The dimensional complexity of the EEG during cognitive tasks reflects the impaired information processing in schizophrenic patients.

The aim of the present study was to investigate whether schizophrenic patients show a different change of the dimensional complexity of the EEG, as represented by the Grassberger-Procaccia correlation dimension D(2,) under cognitive challenge compared to normal control subjects. With respect to results reported in the literature, it was expected that the complexity of the signal under cognitive challenge is higher in schizophrenic patients than in normal control subjects reflecting the impaired information processing abilities of the patients. Eighty-seven schizophrenic and 30 matched control subjects performed two different types of the continuous performance task. The results revealed differences between schizophrenic patients and control subjects for the performance as well as the complexity measures. Schizophrenic patients produced more omission errors than normal subjects did. For the EEG complexity measure no differences occurred under the baseline condition. In contrast, during the first minute under task conditions the control subjects showed a decrease of the dimension while no changes were found for the schizophrenic group. These results occurred for both types of the cognitive task but they reached clear significance only in one of them. The results are interpreted as reflecting the ability of normal subjects to adapt their information processing system to the cognitive challenge and to focus their attention on the task while schizophrenic subjects do not show this adaptation to the task.

Discrimination of Alzheimer's disease and normal aging by EEG data.

Quantitative EEG results in Alzheimer's disease may be summarized by the term 'slowing', i.e. slow frequencies (delta, theta) are increased and fast frequencies (alpha, beta) are decreased. But how can EEG data be used to discriminate AD patients from controls by means of EEG data? Discriminant analysis may produce false predictions using too many predictors, as is often the case in EEG studies. We studied 4 approaches to this problem: Classification by group means, stepwise discriminant analysis, a neuronal network using back propagation and discriminant analysis preceded by principal components analysis (PCA). A maximum of 86.6% correct classifications was reached using the last mentioned approach with EEG data alone. Including age as a moderator variable in a subgroup, 95.9% correct classifications were reached.

[Degree of disability of demented patients as judged by relatives and experts (disability insurance)]. / Die Pflegebedürftigkeit Demenzkranker im Urteil von Angehörigen und Gutachtern (Pflegeversicherung).

Health insurance companies commission medical expert opinions rating the severity of clinical improvement in order to provide adequate nursing support. We compared these ratings on 28 demented patients with the ratings from carers and with our own examination. The results indicate that the expert opinions underestimated the severity of improvement and adequate support in some of the cases. We discuss whether these discrepancies may be due to the peculiarities of dementia.

[The fractal dimension as an imaging parameter in CT scans of patients with anorexia nervosa before and after therapy]. / Die fraktale Dimension als Bildbearbeitungsparameter im CT bei Anorexia nervosa vor und nach Therapie.

Brain development is a self-organizing process and hence the brain structures correspond to a highly recursive system consisting of a multitude of parts. Quantitative analysis of recursive, self-similar structures is possible in CT scans as what is termed synergistic diagnostic using the fractal dimension. In 10 patients with anorexia nervosa (ICD-10, F50.0) we determined the fractal dimension of the cerebral cortex contour in a CT image using the "boxcounting method" after filtering of the data and separation with a defined cut-off. There was a significant difference between the results from CTs obtained before and after therapy. There was a high correlation between the fractal dimension and body weight, brain volume and sulcal cerebrospinal fluid volume, but only a low correlation with ventricular volume. The findings suggest that the qualification of the fractal dimension may be useful as one of postprocessing methods on CT scans. Further studies will be necessary to assess its importance for diagnosis.

[Self and informant perception of clinical manifestations of Alzheimer dementia: results of a structured interview (CAMDEX)]. / Die Selbst-und Fremdeinschätzung klinischer Störungen bei der Alzheimer-Demenz: Ergebnisse eines strukturierten Interviews (CAMDEX).

