Search PubMed⌕ Search

Biomedical subjects

W M Herrmann

Publications and source records attributed to W M Herrmann.

At least 19 recordsLinked to original sources
PubMed2000

Schizophrenia: reduced signal-to-noise ratio and impaired phase-locking during information processing.

OBJECTIVE: This study was performed in order to clarify the mechanisms which underlie the reduced signal-to-noise of event-related potentials in schizophrenic patients. Specifically, we wanted to find out, whether it is reduced activation and/or synchronization (phase-locking) in specific frequency bands of the ongoing EEG which is related to the decreased signal amplitude and signal-to-noise ratio in schizophrenics. METHODS: We investigated 41 unmedicated schizophrenics (10 of them drug-naïve) and compared them with healthy control subjects (n = 233) as well as unmedicated subjects with schizotypal personality (n = 21), who were considered to be high-risk subjects for schizophrenia, and unmedicated depressive patients (n = 71). We measured event-related activity during an acoustical choice reaction paradigm and calculated the signal-to-noise ratio, signal power and noise for a time interval of 50-200 ms after stimulus presentation. Signal-to-noise ratio was calculated from the power of the averaged trials (signal power) divided by the mean power of the single trials minus the power of the average (noise power). Also, we performed a frequency analysis of the pre- and poststimulus EEG based on a factor analytical approach. Group comparisons were performed with ANCOVA. RESULTS: As expected, a decreased signal-to-noise ratio of evoked activity was found in the schizophrenic and a non-significant trend in the schizotypal subjects and the depressive patients. We were able to show that the observed decrease is due to a reduced signal power and an increase of absolute noise power. Frequency analysis of the evoked activity revealed that normals, schizophrenics schizotypal subjects and depressive patients increased theta/delta activity between pre- and poststimulus interval to a similar extend. However, this theta/delta-augmentation does not correlate with signal power in schizophrenics. Also, normals and depressive subjects augment coherence between both temporal lobes during information processing, which is not found in schizophrenics and schizotypal subjects. In contrast, these two groups augment frontal lobe coherence, which goes along with an increase of noise. CONCLUSIONS: Reduced stimulus-induced phase-locking and bitemporal coherence of cortically evoked activity but not a failure to activate the cortex may be responsible for the observed low signal-to-noise ratio during information processing in schizophrenics. Accordingly, schizophrenics increase noise after stimulus presentation instead of building up a signal. This is discussed in the framework of the theory of stochastic resonance.

Acoustic Stimulation↗
PubMed2000

Cyclandelate in the treatment of patients with mild to moderate primary degenerative dementia of the Alzheimer type or vascular dementia: experience from a placebo controlled multi-center study.

A 24-week, double-blind, multi-center, randomised parallel group study compared the efficacy and safety of 800 mg bid cyclandelate with placebo in patients with mild to moderate dementia of primary degenerative or vascular origin. A total of 196 patients entered the study, 147 patients completed treatment in adherence with the protocol. Primary outcome measures were the cognitive score of the Alzheimer's Disease Assessment Scale (ADAS-Cog), the subscale Instrumental Activities of Daily Living of the Nurses' Observation Scale for Geriatric Patients (NOSGER-IADL) and the Clinical Global Impressions of Change (CGI-C). Safety assessments included adverse events, vital signs, ECG and clinical laboratory parameters. The primary efficacy results based on a multi-level responder analysis including ADAS-Cog, NOSGER-IADL and CGI-C failed to demonstrate statistical superiority of cyclandelate in comparison to placebo. The direction of changes favored cyclandelate in each of the variables, but the differences to placebo were small and varied considerably between patients and centers. Retrospective exploratory analyses suggested that efficacy of cyclandelate might be dependent on the severity of the disease. The treatment effects in favor of cyclandelate were statistically significant in the subgroup of moderately impaired patients (MMSE at baseline <18) for ADAS-Cog (delta = -4.0 points, p = 0.015) and CGI-C (delta = -0.4 points, p = 0.043) but not for NOSGER-IADL (delta = -1.6 points, p = 0.059). When patients were stepwise selected for the severity of the disease according to ADAS-Cog at baseline (>15, >20, >25 points), statistical significance was reached for ADAS-Cog and NOSGER-IADL beginning with the step ADAS-Cog >20 points: delta ADAS-Cog = -3.9 points, p = 0.044; delta NOSGER-IADL = -1.0, p = 0.023. The treatment differences increased further with the step ADAS-Cog >25 points: delta ADAS-Cog = -7.0 points, p = 0.008; delta NOSGER-IADL = -1.7, p = 0.003. Treatment differences in CGI-C increased marginally with the stepwise selection but did not reach statistical significance. The drug was safe and well tolerated.

