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PubMed1992

Computer-assisted 3D-reconstruction and statistics of the limbic system. 2. Spatial statistics of the hippocampal formation, the fornix, and the mammillary bodies.

A statistical method is described to show the distribution of neuroanatomical structures within a Cartesian coordinate system from any given number of examinations. The algorithm is based on polygons derived from the outlines of neuroanatomical structures in parallel canthomeatal-orientated cutting planes. These polygons are transformed in virtual voxels, rotated into the bicommissural coordinate system, and projected onto the three main planes of this coordinate system. Areas with the same probability for the structures examined are given in these planes. As an example this method is applied to the hippocampal formation and the results attained are shown.

Hippocampus↗
PubMed2002

Statistical significance of coincident spikes: count-based versus rate-based statistics.

Inspired by different conceptualizations of temporal neural coding schemes, there has been recent interest in the search for signs of precisely synchronized neural activity in the cortex. One method developed for this task is unitary-event analysis. This method tests multiple single neuron recordings for short epochs with significantly more coincident spikes than expected from independent neurons. We reformulated the statistical test underlying this method using a coincidence count distribution based on empirical spike counts rather than on estimated spike probabilities. In the case of two neurons, the requirement of stationary firing rates, originally imposed on both neurons, can be relaxed; only the rate of one neuron needs to be stationary, while the other may follow an arbitrary time course. By analytical calculations of the test power curves of the original and the revised method, we demonstrate that the test power can be increased by a factor of two or more in physiologically realistic regimes. In addition, we analyze the effective significance levels of both methods for neural firing rates ranging between 0.2 Hz and 30 Hz.

Action Potentials↗
PubMed1990

Statistical analysis of K 2 x 2 tables: a comparative study of estimators/test statistics for association and homogeneity.

In order to control for confounding variables, epidemiologists often obtain data in the form of a 2 x 2 table. One variable is usually the disease status, while the other variable represents a dichotomous exposure variable that is suspected of being a risk factor. If a confounding variable is present, the data are often stratified into several 2 x 2 tables. The objectives of the analysis are to test for the association between the suspected risk factor and the disease and to estimate the strength of this relationship. Before estimating a common odds ratio, it is important to check whether the odds ratios are homogeneous. This paper presents the results of a Monte Carlo study that was performed to determine the size and power of a number of tests of association and homogeneity when the data are sparse. We also evaluated the performance of three estimators of the common odds ratio. For the Monte Carlo studies, equal numbers of cases and controls were used in a wide variety of sparse data situations. On the basis of these studies, we recommend the Breslow-Day test for nonsparse data, and the T4 and T5 statistics for sparse data to test for homogeneity. The Mantel-Haenszel test of association is recommended for sparse and nonsparse data sets. With sparse data, none of the odds ratio estimators are entirely satisfactory.

Case-Control Studies↗
PubMed2001

Cosmic statistics of statistics: N-point correlations.

The fully general calculation of the cosmic error on N-point correlation functions and related quantities is presented. More precisely, the variance caused by the finite volume, discreteness, and edge effects is determined for any estimator which is based on a general function of N-tuples, such as multi-point correlation functions and multi-spectra. The results are printed explicitly for the two-point correlation function (or power-spectrum), and for the three-point correlation (or bispectrum). These are the most popular statistics in the study of large-scale structure, yet the general calculation of their variance has not been performed until now.

Journal Article↗
PubMedDate not supplied

[Statistical fluctuations in processes of gene expression regulation: consideration of the problem from point of view of statistical mechanics].

The regulation of gene expression is a basic problem of biology. In some cases, the gene activity is regulated by specific binding of regulatory proteins to DNA. In terms of statistical mechanics, this binding is described as the process of adsorption of ligands on the one-dimensional lattice and has a probability nature. As a random physical process, the adsorption of regulatory proteins on DNA introduces a noise to the regulation of gene activity. We derived equations, which make it possible to estimate this noise in the case of the binding of the lac repressor to the operator and showed that these estimates correspond to experimental data. Many ligands are able to bind nonspecifically to DNA. Nonspecific binding is characterized by a lesser equilibrium constant but a greater number of binding sites on the DNA, as compared with specific binding. Relations are presented, which enable one to estimate the probability of the binding of a ligand on a specific site and on nonspecific sites on DNA. The competition between specific and nonspecific binding of regulatory proteins plays a great role in the regulation of gene activity. Similar to the one-dimensional "lattice gas" of particles, ligands adsorbed on DNA produce "one-dimensional" pressure on proteins located at the termini of free regions of DNA. This pressure, an analog of osmotic pressure, may be of importance in processes leading to changes in chromatin structure and activation of gene expression.