The correlations between (a) the patients' memory complaints, (b) the informants' rating of the patients' cognitive impairment, and (c) cognitive performance according to the Cambridge Examination for Mental Disorders of the Elderly (CAMDEX) were examined in 163 patients with probable or possible Alzheimer's disease. The patients' complaints were weakly correlated with informants' view (p < 0.05), closely correlated with depressive mood (p < 0.0001), but not with cognitive performance or the stage of dementia. The results of Clinical Dementia Rating, Mini-Mental State Examination and the Cambridge Cognitive Examination were significantly correlated with the informants' rating of cognitive impairment (p < 0.0001). These results are in line with previous studies and confirm (1) the suitability of CAMDEX for the structured examination of dementia patients and their caregivers, (2) the association between affective disturbances and the perception of cognitive deficits, and (3) the importance informants' rating for the valid evaluation of demented patients.

Longitudinal cognitive, electroencephalographic and morphological brain changes in ageing and Alzheimer's disease.

BACKGROUND: The natural course of cognitive performance, electrophysiological alterations and brain atrophy in ageing and Alzheimer's disease (AD) has been investigated in numerous studies, but only few attempts have been made to examine the relationship between clinical, electroencephalographic (EEG) and morphological changes with quantitative methods prospectively over longer periods of time. METHOD: Fifty-five patients with clinically diagnosed AD and 66 healthy elderly controls were examined biannually using a cognitive test (CAMCOG), EEG band power and volumetric estimates of brain atrophy. RESULTS: On average cognitive performance deteriorated by 28 points on the CAMCOG in the AD group, the alpha/theta ratio decreased by 0.2, and the proportion of intracranial cerebrospinal fluid volume increased by 3.5% during a 2-year period. Similar changes were observed after a second 2-year interval. A multiple regression model demonstrated a significant influence of age on cognition and atrophy and a significant influence of the estimated duration of symptoms on cognition, alpha/theta ratio and brain atrophy at the initial examination. Cognitive performance at the first examination exerted significant effects on the performance and also on brain atrophy at re-examination after 2 or 4 years, whereas the EEG and neuroimaging findings at the previous examination were exclusively related to the corresponding findings at the follow-up examinations. In the control group no significant cognitive, EEG and morphological changes were observed after 2 and 4 years. CONCLUSION: After 2 consecutive follow-up periods, we were able to verify significant deteriorations of cognition accompanied by neurophysiological and neuroradiological changes in AD, but not in normal ageing. In clinically diagnosed AD, cognitive performance at the followup examination could not be predicted by the previous alpha/theta ratio or by the previous degree of global brain atrophy, whereas the cognitive test score determined not only performance, but also structural findings at follow-up. Performance on cognitive tests appears to be a more sensitive indicator of the degenerative process than EEG band-power and morphological changes in manifest AD. Neuroimaging, neurophysiology and genetic risk markers may be more important for the early differential diagnosis than for the prediction of the course of illness.

[Volumetric brain changes and quantitative EEG in normal aging and Alzheimer's dementia]. / Volumetrische Hirnveränderungen und quantitatives EEG bei normalem Altern und Alzheimer-Demenz.

We studied (1) the differences of volumetric estimates of brain atrophy in normal ageing and Alzheimer's disease (AD); (2) the correlation of these estimates with age and cognitive performance; (3) the differences between absolute EEG power between ageing and AD; (4) the correlation between EEG power and age or cognitive performance; and (5) the correlation between volumetric and EEG data. 84 patients with a clinical diagnosis of AD and 45 age-approximated non-demented controls between 48 and 91 years of age were examined. For statistical comparisons the volumetric estimates of intracranial cerebrospinal fluid (csf) spaces were converted into percentages of total intracranial volume. The EEG was recorded from 17 locations at resting conditions, eyes closed, according to the 10/20 system. Logtransformed absolute band powers were compared between the AD and control groups and correlated with clinical and volumetric findings. The total intracranial csf-space, both lateral ventricles, the third ventricle, anterior, lateral and posterior fissures were significantly larger in AD than in non-demented controls. In normal ageing the csf-volumes were significantly correlated with age, whereas age and cognitive performance were differentially correlated with these variables in AD. In AD, the absolute delta or theta power was significantly higher in all locations, whereas alpha power was lower than in normal controls. These differences were significantly correlated with cognitive performance. There were no significant correlations between the csf-volumes and EEG-power in AD and the control group with one exception: we found a significant inverse correlation between the volumes of the anterior and posterior fissure and the alpha-1 and alpha-2 power independent of electrode location in AD. We conclude that the morphological and EEG-changes in AD are largely independent and suggest that the functional relationship between alpha-power and anterior or posterior fissure volume needs further examination.