Aged↗
PubMed1999

A new concept for melatonin deficit: on pineal calcification and melatonin excretion.

Even though exogenous melatonin has proven to influence sleep and circadian parameters, low endogenous melatonin is not related to sleep disturbances, nor does it predict response to melatonin replacement therapy. In this manuscript, we present a new concept towards a definition of a melatonin deficit. The purpose of the study was to introduce a marker for an intra-individual decrease in melatonin production. Therefore, we developed a method to quantify the degree of pineal calcification (DOC) using cranial computed tomography. Combining pineal DOC with the organs's size, we estimated the uncalcified pineal gland volume. This estimation was positively and significantly associated with 6-sulfatoxymelatonin (aMT6s), collected over 24 hours in urine, in 26 subjects. Data yielded evidence that the decline in aMT6s excretion with age can be sufficiently explained by an increased pineal calcification. These results suggest that DOC might be useful as an indicator of an intra-individual, decreased capability of the pineal gland to produce melatonin. DOC might prove to be a response-marker for melatonin replacement therapy and a vulnerability marker of the circadian timing system.

Adolescent↗
PubMed1999

Cortical activation, signal-to-noise ratio and stochastic resonance during information processing in man.

OBJECTIVES: The goal of this study was to determine the relation between EEG, event-related potentials and information processing as measured by an acoustical choice reaction time task. In particular, we wanted to find out to what extent reaction-time performance is related to the pre-stimulus EEG activity (frequency domain) and the magnitude of signal power as well as noise power (stimulus-uncorrelated activity) after the tones (time domain). MATERIALS AND METHODS: For parametrization, EEG-activity was factorized across pre-defined frequency bands and 19 electrode positions, applying spectral power and coherence analysis. Signal power was estimated by calculating the mean power of the evoked single sweeps. Noise power was computed by subtracting the latter minus the power of the average evoked potential. We investigated 254 healthy subjects who had to perform an acoustical choice reaction task during running EEG. RESULTS: In the frequency domain, it was found that high frontally pronounced delta-power in the pre-stimulus EEG correlates with fast reaction-time performance, which was regarded as the expression of a readiness potential in the frequency domain, reflecting increased cortical activation. In the time domain, fast reaction times were found to be correlated with the amplitude of the event-related potential N100 as well as with the signal power and signal-to-noise ratio of the evoked activity. This result pointed to the frequently described relation between evoked signals and information processing. In accordance with the theory of stochastic resonance, we also found a positive correlation between the magnitude of noise power after the stimulus and reaction-time performance. Besides, noise power was found to be positively correlated with pre-stimulus cortical activation (mainly in the delta and alphal frequency band), whereas no relation was found between pre-stimulus EEG and the signal power of the event-related activity, except for a weak relation to the alpha2 power. CONCLUSION: Our findings support the notion that information processing is not only dependent on signal strength but also on a certain amount of basic noise, reflecting the overall energy state of the brain.

Adolescent↗
PubMed1999

Pharmacokinetics of thymosin alpha1 after subcutaneous injection of three different formulations in healthy volunteers.

OBJECTIVE: Thymosin alpha1, an immunomodulatory endogenous peptide, has been shown to be effective in the treatment of chronic hepatitis B and C. In this study, single- and 5-day multiple-dose pharmacokinetics were characterized in nine Caucasian volunteers after subcutaneous administration of 900 microg/m2 thymosin alpha1. METHODS: Using a randomized, 3-way crossover design three available drug formulations were compared: Zadaxin (SciClone), Timosina (Sclavo), and Thymosin alpha1 (Tal-HLR; Hoffmann La Roche). AUC, Cmax, t(max), t(1/2), Cl/f, and the volume of distribution, V(Z)/f, were derived by model-independent methods. RESULTS: Endogenous serum concentrations were below the limit of quantification (0.10 microg/l) of the enzyme-linked immunosorbent assay method in most subjects. Thymosin alpha1 was well absorbed with a mean t(max) between 1-2 hours from all galenic formulations. Cmax concentrations of 30 to 80 microg/l and AUC(0-infinity) from 95 to 267 microg x h/l did not differ between single- and multiple-dose administration of all drugs. This apparent lack of accumulation was supported by the short elimination half-life of less than 3 hours. As indicated by a V(Z)/f in the range of 30-40 l, thymosin alpha1 appears to distribute within the extracellular volume. AUC and Cmax were similar for Zadaxin and T alpha1-HLR, but higher after administration of Timosina. CONCLUSION: Thymosin alpha1 kinetics from this study are comparable to those previously obtained in Japanese volunteers or cancer patients, but may be influenced by the drug formulation used.

