Neuroimaging of white matter in aging and dementia

In vivo effect of LATE-NC on integrity of white matter connections to the hippocampus

INTRODUCTION

TAR DNA-binding protein 43 (TDP-43) is a highly prevalent proteinopathy that is involved in neurodegenerative processes, including axonal damage. To date, no ante mortem biomarkers exist for TDP-43, and few studies have directly assessed its impact on neuroimaging measures utilizing pathologic quantification.

METHODS

Ante mortem diffusion-weighted images were obtained from community-dwelling older adults. Regression models calculated the relationship between post mortem TDP-43 burden and ante mortem fractional anisotropy (FA) within each voxel in connection with the hippocampus, controlling for coexisting Alzheimer's disease and demographics.

RESULTS

Results revealed a significant negative relationship (false discovery rate [FDR] corrected p < .05) between post mortem TDP-43 and ante mortem FA in one cluster within the left medial temporal lobe connecting to the parahippocampal cortex, entorhinal cortex, and cingulate, aligning with the ventral subdivision of the cingulum. FA within this cluster was associated with cognition.

DISCUSSION

Greater TDP-43 burden is associated with lower FA within the limbic system, which may contribute to impairment in learning and memory.

HIGHLIGHTS

Post mortem TDP-43 pathological burden is associated with reduced ante mortem fractional anisotropy. Reduced FA located in the parahippocampal portion of the cingulum. FA in this area was associated with reduced episodic and semantic memory. FA in this area was associated with increased inward hippocampal surface deformation.

Healthy aging alters the oscillatory dynamics and fronto-parietal connectivity serving fluid intelligence

Fluid intelligence (Gf) involves logical reasoning and novel problem-solving abilities. Often, abstract reasoning tasks like Raven's progressive matrices are used to assess Gf. Prior work has shown an age-related decline in fluid intelligence capabilities, and although many studies have sought to identify the underlying mechanisms, our understanding of the critical brain regions and dynamics remains largely incomplete. In this study, we utilized magnetoencephalography (MEG) to investigate 78 individuals, ages 20-65 years, as they completed an abstract reasoning task. MEG data was co-registered with structural MRI data, transformed into the time-frequency domain, and the resulting neural oscillations were imaged using a beamformer. We found worsening behavioral performance with age, including prolonged reaction times and reduced accuracy. MEG analyses indicated robust oscillations in the theta, alpha/beta, and gamma range during the task. Whole brain correlation analyses with age revealed relationships in the theta and alpha/beta frequency bands, such that theta oscillations became stronger with increasing age in a right prefrontal region and alpha/beta oscillations became stronger with increasing age in parietal and right motor cortices. Follow-up connectivity analyses revealed increasing parieto-frontal connectivity with increasing age in the alpha/beta frequency range. Importantly, our findings are consistent with the parieto-frontal integration theory of intelligence (P-FIT). These results further suggest that as people age, there may be alterations in neural responses that are spectrally specific, such that older people exhibit stronger alpha/beta oscillations across the parieto-frontal network during abstract reasoning tasks.

Segmentation and differentiation of periventricular and deep white matter hyperintensities in 2D T2-FLAIR MRI based on a cascade U-net

Background

White matter hyperintensities (WMHs) are a subtype of cerebral small vessel disease and can be divided into periventricular WMHs (pvWMHs) and deep WMHs (dWMHs). pvWMHs and dWMHs were proved to be determined by different etiologies. This study aimed to develop a 2D Cascade U-net (Cascade U) for the segmentation and differentiation of pvWMHs and dWMHs on 2D T2-FLAIR images.

Methods

A total of 253 subjects were recruited in the present study. All subjects underwent 2D T2-FLAIR scan on a 3.0 Tesla MR scanner. Both contours of pvWMHs and dWMHs were manually delineated by the observers and considered as the gold standard. Fazekas scale was used to evaluate the burdens of pvWMHs and dWMHs, respectively. Cascade U consisted of a segmentation U-net and a differentiation U-net and was trained with a combined loss function. The performance of Cascade U was compared with two other U-net models (Pipeline U and Separate U). Dice similarity coefficient (DSC), Matthews correlation coefficient (MCC), precision, and recall were used to evaluate the performances of all models. The linear correlations between WMHs volume (WMHV) measured by all models and the gold standard were also conducted.

Results

Compared with other models, Cascade U exhibited a better performance on WMHs segmentation and pvWMHs identification. Cascade U achieved DSC values of 0.605 ± 0.135, 0.517 ± 0.263, and 0.510 ± 0.241 and MCC values of 0.617 ± 0.122, 0.526 ± 0.263, and 0.522 ± 0.243 on the segmentation of total WMHs, pvWMHs, and dWMHs, respectively. Cascade U exhibited strong correlations with the gold standard on measuring WMHV (R2 = 0.954, p &lt; 0.001), pvWMHV (R2 = 0.933, p &lt; 0.001), and dWMHV (R2 = 0.918, p &lt; 0.001). A significant correlation was found on lesion volume between Cascade U and gold standard (r &gt; 0.510, p &lt; 0.001).

Conclusion

Cascade U showed competitive results in segmentation and differentiation of pvWMHs and dWMHs on 2D T2-FLAIR images, indicating potential feasibility in precisely evaluating the burdens of WMHs.

Reduced frontal white matter microstructure in healthy older adults with low tactile recognition performance

The aging of the nervous system is a heterogeneous process. It remains a significant challenge to identify relevant markers of pathological and healthy brain aging. A central aspect of aging are decreased sensory acuities, especially because they correlate with the decline in higher cognitive functioning. Sensory and higher cognitive processing relies on information flow between distant brain areas. Aging leads to disintegration of the underlying white matter tracts. While this disintegration is assumed to contribute to higher cognitive decline, data linking structural integrity and sensory function are sparse. The investigation of their interrelation may provide valuable insight into the mechanisms of brain aging. We used a combined behavioral and neuroimaging approach and investigated to what extent changes in microstructural white matter integrity reflect performance declines in tactile pattern recognition with aging. Poor performance in older participants was related to decreased integrity in the anterior corpus callosum. Probabilistic tractography showed that this structure is connected to the prefrontal cortices. Our data point to decreased integrity in the anterior corpus callosum as a marker for advanced brain aging. The correlation between impaired tactile recognition and disintegration in frontal brain networks could provide an explanation why the decrease of sensory function predicts cognitive decline.

Evaluation of MR Visual Rating Scales in Major Forms of Dementia

Objective  The aim of the study is to visually rate major forms of dementia using global cortical atrophy (GCA), medial temporal lobe atrophy (MTA), and Fazeka’s scales and Koedam’s score using magnetic resonance imaging (MRI). The purpose is to correlate the visual rating scales (VRS) with severity of dementia.

