Distribution of cerebral atrophy assessed by magnetic resonance imaging reflects patterns of neuropsychological deficits in Alzheimer's dementia

Medial Temporal Lobe Atrophy is Related to Learning Strategy Changes in Amnestic Mild Cognitive Impairment

OBJECTIVE

Deficits in the semantic learning strategy were observed in subjects with amnestic mild cognitive impairment (aMCI) in our previous study. In the present study, we explored the contributions of executive function and brain structure changes to the decline in the semantic learning strategy in aMCI.

METHODS

A neuropsychological battery was used to test memory and executive function in 96 aMCI subjects and 90 age- and gender-matched healthy controls (HCs). The semantic clustering ratio on the verbal learning test was calculated to evaluate learning strategy. Medial temporal lobe atrophy (MTA) and white matter hyperintensities (WMH) were measured on MRI with the MTA and Fazekas visual rating scales, respectively.

RESULTS

Compared to HCs, aMCI subjects had poorer performance in terms of memory, executive function, and the semantic clustering ratio (P < .001). In aMCI subjects, no significant correlation between learning strategy and executive function was observed. aMCI subjects with obvious MTA demonstrated a lower semantic clustering ratio than those without MTA (P < .001). There was no significant difference in the learning strategies between subjects with high-grade WMH and subjects with low-grade WMH.

CONCLUSION

aMCI subjects showed obvious impairment in the semantic learning strategy, which was attributable to MTA but independent of executive dysfunction and subcortical WMH. These findings need to be further validated in large cohorts with biomarkers identified using volumetric brain measurements. (JINS, 2019, 25, 706-717).

A new age-related cutoff of medial temporal atrophy scale on MRI improving the diagnostic accuracy of neurodegeneration due to Alzheimer's disease in a Chinese population

Background

Visual rating scales are still the most popular tools in assessing atrophy degrees of whole brain and lobes. However, the false negative rate of the previous cutoff score of visual rating scales was relatively high for detecting dementia of Alzheimer’s type (DAT). This study aimed to evaluate the diagnostic value of new cutoffs of visual rating scales on magnetic resonance imaging for discriminating DAT in a Chinese population.

Methods

Out of 585 enrolled subjects, 296 participants were included and diagnosed as normal cognition (NC)(n = 87), 138 diagnosed as amnestic mild cognitive impairment (aMCI), and 71 as dementia of Alzheimer’s type (DAT). Receiver operating characteristic (ROC) curve analyses were used to calculate the diagnostic value of visual rating sales (including medial temporal atrophy (MTA), posterior atrophy rating scale (PA),global cortical atrophy scale (GCA) and medial temporal-lobe atrophy index (MTAi))for detecting NC from DAT .

Results

Scores of MTA correlated to age and Mini-mental state examination score. When used to detect DAT from NC, the MTA showed highest diagnostic value than other scales, and when the cutoff score of 1.5 of MTA scale, it obtained an optimal sensitivity (84.5%) and specificity (79.1%) respectively, with a 15.5% of false negative rate. Cutoff scores and diagnostic values were calculated stratified by age. For the age ranges 50–64, 65–74, 75–84 years, the following cut-offs of MTA should be used, ≥1.0(sensitivity and specificity were 92.3 and 68.4%), ≥1.5(sensitivity and specificity were 90.4 and 85.2%), ≥ 2.0(sensitivity and specificity were 70.8 and 82.3%) respectively. All of the scales showed relatively lower diagnostic values for discriminating aMCI from NC.

Conclusions

The new age-based MTA cutoff showed better diagnostic accuracy for detecting DAT than previous standard, the list of practical cut-offs proposed here might be useful in clinical practice.