Adjuvants, Immunologic↗
PubMed1998

On pineal calcification and its relation to subjective sleep perception: a hypothesis-driven pilot study.

We classified the degree of pineal calcification (DOC) into seven groups using cranial Computer Tomography (cCT) and then correlated pineal DOC to chronic subjective sleep-related disturbances as measured by a sleep questionnaire in 36 patients. Analysed by logistic regression models, age and sex were not, but higher pineal DOC was significantly associated with the presence of daytime tiredness (OR = 4.15, 95% CI: 1.63, 10.54) and sleep disturbance (OR = 1.74, 95% CI: 1.10, 2.74). This study provides initial confirmation of the hypothesis that the increasing degree of pineal calcification (DOC) might indicate a decrease of melatonin production, which consecutively might lead to a disturbed circadian rhythmicity in the sleep-wake cycle, with the principal symptom being daytime tiredness.

Adult↗
PubMed1998

Quantitative EEG (QEEG) predicts relapse in patients with chronic alcoholism and points to a frontally pronounced cerebral disturbance.

The capability of predicting relapse in chronic alcoholism using quantitative EEG was investigated. For this purpose, 78 in-patients with alcoholism underwent EEG recordings (eyes closed) 7 days after the beginning of detoxification. Additionally, other clinical evaluations were carried out. After discharge from hospital, patients were regularly re-evaluated for the duration of 3 months in order to determine whether they relapsed or abstained from alcohol during this time. For classification of the two diagnostic subgroups (relapsers vs. abstainers), multivariate discriminant analysis as well as artificial neural network technology has been applied. Correct classification of patients' EEGs was achieved in 83-85% and thus outperformed classification with clinical variables considerably. Furthermore, artificial neural networks (ANN) improved classification results when compared with discriminant analysis. It was found that, in comparison to abstainers, relapsers had EEGs that were more desynchronized over frontal areas, which was interpreted as a functional disturbance of the prefrontal cortex.

Adult↗
PubMed1998

Analysis of quantitative EEG with artificial neural networks and discriminant analysis--a methodological comparison.

Artificial neural networks (ANN) are widely used to solve problems of differentiating between groups. However, serious comparisons of this method with the traditional procedure for such tasks (discriminant analysis) are rare. Discussing the results of both methods with the example of highly topical data, we try to demonstrate advantages and drawbacks of both methods. For this purpose, quantitative EEGs of 78 alcoholics were investigated in order to determine whether it is possible to predict relapse of these patients at the beginning of treatment. ANN software is available in Kassel (Institute for Computer Sciences and Mathematics).

Alcoholism↗
PubMed1998

On the use of neural network techniques to analyze sleep EEG data. Third communication: robustification of the classificator by applying an algorithm obtained from 9 different networks.

This is the third communication on the use of neural network techniques to classify sleep stages. In our first communication we presented the algorithms and the selection of the feature space and its reduction by using evolutionary and genetic procedures. In our second communication we trained the evolutionary optimized networks on the basis of multiple subject data in context with some smoothing algorithms in analogy of Rechtschaffen and Kales (RK). In this third communication we could demonstrate that the robustness concerning individual specific features of automatically generated sleep profiles could be reasonably improved by an additional modification of the procedure used by SASCIA (Sleep Analysis System to Challenge Innovative Artificial Networks). The outputs of nine different networks that were created by the data of 9 different subjects were used simultaneously for classification. The medians of the values obtained in each output measure were selected for the allocation to a sleep stage. The fitness criteria of 16 automatically generated sleep profiles showed reasonable concordance with the expert profile. Even though in single cases the concordance between conventional RK classifications and automatically generated profiles were a few percentages lower, the average correct classification of the 12 classified subjects improved substantially, thus proving that the classifier is more robust against individuum-specific variability. Despite the fact that the expert generally employs three channels (EEG, EMG and EOG), at least to build up sleep profiles, the SASCIA system was able to produce profiles on the basis of only one EEG channel with 80% concordance and a correlation coefficient of 0.86. The feature selections were performed by genetic algorithms and the topologies of the networks were optimized by evolutionary algorithms. This algorithm will now be used for larger sample forward classification.