Materials and Methods  Thirty patients fulfilling DSM 5 (Diagnostic and Statistical Manual of Mental Disorders) criteria for Alzheimer’s dementia (AD), vascular dementia (VaD), and frontotemporal dementia (FTD) underwent MRI brain. Cortical atrophy, medial temporal, and parietal lobe atrophy were assessed using GCA and MTA scales and Koedam’s score, respectively. White matter hyperintensities were assessed using Fazeka’s scale. Correlation between VRS and mini-mental state exam (MMSE) scores was done using Pearson correlation coefficient.

Results  70% of patients had Grade 2 GCA. More patients with AD had higher MTA scores as compared with others with 57% of AD patients showing abnormal for age MTA scores. Fazeka’s scale was abnormal for age in 58.33% of VaD and 57% AD patients. Majority (75%) showing severe parietal atrophy (Grade 3 Koedam’s score) were AD patients. Disproportionate frontal lobe atrophy was seen in all four (100%) FTD patients. Significant negative correlation was seen between MMSE and GCA scores of all patients ( p -value = 0.003) as well as between MTA and MMSE scores in AD patients ( p -value = 0.00095).

Conclusion  Visual rating of MTA is a reliable method for detecting AD and correlates strongly with memory scores. Atrophy of specific regions is seen more commonly in some conditions, for instance, where MTA and parietal atrophy are specific for AD while asymmetric frontal lobe and temporal pole atrophy favor FTD.

Linking the impact of aging on visual short-term memory capacity with changes in the structural connectivity of posterior thalamus to occipital cortices

Aging impacts both visual short-term memory (vSTM) capacity and thalamo-cortical connectivity. According to the Neural Theory of Visual Attention, vSTM depends on the structural connectivity between posterior thalamus and visual occipital cortices (PT-OC). We tested whether aging modifies the association between vSTM capacity and PT-OC structural connectivity. To do so, 66 individuals aged 20-77 years were assessed by diffusion-weighted imaging used for probabilistic tractography and performed a psychophysical whole-report task of briefly presented letter arrays, from which vSTM capacity estimates were derived. We found reduced vSTM capacity, and aberrant PT-OC connection probability in aging. Critically, age modified the relationship between vSTM capacity and PT-OC connection probability: in younger adults, vSTM capacity was negatively correlated with PT-OC connection probability while in older adults, this association was positive. Furthermore, age modified the microstructure of PT-OC tracts suggesting that the inversion of the association between PT-OC connection probability and vSTM capacity with aging might reflect age-related changes in white-matter properties. Accordingly, our results demonstrate that age-related differences in vSTM capacity links with the microstructure and connectivity of PT-OC tracts.

Whole volume brain extraction for multi-centre, multi-disease FLAIR MRI datasets

Automatic segmentation of the brain from magnetic resonance images (MRI) is a fundamental step in many neuroimaging processing frameworks. There are mature technologies for this task for T1- and T2-weighted MRI; however, a widely-accepted brain extraction method for Fluid-Attenuated Inversion Recovery (FLAIR) MRI has yet to be established. FLAIR MRI are becoming increasingly important for the analysis of neurodegenerative diseases and tools developed for this sequence would have clinical value. To maximize translation opportunities and for large scale research studies, algorithms for brain extraction in FLAIR MRI should generalize to multi-centre (MC) data. To this end, this work proposes a fully automated, whole volume brain extraction methodology for MC FLAIR MRI datasets. The framework is built using a novel standardization framework which reduces acquisition artifacts, standardizes the intensities of tissues and normalizes the spatial coordinates of brain tissue across MC datasets. Using the standardized datasets, an intuitive set of features based on intensity, spatial location and gradients are extracted and classified using a random forest (RF) classifier to segment the brain tissue class. A series of experiments were conducted to optimize classifier parameters, and to determine segmentation accuracy for standardized and unstandardized (original) data, as a function of scanner vendor, feature type and disease type. The models are trained, tested and validated on 156 image volumes (∼8000 image slices) from two multi-centre, multi-disease datasets, acquired with varying imaging parameters from 30 centres and three scanner vendors. The image datasets, denoted as CAIN and ADNI for vascular and dementia disease, respectively, represent a diverse collection of MC data to test the generalization capabilities of the proposed design. Results demonstrate the importance of standardization for segmentation of MC data, as models trained on standardized data yielded a drastic improvement in brain extraction accuracy compared to the original, unstandardized data (CAIN: DSC = 91% and ADNI: DSC = 86% vs. CAIN: 78% and ADNI: 65%). It was also found that models created from one scanner vendor based on unstandardized data yielded poor segmentation results in data acquired from other scanner vendors, which was improved through standardization. These results demonstrate that to create consistency in segmentations from multi-institutional datasets it is paramount that MC variability be mitigated to improve stability and to ensure generalization of machine learning algorithms for MRI.

Cardiovascular symptoms and longitudinal declines in processing speed differentially predict cerebral white matter lesions in older adults

It is well established that cerebral white matter lesions (WML), present in the majority of older adults, are associated with cardiovascular and cerebrovascular diseases and also with cognitive decline. However, much less is known about how WML are related to other important individual characteristics and about the generality vs. brain region-specificity of WML. In a longitudinal study of 112 community-dwelling adults (age 50-71 years at study entry), we used a machine learning approach to evaluate the relative strength of 52 variables in association with WML burden. Variables included socio-demographic, lifestyle, and health indices-as well as multiple cognitive abilities (modeled as latent constructs using factor analysis)-repeatedly measured at three- to six-year intervals. Greater chronological age, symptoms of cardiovascular disease, and processing speed declines were most strongly linked to elevated WML burden (accounting for ∼49% of variability in WML). Whereas frontal lobe WML burden was associated both with elevated cardiovascular symptoms and declines in processing speed, temporal lobe WML burden was only significantly associated with declines in processing speed. These latter outcomes suggest that age-related WML-cognition associations may be etiologically heterogeneous across fronto-temporal cerebral regions.

Brain Atrophy of Secondary REM-Sleep Behavior Disorder in Neurodegenerative Disease

BACKGROUND

Rapid eye movement sleep behavior disorder (RBD) may present as an early manifestation of an evolving neurodegenerative disorder with alpha-synucleinopathy.

OBJECTIVE

We investigated that dementia with RBD might show distinctive cortical atrophic patterns.

