 ≤ 4 Hz), theta (4 ≤ 8 Hz), alpha (8-13 Hz), beta (>13-30 Hz), and gamma (>30-45 Hz) bands. Results: We found that the spectral power ratio between the frontal and temporal lobes is a promising qEEG marker of FTD. Frontal (F)-theta/temporal (T)-alpha, F-alpha/T-theta, F-theta/F-alpha, and T-beta/T-gamma showed a consistently high discrimination score for the diagnosis of FTD for different parameters and referencing methods. Conclusions: The study findings can serve as reference for future research focused on diagnosing FTD and other neurological anomalies.

Brain region-specific synaptic function of FUS underlies the FTLD-linked behavioural disinhibition

Synaptic dysfunction is one of the earliest pathological processes that contribute to the development of many neurological disorders, including Alzheimer's disease and frontotemporal lobar degeneration. However, the synaptic function of many disease-causative genes and their contribution to the pathogenesis of the related diseases remain unclear. In this study, we investigated the synaptic role of fused in sarcoma, an RNA-binding protein linked to frontotemporal lobar degeneration and amyotrophic lateral sclerosis, and its potential pathological role in frontotemporal lobar degeneration using pyramidal neuron-specific conditional knockout mice (FuscKO). We found that FUS regulates the expression of many genes associated with synaptic function in a hippocampal subregion-specific manner, concomitant with the frontotemporal lobar degeneration-linked behavioural disinhibition. Electrophysiological study and molecular pathway analyses further reveal that fused in sarcoma differentially regulates synaptic and neuronal properties in the ventral hippocampus and medial prefrontal cortex, respectively. Moreover, fused in sarcoma selectively modulates the ventral hippocampus-prefrontal cortex projection, which is known to mediate the anxiety-like behaviour. Our findings unveil the brain region- and synapse-specific role of fused in sarcoma, whose impairment might lead to the emotional symptoms associated with frontotemporal lobar degeneration.

Classifying Alzheimer's disease and frontotemporal dementia using machine learning with cross-sectional and longitudinal magnetic resonance imaging data

Alzheimer's disease (AD) and frontotemporal dementia (FTD) are common causes of dementia with partly overlapping, symptoms and brain signatures. There is a need to establish an accurate diagnosis and to obtain markers for disease tracking. We combined unsupervised and supervised machine learning to discriminate between AD and FTD using brain magnetic resonance imaging (MRI). We included baseline 3T-T1 MRI data from 339 subjects: 99 healthy controls (CTR), 153 AD and 87 FTD patients; and 2-year follow-up data from 114 subjects. We obtained subcortical gray matter volumes and cortical thickness measures using FreeSurfer. We used dimensionality reduction to obtain a single feature that was later used in a support vector machine for classification. Discrimination patterns were obtained with the contribution of each region to the single feature. Our algorithm differentiated CTR versus AD and CTR versus FTD at the cross-sectional level with 83.3% and 82.1% of accuracy. These increased up to 90.0% and 88.0% with longitudinal data. When we studied the classification between AD versus FTD we obtained an accuracy of 63.3% at the cross-sectional level and 75.0% for longitudinal data. The AD versus FTD versus CTR classification has reached an accuracy of 60.7%, and 71.3% for cross-sectional and longitudinal data respectively. Disease discrimination brain maps are in concordance with previous results obtained with classical approaches. By using a single feature, we were capable to classify CTR, AD, and FTD with good accuracy, considering the inherent overlap between diseases. Importantly, the algorithm can be used with cross-sectional and longitudinal data.

Structural Plasticity of the Hippocampus in Neurodegenerative Diseases

Neuroplasticity is the capacity of neural networks in the brain to alter through development and rearrangement. It can be classified as structural and functional plasticity. The hippocampus is more susceptible to neuroplasticity as compared to other brain regions. Structural modifications in the hippocampus underpin several neurodegenerative diseases that exhibit cognitive and emotional dysregulation. This article reviews the findings of several preclinical and clinical studies about the role of structural plasticity in the hippocampus in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis. In this study, literature was surveyed using Google Scholar, PubMed, Web of Science, and Scopus, to review the mechanisms that underlie the alterations in the structural plasticity of the hippocampus in neurodegenerative diseases. This review summarizes the role of structural plasticity in the hippocampus for the etiopathogenesis of neurodegenerative diseases and identifies the current focus and gaps in knowledge about hippocampal dysfunctions. Ultimately, this information will be useful to propel future mechanistic and therapeutic research in neurodegenerative diseases.

Association of Cognitive Impairment With Free Water in the Nucleus Basalis of Meynert and Locus Coeruleus to Transentorhinal Cortex Tract

BACKGROUND AND OBJECTIVES

The goal of this work was to determine the relationship between diffusion microstructure and early changes in Alzheimer disease (AD) severity as assessed by clinical diagnosis, cognitive performance, dementia severity, and plasma concentrations of neurofilament light chain.

METHODS

Diffusion MRI scans were collected on cognitively normal participants (CN) and patients with early mild cognitive impairment (EMCI), late mild cognitive impairment, and AD. Free water (FW) and FW-corrected fractional anisotropy were calculated in the locus coeruleus to transentorhinal cortex tract, 4 magnocellular regions of the basal forebrain (e.g., nucleus basalis of Meynert), entorhinal cortex, and hippocampus. All patients underwent a battery of cognitive assessments; neurofilament light chain levels were measured in plasma samples.

RESULTS

FW was significantly higher in patients with EMCI compared to CN in the locus coeruleus to transentorhinal cortex tract, nucleus basalis of Meynert, and hippocampus (mean Cohen d = 0.54; p fdr < 0.05). FW was significantly higher in those with AD compared to CN in all the examined regions (mean Cohen d = 1.41; p fdr < 0.01). In addition, FW in the hippocampus, entorhinal cortex, nucleus basalis of Meynert, and locus coeruleus to transentorhinal cortex tract positively correlated with all 5 cognitive impairment metrics and neurofilament light chain levels (mean r 2 = 0.10; p fdr < 0.05).

DISCUSSION

These results show that higher FW is associated with greater clinical diagnosis severity, cognitive impairment, and neurofilament light chain. They also suggest that FW elevation occurs in the locus coeruleus to transentorhinal cortex tract, nucleus basalis of Meynert, and hippocampus in the transition from CN to EMCI, while other basal forebrain regions and the entorhinal cortex are not affected until a later stage of AD. FW is a clinically relevant and noninvasive early marker of structural changes related to cognitive impairment.

Hippocampal Asymmetry of Regional Development and Structural Covariance in Preterm Neonates

Premature birth is associated with a high prevalence of neurodevelopmental impairments in surviving infants. The hippocampus is known to be critical for learning and memory, yet the putative effects of hippocampal dysfunction remain poorly understood in preterm neonates. In particular, while asymmetry of the hippocampus has been well noted both structurally and functionally, how preterm birth impairs hippocampal development and to what extent the hippocampus is asymmetrically impaired by preterm birth have not been well delineated. In this study, we compared volumetric growth and shape development in the hippocampal hemispheres and structural covariance (SC) between hippocampal vertices and cortical thickness in cerebral cortex regions between two groups. We found that premature infants had smaller volumes of the right hippocampi only. Lower thickness was observed in the hippocampal head in both hemispheres for preterm neonates compared with full-term peers, though preterm neonates exhibited an accelerated age-related change of hippocampal thickness in the left hippocampi. The SC between the left hippocampi and the limbic lobe of the premature infants was severely impaired compared with the term-born neonates. These findings suggested that the development of the hippocampus during the third trimester may be altered following early extrauterine exposure with a high degree of asymmetry.