Dissociable contributions of amygdala and hippocampus to emotion and memory in patients with Alzheimer's disease

The amygdala and the hippocampus are associated with emotional processing and declarative memory, respectively. Studies have shown that patients with bilateral hippocampal damage caused by anoxia/ischemia, and patients with probable Alzheimer's disease (AD), can experience emotions for prolonged periods of time, even when they cannot remember what caused the emotion in the first place (Feinstein et al. (2010) Proc Natl Acad Sci USA 107:7674-7679; Guzmán-Vélez et al. (2014) Cogn Behav Neurol 27:117-129). This study aimed to investigate, for the first time, the roles of the amygdala and hippocampus in the dissociation between feelings of emotion and declarative memory for emotion-inducing events in patients with AD. Individuals with probable AD (N = 12) and age-matched healthy comparisons participants (HCP; N = 12) completed a high-resolution (0.44 × 0.44 × 0.80 mm) T2-weighted structural MR scan of the medial temporal lobe. Each of these individuals also completed two separate emotion induction procedures (sadness and happiness) using film clips. We collected real-time emotion ratings at baseline and multiple times postinduction, and administered a test of declarative memory shortly after each induction. Consistent with previous research, hippocampal volume was significantly smaller in patients with AD compared with HCP, and was positively correlated with memory for the film clips. Sustained feelings of emotion and amygdala volume did not significantly differ between patients with AD and HCP. Follow-up analyses showed a significant negative correlation between amygdala volume and sustained sadness, and a significant positive correlation between amygdala volume and sustained happiness. Our findings suggest that the amygdala is important for regulating and sustaining an emotion independent of hippocampal function and declarative memory for the emotion-inducing event. © 2015 Wiley Periodicals, Inc.

Epoch-based Entropy for Early Screening of Alzheimer’s Disease

In this paper, we introduce a novel entropy measure, termed epoch-based entropy. This measure quantifies disorder of EEG signals both at the time level and spatial level, using local density estimation by a Hidden Markov Model on inter-channel stationary epochs. The investigation is led on a multi-centric EEG database recorded from patients at an early stage of Alzheimer’s disease (AD) and age-matched healthy subjects. We investigate the classification performances of this method, its robustness to noise, and its sensitivity to sampling frequency and to variations of hyperparameters. The measure is compared to two alternative complexity measures, Shannon’s entropy and correlation dimension. The classification accuracies for the discrimination of AD patients from healthy subjects were estimated using a linear classifier designed on a development dataset, and subsequently tested on an independent test set. Epoch-based entropy reached a classification accuracy of 83% on the test dataset (specificity = 83.3%, sensitivity = 82.3%), outperforming the two other complexity measures. Furthermore, it was shown to be more stable to hyperparameter variations, and less sensitive to noise and sampling frequency disturbances than the other two complexity measures.

Automated algorithm to measure changes in medial temporal lobe volume in Alzheimer disease

BACKGROUND

The change in volume of anatomic structures is as a sensitive indicator of Alzheimer disease (AD) progression. Although several methods are available to measure brain volumes, improvements in speed and automation are required. Our objective was to develop a fully automated, fast, and reliable approach to measure change in medial temporal lobe (MTL) volume, including primarily hippocampus.

METHODS

The MTL volume defined in an atlas image was propagated onto each baseline image and a level set algorithm was applied to refine the shape and smooth the boundary. The MTL of the baseline image was then mapped onto the corresponding follow-up image to measure volume change (ΔMTL). Baseline and 24 months 3D T1-weighted images from the Alzheimer Disease Neuroimaging Initiative (ADNI) were randomly selected for 50 normal elderly controls (NECs), 50 subjects with mild cognitive impairment (MCI) and 50 subjects with AD to test the algorithm. The method was compared to the FreeSurfer segmentation tools.

RESULTS

The average ΔMTL (mean±SEM) was 68±35mm(3) in NEC, 187±38mm(3) in MCI and 300±34mm(3) in the AD group and was significantly different (p<0.0001) between all three groups. The ΔMTL was correlated with cognitive decline.

COMPARISON WITH EXISTING METHOD(S)

Results for the FreeSurfer software were similar but did not detect significant differences between the MCI and AD groups.

CONCLUSION

This novel segmentation approach is fully automated and provides a robust marker of brain atrophy that shows different rates of atrophy over 2 years between NEC, MCI, and AD groups.