METHODS

A total of 31 patients with idiopathic Parkinson's disease (IPD), 23 with clinically probable Alzheimer's disease (AD), and 36 healthy controls participated in this study. Patients with AD and IPD were divided into two groups according to results of polysomnography and rated with a validated Korean version of the RBD screening questionnaire (RBDSQ-K), which covers the clinical features of RBD. Voxel-based morphometry was adapted for detection of regional brain atrophy among groups of subjects.

RESULTS

Scores on RBDSQ-K were higher in the IPD group (3.54 ± 2.8) than in any other group (AD, 2.94 ± 2.4; healthy controls, 2.31 ± 1.9). Atrophic changes according to RBDSQ-K scores were characteristically in the posterior part of the brain and brain stem, including the hypothalamus and posterior temporal region including the hippocampus and bilateral occipital lobe. AD patients with RBD showed more specialized atrophic patterns distributed in the posterior and inferior parts of the brain including the bilateral temporal and occipital cortices compared to groups without RBD. The IPD group with RBD showed right temporal cortical atrophic changes.

CONCLUSION

The group of patients with neurodegenerative diseases and RBD showed distinctive brain atrophy patterns, especially in the posterior and inferior cortices. These results suggest that patients diagnosed with clinically probable AD or IPD might have mixed pathologies including α-synucleinopathy.

The role of diffusion tensor imaging and fractional anisotropy in the evaluation of patients with idiopathic normal pressure hydrocephalus: a literature review

OBJECTIVE Diffusion tensor imaging (DTI) for the assessment of fractional anisotropy (FA) and involving measurements of mean diffusivity (MD) and apparent diffusion coefficient (ADC) represents a novel, MRI-based, noninvasive technique that may delineate microstructural changes in cerebral white matter (WM). For example, DTI may be used for the diagnosis and differentiation of idiopathic normal pressure hydrocephalus (iNPH) from other neurodegenerative diseases with similar imaging findings and clinical symptoms and signs. The goal of the current study was to identify and analyze recently published series on the use of DTI as a diagnostic tool. Moreover, the authors also explored the utility of DTI in identifying patients with iNPH who could be managed by surgical intervention. METHODS The authors performed a literature search of the PubMed database by using any possible combinations of the following terms: "Alzheimer's disease," "brain," "cerebrospinal fluid," "CSF," "diffusion tensor imaging," "DTI," "hydrocephalus," "idiopathic," "magnetic resonance imaging," "normal pressure," "Parkinson's disease," and "shunting." Moreover, all reference lists from the retrieved articles were reviewed to identify any additional pertinent articles. RESULTS The literature search retrieved 19 studies in which DTI was used for the identification and differentiation of iNPH from other neurodegenerative diseases. The DTI protocols involved different approaches, such as region of interest (ROI) methods, tract-based spatial statistics, voxel-based analysis, and delta-ADC analysis. The most studied anatomical regions were the periventricular WM areas, such as the internal capsule (IC), the corticospinal tract (CST), and the corpus callosum (CC). Patients with iNPH had significantly higher MD in the periventricular WM areas of the CST and the CC than had healthy controls. In addition, FA and ADCs were significantly higher in the CST of iNPH patients than in any other patients with other neurodegenerative diseases. Gait abnormalities of iNPH patients were statistically significantly and negatively correlated with FA in the CST and the minor forceps. Fractional anisotropy had a sensitivity of 94% and a specificity of 80% for diagnosing iNPH. Furthermore, FA and MD values in the CST, the IC, the anterior thalamic region, the fornix, and the hippocampus regions could help differentiate iNPH from Alzheimer or Parkinson disease. Interestingly, CSF drainage or ventriculoperitoneal shunting significantly modified FA and ADCs in iNPH patients whose condition clinically responded to these maneuvers. CONCLUSIONS Measurements of FA and MD significantly contribute to the detection of axonal loss and gliosis in the periventricular WM areas in patients with iNPH. Diffusion tensor imaging may also represent a valuable noninvasive method for differentiating iNPH from other neurodegenerative diseases. Moreover, DTI can detect dynamic changes in the WM tracts after lumbar drainage or shunting procedures and could help identify iNPH patients who may benefit from surgical intervention.

APPLICATION OF A NOVEL QUANTITATIVE TRACTOGRAPHY-BASED ANALYSIS OF DIFFUSION TENSOR IMAGING TO EXAMINE FIBER BUNDLE LENGTH IN HUMAN CEREBRAL WHITE MATTER

This paper reviews basic methods and recent applications of length-based fiber bundle analysis of cerebral white matter using diffusion magnetic resonance imaging (dMRI). Diffusion weighted imaging (DWI) is a dMRI technique that uses the random motion of water to probe tissue microstructure in the brain. Diffusion tensor imaging (DTI) is an extension of DWI that measures the magnitude and direction of water diffusion in cerebral white matter, using either voxel-based scalar metrics or tractography-based analyses. More recently, quantitative tractography based on diffusion tensor imaging (qtDTI) technology has been developed to help quantify aggregate structural anatomical properties of white matter fiber bundles, including both scalar metrics of bundle diffusion and more complex morphometric properties, such as fiber bundle length (FBL). Unlike traditional scalar diffusion metrics, FBL reflects the direction and curvature of white matter pathways coursing through the brain and is sensitive to changes within the entire tractography model. In this paper, we discuss applications of this approach to date that have provided new insights into brain organization and function. We also discuss opportunities for improving the methodology through more complex anatomical models and potential areas of new application for qtDTI.

Age-Related Modifications of Diffusion Tensor Imaging Parameters and White Matter Hyperintensities as Inter-Dependent Processes

Microstructural changes of White Matter (WM) associated with aging have been widely described through Diffusion Tensor Imaging (DTI) parameters. In parallel, White Matter Hyperintensities (WMH) as observed on a T2-weighted MRI are extremely common in older individuals. However, few studies have investigated both phenomena conjointly. The present study investigates aging effects on DTI parameters in absence and in presence of WMH. Diffusion maps were constructed based on 21 directions DTI scans of young adults (n = 19, mean age = 33 SD = 7.4) and two age-matched groups of older adults, one presenting low-level-WMH (n = 20, mean age = 78, SD = 3.2) and one presenting high-level-WMH (n = 20, mean age = 79, SD = 5.4). Older subjects with low-level-WMH presented modifications of DTI parameters in comparison to younger subjects, fitting with the DTI pattern classically described in aging, i.e., Fractional Anisotropy (FA) decrease/Radial Diffusivity (RD) increase. Furthermore, older subjects with high-level-WMH showed higher DTI modifications in Normal Appearing White Matter (NAWM) in comparison to those with low-level-WMH. Finally, in older subjects with high-level-WMH, FA, and RD values of NAWM were associated with to WMH burden. Therefore, our findings suggest that DTI modifications and the presence of WMH would be two inter-dependent processes but occurring within different temporal windows. DTI changes would reflect the early phase of white matter changes and WMH would appear as a consequence of those changes.

