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Biomedical subjects

G Nolfe

Publications and source records attributed to G Nolfe.

50 records · Page 3Linked to original sources
PubMed1985

Cluster analysis of cognitive performance in elderly and demented subjects.

48 elderly normals, 14 demented subjects and 76 young controls were tested for basic cognitive functions. All the tests were quantified and could therefore be subjected to statistical analysis. The results show a difference in the speed of information processing and in memory load between the young controls and elderly normals but the age groups differed in quantitative terms only. Cluster analysis showed that the elderly and the demented formed two distinctly separate groups at the qualitative level, the basic cognitive processes being damaged in the demented group. Age thus appears to be only a risk factor for dementia and not its cause. It is concluded that batteries based on precise and measurable tasks are the most appropriate not only for the study of dementia but for rehabilitation purposes too.

Age Factors↗
PubMed1985

Quantitative study of action tremor in various patient categories.

An electronic method is proposed for quantifying the action tremor revealed by a threefold test of skill, which distinguishes young adult controls from elderly normals and patients with tremor. Parkinsonian patients can be differentiated from patients with essential tremor. The value of drugs against tremor is discussed.

Adult↗
PubMed1985

Digital sampling rate and ECG analysis.

The influence of sampling rate on the accuracy of measurements of various ECG parameters has been studied. Statistical analysis showed no significant difference between results obtained at sampling rates of 500 and 250 samples s-1. Recordings made at 125 samples s-1, however, showed significant reductions in peak amplitude values. Some interval measurements also varied significantly to both larger and smaller values. Other intervals did not seem to be affected significantly. It is concluded that a sampling rate of 125 samples s-1 could be used in particular conditions when only the measurement of certain intervals is required.

Biomedical Engineering↗
PubMed1985

Relationship between CSF noradrenaline levels, C-EEG indicators of activation and psychosis ratings in drug-free schizophrenic patients.

A significant increase of cerebrospinal fluid (CSF) noradrenaline (NA) levels, probably reflecting a rise of central noradrenergic activity, has been observed in a sample of acute schizophrenic patients as compared with a population of subjects without personal or family history of major psychoses. CSF NA levels have been found to be significantly correlated with computerized EEG (C-EEG) indicators of arousal (negative correlation with alpha relative activity and positive correlation with alpha barycentric frequency and beta relative activity in frontal and central leads). No significant relationship has emerged between CSF NA concentration and psychosis ratings on CPRS as well as platelet MAO activity. These findings seems to confirm the link between central noradrenergic hyperactivity and the condition of enhanced arousal of the schizophrenic patient, although the role of this condition in the pathophysiology of schizophrenia (primary phenomenon or non-specific consequence of the stress related to the illness?) remains to be elucidated.

Adolescent↗
PubMed1980

Computerized EEG in schizophrenics.

20 psychiatric patients without pharmacologic therapy and an homogeneous control group of 19 healthy subjects have been submitted to an electroencephalographic (EEG) investigation. Computerized spectral analyses of the main EEG frequency bands have been performed. The spectra have been determined by some geometrical descriptors: the relative activity, the barycentric frequency and the barycentric radius; also classic descriptors have been used as complementary ones. In the EEG profile significant differences between patients and healthy subjects have been found. Some differences have also been observed among subgroups of schizophrenic patients. The geometrical descriptors applied in the EEG analysis are suggested as a useful method in the description of the basic characteristics of the main EEG frequency bands.

Adult↗
PubMed1979

Alpha increase in puerperium.

Significant increases of both alpha peak amplitude and power were found in the EEG after delivery as compared to those observed at the 32nd week of pregnancy. Controls failed to display the same gain in the alpha rhythm. The frequency was unaffected. Beside these quantitative changes no particular EEG pattern occurred. Neither the methodology nor habituation were considered responsible for these increases, which are also independent of the prolactin levels, because they were observable after blockage by bromocryptine, a drug which also fails to modify the EEG. Significant reduction of anxiety, tension and irritability was scored in the Hamiltonian test for depression. It is likely that both aspects depend on a common humoral process. The role of the progesterone drop is discussed.

Adult↗
PubMed1977

Applications of statistical equivalence to newborn EEG recordings.

Epochs were selected from sleep EEGs of newborns during both quiet and REM phases. A first order parameter analysis was done in order to test the homogeneity (run test and one way variance analysis) of the data within the epochs, follwed by a study of spectral equivalence between epochs. Comparisons were made between average spectra in the frequency range 0.5--4 c/sec; and between their band-by-band components, to test the feasibility of automatic classification of sleep stages by means of frequency analysis. On the basis of the statistical parameters we used, spectral analysis appears to be of limited value for the purpose of automatic classification of newborn EEG records; due to a lack of complete homogeneity of the spectra within each sleep state, it is not possible to identify a characteristic spectrum for active sleep and quiet sleep.