Algorithms↗
PubMed1998

[Antihypertensive action of various talinolol dosages after four week's treatment in comparison with placebo].

The dose dependence of the antihypertensive effect of the beta 1 selective blocker talinolol (CAS 57460-41-0, Cordanum) was investigated in 97 essential hypertensive patients (mild to moderate) using the ambulatory blood pressure monitoring (ABPM) in a single-centre, double-blind, randomized parallel-group study. After 4 weeks of treatment a comparison was made between the once daily administered doses of 50, 100 and 200 mg as well as with placebo. The primary parameter was the mean diastolic blood pressure between 8.00 and 22.00 (dTMW). Furthermore, the duration of action of the once daily administration of 200 mg talinolol was compared with the twice daily application of 100 mg each. With regard to dTMW an increasing antihypertensive effect was determined for the dosage step from 50 mg to 100 mg talinolol/d. No further increase in the blood pressure lowering effect was observed with 200 mg talinolol/d. The highest frequency of therapy responders was found in the 100 mg group with 72.2%. Moreover it could be demonstrated, that within the dosage range of 1 x 100-200 mg Talinolol/d a significant and 24 h lasting reduction of blood pressure and pulse rate was achieved, including the early morning period. There were no differences between the blood pressure profile of the 200 mg group and the 2 x 100 mg group at the end of the 4 weeks treatment. All talinolol dosages investigated in this study were proved to be safe and well tolerated. The observed complaints classified as adverse drug reactions represented typical side effects of beta-blockers of mild to moderate intensity. It can be concluded from the results that the once daily intake of talinolol in the dosage range of 100-200 mg/d shows a reliable efficacy in the treatment of essential hypertension accompanied by a noncritical safety profile.

Adolescent↗
PubMed1997

A controlled study of 2 doses of idebenone in the treatment of Alzheimer's disease.

Two doses of idebenone were studied in a prospective, randomized, double-blind, placebo-controlled multicentre study in patients suffering from dementia of the Alzheimer type (DAT) of mild to moderate degree. Diagnosis was based on DSM-III-R (primary degenerative dementia) and NINCDS-ADRDA criteria (probable Alzheimer's disease). A total of 300 patients were randomized to either placebo, idebenone 30 mg t.i.d. or 90 mg t.i.d. (n = 100, each) and treated for 6 months. The primary outcome measure was the total score of the Alzheimer's Disease Assessment Scale (ADAS-Total) at month 6. Secondary outcome measures were the ADAS cognitive (ADAS-Cog) and noncognitive scores (ADAS-Noncog), the clinical global response (CGI-Improvement), the MMSE, the Digit Symbol Substitution test (DSS) and several scales for the assessment of daily activities (the self- and observer-rating scales NAA and NAB of the Nuremberg Age Inventory NAI and Greene's Assessment). Safety parameters were adverse events, vital signs, ECG and clinical laboratory parameters. Clinical and psychometric evaluations were performed at baseline, and after 1, 3 and 6 months of treatment. After month 6 idebenone 90 mg t.i.d. showed statistically significant improvement in the primary efficacy variable ADAS-Total and in ADAS-Cog. An analysis of therapy responders performed for 3 outcome measures (CGI-global improvement, ADAS-Cog, ADAS-Noncog), selected to represent different domains of assessment, revealed significant superiority of idebenone 90 mg t.i.d. with respect to placebo in each of the 3 variables and in the concordance of responses across the 3 measures. Exploratory results for a subgroup of patients (ADAS-Total > or = 20) showed dose-related superiority of idebenone additionally on ADAS-Noncog and the CGI-Improvement scale. Safety results were inconspicuous for all assessments. The study results demonstrate the efficacy and safety of idebenone in the treatment of DAT patients.

Aged↗
PubMed1997

The AMDP modules I-IV: recommendations for a standardized acquisition of EEG data in psychiatry. Association for Methodology and Documentation in Psychiatry.