Quantitative EEG in frontal lobe dementia.

A study on quantitative EEG in 14 patients with frontal lobe dementia (FLD), 14 patients with Alzheimer's disease (AD), and 14 healthy controls was conducted using a complete set of EEG parameters: band power, coherence and fractal dimension. Contrary to earlier studies, we observed higher theta power and sagittal interactions in higher frequency bands in the FLD than in the control group. Lateral interactions of coherence and two indices of fractal dimension were lower in FLD than in controls. There was greater electrophysiological resemblance between the control group and FLD than between any of these groups and AD. This was documented by the results of a discriminant analysis which led to a correct overall classification of 66% of the subjects with misclassifications occurring primarily between control and FLD group.

Frontal lobe degeneration and Alzheimer's disease: a controlled study on clinical findings, volumetric brain changes and quantitative electroencephalography data.

Ten patients with a clinical diagnosis of frontal lobe degeneration (FLD) were compared with a group of patients with probable Alzheimer's disease (AD) and with nondemented controls matched for gender and age. In comparison with AD, the duration of illness was slightly shorter and cognitive performance was better in patients with FLD. The greatest enlargement of cerebrospinal fluid volumes was found in FLD and this effect was most pronounced in the anterior fissure and lateral ventricles. Estimates of EEG band-power and EEG coherence in FLD were not remarkably different from nondemented controls, whereas delta- and theta-power were significantly increased in AD. These observations may indicate different disease processes with a dissociation of volumetric computed tomography and quantitative EEG changes, which may be of differential diagnostic value.

Brain atrophy in normal ageing and Alzheimer's disease. Volumetric discrimination and clinical correlations.

BACKGROUND: We examined the differences in volume of the ventricular and extracerebral cerebrospinal fluid spaces in normal ageing and in probable Alzheimer's disease (AD) and we tried to investigate the effects of the severity of illness on the morphometric differentiation of AD and ageing, the principal components underlying brain atrophy in both conditions, and the correlations of these measurements with clinical findings. METHOD: Forty patients with probable AD were matched with 40 non-demented elderly controls. Both groups underwent standardised clinical tests and unenhanced cranial computed tomography for post hoc volumetric analysis. RESULTS: The lateral and third ventricles and the anterior and lateral fissures were significantly larger in AD than in normal ageing. The volumes of the lateral ventricle and lateral fissure permitted a highly efficient differentiation between normal ageing and AD even at the mild stage of dementia, and this differentiation was improved further in the more severe stages of illness. We identified one principal component underlying brain atrophy in normal ageing and two components in AD: a 'grey matter' component accounting for sulcal and third ventricular enlargement, and a 'white matter' component for lateral ventricular enlargement. In AD, most of the volumetric measurements were significantly correlated with cognitive impairment, but in the group of non-demented elderly controls they were correlated with age. CONCLUSION. Volumetric indices of brain atrophy permit a highly efficient differentiation between normal ageing and AD even in the mild stages of illness and this demonstrates that substantial structural brain changes have developed in the preclinical phase of illness. We suggest that there is an uncoupling between lateral ventricular enlargement and cortical brain atrophy in AD.

Parameters of EEG dimensional complexity in Alzheimer's disease.

The dimensional complexity or fractal dimension of the EEG recorded at 17 locations from the 10-20 system was studied using a very fast new algorithm. The paper contains 2 parts. First, the influence of several parameters (embedding dimension, delay time, high and low frequency cutoff, ADC precision and sweep length) on the estimation of dimensional complexity is investigated. Then it is shown that patients with Alzheimer's disease (n = 50) have significantly lower dimensional complexity than age-approximated non-demented controls (n = 42).