Neuroimaging criteria and cognitive performance in vascular mild cognitive impairment: A systematic review

The recognition of Cerebrovascular Disease (CVD) at earlier clinical stages may favor the control of vascular risk factors and prevention of dementia. However, operational criteria for symptomatic phases at non-dementia stages are often difficult, as the current criteria normally require the evidence of extensive subcortical disease.

MRI correlates of general intelligence in neurotypical adults

There is growing interest in the neurobiological substrate of general intelligence. Psychometric estimates of general intelligence are reduced in a range of neurological disorders, leading to practical application as sensitive, but non-specific, markers of cerebral disorder. This study examined estimates of general intelligence in neurotypical adults using diffusion tensor imaging and resting-state functional connectivity analysis. General intelligence was related to white matter organisation across multiple brain regions, confirming previous work in older healthy adults. We also found that variation in general intelligence was related to a large functional sub-network involving all cortical lobes of the brain. These findings confirm that individual variance in general intelligence is related to diffusely represented brain networks.

Brain white matter structure and information processing speed in healthy older age

Cognitive decline, especially the slowing of information processing speed, is associated with normal ageing. This decline may be due to brain cortico-cortical disconnection caused by age-related white matter deterioration. We present results from a large, narrow age range cohort of generally healthy, community-dwelling subjects in their seventies who also had their cognitive ability tested in youth (age 11 years). We investigate associations between older age brain white matter structure, several measures of information processing speed and childhood cognitive ability in 581 subjects. Analysis of diffusion tensor MRI data using Tract-based Spatial Statistics (TBSS) showed that all measures of information processing speed, as well as a general speed factor composed from these tests (g_speed), were significantly associated with fractional anisotropy (FA) across the white matter skeleton rather than in specific tracts. Cognitive ability measured at age 11 years was not associated with older age white matter FA, except for the g_speed-independent components of several individual processing speed tests. These results indicate that quicker and more efficient information processing requires global connectivity in older age, and that associations between white matter FA and information processing speed (both individual test scores and g_speed), unlike some other aspects of later life brain structure, are generally not accounted for by cognitive ability measured in youth.

Classifying dementia using local binary patterns from different regions in magnetic resonance images

Dementia is an evolving challenge in society, and no disease-modifying treatment exists. Diagnosis can be demanding and MR imaging may aid as a noninvasive method to increase prediction accuracy. We explored the use of 2D local binary pattern (LBP) extracted from FLAIR and T1 MR images of the brain combined with a Random Forest classifier in an attempt to discern patients with Alzheimer's disease (AD), Lewy body dementia (LBD), and normal controls (NC). Analysis was conducted in areas with white matter lesions (WML) and all of white matter (WM). Results from 10-fold nested cross validation are reported as mean accuracy, precision, and recall with standard deviation in brackets. The best result we achieved was in the two-class problem NC versus AD + LBD with total accuracy of 0.98 (0.04). In the three-class problem AD versus LBD versus NC and the two-class problem AD versus LBD, we achieved 0.87 (0.08) and 0.74 (0.16), respectively. The performance using 3DT1 images was notably better than when using FLAIR images. The results from the WM region gave similar results as in the WML region. Our study demonstrates that LBP texture analysis in brain MR images can be successfully used for computer based dementia diagnosis.

Diffuse white matter tract abnormalities in clinically normal ageing retired athletes with a history of sports-related concussions

Sports-related concussions have been shown to lead to persistent subclinical anomalies of the motor and cognitive systems in young asymptomatic athletes. In advancing age, these latent alterations correlate with detectable motor and cognitive function decline. Until now, the interacting effects of concussions and the normal ageing process on white matter tract integrity remain unknown. Here we used a tract-based spatial statistical method to uncover potential white matter tissue damage in 15 retired athletes with a history of concussions, free of comorbid medical conditions. We also investigated potential associations between white matter integrity and declines in cognitive and motor functions. Compared to an age- and education-matched control group of 15 retired athletes without concussions, former athletes with concussions exhibited widespread white matter anomalies along many major association, interhemispheric, and projection tracts. Group contrasts revealed decreases in fractional anisotropy, as well as increases in mean and radial diffusivity measures in the concussed group. These differences were primarily apparent in fronto-parietal networks as well as in the frontal aspect of the corpus callosum. The white matter anomalies uncovered in concussed athletes were significantly associated with a decline in episodic memory and lateral ventricle expansion. Finally, the expected association between frontal white matter integrity and motor learning found in former non-concussed athletes was absent in concussed participants. Together, these results show that advancing age in retired athletes presenting with a history of sports-related concussions is linked to diffuse white matter abnormalities that are consistent with the effects of traumatic axonal injury and exacerbated demyelination. These changes in white matter integrity might explain the cognitive and motor function declines documented in this population.

Prevalence of depression among memory clinic patients as measured by the Cornell Scale of Depression in Dementia

OBJECTIVES

Depression in dementia is common, but the prevalence rates differ according to the populations studied and which diagnostic tools are being used. The aim of this study is to explore the prevalence of depression among patients referred to a memory clinic or an outpatient clinic as measured by the Cornell Scale of Depression in dementia (CSDD) and to investigate which factors are associated with depression.

METHOD

The CSDD was completed for 1470 patients on their first visit to a memory clinic or an outpatient clinic. The prevalence of depression using three different cut-off points was calculated. Logistic regression and correlation analyses were performed.

RESULTS

Half of the patients had dementia. The mean CSDD was 6.7 (SD: 5.3) for the whole group, and 50.2% had a score above 5, whereas 37.5% had depression defined as a CSDD score above 7, and 14.1% had a score above 12. The mean scores were higher among those with dementia other than Alzheimer's disease, those with previous depression, and those with greater impairment in the activities of daily living (ADL). In the logistic regression analyses, younger age, ADL dysfunction, and previous depression were significantly associated with higher CSDD scores.

CONCLUSION

We found that depressive symptoms are common among patients referred for a dementia assessment in specialist health care. The strongest factors associated with depressive symptoms were younger age, ADL impairment, and previous depression.