Adsorption↗
PubMed1992

[Clinical statistics of the Urological Clinic of Sapporo Sanjukai Hospital. Clinical statistics on patients admitted from 1985 to 1989].

A clinical statistic survey was carried out on the patient admitted, diseases and operations experienced at our urological clinic during 1985-1989. The total number of inpatients was 8,750 (The male to female ratio was 2.8:1). The major diseases of the inpatients were urolithiasis (4,134 cases, 47.2%) and benign prostatic hypertrophy (1,529 cases, 17.5%). Among the operations extracorporeal shock-wave lithotripsy 2,589 cases (44.6%) and transurethral resection of prostate 1,295 cases (22.3%) were predominant.

Adolescent↗
PubMed1985

[Clinical statistics of the Urological Clinic of East Sapporo Sanjukai Hospital. V: Clinical statistics on patients admitted in 1984].

A clinical statistic survey was carried out on the patients, diseases and operations experienced at our urological clinic in 1984. The total number of inpatients was 1314, the male to female ratio being 2.97:1. The major diseases of the inpatients were urolithiasis (452 cases, 34.4%), and BPH (297 cases, 22.6%). Among the operations, TUR-P 34.1%, ESWL 33.0%, TUR-BT 6.9% were predominant.

Adolescent↗
PubMed1980

[Selection of a statistical model for the evaluation of the reliability of the results of toxicological analyses. II. Selection of our statistical model for the evaluation].

Part II presents a statistical model devised by the authors for evaluating toxicological analyses results. The model includes: 1. Establishment of a reference value, basing on our own measurements taken by two independent analytical methods. 2. Selection of laboratories -- basing on the deviation of the obtained values from reference ones. 3. On consideration of variance analysis, t-student's test and differences test, subsequent quality controls and particular laboratories have been evaluated.

Analysis of Variance↗
PubMed1980

[Selection of a statistical model for evaluation of the reliability of the results of toxicological analyses. I. Discussion on selected statistical models for evaluation of the systems of control of the results of toxicological analyses].

2 statistical models for evaluation of toxicological studies results have been presented. Model I. after R. Hoschek and H. J. Schittke (2) involves: 1. Elimination of the values deviating from most results-by Grubbs' method (2). 2. Analysis of the differences between the results obtained by the participants of the action and tentatively assumed value. 3. Evaluation of significant differences between the reference value and average value for a given series of measurements. 4. Thorough evaluation of laboratories based on evaluation coefficient fx. Model II after Keppler et al. As a criterion for evaluating the results the authors assumed the median. Individual evaluation of laboratories was performed on the basis of: 1. Adjusted test "t" 2. Linear regression test.

Models, Theoretical↗
PubMed1998

Improvement of the quality and comparability of causes-of-death statistics inside the European Community. EUROSTAT Task Force on "causes of death statistics".

BACKGROUND: Cause-of-death statistics are widely used for comparing health characteristics of European Community (EC) countries. Before attempting to interpret between-country differences, it is essential to assess the biases affecting the comparability of the data. EUROSTAT decided to address globally this problem with the objective to improve the quality and comparability of cause-of-death data within the EC. METHODS: The material is based on a review of results of international comparative cause-of-death studies and on specific inquiries among EC. Both cause-of-death certification and codification practices are analysed. Certification is studied comparing the models of death certificates, the type of information captured, certifiers training and querying practices. The different coding systems are analysed (International classification of diseases (ICD) in use, interpretation of the ICD rules, implementation of automated coding systems). RESULTS: International studies on comparability of certification and coding practices between countries are rare. These studies are based on certification of cases histories and recoding of samples of death certificates. Recent studies on respiratory diseases, cancers and diabetes outline differences that influenced on the reported level of mortality. The specific EUROSTAT investigation (1997) outline general discrepancies: models of death certificates, nature and amount of information entered, way to establish the diagnosis, degree of consistency of the certification process, autopsy practices, certifiers practices, implementation of ICD-10 and implementation of automated coding systems. CONCLUSION: EUROSTAT studies are now focused on causes of death requiring special attention for comparability (e.g. suicide, accidental deaths, drug and alcohol related deaths, unknown and ill-defined causes), on procedures to improve the homogeneity of certifiers training and querying practices, on the effect of the transition to ICD-10. The international model of death certificate recommended by the World Health Organization should be adopted as widely as possible. Uniform complementary information (e.g. surgery, pregnancy, autopsy, place of occurrence of accidental deaths, work accident) should also be adopted. The EUROSTAT investigations must result in definitions of common recommendations and guidelines to EC.

Cause of Death↗