MRI-guided histology of TDP-43 knock-in mice implicates parvalbumin interneuron loss, impaired neurogenesis and aberrant neurodevelopment in amyotrophic lateral sclerosis-frontotemporal dementia

Amyotrophic lateral sclerosis and frontotemporal dementia are overlapping diseases in which MRI reveals brain structural changes in advance of symptom onset. Recapitulating these changes in preclinical models would help to improve our understanding of the molecular causes underlying regionally selective brain atrophy in early disease. We therefore investigated the translational potential of the TDP-43Q331K knock-in mouse model of amyotrophic lateral sclerosis-frontotemporal dementia using MRI. We performed in vivo MRI of TDP-43Q331K knock-in mice. Regions of significant volume change were chosen for post-mortem brain tissue analyses. Ex vivo computed tomography was performed to investigate skull shape. Parvalbumin neuron density was quantified in post-mortem amyotrophic lateral sclerosis frontal cortex. Adult mutants demonstrated parenchymal volume reductions affecting the frontal lobe and entorhinal cortex in a manner reminiscent of amyotrophic lateral sclerosis-frontotemporal dementia. Subcortical, cerebellar and brain stem regions were also affected in line with observations in pre-symptomatic carriers of mutations in C9orf72, the commonest genetic cause of both amyotrophic lateral sclerosis and frontotemporal dementia. Volume loss was also observed in the dentate gyrus of the hippocampus, along with ventricular enlargement. Immunohistochemistry revealed reduced parvalbumin interneurons as a potential cellular correlate of MRI changes in mutant mice. By contrast, microglia was in a disease activated state even in the absence of brain volume loss. A reduction in immature neurons was found in the dentate gyrus, indicative of impaired adult neurogenesis, while a paucity of parvalbumin interneurons in P14 mutant mice suggests that TDP-43Q331K disrupts neurodevelopment. Computerized tomography imaging showed altered skull morphology in mutants, further suggesting a role for TDP-43Q331K in development. Finally, analysis of human post-mortem brains confirmed a paucity of parvalbumin interneurons in the prefrontal cortex in sporadic amyotrophic lateral sclerosis and amyotrophic lateral sclerosis linked to C9orf72 mutations. Regional brain MRI changes seen in human amyotrophic lateral sclerosis-frontotemporal dementia are recapitulated in TDP-43Q331K knock-in mice. By marrying in vivo imaging with targeted histology, we can unravel cellular and molecular processes underlying selective brain vulnerability in human disease. As well as helping to understand the earliest causes of disease, our MRI and histological markers will be valuable in assessing the efficacy of putative therapeutics in TDP-43Q331K knock-in mice.

Volume Analysis of Brain Cognitive Areas in Alzheimer's Disease: Interim 3-Year Results from the ASCOMALVA Trial

Background:

Cerebral atrophy is a common feature of several neurodegenerative disorders, including Alzheimer’s disease (AD). In AD, brain atrophy is associated with loss of gyri and sulci in the temporal and parietal lobes, and in parts of the frontal cortex and cingulate gyrus.

Objective:

The ASCOMALVA trial has assessed, in addition to neuropsychological analysis, whether the addition of the cholinergic precursor choline alphoscerate to treatment with donepezil has an effect on brain volume loss in patients affected by AD associated with cerebrovascular injury.

Methods:

56 participants to the randomized, placebo-controlled, double-blind ASCOMALVA trial were assigned to donepezil + placebo (D + P) or donepezil + choline alphoscerate (D + CA) treatments and underwent brain magnetic resonance imaging and neuropsychological tests every year for 4 years. An interim analysis of 3-year MRI data was performed by voxel morphometry techniques.

Results:

The D + P group (n = 27) developed atrophy of the gray and white matter with concomitant increase in ventricular space volume. In the D + CA group (n = 29) the gray matter atrophy was less pronounced compared to the D + P group in frontal and temporal lobes, hippocampus, and amygdala. These morphological data are consistent with the results of the neuropsychological tests.

Conclusion:

Our findings indicate that the addition of choline alphoscerate to standard treatment with the cholinesterase inhibitor donepezil counters to some extent the loss in volume occurring in some brain areas of AD patients. The observation of parallel less pronounced decrease in cognitive and functional tests in patients with the same treatment suggests that the morphological changes observed may have functional relevance.

Hippocampal shape across the healthy lifespan and its relationship with cognition

The study of the hippocampus across the healthy adult lifespan has rendered inconsistent findings. While volumetric measurements have often been a popular technique for analysis, more advanced morphometric techniques have demonstrated compelling results that highlight the importance and improved specificity of shape-based measures. Here, the MAGeT Brain algorithm was applied on 134 healthy individuals aged 18-81 years old to extract hippocampal subfield volumes and hippocampal shape measurements, namely: local surface area (SA) and displacement. We used linear-, second- or third-order natural splines to examine the relationships between hippocampal measures and age. In addition, partial least squares analyses were performed to relate volume and shape measurements with cognitive and demographic information. Volumetric results indicated a relative preservation of the right cornus ammonis 1 with age and a global volume reduction linked with older age, female sex, lower levels of education and cognitive performance. Vertex-wise analysis demonstrated an SA preservation in the anterior hippocampus with a peak during the sixth decade, while the posterior hippocampal SA gradually decreased across lifespan. Overall, SA decrease was linked to older age, female sex and, to a lesser extent lower levels of education and cognitive performance. Outward displacement in the lateral hippocampus and inward displacement in the medial hippocampus were enlarged with older age, lower levels of cognition and education, indicating an accentuation of the hippocampal "C" shape with age. Taken together, our findings suggest that vertex-wise analyses have higher spatial specifity and that sex, education, and cognition are implicated in the differential impact of age on hippocampal subregions throughout its anteroposterior and medial-lateral axes. This article is part of the Virtual Special Issue titled COGNITIVE NEU- ROSCIENCE OF HEALTHY AND PATHOLOGICAL AGING. The full issue can be found on ScienceDirect at https://www.sciencedirect.com/journal/neurobiology-of-aging/special-issue/105379XPWJP.

Spatial correlation maps of the hippocampus with cerebrospinal fluid biomarkers and cognition in Alzheimer's disease: A longitudinal study

This study is an observational study that takes the existing longitudinal data from Alzheimer's disease Neuroimaging Initiative to examine the spatial correlation map of hippocampal subfield atrophy with CSF biomarkers and cognitive decline in the course of AD. This study included 421 healthy controls (HC), 557 patients of stable mild cognitive impairment (s‐MCI), 304 Alzheimer's Disease (AD) patients, and 241 subjects who converted to be AD from MCI (c‐MCI), and 6,525 MRI scans in a period from 2004 to 2019. Our findings revealed that all the hippocampal subfields showed their accelerated atrophy rate from cognitively normal aging to stable MCI and AD. The presubiculum, dentate gyrus, and fimbria showed greater atrophy beyond the whole hippocampus in the HC, s‐MCI, and AD groups and corresponded to a greater decline of memory and attention in the s‐MCI group. Moreover, the higher atrophy rates of the subiculum and CA2/3, CA4 were also associated with a greater decline in attention in the s‐MCI group. Interestingly, patients with c‐MCI showed that the presubiculum atrophy was associated with CSF tau levels and corresponded to the onset age of AD and a decline in attention in patients with c‐MCI. These spatial correlation findings of the hippocampus suggested that the hippocampal subfields may not be equally impacted by normal aging, MCI, and AD, and their atrophy was selectively associated with declines in specific cognitive domains. The presubiculum atrophy was highlighted as a surrogate marker for the AD prognosis along with tau pathology and attention decline.