During the last few years, the working group 'Psychophysiology' of the Association for Methodology and Documentation in Psychiatry (AMDP) discussed the possibility of the establishment of defined EEG modules in psychiatry. It was the aim to create a common data pool in order to be able to have access to larger data sets. The installation of such a common data pool was regarded as an important prerequisite for a future diagnostic application of EEG and EP data in clinical practice. The most relevant arguments are: From a statistical point of view, multivariate investigations can be improved when relatively large data sets are available. Subgrouping of patients is facilitated. Different centers have access to different populations of patients. Furthermore, compliance with the recommendations contributes to a reduction in misunderstanding and false interpretation of other investigators' results. The working group 'Psychophysiology' of the AMDP now recommends EEG modules to be registered in psychiatry. The recommendations are based on investigations using these modules in clinical research and practice as well as several years of discussion within the working group. Four AMDP modules (I-IV) are presented: MI: resting EEG (closed eyes), MII: resting EEG (eyes open), MIII: EEG during videotracking, and MIV: EEG during choice reaction time. Recommendations for additional modules are planned in the near future: MV: EEG during geometry test, MVI: EEG during labyrinth test, and MVII: amplitude stimulus intensity function. MIII-MVI is paralleled by an EEG recording so that psychomotor performance can be measured and EEG data under different activation conditions are available. Compliance with the recommendations guarantees the possibility of access to the common data pool. Computer software is available in Berlin.

Electroencephalography↗
PubMed1997

On the use of neural network techniques to analyse sleep EEG data. First communication: application of evolutionary and genetic algorithms to reduce the feature space and to develop classification rules.

To automate sleep stage scoring, the system sleep analysis system to challenge innovative artificial networks (SASCIA) has been developed and implemented. The aims of our investigation were twofold: In addition to automatic sleep stage scoring the hypothesis was tested that the information of only 1 EEG channel (C4-A2) should be sufficient to automatically generate sleep profiles which are comparable with profiles made by sleep experts on the basis of at least 3-channel EEG (C4-A2), EOG and EMG, as EOG and EMG are seen as epiphenomena during sleep and the full information about the sleep stage should--according to our hypothesis--be available in the EEG. The main components of the SASCIA sleep analysis system are designed to meet the requirements of flexible adaptation to the interindividual differences of the sleep EEG. The core of the SASCIA sleep analysis system consists of neural networks. Supervised learning was implemented and the experts' scorings were included into the learning set and test set. The feature selections out of a large number (118) are performed by genetic algorithms and the topologies of the networks are optimized by evolutionary algorithms. Different mathematical procedures were used to evaluate and optimize the efficiency of the system. The profiles generated by SASCIA are in reasonable agreement with the sleep stages scored by experts according to RKR. The development of the system is communicated in three parts: the first communication deals with the application of the neural network techniques using evolutionary and genetic algorithms and with the selection of feature space. The second communication shows the training of these evolutionary optimized network techniques with multiple subjects and the application of context rules, while the third communication shows an improvement in the robustness by the simultaneous application of 9 different networks obtained from 9 subject types which were used in combination with context rules.

Algorithms↗
PubMed1996

Proof of efficacy of the ginkgo biloba special extract EGb 761 in outpatients suffering from mild to moderate primary degenerative dementia of the Alzheimer type or multi-infarct dementia.

The efficacy of the ginkgo biloba special extract EGb 761 in outpatients with presenile and senile primary degenerative dementia of the Alzheimer type (DAT) and multi-infarct dementia (MID) according to DSM-III-R was investigated in a prospective, randomized, double-blind, placebo-controlled, multi-center study. After a 4-week run-in period, 216 patients were included in the randomized 24-week treatment period. These received either a daily oral dose of 240 mg EGb 761 or placebo. In accordance with the recommended multi-dimensional evaluation approach, three primary variables were chosen: the Clinical Global Impressions (CGI Item 2) for psychopathological assessment, the Syndrom-Kurztest (SKT) for the assessment of the patient's attention and memory, and the Nürnberger Alters-Beobachtungsskala (NAB) for behavioral assessment of activities of daily life. Clinical efficacy was assessed by means of a responder analysis, with therapy response being defined as response in at least two of the three primary variables. The data from the 156 patients who completed the study in accordance with the study protocol were taken into account in the confirmatory analysis of valid cases. The frequency of therapy responders in the two treatment groups differed significantly in favor of EGb 761, with p < 0.005 in Fisher's Exact Test. The intent-to-treat analysis of 205 patients led to similar efficacy results. Thus, the clinical efficacy of the ginkgo biloba special extract EGb 761 in dementia of the Alzheimer type and multi-infarct dementia was confirmed. The investigational drug was found to be well tolerated.