Association between fully automated MRI-based volumetry of different brain regions and neuropsychological test performance in patients with amnestic mild cognitive impairment and Alzheimer's disease

Fully automated magnetic resonance imaging (MRI)-based volumetry may serve as biomarker for the diagnosis in patients with mild cognitive impairment (MCI) or dementia. We aimed at investigating the relation between fully automated MRI-based volumetric measures and neuropsychological test performance in amnestic MCI and patients with mild dementia due to Alzheimer's disease (AD) in a cross-sectional and longitudinal study. In order to assess a possible prognostic value of fully automated MRI-based volumetry for future cognitive performance, the rate of change of neuropsychological test performance over time was also tested for its correlation with fully automated MRI-based volumetry at baseline. In 50 subjects, 18 with amnestic MCI, 21 with mild AD, and 11 controls, neuropsychological testing and T1-weighted MRI were performed at baseline and at a mean follow-up interval of 2.1 ± 0.5 years (n = 19). Fully automated MRI volumetry of the grey matter volume (GMV) was performed using a combined stereotactic normalisation and segmentation approach as provided by SPM8 and a set of pre-defined binary lobe masks. Left and right hippocampus masks were derived from probabilistic cytoarchitectonic maps. Volumes of the inner and outer liquor space were also determined automatically from the MRI. Pearson's test was used for the correlation analyses. Left hippocampal GMV was significantly correlated with performance in memory tasks, and left temporal GMV was related to performance in language tasks. Bilateral frontal, parietal and occipital GMVs were correlated to performance in neuropsychological tests comprising multiple domains. Rate of GMV change in the left hippocampus was correlated with decline of performance in the Boston Naming Test (BNT), Mini-Mental Status Examination, and trail making test B (TMT-B). The decrease of BNT and TMT-A performance over time correlated with the loss of grey matter in multiple brain regions. We conclude that fully automated MRI-based volumetry allows detection of regional grey matter volume loss that correlates with neuropsychological performance in patients with amnestic MCI or mild AD. Because of the high level of automation, MRI-based volumetry may easily be integrated into clinical routine to complement the current diagnostic procedure.

Hippocampal volume reduction and autobiographical memory deficits in chronic schizophrenia

Although autobiographical memory (AM) deficits and hippocampal changes are frequently found in schizophrenia, their actual association remained yet to be established. AM performance and hippocampal volume were examined in 33 older, chronic schizophrenic patients and 21 healthy volunteers matched for age, gender and education. Psychopathological symptoms and additional neuropsychological parameters were assessed by using appropriate rating scales; magnetic resonance imaging (MRI) 3-T data were analyzed via an automated region-of-interest procedure. When compared with the control subjects, patients showed significantly decreased left anterior and posterior hippocampal volumes. Episodic but not semantic AM performance was significantly lower in the patients than in the healthy controls. Both episodic and semantic AM deficits were significantly correlated with volume of the left hippocampus in the patient group. In contrast, deficits in verbal memory, working memory and remote semantic memory observed in the patients did not relate to hippocampal volume. Our findings indicate that AM deficits in chronic schizophrenia are associated with hippocampal volume reductions and underline the importance of this pathology in schizophrenia.

Association of cerebral small vessel disease with delusions in patients with Alzheimer's disease

BACKGROUND

Cerebral small vessel disease (SVD) is frequently observed in patients with Alzheimer's disease (AD). However, the association between SVD and clinical symptoms exhibited by patients with AD remains unclear. This study examined the association of SVD as observed on magnetic resonance imaging (MRI) with behavioural and psychological symptoms of dementia and cognitive function of patients with probable AD.

METHODS

A total of 163 consecutive patients (55 men, 108 women) with probable AD were included in this cross-sectional study of a prospective cohort. Patients were divided into two groups based on the presence or absence of cerebral SVD [white matter hyperintensities (WMH) grade 0/1 (Fazekas scale) and no lacunes: SVD absent, WMH grade 2/3 (Fazekas scale) or the number of lacunes ≥1: SVD present]. Cognitive functions were assessed using the Mini mental state examination, word recall and recognition subtests in the Alzheimer's Disease Assessment Scale-Cognitive Subscale, as well as the letter fluency task and the category fluency task. Psychiatric symptoms were rated according to Neuropsychiatric Inventory.

