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PubMed2006

Operant behavior of rats under fixed-interval reinforcement schedules: a dynamical analysis via the extended return map.

The extended-return-map was employed to analyze the inter-response time data of operant experiments using fixed-interval schedules and food reinforcement. After intensive training over numerous sessions, rats gradually developed several types of temporal patterns of lever pressing behaviors, which were visualized through different patterns of data point distributions in the extended-return-map. Analyses with randomly shuffled data sets confirmed that these patterns depended on the sequential order of the inter-response time data, indicating that they reflected dynamics of the behavior. A procedure was developed to quantify the difference between patterns in the extended-return-maps, thus, enabling the comparison between sessions, and between animals. Simulations suggested that, in addition to the two-state break-and-burst responding, both multiple switches of behavioral states during the inter-reinforcement periods and the acceleration of lever pressing rate should be taken into consideration for the dynamics found in the data.

Animals↗
PubMed2006

Magnocellular and parvocellular visual pathways have different blood oxygen level-dependent signal time courses in human primary visual cortex.

PURPOSE: The magnocellular and parvocellular pathways (M and P pathways) are the major pathways of the visual system, with distinct histologic and physiologic properties that may also have different metabolic characteristics. We hypothesize that the differences of the 2 visual pathways would also manifest as differences in the signal time course of blood oxygen level-dependent functional MR imaging (BOLD fMRI). The differences in BOLD signal time course may provide insight into the metabolic requirements of the 2 pathways. METHODS: Eleven fMRI sessions on 6 subjects were performed using stimuli that preferentially activated the 2 pathways. Regions commonly activated by both the M and P stimuli in the primary visual cortex (V1) were determined, and the contrast elicited by the stimulus, time-to-peak (TTP), and the full width at half maximum (FWHM) of the BOLD signal time course were measured. RESULTS: The functional stimuli activated cortical regions described previously in the literature, such as V1, V4, and V5. Within V1, the TTP of the signal time course of the 2 stimuli were statistically different, with the P stimulus generating TTPs that were on average 12% faster than the M stimulus (P = .0037). CONCLUSION: We have demonstrated the ability to functionally differentiate the M and P stimuli in a commonly activated anatomic region. Because the BOLD response is dependent on the ratio of oxyhemoglobin and deoxyhemoglobin in the blood, the difference in the BOLD time course between the 2 stimuli suggests that the oxygen demand of the 2 pathways may be different.

Brain Mapping↗
PubMed1989

[Computer-assisted measurement of biomechanical values exemplified by the renovascular system].

The high innovation in electronics and measuring techniques has influenced the development of medical equipment. The progressive miniaturization of integrated circuits yields in an increased possibility of functions with the respective technical equipments. Therewith also in medical technology more universal equipments are available. Unfortunately the development of sensors did not match the development rate in microelectronics. Hence computer-aided measuring (indirect measuring) becomes more and more important, to pick up normally non-measurable biomechanical quantities, which will be shown for the case study of the renovascular system.

Biomechanical Phenomena↗
PubMed1995

[Strategies for data analysis of brain activation studies with functional MR tomography].

The sensitivity of gradient-echo magnetic resonance imaging (MRI) to changes in cerebral blood oxygenation has been introduced for mapping functional brain activation. To benefit from the high spatial and temporal resolution of the respective dynamic MRI data sets, their analysis requires algorithms that are capable of both precisely delineating task-related activation patterns and demonstrating functional connectivity of interacting areas. Here, we present various strategies for data evaluation by means of correlational analyses that surpass the quality of subtraction-based activation maps by improving both sensitivity and robustness. On a pixel-by-pixel basis the approach correlates signal time courses with a reference function, reflecting the temporal sequence of activated and control states. Extended versions employ the calculation of auto- or cross-correlation functions that increase sensitivity, but require periodic stimulations. Following individual correction for non-specific but correlated signal fluctuations, mapping of task-related coherent activation can be improved using neighborhood principles. Such refined strategies are expected to enhance the usefulness of oxygenation-sensitive MRI for studying the functional anatomy of the human brain under both physiological and pathological conditions.

Algorithms↗
PubMed1993

Recent progress in QSAR-technology.