Brain Functional and Structural Changes in Alzheimer's Disease With Sleep Disorders: A Systematic Review

Introduction: Sleep disorders (SLD) are supposed to be associated with increased risk and development of Alzheimer's disease (AD), and patients with AD are more likely to show SLD. However, neurobiological performance of patients with both AD and SLD in previous studies is inconsistent, and identifying specific patterns of the brain functional network and structural characteristics in this kind of comorbidity is warranted for understanding how AD and SLD symptoms interact with each other as well as finding effective clinical intervention. Thus, the aims of this systematic review were to summarize the relevant findings and their limitations and provide future research directions. Methods: A systematic search on brain functional and structural changes in patients with both AD and SLD was conducted from PubMed, Web of Science, and EMBASE databases. Results: Nine original articles published between 2009 and 2021 were included with a total of 328 patients with comorbid AD and SLD, 367 patients with only AD, and 294 healthy controls. One single-photon emission computed tomography study and one multislice spiral computed tomography perfusion imaging study investigated changes of cerebral blood flow; four structural magnetic resonance imaging (MRI) studies investigated brain structural changes, two of them used whole brain analysis, and another two used regions of interest; two resting-state functional MRI studies investigated brain functional changes, and one 2-deoxy-2-(18F)fluoro-d-glucose positron emission tomography (18F-FDG-PET) investigated 18F-FDG-PET uptake in patients with comorbid AD and SLD. Findings were inconsistent, ranging from default mode network to sensorimotor cortex, hippocampus, brain stem, and pineal gland, which may be due to different imaging techniques, measurements of sleep disorder and subtypes of AD and SLD. Conclusions: Our review provides a systematic summary and promising implication of specific neuroimaging dysfunction underlying co-occurrence of AD and SLD. However, limited and inconsistent findings still restrict its neurobiological explanation. Further studies should use unified standards and comprehensive brain indices to investigate the pathophysiological basis of interaction between AD and SLD symptoms in the development of the disease spectrums.

Recall and Recognition in Alzheimer's Disease and Frontotemporal Dementia

BACKGROUND

It has long been debated whether performance on recall and recognition tests depends on the same or different memory systems and whether performance on these two tasks is dissociated in clinical populations. According to Dual process theories of recall, performance on recall and recognition tests dissociates in the relative reliance on frontal lobe related activities; in fact, the recall test requires more strategic retrieval of memoranda than the recognition task. By contrast, Dual process theories of recognition posit that performance on these tests differs in the relative contribution of recollection and familiarity memory processes in the two tasks: both recollection and familiarity contribute to recognition judgments, but only recollection supports recall performance.

OBJECTIVE

The aim of this study was to clarify the cognitive processes involved in recall and recognition in patients with dementia.

METHODS

We administered a 15-word recall task followed by a yes/no recognition paradigm to 28 patients with Alzheimer's disease (AD), 22 patients with the behavioral variant of frontotemporal dementia (bvFTD), and 45 normal controls (NCs).

RESULTS

Results showed that on the delayed recall task, bvFTD patients performed much better than AD patients but the two groups did not differ on any index of recognition performance.

CONCLUSION

The present data support the hypothesis that the performance of the two groups is expression of the different reliance on recollection (more impaired in the AD than in the bvFTD group) and familiarity (similarly impaired in the two groups) in performance on recall and recognition tasks.

Aging Disrupts the Circadian Patterns of Protein Expression in the Murine Hippocampus

Aging is associated with cognitive decline and dysregulation of the circadian system, which modulates hippocampal-dependent memory as well as biological processes underlying hippocampal function. While circadian dysfunction and memory impairment are common features of aging and several neurodegenerative brain disorders, how aging impacts the circadian expression patterns of proteins involved in processes that underlie hippocampal-dependent memory is not well understood. In this study, we profiled the hippocampal proteomes of young and middle-aged mice across two circadian cycles using quantitative mass spectrometry in order to explore aging-associated changes in the temporal orchestration of biological pathways. Of the ∼1,420 proteins that were accurately quantified, 15% (214 proteins) displayed circadian rhythms in abundance in the hippocampus of young mice, while only 1.6% (23 proteins) were rhythmic in middle-aged mice. Remarkably, aging disrupted the circadian regulation of proteins involved in cellular functions critical for hippocampal function and memory, including dozens of proteins participating in pathways of energy metabolism, neurotransmission, and synaptic plasticity. These included processes such as glycolysis, the tricarboxylic acid cycle, synaptic vesicle cycling, long-term potentiation, and cytoskeletal organization. Moreover, aging altered the daily expression rhythms of proteins implicated in hallmarks of aging and the pathogenesis of several age-related neurodegenerative brain disorders affecting the hippocampus. Notably, we identified age-related alterations in the rhythmicity of proteins involved in mitochondrial dysfunction and loss of proteostasis, as well as proteins involved in the pathogenesis of disorders such as Alzheimer’s disease and Parkinson’s disease. These insights into aging-induced changes in the hippocampal proteome provide a framework for understanding how the age-dependent circadian decline may contribute to cognitive impairment and the development of neurodegenerative diseases during aging.

Tracking white matter degeneration in asymptomatic and symptomatic MAPT mutation carriers

Our aim was to investigate the patterns and trajectories of white matter (WM) diffusion abnormalities in microtubule-associated protein tau (MAPT) mutations carriers. We studied 22 MAPT mutation carriers (12 asymptomatic, 10 symptomatic) and 20 noncarriers from 8 families, who underwent diffusion tensor imaging (DTI) and a subset (10 asymptomatic, 6 symptomatic MAPT mutation carriers, and 10 noncarriers) were followed annually (median = 4 years). Cross-sectional and longitudinal changes in mean diffusivity (MD) and fractional anisotropy were analyzed. Asymptomatic MAPT mutation carriers had higher MD in entorhinal WM, which propagated to the limbic tracts and frontotemporal projections in the symptomatic stage compared with noncarriers. Reduced fractional anisotropy and increased MD in the entorhinal WM were associated with the proximity to estimated and actual age of symptom onset. The annualized change of entorhinal MD on serial DTI was accelerated in MAPT mutation carriers compared with noncarriers. Entorhinal WM diffusion abnormalities precede the symptom onset and track with disease progression in MAPT mutation carriers. Our cross-sectional and longitudinal data showed a potential clinical utility for DTI to track neurodegenerative disease progression for MAPT mutation carriers in clinical trials.

Precuneus-Dominant Degeneration of Parietal Lobe Is at Risk of Epilepsy in Mild Alzheimer's Disease

Introduction: Alzheimer's disease (AD) is the leading cause of cognitive decline. Epilepsy is a frequent comorbid condition of AD. While previous studies analyzed the risk factors of AD-related epileptic seizures, we still lack biomarkers of epilepsy in mild AD cases.

Purpose: The aim of our study was to analyze the correlations between neuropsychology, cortical thickness, and brain volumetric measurements in mild Alzheimer patients with concomitant epileptic seizures.