RESULTS

Patients with probable AD with cerebral SVD had significantly more delusions and depression than those without SVD. No significant differences were observed in other neuropsychiatric symptoms, MMSE or word recall and recognition tests between both groups.

CONCLUSIONS

Our results suggest that cerebral SVD observed on MRI of patients with AD is associated with delusions and depression.

Voxel and surface-based topography of memory and executive deficits in mild cognitive impairment and Alzheimer's disease

Mild cognitive impairment (MCI) and Alzheimer's disease (AD) are associated with a progressive loss of cognitive abilities. In the present report, we assessed the relationship of memory and executive function with brain structure in a sample of 810 Alzheimer's Disease Neuroimaging Initiative (ADNI) participants, including 188 AD, 396 MCI, and 226 healthy older adults (HC). Composite scores of memory (ADNI-Mem) and executive function (ADNI-Exec) were generated by applying modern psychometric theory to item-level data from ADNI's neuropsychological battery. We performed voxel-based morphometry (VBM) and surface-based association (SurfStat) analyses to evaluate relationships of ADNI-Mem and ADNI-Exec with grey matter (GM) density and cortical thickness across the whole brain in the combined sample and within diagnostic groups. We observed strong associations between ADNI-Mem and medial and lateral temporal lobe atrophy. Lower ADNI-Exec scores were associated with advanced GM and cortical atrophy across broadly distributed regions, most impressively in the bilateral parietal and temporal lobes. We also evaluated ADNI-Exec adjusted for ADNI-Mem, and found associations with GM density and cortical thickness primarily in the bilateral parietal, temporal, and frontal lobes. Within-group analyses suggest these associations are strongest in patients with MCI and AD. The present study provides insight into the spatially unbiased associations between brain atrophy and memory and executive function, and underscores the importance of structural brain changes in early cognitive decline.

Bihemispheric cerebral FDG PET correlates of cognitive dysfunction as assessed by the CERAD in Alzheimer's disease

Alzheimer's disease (AD) is characterized by a variety of cognitive deficits which can be reliably assessed by the neuropsychological test battery of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD), but the cerebral changes underlying the respective cognitive deficits are only partly understood. Measures of severity of dementia in AD as well as delayed episodic memory performance in mild cognitive impairment significantly correlated with bihemispheric cerebral glucose hypometabolism. We therefore hypothesized that the CERAD cognitive battery may represent cerebral dysfunction of both hemispheres in patients with AD. In 32 patients with AD, cerebral glucose metabolism was investigated using positron-emission-tomography with 18Fluorodeoxyglucose (FDG PET) and associated with the test scores of the CERAD cognitive battery by statistical parametric mapping. Episodic memory scores significantly correlated with temporopari etal glucose metabolism of both hemispheres while delayed episodic memory significantly was correlated with the right frontotemporal cortices. Verbal fluency and naming scores significantly correlated with glucose metabolism in left temporoparietal and right frontal cortices, whereas constructional praxis predominantly correlated significantly with the bilateral precuneus. In conclusion, the results of our study demonstrate that not only memory function but also functions of language and constructional praxis in AD are associated with glucose metabolism as revealed by FDG PET in subsets of uni- and bilateral brain areas. The findings of our study for the first time demonstrate that in AD neuropsychological deficits as assessed by the CERAD refer to different cerebral sites of both hemispheres.