Age-associated memory impairment and early Alzheimer's disease. Only time will tell the difference.

A reliable and early diagnosis of incipient Alzheimer's disease (AD) is one of the obligatory requirements for timely and potentially successful therapeutic intervention. The potential diagnostic significance of mild cognitive impairment and subjective memory complaints was examined. Groups of patients with age-associated memory impairment (AAMI) and with AD were examined prospectively and their subjective complaints, cognitive performance and neuroimaging findings were compared with those of healthy elderly controls. Subjective complaints were most severe in the AD group. Both, memory complaints and depressive disturbances had high loadings on one underlying principal component. There was no statistical correlation between a global score of cognitive performance and subjective complaints in the patient groups, but the correlation between performance and brain atrophy was statistically significant. The degree of brain atrophy, but not subjective complaints (or the diagnostic distinction between AAMI and AD) were associated with the severity of cognitive deterioration during a 2-year follow-up period. This, and the observation of an increased frequency of the apolipoprotein E allele 4 in the AD and AAMI groups, suggest that biological risk markers will be of greater significance for the early diagnosis of AD than the patient's subjective complaints. Patients satisfying criteria for AAMI need to be followed-up, because no reliable diagnostic markers for the earliest or preclinical stages of AD are available to date.

[Apolipoprotein E and Alzheimer dementia. Personal results and brief literature review]. / Apolipoprotein E und Alzheimer-Demenz. Eigene Ergebnisse und kurze Literaturübersicht.

The apolipoprotein E allele (Apo-E gene) status was determined in 147 individuals from a longitudinal study. 53 satisfied NINCDS-ADRDA criteria for probable or possible Alzheimer's disease (AD), 37 were non-demented healthy controls. 31 patients with AD had one or two Apo-E 4 alleles (phenotypes 1 x 4-2; 20 x 4-3; 10 x 4-4) compared with only 9 controls (8 x 4-3; 1 x 4-4). Within the AD group, patients homozygous for Apo-E 4 had an earlier onset of illness (7 of 10 cases were presenile) and more severe cognitive impairment at the time of examination after similar durations of illness as patients without Apo-E 4. This may reflect an influence of the Apo-E 4 gene dosage on the onset and course of illness, which is probably independent of chromosome 14 mutations.

[Frontal and temporal onset of brain atrophy. Clinical and instrumental findings]. / Frontal und temporal beginnende Hirnatrophie. Klinische und apparative Befunde.

We report the cases of a 70-year old man with left temporal brain atrophy and of a 39-year-old man with neuropathologically verified frontal lobe degeneration (FLD) of Non-Alzheimer type. 10 patients with FLD collected during a prospective study on degenerative dementia had more severe volumetric brain changes and less severe quantitative band power changes than a group of matched patients with clinically diagnosed Alzheimer's disease.

EEG coherence in Alzheimer disease.

A novel approach is introduced to examine EEG coherence in different frequency bands of 17 locations from the 10-20 system. Fifty patients with clinically diagnosed Alzheimer's disease were compared with 42 age-approximated non-demented controls. We determined the average coherence between individual electrodes and all neighbouring electrodes. Coherence was decreased in the sample of demented patients and this effect was most pronounced in the frontal and central derivations of the theta, alpha and beta frequency bands. The results can be interpreted as the effects of neuronal loss and neocortical disconnection.

Delusional misidentification in Alzheimer's disease: a summary of clinical and biological aspects.

Delusional misidentification symptoms (DMS) are common in Alzheimer's disease (AD) and they are frequent sources of serious distress for patients and particularly caregivers. We observed DMS in around 30% of the patients with moderate to severe AD in two independent prospective studies; the Capgras type, phantom boarder, mirror and TV DMS were found most frequently. Patients with DMS showed increased EEG delta-power over the right hemisphere, their CT scans showed more severe right frontal lobe atrophy, and the number of their pyramidal cells in area CA1 was lower than in the patients without DMS. This may indicate that the development of DMS in AD can be promoted by certain patterns of brain degeneration which affect systems relevant to the recognition and updating of memories, while verbal skills may initially be left largely intact.