Frontal white matter alterations are associated with executive cognitive function in euthymic bipolar patients

BACKGROUND

Bipolar affective disorder (BD) is often associated with cognitive dysfunction in executive domains. However the biological underpinnings of cognitive deficits in BD are not sufficiently understood. A growing body of evidence indicates a loss of microstructural integrity in various white matter (WM) fiber tracts in BD. The aim of the current study was to assess potential links between WM structural abnormalities and cognitive performance in euthymic middle-aged BD patients (n=30) and matched healthy controls (n=32).

METHODS

Diffusion tensor imaging (DTI) data was carried out with both voxelwise (tract based spatial statistics, TBSS) and region-of-interest (ROI) based analysis. We compared multiple indices of diffusion including fractional anisotropy (FA), radial (DR), axial (DA) and mean diffusivities (MD).

RESULTS

Increased mean diffusivity was found in the fornix, anterior thalamic radiation, splenium and the truncus of the corpus callosum in BD patients compared with controls. These diffusion changes were significantly associated with poorer performance in executive tasks in BD patients.

CONCLUSIONS

Our results indicate a direct link between executive cognitive functioning and abnormal WM microstructural integrity of fronto-limbic tracts in remitted BD patients, and add evidence to the neuronal disruption that underlies the residual symptomatology of BD.

Central nervous system imaging in diabetic cerebrovascular diseases and white matter hyperintensities

Diabetes mellitus is an important vascular risk factor for cerebrovascular disease. This occurs through pathophysiologic changes to the microcirculation as arteriolosclerosis and to the macrocirculation as large artery atherosclerosis. Imaging techniques can provide detailed visualization of the cerebrovasculature using CT (computed tomography) angiography and MR (magnetic resonance) angiography. Newer techniques focused on advanced parenchymal imaging include CT perfusion, quantitative MRI, and diffusion tensor imaging; each identifies brain lesion burden due to diabetes mellitus. These imaging approaches have provided insights into the diabetes mellitus brain and cerebral circulation pathophysiology. Imaging has taught us that diabetics develop cerebral atrophy, silent infarcts, and white matter disease more rapidly than other patient populations. Longitudinal studies are needed to quantify the rate and extent of such structural brain and blood vessel changes and how they relate to cognitive decline. Diabetes prevention and treatment strategies will then be possible to slow the development of such changes.

DTI tractography and white matter fiber tract characteristics in euthymic bipolar I patients and healthy control subjects

With the introduction of diffusion tensor imaging (DTI), structural differences in white matter (WM) architecture between psychiatric populations and healthy controls can be systematically observed and measured. In particular, DTI-tractography can be used to assess WM characteristics over the entire extent of WM tracts and aggregated fiber bundles. Using 64-direction DTI scanning in 27 participants with bipolar disorder (BD) and 26 age-and-gender-matched healthy control subjects, we compared relative length, density, and fractional anisotrophy (FA) of WM tracts involved in emotion regulation or theorized to be important neural components in BD neuropathology. We interactively isolated 22 known white matter tracts using region-of-interest placement (TrackVis software program) and then computed relative tract length, density, and integrity. BD subjects demonstrated significantly shorter WM tracts in the genu, body and splenium of the corpus callosum compared to healthy controls. Additionally, bipolar subjects exhibited reduced fiber density in the genu and body of the corpus callosum, and in the inferior longitudinal fasciculus bilaterally. In the left uncinate fasciculus, however, BD subjects exhibited significantly greater fiber density than healthy controls. There were no significant differences between groups in WM tract FA for those tracts that began and ended in the brain. The significance of differences in tract length and fiber density in BD is discussed.

Disconnected aging: cerebral white matter integrity and age-related differences in cognition

Cognition arises as a result of coordinated processing among distributed brain regions and disruptions to communication within these neural networks can result in cognitive dysfunction. Cortical disconnection may thus contribute to the declines in some aspects of cognitive functioning observed in healthy aging. Diffusion tensor imaging (DTI) is ideally suited for the study of cortical disconnection as it provides indices of structural integrity within interconnected neural networks. The current review summarizes results of previous DTI aging research with the aim of identifying consistent patterns of age-related differences in white matter integrity, and of relationships between measures of white matter integrity and behavioral performance as a function of adult age. We outline a number of future directions that will broaden our current understanding of these brain-behavior relationships in aging. Specifically, future research should aim to (1) investigate multiple models of age-brain-behavior relationships; (2) determine the tract-specificity versus global effect of aging on white matter integrity; (3) assess the relative contribution of normal variation in white matter integrity versus white matter lesions to age-related differences in cognition; (4) improve the definition of specific aspects of cognitive functioning related to age-related differences in white matter integrity using information processing tasks; and (5) combine multiple imaging modalities (e.g., resting-state and task-related functional magnetic resonance imaging; fMRI) with DTI to clarify the role of cerebral white matter integrity in cognitive aging.

Processing speed in normal aging: effects of white matter hyperintensities and hippocampal volume loss

Changes in cognitive functioning are said to be part of normal aging. Quantitative MRI has made it possible to measure structural brain changes during aging which may underlie these decrements which include slowed information processing and memory loss. Much has been written on white matter hyperintensities (WMH), which are associated with cognitive deficits on tasks requiring processing speed and executive functioning, and hippocampal volume loss, which is associated with memory decline. Here we examine volumetric MRI measures of WMH and hippocampal volume loss together in relation to neuropsychological tests considered to be measures of executive functioning and processing speed in 81 non-demented elderly individuals, aged 75-90. Correlational analysis showed that when controlling for age, both greater WMH volume and smaller hippocampal volume were correlated with slower performances on most tests with the exception of a battery of continuous performance tests in which only WMH was correlated with slower reaction time (RT). We then performed a series of hierarchical multiple regression analyses to examine the independent contributions of greater WMH volume and reduced hippocampal volume to executive functioning and processing speed. The results showed that for the four measures requiring executive functioning and speed of processing, WMH volume and hippocampal volume combined predicted between 21.4% and 37% of the explained variance. These results suggest that WM integrity and hippocampal volume influence cognitive decline independently on tasks involving processing speed and executive function independent of age.