The influence of 5-HTT and COMT genotypes on verbal fluency in ecstasy users

Deficits in verbal fluency associated with ecstasy use have been well established; however, the mechanisms underlying this impairment have yet to be elucidated. In this study we investigated for the first time whether there was a disproportionate impairment in two cognitive subcomponents of verbal fluency: clustering (ability to generate words within the same subcategory) and switching (ability to change the subcategory). We also investigated a possible association between ecstasy use and verbal fluency in subjects genotyped for 5-HTT (5-HTTLPR and 5-HTTVNTR) and COMT (val(108/158)met, rs165599 and rs2097603) polymorphisms, in order to find a potential implication of genetic factors. Ecstasy polydrug users (n = 30) and non-ecstasy users (n = 41) were evaluated in both semantic and phonemic fluency. Results showed that ecstasy users had poorer semantic (but not phonemic) fluency performance than controls. Detailed analysis of clustering and switching performance revealed that this impairment was associated with poorer clustering mechanisms. Clustering was also modulated by the COMT rs165599 polymorphism independently of the group. A specific effect of the 5-HTTLPR polymorphism on switching performance was also found, with ss carriers performing significantly worse than ls and ll carriers, suggesting a serotonin modulation of frontal-executive flexibility. Based on the impaired clustering and switching strategies observed in ecstasy users, it might be proposed that both semantic knowledge and retrieval are impaired in this population. The verbal fluency deficit in ecstasy users may be attributable to a disruption of frontal-striatal circuits directly related with the serotonin function as well as a depletion of lexical-semantic stores mediated by temporal structures.

Galantamine-induced improvements in cognitive function are not related to alterations in alpha(4)beta (2) nicotinic receptors in early Alzheimer's disease as measured in vivo by 2-[18F]fluoro-A-85380 PET

INTRODUCTION

The nicotinic acetylcholine receptor (nAChR) system plays a regulatory role in a number of cognitive processes. Cholinesterase inhibitors (i.e., galantamine) that potentiate cholinergic neurotransmission improve cognitive function in Alzheimer's disease (AD); however, the relationship between these effects and associated changes in nAChRs are yet to be established in vivo.

MATERIALS AND METHODS

2-[18F]Fluoro-A-85380 (2-FA) binds to nAChRs and with positron emission tomography (PET) imaging provides a composite measure of receptor density and ligand affinity. This study aimed to: (1) quantify nAChRs in vivo in 15 drug-naïve patients with mild AD before and after chronic treatment with galantamine, using 2-FA and PET, and (2) examine the relationship between treatment-induced changes in nAChRs and improvements in cognitive function. Participants were nonsmokers and underwent extensive cognitive testing and a PET scan after injection of approximately 200 MBq of 2-FA on two occasions (before and after 12 weeks, galantamine treatment). A 3-day washout period preceded the second scan. Brain regional 2-FA binding was assessed through a simplified estimation of distribution volume (DV(S)).

RESULTS

Performance on global measures of cognition significantly improved following galantamine treatment (p < 0.05). This improvement extended to specific cognitive measures of language and verbal learning. No significant differences in nAChR DV(S) before and after galantamine treatment were found. The treatment-induced improvement in cognition was not correlated with regional or global nAChR DV(S), suggesting that changes in nAChRs may not be responsible for the improvements in cognition following galantamine in patients with mild AD.

Clustering and switching in semantic fluency: predictors of the development of Alzheimer's disease

OBJECTIVE

The aims of the study are twofold: (1) to compare semantic fluency, clustering and switching performance among subjects with memory complaints, patients with Alzheimer Disease (AD), and healthy controls; and (2) to examine the clinical utility of the clustering/switching scoring system in the prediction of incident AD in subjects with memory complaints.

METHODS

A semantic fluency task was used to compare thirty eight subjects with memory complaints, forty two AD patients and twenty five healthy controls on the total number of words generated, clustering and switching performance. Subjects with memory complaints were followed-up for a maximum period of two years and re-evaluated. They remained in the memory complaints group (twenty eight subjects) or were defined as probable AD (ten subjects).

RESULTS

AD patients generated fewer correct words (p < 0.001) and showed a reduction in clustering (p = 0.008) and switching (p < 0.001). Subjects with memory complaints showed a significant reduction in correct words (p < 0.001) and clustering performance (p = 0.008) compare to controls. In the first evaluation, the subgroup of patients who converted to AD at follow up produced less correct words (p < 0.01) and smaller clusters (p = 0.007) than the subgroup who did not become demented. There were no differences in switching between these two subgroups. AD development was better predicted by cluster size than by the total number of words generated or by switching.

CONCLUSIONS

Subjects with memory complaints and AD patients have an alteration in both qualitative and quantitative aspects of semantic fluency. A clustering analysis could enhance the reliability of early AD diagnosis.