Materials and methods: We selected mild AD patients from our database to examine them with structural magnetic resonance imaging, 24 h electroencephalography, and detailed neuropsychology. We made the diagnosis of epilepsy based on epileptology data including neurophysiology. We retrospectively analyzed the neuropsychology pattern, clinical and epidemiologic features, cortical thickness, and volumetric values of mild AD patients with and without overt clinical seizures using covariance weighted general linear model.

Results: We found epileptic seizures in 26% of mild AD patients. Patients with seizures performed worse in visuo-spatial scores than patients without (p = 0.003). Patients with seizures had smaller parietal thickness (p = 0.018), being associated to reduced thickness of left (p = 0.007), and right precunei (p = 0.005). The visuo-spatial performance positively and strongly correlated with the thickness of the parietal lobe (r = 0.67; p = 0.002) and with the volume of the precuneus (r = 0.612; p = 0.005).

Conclusion: Epileptic seizures are common even in mild AD. We found that a prominent deficit in visuo-spatial skills is a red flag for epileptic seizures in the initial phase of AD, indicating the early involvement of parietal lobe in the neurodegenerative process. Because our findings suggest that the degeneration of precuneus is a sensitive marker of seizures associated to mild AD, clinicians need to pay special attention to the pattern of atrophy shown by structural MRI. Our results confirm previous data suggesting that epileptic seizures might be associated to a faster progressing type of AD with the early degeneration of posterior cortical areas.

Prevalence, Semiology, and Risk Factors of Epilepsy in Alzheimer's Disease: An Ambulatory EEG Study

BACKGROUND

Alzheimer's disease (AD) is the primary cause of cognitive decline. A growing body of evidence suggests that AD patients have a higher risk to develop epileptic seizures; however, results are contradictory due to different methodological approaches of previous studies.

OBJECTIVE

We aimed to identify the prevalence, semiology, and risk factors of epilepsy in AD using long-term EEG.

METHODS

We selected forty-two AD patients and examined them using 24-hour ambulatory EEG. Neurological and epileptological data were collected with retro- and prospective methods. We analyzed the semiology of the identified seizures and the possible risk factors using logistic regression analysis.

RESULTS

We identified seizures confirmed by EEG in 24%. The majority of the seizures were aware focal (72%) without any motor activity (55%). We found epileptiform discharges without seizures in 28%. Patients with seizures and only with epileptic EEG activity showed similar clinical and demographical features. Higher education (OR:1.8) and lower Addenbrooke Examination Score (OR: 0.9) were identified as risk factors of epilepsy. Increase of 0.1 point in the Verbal-Language/Orientation-Memory ratio (VLOM) was associated with higher epilepsy risk as well (OR:2.9).

CONCLUSION

Epilepsy is a frequent comorbidity of AD. Since most of the seizures are aware non-motor focal seizures, sensitive EEG techniques are required for precise diagnosis of epilepsy. Long-term ambulatory EEG is a safe and well-tolerated option. Epileptiform EEG in AD signals the presence of concomitant epilepsy. Clinicians have to pay attention to comorbid epilepsy in dementia patients with high education, with high VLOM ratio and severe stage.

Invited Review: APOE at the interface of inflammation, neurodegeneration and pathological protein spread in Alzheimer's disease

Despite more than a century of research, the aetiology of sporadic Alzheimer's disease (AD) remains unclear and finding disease modifying treatments for AD presents one of the biggest medical challenges of our time. AD pathology is characterized by deposits of aggregated amyloid beta (Aβ) in amyloid plaques and aggregated tau in neurofibrillary tangles. These aggregates begin in distinct brain regions and spread throughout the brain in stereotypical patterns. Neurodegeneration, comprising loss of synapses and neurons, occurs in brain regions with high tangle pathology, and an inflammatory response of glial cells appears in brain regions with pathological aggregates. Inheriting an apolipoprotein E ε4 (APOE4) allele strongly increases the risk of developing AD for reasons that are not yet entirely clear. Substantial amounts of evidence support a role for APOE in modulating the aggregation and clearance of Aβ, and data have been accumulating recently implicating APOE4 in exacerbating neurodegeneration, tau pathology and inflammation. We hypothesize that APOE4 influences all the pathological hallmarks of AD and may sit at the interface between neurodegeneration, inflammation and the spread of pathologies through the brain. Here, we conducted a systematic search of the literature and review evidence supporting a role for APOE4 in neurodegeneration and inflammation. While there is no direct evidence yet for APOE4 influencing the spread of pathology, we postulate that this may be found in future based on the literature reviewed here. In conclusion, this review highlights the importance of understanding the role of APOE in multiple important pathological mechanisms in AD.

Activity-Dependent Reconnection of Adult-Born Dentate Granule Cells in a Mouse Model of Frontotemporal Dementia

Frontotemporal dementia (FTD) is characterized by neuronal loss in the frontal and temporal lobes of the brain. Here, we provide the first evidence of striking morphological alterations in dentate granule cells (DGCs) of FTD patients and in a mouse model of the disease, Tau^VLW mice. Taking advantage of the fact that the hippocampal dentate gyrus (DG) gives rise to newborn DGCs throughout the lifetime in rodents, we used RGB retroviruses to study the temporary course of these alterations in newborn DGCs of female Tau^VLW mice. In addition, retroviruses that encode either PSD95:GFP or Syn:GFP revealed striking alterations in the afferent and efferent connectivity of newborn Tau^VLW DGCs, and monosynaptic retrograde rabies virus tracing showed that these cells are disconnected from distal brain regions and local sources of excitatory innervation. However, the same cells exhibited a predominance of local inhibitory innervation. Accordingly, the expression of presynaptic and postsynaptic markers of inhibitory synapses was markedly increased in the DG of Tau^VLW mice and FTD patients. Moreover, an increased number of neuropeptide Y-positive interneurons in the DG correlated with a reduced number of activated egr-1⁺ DGCs in Tau^VLW mice. Finally, we tested the therapeutic potential of environmental enrichment and chemoactivation to reverse these alterations in mice. Both strategies reversed the morphological alterations of newborn DGCs and partially restored their connectivity in a mouse model of the disease. Moreover, our data point to remarkable morphological similarities between the DGCs of Tau^VLW mice and FTD patients.SIGNIFICANCE STATEMENT We show, for the first time to our knowledge, that the population of dentate granule cells is disconnected from other regions of the brain in the neurodegenerative disease frontotemporal dementia (FTD). These alterations were observed in FTD patients and in a mouse model of this disease. Moreover, we tested the therapeutic potential of two strategies, environmental enrichment and chemoactivation, to stimulate the activity of these neurons in mice. We found that some of the alterations were reversed by these therapeutic interventions.

Quantitative MRI Brain Studies in Mild Cognitive Impairment and Alzheimer's Disease: A Methodological Review

Classifying and predicting Alzheimer's disease (AD) in individuals with memory disorders through clinical and psychometric assessment is challenging, especially in mild cognitive impairment (MCI) subjects. Quantitative structural magnetic resonance imaging acquisition methods in combination with computer-aided diagnosis are currently being used for the assessment of AD. These acquisitions methods include voxel-based morphometry, volumetric measurements in specific regions of interest (ROIs), cortical thickness measurements, shape analysis, and texture analysis. This review evaluates the aforementioned methods in the classification of cases into one of the following three groups: normal controls, MCI, and AD subjects. Furthermore, the performance of the methods is assessed on the prediction of conversion from MCI to AD. In parallel, it is also assessed which ROIs are preferred in both classification and prognosis through the different states of the disease. Structural changes in the early stages of the disease are more pronounced in the medial temporal lobe, especially in the entorhinal cortex, whereas with disease progression, both entorhinal cortex and hippocampus offer similar discriminative power. However, for the conversion from MCI subjects to AD, entorhinal cortex provides better predictive accuracies rather than other structures, such as the hippocampus.