Vascular disease and dementias: paradigm shifts to drive research in new directions

Vascular disease was once considered the principal cause of aging-related dementia. More recently, however, research emphasis has shifted to studies of progressive neurodegenerative disease processes, such as those giving rise to neuritic plaques, neurofibrillary tangles, and Lewy bodies. Although these studies have led to critical insights and potential therapeutic strategies, interest in the role of systemic and cerebrovascular disease mechanisms waned and has received relatively less attention and research support. Recent studies suggest that vascular disease mechanisms play an important role in the risk for aging-related cognitive decline and disorders. Vascular disease frequently coexists with cognitive decline in aging individuals, shares many risk factors with dementias considered to be of the "Alzheimer type," and is observed more frequently than expected in postmortem material from individuals manifesting "specific" disease stigmata, such as abundant plaques and tangles. Considerable difficulties have emerged in attempting to classify dementias as being related to vascular versus neurodegenerative causes, and several systems of criteria have been used. Despite multiple attempts, a lack of consensus remains regarding the optimal means of incorporating vascular disease into clinical diagnostic, neurocognitive, or neuropathologic classification schemes for dementias. We propose here an integrative, rather than a strictly taxonomic, approach to the study and elucidation of how vascular disease mechanisms contribute to the development of dementias. We argue that, instead of discriminating between, for example, "Alzheimer's disease," "vascular dementia," and other diseases, there is a greater need to focus clinical and research efforts on elucidating specific pathophysiologic mechanisms that contribute to dementia phenotypes and neuropathologic outcomes. We outline a multitiered strategy, beginning with clinical and public health interventions that can be implemented immediately, enhancements to ongoing longitudinal studies to increase their informative value, and new initiatives to capitalize on recent advances in systems biology and network medicine. This strategy will require funding from multiple public and private sources to support collaborative and interdisciplinary research efforts to take full advantage of these opportunities and realize their societal benefits.

Testing the white matter retrogenesis hypothesis of cognitive aging

The retrogenesis hypothesis postulates that late-myelinated white matter fibers are most vulnerable to age- and disease-related degeneration, which in turn mediate cognitive decline. While recent evidence supports this hypothesis in the context of Alzheimer's disease, it has not been tested systematically in normal cognitive aging. In the current study, we examined the retrogenesis hypothesis in a group (n = 282) of cognitively normal individuals, ranging in age from 7 to 87 years, from the Brain Resource International Database. Participants were evaluated with a comprehensive neuropsychological battery and were imaged with diffusion tensor imaging. Fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (DA), measures of white matter coherence, were computed in 2 prototypical early-myelinated fiber tracts (posterior limb of the internal capsule, cerebral peduncles) and 2 prototypical late-myelinated fiber tracts (superior longitudinal fasciculus, inferior longitudinal fasciculus) chosen to parallel previous studies; mean summary values were also computed for other early- and late-myelinated fiber tracts. We examined age-associated differences in FA, RD, and DA in the developmental trajectory (ages 7-30 years) and degenerative trajectory (ages 31-87 years), and tested whether the measures of white matter coherence mediated age-related cognitive decline in the older group. FA and DA values were greater for early-myelinated fibers than for late-myelinated fibers, and RD values were lower for early-myelinated than late-myelinated fibers. There were age-associated differences in FA, RD, and DA across early- and late-myelinated fiber tracts in the younger group, but the magnitude of differences did not vary as a function of early or late myelinating status. FA and RD in most fiber tracts showed reliable age-associated differences in the older age group, but the magnitudes were greatest for the late-myelinated tract summary measure, inferior longitudinal fasciculus (late fiber tract), and cerebral peduncles (early fiber tract). Finally, FA in the inferior longitudinal fasciculus and cerebral peduncles and RD in the cerebral peduncles mediated age-associated differences in an executive functioning factor. Taken together, the findings highlight the importance of white matter coherence in cognitive aging and provide some, but not complete, support for the white matter retrogenesis hypothesis in normal cognitive aging.

Factors associated with a depressive disorder in Alzheimer's disease are different from those found for other dementia disorders

Background

This study explores factors associated with depression in Alzheimer's disease (AD) compared with mild cognitive impairment (MCI) and other dementia disorders.

Method

In a prospective study we included 195 patients: 31 with MCI, 112 with AD and 52 with other dementias.

Results

According to the ICD-10 and the DSM-IV criteria, 88 (44.1%) and 59 (30.3%), respectively, had a depressive disorder. An adjusted multiple regression analysis showed that previous depression (p < 0.05) was significantly associated with depression in AD patients. Severity of dementia (p < 0.05) was significantly associated with a depressive disorder in a group of patients with frontotemporal dementia, vascular dementia, or dementia due to Lewy Body disease or Parkinson's disease.

Conclusion

We found different factors associated with a depressive disorder in AD compared to those found for other dementia disorders.

Robust white matter lesion segmentation in FLAIR MRI

This paper discusses a white matter lesion (WML) segmentation scheme for fluid attenuation inversion recovery (FLAIR) MRI. The method computes the volume of lesions with subvoxel precision by accounting for the partial volume averaging (PVA) artifact. As WMLs are related to stroke and carotid disease, accurate volume measurements are most important. Manual volume computation is laborious, subjective, time consuming, and error prone. Automated methods are a nice alternative since they quantify WML volumes in an objective, efficient, and reliable manner. PVA is initially modeled with a localized edge strength measure since PVA resides in the boundaries between tissues. This map is computed in 3-D and is transformed to a global representation to increase robustness to noise. Significant edges correspond to PVA voxels, which are used to find the PVA fraction α (amount of each tissue present in mixture voxels). Results on simulated and real FLAIR images show high WML segmentation performance compared to ground truth (98.9% and 83% overlap, respectively), which outperforms other methods. Lesion load studies are included that automatically analyze WML volumes for each brain hemisphere separately. This technique does not require any distributional assumptions/parameters or training samples and is applied on a single MR modality, which is a major advantage compared to the traditional methods.

Diffusion tensor imaging reveals supplementary lesions to frontal white matter in idiopathic normal pressure hydrocephalus

BACKGROUND

Idiopathic normal-pressure hydrocephalus (INPH) is associated with white matter lesions, but the extent and severity of the lesions do not cohere with symptoms or improvement after shunting, implying the presence of further, yet undisclosed, injuries to white matter in INPH.

OBJECTIVE

To apply diffusion tensor imaging (DTI) to explore white matter lesions in patients with INPH before and after drainage of cerebrospinal fluid (CSF).

METHODS

Eighteen patients and 10 controls were included. DTI was performed in a 1.5T MRI scanner before and after 3-day drainage of 400 mL of CSF. Regions of interest included corpus callosum, capsula interna, frontal and lateral periventricular white matter, and centrum semiovale. White matter integrity was quantified by assessing fractional anisotropies (FA) and apparent diffusion coefficients (ADC), comparing them between patients and controls and between patients before and after drainage. The significance level corresponded to .05 (Bonferroni corrected).

RESULTS

Decreased FA in patients was found in 3 regions (P<.002, P<.001, and P<.001) in anterior frontal white matter, whereas elevated ADC was found in genu corpus callosum (P<.001) and areas of centrum semiovale associated with the precentral gyri (P<.002). Diffusion patterns in these areas did not change after drainage.