Behavioural and psychological symptoms are not related to white matter hyperintensities and medial temporal lobe atrophy in Alzheimer's disease

BACKGROUND

The neuropathology of behavioural and psychological symptoms is much less understood than the neuropathology of cognitive impairment in AD. On MRI, medial temporal lobe atrophy (MTA) is presumed to reflect Alzheimer- type pathology. White matter hyperintensities (WMH) are considered markers of vascular pathology.

AIM

We investigated differences in prevalence of behavioural and psychological symptoms in AD according to the presence of MTA and WMH on MRI.

METHODS

Behavioural and psychological symptoms of 111 consecutive AD patients were assessed using the Neuropsychatric Inventory (NPI). Symptoms were considered present when the score was > or =1. On MRI, MTA was rated using the five-point Scheltens-scale and WMH using the four-point Fazekas-scale. Both MRI measures were dichotomised (MTA: absent 0/1, present 2-4; WMH absent 0/1, present 2/3).

RESULTS

Of the 111 AD patients, 60(55%) had MTA, and 32(29%) had WMH. The presence of MTA was associated with the presence of WMH (chi (2) = 11.8, p < 0.001). The prevalence of behavioural and psychological symptoms--defined as a NPI score of > or =1 on at least one symptom--was 74%.The median NPI score of the total study population was 6(0-41). There was no difference in prevalence according to MTA (p = 0.53) or WMH (p = 0.18). On inspection of individual NPI items, neither MTA, nor WMH was related to any of the symptoms.

CONCLUSIONS

There were no differences in prevalence of behavioural and psychological symptoms according to MTA or WMH, as rated on MRI. This suggests that the occurrence of those symptoms depends on other determinants, such as coping style or genetic make-up.

Predicting memory decline in normal elderly: Genetics, MRI, and cognitive reserve

Major predictors of Alzheimer's disease (AD) include apolipoprotein E (APOE)-epsilon4, hippocampal atrophy on magnetic resonance imaging (MRI), and memory dysfunction prior to diagnosis. We examined 159 normal elderly subjects with MRI and the California Verbal Learning Test (CVLT); 84 returned for longitudinal follow-up 5 years later. Analyses at baseline revealed significant variance in hippocampal volume accounted for by cerebral volume and age but not by APOE isoform. However, interactions involving APOE isoform and laterality were observed. As hypothesized, an APOE x time interaction was revealed for CVLT long-delay free recall: APOE-epsilon3/4 subjects had significantly poorer performance than APOE-epsilon3/3 subjects at follow-up. Forward stepwise multiple regression analysis predicting follow-up long-delay free recall selected baseline recall, followed by number of APOE-epsilon4 alleles, followed by left-hippocampal volume. Age and sex did not enter into the model. We conclude that APOE-epsilon4 predicts longitudinal memory decline in healthy controls and that MRI morphometry of hippocampus adds slightly to predictive value.

EEG and MRI correlates of mild cognitive impairment and Alzheimer's disease

OBJECTIVE

To investigate whether cognitive function in the spectrum of normal aging to Alzheimer's disease is better reflected in MRI or EEG measures, or a combination of both.

METHODS

Cognitive functions were tested in 33 elderly subjects: 10 with probable Alzheimer's disease, 11 with mild cognitive impairment and 12 controls. Structural brain parameters were derived from conventional MRI and a quantitative MR technique called magnetization transfer imaging. The EEG provided measures of brain function. We performed multiple linear regression analyses to relate EEG and MRI parameters to global cognition, memory, language and psychomotor speed.

RESULTS

The model showed EEG alpha reactivity during eyes open to be the primary factor associated with global cognition, memory and language skills. Brain atrophy was the primary factor associated with psychomotor speed. Furthermore, EEG alpha reactivity during eyes open explained significant additional variability in psychomotor speed.

CONCLUSION

EEG and MRI are each associated with different aspects of cognitive function and complement each other in their relations to psychomotor speed.