A Role for Phosphodiesterase 11A (PDE11A) in the Formation of Social Memories and the Stabilization of Mood

The most recently discovered 3',5'-cyclic nucleotide phosphodiesterase family is the Phosphodiesterase 11 (PDE11) family, which is encoded by a single gene PDE11A. PDE11A is a dual-specific PDE, breaking down both cAMP and cGMP. There are four PDE11A splice variants (PDE11A1-4) with distinct tissue expression profiles and unique N-terminal regulatory regions, suggesting that each isoform could be individually targeted with a small molecule or biologic. PDE11A4 is the PDE11A isoform expressed in brain and is found in the hippocampal formation of humans and rodents. Studies in rodents show that PDE11A4 mRNA expression in brain is, in fact, restricted to the hippocampal formation (CA1, possibly CA2, subiculum, and the adjacently connected amygdalohippocampal area). Within the hippocampal formation of rodents, PDE11A4 protein is expressed in neurons but not astrocytes, with a distribution across nuclear, cytoplasmic, and membrane compartments. This subcellular localization of PDE11A4 is altered in response to social experience in mouse, and in vitro studies show the compartmentalization of PDE11A4 is controlled, at least in part, by homodimerization and N-terminal phosphorylation. PDE11A4 expression dramatically increases in the hippocampus with age in the rodent hippocampus, from early postnatal life to late aging, suggesting PDE11A4 function may evolve across the lifespan. Interestingly, PDE11A4 protein shows a three to tenfold enrichment in the rodent ventral hippocampal formation (VHIPP; a.k.a. anterior in primates) versus dorsal hippocampal formation (DHIPP). Consistent with this enrichment in VHIPP, studies in knockout mice show that PDE11A regulates the formation of social memories and the stabilization of mood and is a critical mechanism by which social experience feeds back to modify the brain and subsequent social behaviors. PDE11A4 likely controls behavior by regulating hippocampal glutamatergic, oxytocin, and cytokine signaling, as well as protein translation. Given its unique tissue distribution and relatively selective effects on behavior, PDE11A may represent a novel therapeutic target for neuropsychiatric, neurodevelopmental, or age-related disorders. Therapeutically targeting PDE11A4 may be a way to selectively restore aberrant cyclic nucleotide signaling in the hippocampal formation while leaving the rest of the brain and periphery untouched, thus, relieving deficits while avoiding unwanted side effects.

TDP-43 misexpression causes defects in dendritic growth

Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Dementia (FTD) share overlapping genetic causes and disease symptoms, and are linked neuropathologically by the RNA binding protein TDP-43 (TAR DNA binding protein-43 kDa). TDP-43 regulates RNA metabolism, trafficking, and localization of thousands of target genes. However, the cellular and molecular mechanisms by which dysfunction of TDP-43 contributes to disease pathogenesis and progression remain unclear. Severe changes in the structure of neuronal dendritic arbors disrupt proper circuit connectivity, which in turn could contribute to neurodegenerative disease. Although aberrant dendritic morphology has been reported in non-TDP-43 mouse models of ALS and in human ALS patients, this phenotype is largely unexplored with regards to TDP-43. Here we have employed a primary rodent neuronal culture model to study the cellular effects of TDP-43 dysfunction in hippocampal and cortical neurons. We show that manipulation of TDP-43 expression levels causes significant defects in dendritic branching and outgrowth, without an immediate effect on cell viability. The effect on dendritic morphology is dependent on the RNA-binding ability of TDP-43. Thus, this model system will be useful in identifying pathways downstream of TDP-43 that mediate dendritic arborization, which may provide potential new avenues for therapeutic intervention in ALS/FTD.

Interictal Epileptiform Activity in the Foramen Ovale Electrodes of a Frontotemporal Dementia Patient

Frontotemporal dementia (FTD) is a frequent cause of cognitive decline. While epilepsy is an important comorbidity of Alzheimer’s disease, we lack studies on its presence in FTD. We report on an FTD patient with transient, short-term changes of behavior and cognitive performance suggesting non-convulsive epilepsy. Video-EEG recording with foramen ovale (FO) electrodes revealed mesio-temporal epileptiform potentials, undetectable by scalp leads. We also found beta spindles in the FO electrodes, not described in the literature. We conclude that video-EEG monitoring with FO electrodes might usefully complement the assessment of dementia-associated epilepsy opening new perspectives in dementia-research.

Longitudinal Analysis for Disease Progression via Simultaneous Multi-Relational Temporal-Fused Learning

It is highly desirable to predict the progression of Alzheimer's disease (AD) of patients [e.g., to predict conversion of mild cognitive impairment (MCI) to AD], especially longitudinal prediction of AD is important for its early diagnosis. Currently, most existing methods predict different clinical scores using different models, or separately predict multiple scores at different future time points. Such approaches prevent coordinated learning of multiple predictions that can be used to jointly predict clinical scores at multiple future time points. In this paper, we propose a joint learning method for predicting clinical scores of patients using multiple longitudinal prediction models for various future time points. Three important relationships among training samples, features, and clinical scores are explored. The relationship among different longitudinal prediction models is captured using a common feature set among the multiple prediction models at different time points. Our experimental results based on the Alzheimer's disease neuroimaging initiative (ADNI) database shows that our method achieves considerable improvement over competing methods in predicting multiple clinical scores.

Behavioral Changes and Hippocampus Glucose Metabolism in APP/PS1 Transgenic Mice via Electro-acupuncture at Governor Vessel Acupoints

Objective: Investigating the effects of electro-acupuncture (EA) treatment on mice with Alzheimer’s disease (AD), using Morris water maze (MWM) for spatial learning and memory behavior tests combined with micro-positron emission tomography (micro-PET) imaging for glucose metabolism in hippocampus.

Methods: Thirty seven-month-old APP/PS1 mice were randomly divided into AD Model group (AD group), medicine group (M group) and EA group, C57BL/6 mice were used for Normal control group (N group), n = 10 in each group. Mice in M group received donepezil intervention by gavage with dose at 0.92 mg/kg. EA was applied at Baihui (GV20) and Yintang (GV29) acupoints for 20 min then pricked at Shuigou (GV26) acupoint, while mice in N, M and AD groups were received restriction for 20 min, with all treatment administrated once a day for 15 consecutive days. After the treatment, MWM was performed to observe behavioral changes in mice, then hippocampus glucose metabolism level was tested by micro-PET imaging.

Results: Compared with that of AD group, the escape latency of M and EA groups declined significantly (P < 0.01), while the proportion of the platform quadrant swimming distance in total swimming distance showed an obvious increase (P < 0.01), and EA group occupied a higher percentage than that in M group. The micro-PET imaging showed that mice in AD group performed a lower glucose metabolic rate in hippocampus compared with N group (P < 0.01). Both M and EA groups presented a significant higher injected dose compared with AD group (P < 0.01), and the uptake rate of EA group was higher than M group.

Conclusion: Both donepezil and EA have therapeutic effects on AD mice. To a certain extent, EA shows a better efficacy in treatment of AD by improving the spatial learning and memory ability, while also enhancing glucose metabolism in hippocampus.