Apolipoprotein E-4 gene dose in clinically diagnosed Alzheimer's disease: prevalence, plasma cholesterol levels and cerebrovascular change.

The prevalence of the apolipoprotein E-4 allele (ApoE-4) was significantly higher in a referral population of 40 patients with clinically diagnosed Alzheimer's disease than in a sample of non-demented elderly controls (P < 0.01). The highest plasma cholesterol levels were found in demented patients homozygotic for Apo E-4, but no significant increases of glucose, triglycerides and thyroxine or of leuko-araiosis and brain infarcts were verified in this preliminary study.

[Incidence and importance of "non-cognitive" symptoms in dementia of the Alzheimer type: productive psychotic symptoms, depressive disorders and behavioral disorders]. / Häufigkeit und Bedeutung "nicht-kognitiver" Symptome bei der Demenz vom Alzheimer-Typ: produktiv psychotische Symptomatik, depressive Störungen und Störungen des Verhaltens.

A semi-structured interview was administered to the closest relatives of 50 patients with presenile or senile dementia of the Alzheimer type. The disturbances most frequently reported were: wandering/pacing (56%, cumulative percentage), aggressive behavior (44%) and - significantly related to more severe stages of dementia - apathy/loss of drive (58%), eating disturbances (46%) and disturbances of the sleep-waking cycle (32%). Depressive symptoms were observed in 58% of the patients, preferentially in the early stages of illness with preserved insight. Signs of paranoid delusions (46%), delusional misidentification (34%), visual (32%) and auditory hallucinations (16%) were encountered temporarily in a large number of patients. The importance of "non-cognitive" symptoms in Alzheimer's disease is underlined by their subjective significance for the caregivers.

Psychotic features and the course of Alzheimer's disease: relationship to cognitive, electroencephalographic and computerized tomography findings.

Thirty-one of 50 patients satisfying the NINCDS-ADRDA criteria of probable or possible Alzheimer's disease showed psychotic features during a 2-year observation period. Paranoid delusions were reported in 23 patients, delusional misidentification in 17, visual hallucinations in 16 and auditory hallucinations in 8. All of the 7 patients who died within the observation period had suffered from psychotic features even before the preterminal phase of illness. A faster progression of illness towards more severe stages of dementia was associated with paranoid delusions and hallucinations but not with delusional misidentification. We could not prove a significant influence of age, age of onset, cognitive performance, ventricular enlargement or the severity of quantitative electroencephalographic changes at initial examination on the course of illness. This may indicate that specific psychotic features and their potential organic substrate exert an effect on the progression of illness and on survival in Alzheimer's disease, which is not related to gross brain atrophy and generalized neurophysiological changes.

EEG power and coherence while male adults watch emotional video films.

Quantitative EEG analysis recorded at F3, F4, T3, T4, P3, P4 was performed for a group of healthy right-handed male adults (n = 9) viewing video films varying in their inductiveness on the affective valence dimension. Digital EOG-correction permitted the inclusion of trials with eye movements. Muscle artifacts were statistically treated by means of analysis of covariance (ANCOVA). The configuration of topographically motivated EEG parameters corresponded to the subjective valence rating of different video films. Low broad band coherences (COHs) ranked films along the subjective ratings within each hemisphere by the fronto-temporal COHs and interhemispherically by the T4-T3 COH, as did, restricted to the right hemisphere, similarity of beta 2 band power topography over time. High frequencies may be involved in the processing and low frequencies in the transmission of differential affective information, which to integrate seemed to utilize resources of both hemispheres. Alpha 2 and beta 1 COHs were sensitive to variations in an integrality/disassociation dimension with regard to the arrangement of verbal-visual affective cues. Power fluctuations at frontal leads pointed to difficulties in interpreting interhemispheric EEG asymmetries in emotion research, if information on time dynamics is discarded.