Treatment of dementia in parkinsonian syndromes with cholinesterase inhibitors

In Parkinsonian syndromes behavioural symptoms and dementia can be even more debilitating than motor symptoms and are an important predictor for nursing home placement and mortality. Neuropathologically, dementia seems to be primarily related to cortical changes rather than to subcortical alterations. Concerning neurotransmitter systems, the cholinergic system has been proposed to play a key role in cognitive disturbances. Based on studies with patients with Alzheimer disease, the application of cholinesterase inhibitors is vividly discussed also for dementia associated with parkinsonian syndromes. This review focuses on the specific symptoms of dementia in different parkinsonian syndromes and critically questions the effect of cholinergic treatment on cognitive functions in patients with extrapyramidal syndromes and dementia. There is evidence that medication with some cholinesterase inhibitors can enhance cognition as well as activities of daily living in dementia with Parkinson's disease and seems to reduce behavioural disturbances in both dementia with Parkinson's disease and dementia with Lewy bodies. The effect of treatment with cholinesterase inhibitors in progressive supranuclear palsy and corticobasal degeneration warrants carefully designed studies including a sufficient number of patients and symptom-adopted dementia scales.

Reduced cerebral glucose metabolism in patients at risk for Alzheimer's disease

While significantly reduced glucose metabolism in fronto-temporo-parietal and cingulate cortices has been demonstrated in Alzheimer's disease (AD) compared with controls, cerebral glucose metabolism in patients with mild cognitive impairment who subsequently develop AD is less well-defined. In the present study we measured cerebral glucose metabolism by positron emission tomography (PET) with (18)F-2-fluoro-2-deoxy-D-glucose in 14 patients with aging-associated cognitive decline (AACD), 44 patients with AD, and 14 healthy control subjects at baseline. The AACD patients were clinically followed up, and conversion to AD was determined. Compared with controls, AACD patients had significantly reduced glucose metabolism in the right precuneus, posterior cingulate, right angular gyrus, and bilateral middle temporal cortices, while the respective deficits were more pronounced in AD patients and also involved the frontal cortices. AACD patients who subsequently converted to AD (AACD-converters) showed more extended metabolic changes which also involved the frontal and temporal cortices, right cingulate gyrus, right thalamus, and bilateral precuneus.

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

Alzheimer's disease (AD) is associated with widespread brain atrophy including structures subserving memory. We applied an improved structural detection methodology to examine the less well known progression of atrophy in early-stage AD. We sought to i) longitudinally study volumetric differences in patients with early-stage AD and healthy volunteers; and ii) test the hypothesis that hippocampal volumes would be correlated with clinically relevant cognitive function. Seven patients and eleven healthy subjects underwent two structural MRI scans and neuropsychological assessments. Scans were normalised to a study-specific template and 'morphologically opened' to reduce tissue misclassification. Using brain-parcellation, patient atrophy was localised to left fusiform and parahippocampal gyri, whilst left hippocampal volumes were correlated with a cognitive performance measure. A whole-brain search methodology, showed that patients had reduced volumes including fronto-temporal regions bilaterally, in hippocampi and amygdalae and right cerebellum. Whole-brain correlational analyses revealed that cognitive performance was correlated with volumes of both hippocampi, superior temporal gyri and left insula. Neither group exhibited significant longitudinal volumetric changes. Utilising a novel methodology, we have shown that in early-stage AD, clinically relevant cognitive deficits are correlated with regionally specific grey-matter volumes, which are detectable at an early stage of the illness.