Forebrain depletion of Rheb GTPase elicits spatial memory deficits in mice

The precise molecular and cellular events responsible for age-dependent cognitive dysfunctions remain unclear. We report that Rheb (ras homolog enriched in brain) GTPase, an activator of mammalian target of rapamycin (mTOR), regulates memory functions in mice. Conditional depletion of Rheb selectively in the forebrain of mice obtained from crossing Rheb^f/f and CamKII^Cre results in spontaneous signs of age-related memory loss, that is, spatial memory deficits (T-maze, Morris water maze) without affecting locomotor (open-field test), anxiety-like (elevated plus maze), or contextual fear conditioning functions. Partial depletion of Rheb in forebrain was sufficient to elicit memory defects with little effect on the neuronal size, cortical thickness, or mammalian target of rapamycin activity. Rheb depletion, however, increased the levels of beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), a protein elevated in aging and Alzheimer's disease. Overall, our study demonstrates that forebrain Rheb promotes aging-associated cognitive defects. Thus, molecular understanding of Rheb pathway in brain may provide new therapeutic targets for aging and/or Alzheimer's disease-associated memory deficits.

Dynamic expression of the mouse orthologue of the human amyotropic lateral sclerosis associated gene C9orf72 during central nervous system development and neuronal differentiation

The hexanucleotide repeat in the first intron of the C9orf72 gene is the most significant cause of amyotropic lateral sclerosis as well as some forms of fronto-temporal dementia. The C9orf72 protein has been previously reported to be expressed in post-mortem human brain as well as in late embryonic and some postnatal stages in mice. Herein, we present a detailed study of the distribution of C9orf72 protein in the embryonic, postnatal and adult mouse brain, spinal cord as well as during the differentiation of P19 embryonal carcinoma cells to neurons including motor neurons. We show that the expression levels of the C9orf72 transcripts in the developing and adult mouse brain as well as in differentiating neurons, are dynamic. Besides the strong expression in the cerebellum and motor cortex reported previously, we show for the first time that C9orf72 is expressed strongly in the olfactory bulb and also in the hippocampus. Our immunostaining data also reveal a hitherto unreported switch in the cellular distribution of C9orf72 from a predominantly cytoplasmic to a nucleo-cytoplasmic distribution during corticogenesis. This switch in distribution was also observed during differentiation of the pluripotent embryonal carcinoma P19 cell line to mature neurons. Our findings have implications for interpreting the pathophysiology caused by the repeat expansions in C9orf72 in mouse models.

Using the Disease State Fingerprint Tool for Differential Diagnosis of Frontotemporal Dementia and Alzheimer's Disease

BACKGROUND

Disease State Index (DSI) and its visualization, Disease State Fingerprint (DSF), form a computer-assisted clinical decision making tool that combines patient data and compares them with cases with known outcomes.

AIMS

To investigate the ability of the DSI to diagnose frontotemporal dementia (FTD) and Alzheimer's disease (AD).

METHODS

The study cohort consisted of 38 patients with FTD, 57 with AD and 22 controls. Autopsy verification of FTD with TDP-43 positive pathology was available for 14 and AD pathology for 12 cases. We utilized data from neuropsychological tests, volumetric magnetic resonance imaging, single-photon emission tomography, cerebrospinal fluid biomarkers and the APOE genotype. The DSI classification results were calculated with a combination of leave-one-out cross-validation and bootstrapping. A DSF visualization of a FTD patient is presented as an example.

RESULTS

The DSI distinguishes controls from FTD (area under the receiver-operator curve, AUC = 0.99) and AD (AUC = 1.00) very well and achieves a good differential diagnosis between AD and FTD (AUC = 0.89). In subsamples of autopsy-confirmed cases (AUC = 0.97) and clinically diagnosed cases (AUC = 0.94), differential diagnosis of AD and FTD performs very well.

CONCLUSIONS

DSI is a promising computer-assisted biomarker approach for aiding in the diagnostic process of dementing diseases. Here, DSI separates controls from dementia and differentiates between AD and FTD.

Differential diagnosis of neurodegenerative diseases using structural MRI data

Different neurodegenerative diseases can cause memory disorders and other cognitive impairments. The early detection and the stratification of patients according to the underlying disease are essential for an efficient approach to this healthcare challenge. This emphasizes the importance of differential diagnostics. Most studies compare patients and controls, or Alzheimer's disease with one other type of dementia. Such a bilateral comparison does not resemble clinical practice, where a clinician is faced with a number of different possible types of dementia.

Here we studied which features in structural magnetic resonance imaging (MRI) scans could best distinguish four types of dementia, Alzheimer's disease, frontotemporal dementia, vascular dementia, and dementia with Lewy bodies, and control subjects. We extracted an extensive set of features quantifying volumetric and morphometric characteristics from T1 images, and vascular characteristics from FLAIR images. Classification was performed using a multi-class classifier based on Disease State Index methodology. The classifier provided continuous probability indices for each disease to support clinical decision making.

A dataset of 504 individuals was used for evaluation. The cross-validated classification accuracy was 70.6% and balanced accuracy was 69.1% for the five disease groups using only automatically determined MRI features. Vascular dementia patients could be detected with high sensitivity (96%) using features from FLAIR images. Controls (sensitivity 82%) and Alzheimer's disease patients (sensitivity 74%) could be accurately classified using T1-based features, whereas the most difficult group was the dementia with Lewy bodies (sensitivity 32%). These results were notable better than the classification accuracies obtained with visual MRI ratings (accuracy 44.6%, balanced accuracy 51.6%). Different quantification methods provided complementary information, and consequently, the best results were obtained by utilizing several quantification methods.

The results prove that automatic quantification methods and computerized decision support methods are feasible for clinical practice and provide comprehensive information that may help clinicians in the diagnosis making.

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Differential diagnostics of dementias was studied using structural MRI data.

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504 patients with both T1 and FLAIR MRIs from five patient classes were evaluated.

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Different fully automatic quantification methods were compared and combined.

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Classification accuracy of 70.6% was obtained for 5-class classification problem.

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Combination of several quantification methods was needed for optimal accuracy.

Evaluating Behavior in Mouse Models of the Behavioral Variant of Frontotemporal Dementia: Which Test for Which Symptom?

The behavioral variant of frontotemporal dementia (bvFTD) is a neurodegenerative disease affecting people in their early sixties, characterized by dramatic changes in individual and social behavior. Despite the heterogeneity in the presentation of the clinical symptoms of bvFTD, some characteristic changes can be highlighted. Social disinhibition, changes in food preferences as well as loss of empathy and apathy are commonly described. This is accompanied by a characteristic and dramatic atrophy of the prefrontal cortex with the accumulation of protein aggregates in the neurons in this area. Several causative mutations in different genes have been discovered, allowing the development of transgenic animal models, especially mouse models. In mice, attention has been focused on the histopathological aspects of the pathology, but now studies are taking interest in assessing the behavioral phenotype of FTD models. Finding the right test corresponding to human symptoms is quite challenging, especially since the frontal cortex is much less developed in mice than in humans. Although challenging, the ability to detect relevant prefrontal cortex impairments in mice is crucial for therapeutic approaches. In this review, we aim to present the approaches that have been used to model the behavioral symptoms of FTD and to explore other relevant approaches to assess behavior involving the prefrontal cortex, as well as the deficits associated with FTD.

