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J Möcks

Publications and source records attributed to J Möcks.

26 records · Page 2Linked to original sources
PubMed1984

How to select epochs of the EEG at rest for quantitative analysis.

Before performing a quantitative analysis of the EEG at rest, it has to be specified how many seconds are to be used later on, and a criterion has to be set down according to which data are selected for further analysis. In this paper it is investigated which duration is appropriate for an analysis of background, non-transient activity. Furthermore, different criteria for automatically selecting such epochs for quantitative analysis are compared with respect to broad-band parameters of a sample of 42 children. A length of 20 sec turned out to be sufficient, since using 40 sec or 60 sec did not improve the statistical variability. Moreover, a criterion based on minimizing EOG power from 1.5 to 7.5 Hz was mildly superior to other criteria considered. The particular choice of epoch was, however, less crucial than anticipated.

Adolescent↗
PubMed1983

Graphical representation of multidimensional EEG data and classificatory aspects.

EEG data are intrinsically multidimensional and this applies also to a set of broad band spectral parameters (6 parameters per derivation). Non-metric multidimensional scaling (MDS) and principal component analysis (PCA) are compared with respect to their capacity to achieve an adequate few-dimensional representation for the graphical comparison of groups and the identification of subgroups. In an application to neurophysiological aspects of mental retardation and learning disability, MDS proved to be somewhat superior to PCA. Both methods profited from the introduction of (1-p)-convex hulls to define a normative region.

Adolescent↗
PubMed1983

The EEG of mildly retarded children: developmental, classificatory, and topographic aspects.

Our investigation was concerned with 25 children, 10-13 years old, with an IQ 50-70 ("mild mental retardation," following the ICD). Among these, 14 attended a school for the mentally retarded and 11 one for the learning disabled. A control group was recruited, matched in age, sex and social class. The unipolar 8-channel record of EEG at rest was subjected to blind clinical rating, and a computerized analysis (broad band spectral parameters delta, theta, alpha 1, alpha 2, beta 1, beta 2). A significantly higher frequency of paroxysms was found by the clinical rating. It also allowed the diagnosis of a maturational lag with respect to the items "maturity" and "prominence of alpha rhythm"). Spectral parameters differentiated the two matched groups particularly in bands and leads of developmental relevance (theta, delta, and fronto-central beta in absolute power and theta, delta occipitally and alpha 2, with the exception of frontal leads for relative power).: As is well known, the mentally retarded constitute a heterogeneous group: this could also be verified with respect to EEG activity for the segment of mild mental retardation. A multivariate classification by nonmetric multidimensional scaling yielded a subgroup of 10 children deviant with respect to its overall EEG activity and a group of 15 children within the normal range. This assignment did not overlap with the assignment to the two schools. By computing ratios of broad band power in antero-posterior and symmetric-interhemispheric leads a reduced topographic differentiation was found for the experimental group in their antero-posterior distribution.

Adolescent↗
PubMed1983

SELAVCO: a method to deal with trial-to-trial variability of evoked potentials.

The possibility and the potential dangers of the inhomogeneity of potentials to repeated stimuli have been recognized for some time. The predominant method of averaging sweeps of brain activity time locked to the stimuli relies on the assumption of an invariant response. In this paper, a method is proposed for dealing more effectively with the variability of single potentials than does averaging. This method operates by weighted averaging and the weights are determined from the data after suitable filtering operations. SELAVCO is validated and compared to the average for real data and in a controlled design close to reality.

Adolescent↗
PubMed1982

Transformations towards the normal distribution of broad band spectral parameters of the EEG.

In this report transformations are evaluated for obtaining normally distributed broad band spectral parameters (both for absolute and relative power) in a sample of healthy individuals. This problem leads automatically to the question of defining a normative sample, both in terms of sampling and recording conditions; as to the latter, the electro-oculogram proved to be crucial. For relative power the transformation log(x/(1-x)) was excellent in all regards, whereas the best transformation for absolute power--log(x)--was not fully satisfactory for all bands.

Adolescent↗
PubMedDate not supplied

Comparison of mid-infrared and Raman spectroscopy in the quantitative analysis of serum.

Mid-infrared or Raman spectroscopy together with multivariate data analysis provides a novel approach to clinical laboratory analysis, offering benefits due to its reagent-free nature, the speed of the analysis and the possibility of obtaining a variety of information from one single measurement. We compared mid-infrared and Raman spectra of the sera obtained from 247 blood donors. Partial least squares analysis of the vibrational spectra allowed for the quantification of total protein, cholesterol, high and low density lipoproteins, triglycerides, glucose, urea and uric acid. Glucose (mean concentration: 154 mg/dl) is frequently used as a benchmark for spectroscopic analysis and we achieved a root mean square error of prediction of 14.7 and 17.1 mg/dl for mid-infrared and Raman spectroscopy, respectively. Using the same sample set, comparable sample throughput, and identical mathematical quantification procedures Raman and mid-infrared spectroscopy of serum deliver similar accuracies for the quantification of the analytes under investigation. In our experiments vibrational spectroscopy-based quantification appears to be limited to accuracies in the 0.1 mmol/l range.

Biomarkers↗