Aged↗
PubMed1996

Effect and efficacy--on the function of models in controlled phase III trials and the need for prospective pharmacoepidemiological studies.

While the "effect" of a drug can be observed or deduced from observational data, the concept of "therapeutic efficacy" represents mainly a theoretical construction of a high degree of abstraction which is inconceivable without reciprocal combination with other theoretical constructs. The "therapeutic efficacy" of drugs can be investigated only via clinical-pharmacological or clinical "models". Several examples are given and discussed against the background of the actual considerations for shortening phase III studies and extending pharmacoepidemiological phase IV studies for scientific, practical and economic reasons. Of special relevance is the question whether study data of phase III allow an extrapolation to the wider patient population which it is intended to treat. Thus, it is well known that the criteria for representativeness in the investigated population are rarely achieved in phase III studies. Furthermore, observations have shown that various intervening moderator variables, such as the investigated subgroup or the trial setting (e.g. Inpatient or respectively out-patient treatment), might influence therapeutic efficacy and the possibility of generalizing the results. This again raises the crucial question of clinical relevance of significant effects. Possible ways of overcoming this unsatisfactory situation are suggested.

Clinical Trials, Phase III as Topic↗
PubMed1996

The future of computer-assisted investigation of the polysomnogram: sleep microstructure.

Previous attempts at automated analysis of sleep were mainly directed towards imitating the Rechtschaffen and Kales rules (RKR) in order to save scoring time and further objectify the procedure. RKR, however, do not take into consideration the sleep microstructure of REM, stage 2, and SWS. While the microstructure of stage 2 has been analyzed in the past decade, the microstructure of REM and SWS are virtually unknown. In stage 2 the amount and distribution of spindles, K complexes, and arousal reactions have been studied. At least two types of spindles (12/s and 14/s) with different dynamics and locations have been identified. Two different shapes for K complexes have been described: one related to external sensory stimuli with similarities to evoked potentials and another one more related to sinusoidal slow wave activity seen in SWS. These two different K complex shapes have different distributions and, obviously, different functions. The authors also suggest that one should differentiate between arousal reactions and true arousals. Recent investigations suggest two types of delta waves in SWS. The more sinusoidal 1-3/s delta waves with a frontal maximum are already seen with lower amplitude in late stage 2 and increase their amplitude and incidence towards stage 3 and Stage 4. The other delta-wave type is slower (< 1/s), polymorphic, and has varying amounts of theta and higher frequency waves superimposed. During REM sleep it seems to be important to separate phases with rapid eye movements from those with none (REM sine REM), and count the amount and distribution of sawtooth activity. Background activity during REM and REM sine REM, as well as intra- and interhemispheric coherence should be analyzed separately. Only if the microstructure of the sleep EEG can be analyzed automatically using newer techniques such as transformation into wavelets and pattern classification with neuronal networks, and only if we learn more about the importance of microstructure elements, can automated sleep analysis go beyond the limited information obtained from scoring according to RKR.

Arousal↗
PubMed1996

The use of diurnal vigilance changes in the EEG to verify vigilance-enhancing effects of memantine in a clinical pharmacological study.

In elderly subjects there is a vigilance decrease from morning to noon which was used in a clinical pharmacological model as a state condition to verify vigilance-enhancing effects of an antidementia drug. In this model the effects of Memantine (20 mg, single-dose application) on the quantified EEG were investigated in 16 elderly (mean age: 65 +/- 5 years), healthy subjects (10 females, 6 males) in a randomised, twofold cross-over design vs. placebo under double-blind conditions. EEG was recorded before medication, and 2 and 4 h after medication under reaction time (RT) and resting (RS) conditions. EEG data were subjected to spectral analysis and the topographic distribution of the amplitude values was mapped. The results show that a time-dependent decrease (from morning to noon) in vigilance (indicated by an increase in average EEG amplitudes caused by increased synchronisation in the alpha and beta range and an increase in delta) occurred under placebo which was counteracted by Memantine. The diurnal variations of the EEG and their compensation by a pharmacological agent represent an effective model for investigating the vigilance-enhancing effects of antidementia drugs.

Aged↗