Delusion of pregnancy: an unusual symptom in the context of dementia

BACKGROUND

Delusions can complicate practically all brain disorders. They may be dramatic and bizarre. An example is the so-called delusion of pregnancy.

OBJECTIVE

To identify the characteristic of a psychotic symptom, the phenomenon of delusion of pregnancy, in the context of dementia.

METHOD

MEDLINE and Google Scholar searches were conducted for relevant articles, chapters, and books published before 2014. Search terms used included delusion of pregnancy, uncommon presentation, behavioral and psychological symptoms, dementia, Alzheimer's disease, and frontotemporal dementia (FTD). Publications found through this indexed search were reviewed for further relevant references. We included case reports that highlight the relationship and overlap between dementia presenting as schizophrenia-like psychosis and schizophrenia.

RESULTS

Literature on delusion of pregnancy in the course of dementia consists mostly of case reports and small samples of patients.

CONCLUSION

Psychotic phenomena such as delusion of pregnancy may be a feature in some cases of dementia. If this bizarre features of dementia appears as early presentation of FTD whose usual onset is in the presenium, it may be mistaken for schizophrenia.

Manifold regularized multitask feature learning for multimodality disease classification

Multimodality based methods have shown great advantages in classification of Alzheimer's disease (AD) and its prodromal stage, that is, mild cognitive impairment (MCI). Recently, multitask feature selection methods are typically used for joint selection of common features across multiple modalities. However, one disadvantage of existing multimodality based methods is that they ignore the useful data distribution information in each modality, which is essential for subsequent classification. Accordingly, in this paper we propose a manifold regularized multitask feature learning method to preserve both the intrinsic relatedness among multiple modalities of data and the data distribution information in each modality. Specifically, we denote the feature learning on each modality as a single task, and use group-sparsity regularizer to capture the intrinsic relatedness among multiple tasks (i.e., modalities) and jointly select the common features from multiple tasks. Furthermore, we introduce a new manifold-based Laplacian regularizer to preserve the data distribution information from each task. Finally, we use the multikernel support vector machine method to fuse multimodality data for eventual classification. Conversely, we also extend our method to the semisupervised setting, where only partial data are labeled. We evaluate our method using the baseline magnetic resonance imaging (MRI), fluorodeoxyglucose positron emission tomography (FDG-PET), and cerebrospinal fluid (CSF) data of subjects from AD neuroimaging initiative database. The experimental results demonstrate that our proposed method can not only achieve improved classification performance, but also help to discover the disease-related brain regions useful for disease diagnosis.

Two distinct amnesic profiles in behavioral variant frontotemporal dementia

BACKGROUND

Whether or not episodic memory deficit is a characteristic of behavioral variant frontotemporal dementia (bvFTD) is a crucial question for its diagnosis and management.

METHODS

We compared the episodic memory performance profile of bvFTD patients with healthy control subjects and patients with Alzheimer's disease (AD) as defined by clinical and biological criteria. Episodic memory was assessed with the Free and Cued Selective Reminding Test, which controls for effective encoding and identifies memory storage ability resulting from consolidation processing. One hundred thirty-four participants were evaluated: 56 patients with typical clinical presentation of AD and pathophysiological evidence as defined by cerebrospinal fluid AD biomarker profile and/or significant amyloid retention on Pittsburgh Compound B positron emission tomography; 56 patients diagnosed with bvFTD with no evidence of AD-cerebrospinal fluid biomarkers when a profile was available (28/56), including 44 progressive (bvFTD) and 12 nonprogressive (phenocopies) patients; and 22 control subjects with negative amyloid imaging.

RESULTS

Memory scores could not differentiate bvFTD from AD patients (sensitivity and specificity <50%). Taking into account the individual distribution of Free and Cued Selective Reminding Test scores, half of bvFTD patients had a deficit of free recall, total (free + cued) recall, and delayed recall as severe as AD patients. The other half had subnormal scores similar to phenocopies and a delayed recall score similar to control subjects.

CONCLUSIONS

We observed two distinct amnesic profiles in bvFTD patients that could reflect two types of hippocampal structure and Papez circuit involvement. These findings on episodic memory profiles could contribute to discussions on the recent international consensus criteria for bvFTD.

Axonal tract tracing for delineating interacting brain regions: implications for Alzheimer's disease-associated memory

We are studying the projections from the entorhinal cortex to the hippocampal formation in the mouse. The dentate gyrus is innervated by the lateral entorhinal cortex (lateral perforant path) and medial entorhinal cortex (medial perforant path). The entorhinal cortex also projects to hippocampal areas CA3 and CA1, and to the subiculum. In young transgenic Alzheimer's disease mouse models (before amyloid-β pathology), the connections are not different from normal mice. In Alzheimer's disease mice with pathology, two changes occur: first, dystrophic axon endings appear near amyloid-β plaques, and second, there are sparse aberrant axon terminations not in the appropriate area or lamina of the hippocampus. Furthermore, MRI-diffusion tensor imaging analysis indicates a decrease in the quality of the white matter tracts connecting the hippocampus to the brain; in other words, the fimbria/fornix and perforant path. Similar changes in white matter integrity have been found in Alzheimer's disease patients and could potentially be used as early indicators of disease onset.

Glutamate metabolism is impaired in transgenic mice with tau hyperphosphorylation

In neurodegenerative diseases including Alzheimer's disease and frontotemporal dementia, the protein tau is hyperphosphorylated and eventually aggregates to develop neurofibrillary tangles. Here, the consequences of tau hyperphosphorylation on both neuronal and astrocytic metabolism and amino-acid neurotransmitter homeostasis were assessed in transgenic mice expressing the pathogenic mutation P301L in the human tau gene (pR5 mice) compared with nontransgenic littermate controls. Mice were injected with the neuronal and astrocytic substrate [1-(13)C]glucose and the astrocytic substrate [1,2-(13)C]acetate. Hippocampus and cerebral cortex extracts were analyzed using (1)H and (13)C nuclear magnetic resonance spectroscopy, gas chromatography-mass spectrometry and high-performance liquid chromatography. The glutamate level was reduced in the hippocampus of pR5 mice, accompanied by reduced incorporation of (13)C label derived from [1-(13)C]glucose in glutamate. In the cerebral cortex, glucose utilization as well as turnover of glutamate, glutamine, and GABA, were increased. This was accompanied by a relative increase in production of glutamate via the pyruvate carboxylation pathway in cortex. Overall, we revealed that astrocytes as well as glutamatergic and GABAergic neurons in the cortex of pR5 mice were in a hypermetabolic state, whereas in the hippocampus, where expression levels of mutant human tau are the highest, glutamate homeostasis was impaired.

Distinct patterns of medial temporal impairment in degenerative dementia: a brain SPECT perfusion study in Alzheimer's disease and frontotemporal dementia

PURPOSE

Medial temporal impairment can be detected clinically and by morphological imaging during Alzheimer's disease (AD), but the existence of a functional impairment in this area seems to be less well established. Yet such functional impairment is classically found in other degenerative cortical dementias, such as the frontal variant of frontotemporal dementia (fv-FTD). The aim of this study was to characterize and compare brain SPECT perfusion of the medial temporal lobe in AD and fv-FTD.

METHODS

Voxel-based comparisons were performed using SPM8 between cerebral SPECT images from 85 AD patients, 25 fv-FTD patients and 12 healthy controls at the whole-brain level and the medial temporal lobe level using a region of interest approach (p < 0.001, corrected for the cluster).