Electroencephalography↗
PubMedDate not supplied

EEG power spectrum typical of vascular dementia in a subgroup of Alzheimer patients.

A statistical comparative study was carried out between two subgroups of patients with dementia, i.e. 22 with Alzheimer's dementia (AD, 44% of the entire Alzheimer group examined) and 36 with vascular dementia (VaD, 97% of the entire vascular group). The selection of the two subgroups was based on a similar EEG spectral profile in the rest eyes closed condition: a great increase in low frequency powers and a dominant activity in the 6.5-12 Hz band. The aim was to identify any possible difference between the two groups analysing the spectral descriptors, of the two conditions eyes closed and open, the demographic figures and the mental deterioration scores. The results are as follows: (i) the spectral profiles and their numerical descriptors of the AD subgroup patients are not distinguishable from the same parametric figures of the VaD patients; (ii) the spectral analysis becomes useful in differentiating the two types of dementia when a dynamic EEG is processed, i.e. the power ratio of recordings during eyes closed and open; (iii) a more severe mental deterioration, especially in attention and spatial and temporal orientation was found in the AD group as compared to the VaD. The findings are explained in the light of the changes in neural mechanisms which underlie both the alpha and slow rhythms.

Journal Article↗
PubMedDate not supplied

Chest conduction properties and ECG equalization.

In common practice of detecting and recording biomedical signals, it is often implicitly assumed that the propagation, through the whole circuit human body-electrodes recording devices, is frequency and voltage independent. As a consequence, clinicians are not aware that recorded signals do not correspond faithfully to the original electrical activity of organs under investigation. We have studied the transmission of electrical signals in human body at various voltages and frequencies to understand if and to which extent the most diffused stimulating and recording techniques used in medicine are affected by global body conduction properties. Our results show that, in order to obtain a more faithful detection of electrical activity produced or evoked by human organs (e.g. EGG, electromyography, etc.), it is convenient to 'equalize'' recorded signals. To this purpose, two equalization techniques are proposed, based, respectively, on a simple hardware filtering during acquisition, or FFT post-processing of the acquired signals. As an application, we have studied the transmission of electrical signal in human chest and have compared equalized high frequency ECG signals with raw (original) recordings.

Electric Conductivity↗
PubMedDate not supplied

[Our experience with rheoencephalography. Qualitative REG study of 1000 cases of verified chronic cerebrovascular insufficiency].

After a detailed review of literature basic and clinical data on rheoencephalography (R.E.G.) the findings of 1000 patients suffering from verified brain blood supply impairment submitted to REG studies are exposed. Following parameters of REG curve have been analysed: sphygmic amplitude, sphygmic interrelations between two homologous brain regions; sphygmic speed, rise time, slope of REG curve, dicrotic incisure, random oscillations of catacrotic phase. A reduction in sphygmic speed has been observed in 70 % of cases, with changes in slope of REG curve in 90 % and reduction or disappearance of catacrotic dicrotism in 93.5 % and progressively less frequent changes in the remaining REG parameters. The obtained data have been submitted to statistical analysis. Significant associations have been observed between two or more pathological REG parameters and between the pathology of REG curve as a whole and the different invasive methods employed for assessing the cerebrovascular insufficiency such as CT, CBF studies and angiographic data. Not significant correlations between the focal REG pathology, and the focal changes of REG or of the invasive methods have been found. The systematic employment of REG study as a non invasive method for the screening of cerebral blood impairment is recommended.

Adult↗
PubMedDate not supplied

Multimodality evoked potentials in sporadic amyotrophic lateral sclerosis: a statistical approach.

The involvement of sensory pathways in patients suffering from amyotrophic lateral sclerosis (ALS) is well reported in histopathological studies. Several laboratories have also used evoked potentials to evidentiate subtle dysfunctions of sensory systems in such patients. However, conflicting results have been presented in studies using evoked potentials. In the present experiment we have evaluated multimodality evoked potentials in subjects with sure diagnosis of sporadic ALS, by means of the Bonferroni multiple comparisons procedure. Our principal findings are: a) no statistical difference between patients and controls in BAEP and VEP recordings; b) a reduction of N13 amplitude and a prolonged P22 latency in SEP recordings. Due to the sources of N13 and P22, these latter alterations, however, do not implicate the involvement of somatosensory pathway. In conclusion, the current investigation does not provide an electrophysiological support for the involvement of sensory systems in the sporadic ALS.

Aged↗