Störungen des autobiographischen Gedächtnisses bei Alzheimer-Demenz

Zusammenfassung: Störungen der Gedächtnisfunktionen bilden das Achsensymptom demenzieller Erkrankungen, insbesondere der Alzheimer-Demenz (AD) als ihrer häufigsten Form. Gerade Defizite des autobiographischen Gedächtnisses entstehen schon in den Anfangsstadien der Erkrankung und betreffen primär Erinnerungen an selbst Erfahrenes einschließlich prägender Lebensereignisse, während äußere Lebensdaten noch lange abrufbar bleiben. Autobiographische Gedächtnisdefizite wurden nur selten untersucht, vor allem da derartige Studien besondere methodische Anforderungen stellen, die sich aus der Individualität des erinnerten Materials und dem Charakter demenzieller Erkrankungen ergeben. Wir haben deshalb autobiographische Gedächtnisdefizite differenziert nach semantischen und episodischen Qualitäten mit dem “Bielefelder Autobiographischen Gedächtnisinventar” (BAGI) in einer modifizierten Version bei 230 Heimbewohnern (24 kognitiv Gesunde; 28 mit leichter kognitiver Beeinträchtigung; 178 mit manifester AD) untersucht. Eine nachhaltige Beeinträchtigung des autobiographischen Gedächtnisses zeigte sich dabei schon in frühen Phasen der AD. Bereits Bewohner mit leichter kognitiver Beeinträchtigung wiesen ausgeprägte Defizite des episodischen Gedächtnisses auf, die bei mittelgradiger oder schwerer AD fortbestanden. Demgegenüber gingen semantische autobiographische Gedächtnisinhalte graduell verloren, sodass weitreichende Defizite erst bei stark Eingeschränkten entstanden. Die Kenntnis dieser Zusammenhänge vertieft nicht nur unser Verständnis der Alzheimer- Demenz, sondern erweitert auch das verfügbare diagnostische Instrumentarium.

Correlation between disease severity and brain electric LORETA tomography in Alzheimer's disease

OBJECTIVE

To compare EEG power spectra and LORETA-computed intracortical activity between Alzheimer's disease (AD) patients and healthy controls, and to correlate the results with cognitive performance in the AD group.

METHODS

Nineteen channel resting EEG was recorded in 21 mild to moderate AD patients and in 23 controls. Power spectra and intracortical LORETA tomography were computed in seven frequency bands and compared between groups. In the AD patients, the EEG results were correlated with cognitive performance (Mini Mental State Examination, MMSE).

RESULTS

AD patients showed increased power in EEG delta and theta frequency bands, and decreased power in alpha2, beta1, beta2 and beta3. LORETA specified that increases and decreases of power affected different cortical areas while largely sparing prefrontal cortex. Delta power correlated negatively and alpha1 power positively with the AD patients' MMSE scores; LORETA tomography localized these correlations in left temporo-parietal cortex.

CONCLUSIONS

The non-invasive EEG method of LORETA localized pathological cortical activity in our mild to moderate AD patients in agreement with the literature, and yielded striking correlations between EEG delta and alpha1 activity and MMSE scores in left temporo-parietal cortex.

SIGNIFICANCE

The present data support the hypothesis of an asymmetrical progression of the Alzheimer's disease.

Neural Synchrony in Brain Disorders: Relevance for Cognitive Dysfunctions and Pathophysiology

Following the discovery of context-dependent synchronization of oscillatory neuronal responses in the visual system, novel methods of time series analysis have been developed for the examination of task- and performance-related oscillatory activity and its synchronization. Studies employing these advanced techniques revealed that synchronization of oscillatory responses in the beta- and gamma-band is involved in a variety of cognitive functions, such as perceptual grouping, attention-dependent stimulus selection, routing of signals across distributed cortical networks, sensory-motor integration, working memory, and perceptual awareness. Here, we review evidence that certain brain disorders, such as schizophrenia, epilepsy, autism, Alzheimer's disease, and Parkinson's are associated with abnormal neural synchronization. The data suggest close correlations between abnormalities in neuronal synchronization and cognitive dysfunctions, emphasizing the importance of temporal coordination. Thus, focused search for abnormalities in temporal patterning may be of considerable clinical relevance.

The role of quantitative structural imaging in the early diagnosis of Alzheimer's disease

The goal of this article is to review the role of structural neuroimaging in the diagnosis of Alzheimer's disease (AD). We present relevant neuroanatomy, highlight progress in the domain of AD imaging, and review the clinical characteristics of the prodromal phase of AD. We describe the history of the diagnostic issue by examining at cross-section and longitudinally the differences between patients who have AD and normal controls. We also present how subsequent works applied these characteristic traits to the early detection of the prodromal disease and to prediction of future decline. The article delineates the differences between subjects who have mild cognitive impairment and AD, which illustrate the spreading of the pathology with disease progression. The last section describes problems encountered in the differential diagnosis.