RESULTS

In the free and cued selective reminding test, used to evaluate medial temporal memory function, AD patients had significantly lower scores than the fv-FTD patients (p < 0.005). AD and fv-FTD patients showed hypoperfused medial temporal structures in comparison to normal controls. However, fv-FTD patients had more pronounced hypoperfusion in this area, with a different topography, more anterior and more parahippocampal.

CONCLUSION

These results show that medial temporal hypoperfusion can be detected in degenerative dementias by SPECT. Paradoxically, the hypoperfusion is more severe in fv-FTD than in AD patients, even though the mnesic profile of AD is more altered, suggesting the existence of inefficient compensatory mechanisms.

Frontal presentation of Alzheimer's disease: a series of patients with biological evidence by CSF biomarkers

Besides its typical amnesic presentation, focal atypical presentations of Alzheimer's disease (AD) have been described in neuropathological studies. These phenotypical variants of AD (so-called "atypical AD") do not follow the typical amnestic pattern and include non-amnestic focal cortical syndromes, such as posterior cortical atrophy and frontal variant AD. These variants exhibit characteristic histological lesions of Alzheimer pathology at post-mortem exam. By using physiopathological markers, such as cerebrospinal fluid markers, it is now possible to establish in vivo a biological diagnosis of AD in these focal cortical syndromes. We report a series of eight patients who were diagnosed with behavioural variant frontotemporal dementia based on their clinical, neuropsychological and neuroimaging findings, while CSF biomarkers showed an AD biological profile, thus supporting a diagnosis of frontal variant of AD.

Structural MRI in frontotemporal dementia: comparisons between hippocampal volumetry, tensor-based morphometry and voxel-based morphometry

BACKGROUND

MRI is an important clinical tool for diagnosing dementia-like diseases such as Frontemporal Dementia (FTD). However there is a need to develop more accurate and standardized MRI analysis methods.

OBJECTIVE

To compare FTD with Alzheimer's Disease (AD) and Mild Cognitive Impairment (MCI) with three automatic MRI analysis methods - Hippocampal Volumetry (HV), Tensor-based Morphometry (TBM) and Voxel-based Morphometry (VBM), in specific regions of interest in order to determine the highest classification accuracy.

METHODS

Thirty-seven patients with FTD, 46 patients with AD, 26 control subjects, 16 patients with progressive MCI (PMCI) and 48 patients with stable MCI (SMCI) were examined with HV, TBM for shape change, and VBM for gray matter density. We calculated the Correct Classification Rate (CCR), sensitivity (SS) and specificity (SP) between the study groups.

RESULTS

We found unequivocal results differentiating controls from FTD with HV (hippocampus left side) (CCR = 0.83; SS = 0.84; SP = 0.80), with TBM (hippocampus and amygdala (CCR = 0.80/SS = 0.71/SP = 0.94), and with VBM (all the regions studied, especially in lateral ventricle frontal horn, central part and occipital horn) (CCR = 0.87/SS = 0.81/SP = 0.96). VBM achieved the highest accuracy in differentiating AD and FTD (CCR = 0.72/SS = 0.67/SP = 0.76), particularly in lateral ventricle (frontal horn, central part and occipital horn) (CCR = 0.73), whereas TBM in superior frontal gyrus also achieved a high accuracy (CCR = 0.71/SS = 0.68/SP = 0.73). TBM resulted in low accuracy (CCR = 0.62) in the differentiation of AD from FTD using all regions of interest, with similar results for HV (CCR = 0.55).

CONCLUSION

Hippocampal atrophy is present not only in AD but also in FTD. Of the methods used, VBM achieved the highest accuracy in its ability to differentiate between FTD and AD.

Hippocampal shape analysis in Alzheimer's disease and frontotemporal lobar degeneration subtypes

Hippocampal pathology is central to Alzheimer's disease (AD) and other forms of dementia such as frontotemporal lobar degeneration (FTLD). Autopsy studies have shown that certain hippocampal subfields are more vulnerable than others to AD and FTLD pathology, in particular the subiculum and cornu ammonis 1 (CA1). We conducted shape analysis of hippocampi segmented from structural T1 MRI images on clinically diagnosed dementia patients and controls. The subjects included 19 AD and 35 FTLD patients [13 frontotemporal dementia (FTD), 13 semantic dementia (SD), and 9 progressive nonfluent aphasia (PNFA)] and 21 controls. Compared to controls, SD displayed severe atrophy of the whole left hippocampus. PNFA and FTD also displayed atrophy on the left side, restricted to the hippocampal head in FTD. Finally, AD displayed most atrophy in left hippocampal body with relative sparing of the hippocampal head. Consistent with neuropathological studies, most atrophic deformation was found in CA1 and subiculum areas in FTLD and AD.

Structural brain changes in First Episode Schizophrenia compared with Fronto-Temporal Lobar Degeneration: a meta-analysis

BACKGROUND

The authors sought to compare gray matter changes in First Episode Schizophrenia (FES) compared with Fronto-Temporal Lobar Degeneration (FTLD) using meta-analytic methods applied to neuro-imaging studies.

METHODS

A systematic search was conducted for published, structural voxel-based morphometric MRI studies in patients with FES or FTLD. Data were combined using anatomical likelihood estimation (ALE) to determine the extent of gray matter decreases and analysed to ascertain the degree of overlap in the spatial distribution of brain changes in both diseases.

RESULTS

Data were extracted from 18 FES studies (including a total of 555 patients and 621 comparison subjects) and 20 studies of FTLD or related disorders (including a total of 311 patients and 431 comparison subjects). The similarity in spatial overlap of brain changes in the two disorders was significant (p = 0.001). Gray matter deficits common to both disorders included bilateral caudate, left insula and bilateral uncus regions.

CONCLUSIONS

There is a significant overlap in the distribution of structural brain changes in First Episode Schizophrenia and Fronto-Temporal Lobar Degeneration. This may reflect overlapping aetiologies, or a common vulnerability of these regions to the distinct aetio-pathological processes in the two disorders.

Lipocalin 2: novel component of proinflammatory signaling in Alzheimer's disease

Alzheimer's disease (AD) is associated with an altered immune response, resulting in chronic increased inflammatory cytokine production with a prominent role of TNF-α. TNF-α signals are mediated by two receptors: TNF receptor 1 (TNFR1) and TNF receptor 2 (TNFR2). Signaling through TNFR2 is associated with neuroprotection, whereas signaling through TNFR1 is generally proinflammatory and proapoptotic. Here, we have identified a TNF-α-induced proinflammatory agent, lipocalin 2 (Lcn2) via gene array in murine primary cortical neurons. Further investigation showed that Lcn2 protein production and secretion were activated solely upon TNFR1 stimulation when primary murine neurons, astrocytes, and microglia were treated with TNFR1 and TNFR2 agonistic antibodies. Lcn2 was found to be significantly decreased in CSF of human patients with mild cognitive impairment and AD and increased in brain regions associated with AD pathology in human postmortem brain tissue. Mechanistic studies in cultures of primary cortical neurons showed that Lcn2 sensitizes nerve cells to β-amyloid toxicity. Moreover, Lcn2 silences a TNFR2-mediated protective neuronal signaling cascade in neurons, pivotal for TNF-α-mediated neuroprotection. The present study introduces Lcn2 as a molecular actor in neuroinflammation in early clinical stages of AD.