CONCLUSION

DTI reveals subtle injuries-interpreted as axonal loss and gliosis-to anterior frontal white matter where high-order motor systems between frontal cortex and basal ganglia travel, further supporting the notion that motor symptoms in INPH are caused by a chronic ischemia to the neuronal systems involved in the planning processes of movements.

Granulocyte-colony stimulating factor (G-CSF) in stroke patients with concomitant vascular disease--a randomized controlled trial

Background

G-CSF has been shown in animal models of stroke to promote functional and structural regeneration of the central nervous system. It thus might present a therapy to promote recovery in the chronic stage after stroke.

Methods

Here, we assessed the safety and tolerability of G-CSF in chronic stroke patients with concomitant vascular disease, and explored efficacy data. 41 patients were studied in a double-blind, randomized approach to either receive 10 days of G-CSF (10 µg/kg body weight/day), or placebo. Main inclusion criteria were an ischemic infarct >4 months prior to inclusion, and white matter hyperintensities on MRI. Primary endpoint was number of adverse events. We also explored changes in hand motor function for activities of daily living, motor and verbal learning, and finger tapping speed, over the course of the study.

Results

Adverse events (AEs) were more frequent in the G-CSF group, but were generally graded mild or moderate and from the known side-effect spectrum of G-CSF. Leukocyte count rose after day 2 of G-CSF dosing, reached a maximum on day 8 (mean 42/nl), and returned to baseline 1 week after treatment cessation. No significant effect of treatment was detected for the primary efficacy endpoint, the test of hand motor function.

Conclusions

These results demonstrate the feasibility, safety and reasonable tolerability of subcutaneous G-CSF in chronic stroke patients. This study thus provides the basis to explore the efficacy of G-CSF in improving chronic stroke-related deficits.

Trial Registration

ClinicalTrials.gov NCT00298597

Diffusion abnormality of corpus callosum in Alzheimer's disease

This study investigated diffusion abnormalities in the parts of corpus callosum (CC) of patients with Alzheimer's disease (AD) using diffusion tensor magnetic resonance imaging (DT-MRI). Twenty-one patients with AD and 20 healthy volunteers participated in the study. MRI was performed with a 1.5 T system. Conventional MR images and diffusion tensor images were obtained for all participants. We divided the CC into three parts as rostrum, body and splenium. The apparent diffusion coefficiency (ADC) and fractional anisotropy (FA) were measured in all parts. FA values for the CC were lower in AD patients than the values of controls. In AD patients the lowest values were found in the rostrum of the CC and CC body FA values were also lower than the splenium, but the difference did not reach statistical significance. DT-MRI is a promising technique to investigate microstructural changes in white matter regions in AD. Early detection of the disease has been increasingly studied in AD. Further studies with larger populations are needed to confirm the role of diffusion tensor imaging in the evaluation of memory impairment.

Edge-based partial volume averaging estimation for FLAIR MRI with white matter lesions

Through the combination of intensity and fuzzy edge strength measures, a new partial volume averaging (PVA) quantification technique for FLAIR MRI with white matter lesions (WML) is developed. It is focused on an edge-based approach, which "probes" for PVA voxels via a global estimate for the change in the proportion of tissues α'. This estimate is refined according to a probabilistic threshold, and the result is decoded to find the proportion of tissues fraction α - the percentage of one tissue found in a mixture voxel. The results from several images are shown illustrating how the technique may be used to segment PVA and pure tissue classes. The result is a non-model based approach to the detection and quantification of PVA.

Influence of white matter hyperintensities on the cognition of patients with Parkinson disease

BACKGROUND

White matter hyperintensities (WMH) have been associated with cognitive impairment in elderly persons and in patients with Alzheimer disease. However, the role of WMH in Parkinson disease (PD) dementia remains to be elucidated.

METHODS

The cohort for this study comprised 71 consecutive patients with PD, all of whom completed a clinical assessment, neuropsychologic investigation, and magnetic resonance imaging of brain. WMH were rated using the semiquantitative visual rating system proposed by Scheltens et al.

RESULTS

The PD dementia group had significantly more WMH than the PD without dementia group in the evaluated brain regions except for the infratentorial area. The WMH showed a significant correlation with age, Unified Parkinson's Disease Rating Scale, Mini-Mental State Examination, sum of the box of Clinical Dementia Rating, and many of the cognitive domains. The linear regression model showed that the WMH was independently associated with cognitive impairment in patients with PD, regardless of age, sex, duration or severity of PD symptoms, and vascular risk factors.

CONCLUSIONS

These findings confirm that WMH might be associated with cognitive decline in patients with PD, regardless of age, sex, education status, duration or severity of PD symptoms, and vascular risk factors. This result suggests that other nonvascular factors contribute to the progression of dementia in patients with PD.

The role of diffusion tensor imaging in the study of cognitive aging

This chapter gives an overview of the role that diffusion tensor MRI (DTI) can play in the study of cognitive decline that is associated with advancing age. A brief overview of biological injury processes that impinge on the aging brain is provided, and their overall effect on the integrity of neural architecture is described. Cognitive decline associated with aging, and white matter connectivity degradation as a biological substrate for that decline, is then described. We then briefly describe the technology of DTI as a means for in vivo, non-invasive interrogation of white matter connectivity, and relate it to FLAIR, a more traditional MRI method for assessing white matter injury. We then survey the existing findings on relationships between aging-associated neuropathological processes and DTI measurements on one hand; and relationships between DTI measurements and late-life cognitive function on the other. We conclude with a summary of current research directions in relation to DTI studies of cognitive aging.

MR diffusion tensor imaging: a window into white matter integrity of the working brain

As Norman Geschwind asserted in 1965, syndromes resulting from white matter lesions could produce deficits in higher-order functions and "disconnexion" or the interruption of connection between gray matter regions could be as disruptive as trauma to those regions per se. The advent of in vivo diffusion tensor imaging, which allows quantitative characterization of white matter fiber integrity in health and disease, has served to strengthen Geschwind's proposal. Here we present an overview of the principles of diffusion tensor imaging (DTI) and its contribution to progress in our current understanding of normal and pathological brain function.

The Relationship between age, injury severity, and MRI findings after traumatic brain injury

Age and injury severity are among the most significant predictors of outcome after traumatic brain injury (TBI). However, only a few studies have investigated the association between, age, injury severity, and the extent of brain damage in TBI. The purpose of this study was to investigate the association between age, measures of injury severity, and brain lesion volumes, as well as viable brain volumes, following TBI. Ninety-eight individuals with mild to very severe TBI (75.5% male, mean age at injury 34.5 years) underwent a structural MRI scan, performed with a 1.5-Tesla machine, on average 2.3 years post-injury. Lesion volumes were highly skewed in their distribution and were dichotomized for statistical purposes. Measures of injury severity were Glasgow Coma Scale score (GCS) and duration of post-traumatic amnesia (PTA). Logistic regression analyses predicting lesion volumes, controlling for participants' gender, cause of injury, time from injury to MRI scan, and total brain volume, revealed that both older age and longer PTA were associated with larger lesion volumes in both grey and white matter in almost all brain regions. Older age was also associated with smaller viable grey matter volumes in most neo-cortical brain regions, while longer PTA was associated with smaller viable white matter volumes in most brain regions. The results suggest that older age worsens the impact of TBI on the brain. They also indicate the validity of duration of PTA as a measure of injury severity that is not just related to one particular injury location.

Cerebral white matter integrity and cognitive aging: contributions from diffusion tensor imaging

The integrity of cerebral white matter is critical for efficient cognitive functioning, but little is known regarding the role of white matter integrity in age-related differences in cognition. Diffusion tensor imaging (DTI) measures the directional displacement of molecular water and as a result can characterize the properties of white matter that combine to restrict diffusivity in a spatially coherent manner. This review considers DTI studies of aging and their implications for understanding adult age differences in cognitive performance. Decline in white matter integrity contributes to a disconnection among distributed neural systems, with a consistent effect on perceptual speed and executive functioning. The relation between white matter integrity and cognition varies across brain regions, with some evidence suggesting that age-related effects exhibit an anterior-posterior gradient. With continued improvements in spatial resolution and integration with functional brain imaging, DTI holds considerable promise, both for theories of cognitive aging and for translational application.

Peripheral arterial disease and cognitive function

As a marker of generalized atherosclerosis, peripheral arterial disease (PAD) has implications not only for the affected lower extremity but also to overall cardiovascular health. It confers an increased risk of non-fatal and fatal vascular events which increases with the severity of the disease. Patient-based studies have shown that individuals with advanced PAD tend to perform poorly on cognitive tests compared to controls. In population studies, PAD is associated with an increased cognitive decline independently of previous cerebrovascular disease and cardiovascular risk factors. A low ankle-brachial index (ABI) may be an early predictor of cognitive decline and of potential value in identifying individuals at increased risk of cognitive impairment. In patients with PAD, secondary preventive measures directed at decreasing the long-term systemic vascular complications may also be important to the preservation of cognitive health. However, evidence suggests that PAD patients may be undertreated with regard to atherosclerotic risk factors, as demonstrated by an undue emphasis on symptom relief rather than essential risk factor reduction. More research needs to be carried out to determine the predictors of cognitive function in PAD patients, whether subtle cognitive disturbances are related to activities of daily living, including medical treatment compliance, and whether neuroprotective strategies and atherosclerotic risk factor control positively influence cognitive function in these high-risk patients.

Aging of cerebral white matter: a review of MRI findings

BACKGROUND

Cerebral aging is a complex and heterogeneous process that is associated with a high degree of inter-individual variability. Structural magnetic resonance imaging (MRI) can be used to identify and quantify non-disease-related aging of the cerebral white matter.

METHODS

The present article reviews the findings from several MRI techniques, including morphometric approaches, study of white matter hyperintensities, diffusion tensor imaging, and magnetization transfer imaging, that have been used to examine aging of the cerebral white matter. Furthermore, the relationship of MRI indices of white matter integrity to age-related cognitive declines is reported.

RESULTS

A general pattern of age-related preservation and decline emerges indicating that the prefrontal white matter is most susceptible to the influence of age. Studies that combine MRI with cognitive measures suggest that such age-related reductions in white matter integrity may produce a disconnection state that underlies some of the age-related performance declines in age-sensitive cognitive domains.

CONCLUSIONS

White matter aging may contribute to a disconnection state that is associated with declines in episodic memory, executive functions, and information processing speed.

Neuroradiological characterization of normal adult ageing

This paper provides a review of MRI and diffusion tensor imaging (DTI) findings in normal ageing as an essential context for evaluating imaging in dementia, and adding to the ever-growing number of such overviews. An additional extensive literature details the physics, MR acquisition, image reconstruction and mathematical computation approaches to both imaging modalities. The aim of this review is to illustrate how MR imaging modalities, spanning structural and diffusion tensor imaging, are suitable for visualizing and quantifying the macrostructural and microstructural disruptions sustained by the brain in normal ageing and to recognize the importance of normative data for identifying abnormalities characterizing neurodegenerative diseases and other conditions affecting brain tissue integrity.

fMRI activation during episodic encoding and metacognitive appraisal across the lifespan: risk factors for Alzheimer's disease

In the present study, we used fMRI to examine the influence of age on two other known risk factors for Alzheimer's disease (AD), APOE genotype and parental history of AD (FH status), during episodic encoding (ENC) and metacognitive self-appraisal (SA) paradigms. These paradigms have previously been shown to evoke activity from brain regions that are implicated in AD. First we examined the effect of age across the adult lifespan (age 18-84 years) on cerebral activity in a large sample (n=231) of cognitively healthy individuals. Next we examined a subset (n=155) on whom APOE status and FH status were known. For ENC, we found that increasing age was associated with reduced activity in the ventral temporal lobes and hippocampus. Our analysis of risk factors suggested that FH and age exerted independent effects, but APOE interacted with age such that APOE e4 carriers exhibit age-related increases in activity in the hippocampus. For the metacognitive SA task, increasing age was found to be associated with reduced activity in the medial prefrontal cortex, and increased activity in the mesial temporal lobe, posterior orbital cortex and striatum. Neither AD risk factor significantly modified age-related changes in brain activity during SA. These results suggest that FH and aging are exerting independent effects in both tasks while APOE affected the relationship with age in the hippocampus in one of the two tasks given.

Growing old with epilepsy: the neglected issue of cognitive and brain health in aging and elder persons with chronic epilepsy

The purpose of this review is to examine what is known about cognitive and brain aging in elders with chronic epilepsy. We contend that much remains to be learned about the ultimate course of cognition and brain structure in persons with chronic epilepsy and concern appears warranted. Individuals with chronic epilepsy are exposed to many risk factors demonstrated to be associated with abnormal cognitive and brain aging in the general population, with many of these risk factors present in persons with chronic epilepsy as early as midlife. We suggest that a research agenda be developed to systematically identify and treat known modifiable risk factors in order to protect and promote cognitive and brain health in aging and elder persons with chronic epilepsy.