A short overview is given of some key developments in the field of structure-property correlations (SPC). Important improvements in hard- and software, as well as in methodology has given the chemist a number of tools permitting a rapid testing of structure-property ideas and which may be highly useful in unravelling the most relevant molecular properties in a particular series of compounds. Two main topics will be treated: method development and the use and understanding of molecular descriptors in SPC studies.

Computer-Aided Design↗
PubMed1995

A desk top computer program for visualized statistical analysis of lesional images in intracerebral hemorrhage.

Statistically identified information on the relationships between the sites of lesions in intracerebral hemorrhage (ICH), risk factors such as a smoking or drinking habit, anamnesis, and biochemical data through blood tests will extend assistance to neuromedical clinicians on their daily clinical duties. It will provide them with a useful guide to determine the method of treatment. Also, it will be a basic research material for their clinical studies on diagnosis, progress, or prognosis in ICH. In order to obtain such statistics with the help of the computer, we need to have a computationally effective image database system. As is generally known, medical image data especially requires a great amount of storage; high-speed processing techniques are therefore also needed to deal with such data effectively. In addition, it is desired that we have outputs from the analysis edited with well-visualized effect, using 3D computer graphics, etc. These are why most existing image processing systems have been designed to work on comparatively large-scale computers. So far as we know, it is hard to find a practical and inexpensive personal computer-based application system for visualized statistical analysis of lesional images in ICH. We have developed a desk top computer-based program for statistical analysis of lesional image data of ICH. With this system, we can organize a medical image database that consists of the personal data of patients with ICH (sex, age, occupation, diagnosis, symptoms, part of physical disorder, etc.), risk factors, anamnesis (cerebral apoplexy, hypertension, hypotension, corpulence, diabetes, hyperlipidemia, atrial fibrillation, valvular endocarditis, etc.), biochemical data of blood, and lesional image data from CT or MRI. This system consists of the following components: 1) database management, 2) information retrieval (IR), 3) lesional image processing, 4) statistical analysis, and 5) prognostic prediction. The images are drawn manually on prescribed data sheets by tracing CT or MRI films and are read through the image scanner; then the compressed data of the digitized images is recorded in the database. Each recorded image data consists of the following two components: the frame image that corresponds to the contour of tissues of interest on the corresponding sliced section, and the actual image that corresponds to the lesion itself. In our system, these two images are separately stored and managed so that we can effectively perform subsequent image analysis. Other variables in the database (risk factors, anamnesis, etc.) are mainly used as search keys for making the aggregate of image data by the IR subsystem. In any aggregate, its elements, namely image data, have common medical background descriptions with the search keys. These aggregates can be used as input for the lesional image processing subsystem. With this subsystem, we can obtain the accumulated distribution of frequencies within a specified range of any sliced section, display planar color maps and profiles associated with the distribution, reconstruct it in 3D form, perform transformations of 3D images (zooming, enhancement, rotation, etc.), and test the significant difference of frequencies between any two different sites. We have been making practical use of this system to find the neurological relationship between the symptom (dysarthria, and paralysis of upper/lower limbs) and the site of lesion with cerebral infarction in pons. This study is quite important since the distributions of pyramidal tract related to the above symptom in pons are not well-known compared to those in cerebral cortex, internal capsule, or cerebral peduncle. With our system, we have obtained several findings expected to be helpful for this study. However, since this study is still in the initial phases, we will only present the outcome as a working example of our system. Our system was originally developed for analyzing lesional images with ICH. However, it could

Cerebral Hemorrhage↗
PubMed1996

Baroreflex modulation of the cardiovascular system: new insights from the joint analysis of blood pressure and heart rate signals.

This paper focuses on a number of methods for the analysis of the relationship between the arterial baroreflex and different components of blood pressure and heart rate variability. Broad-band spectral analysis techniques have allowed us to obtain experimental evidence that the arterial baroreflex exerts its influence not only on fast but also on slow components of blood pressure and heart rate, i.e., on components with periods longer than 60 sec. Focusing on faster changes in blood pressure and heart rate, both time domain and frequency domain techniques have been developed to track the sensitivity of baroreflex heart rate modulation over time, either in laboratory or in daily life conditions. These approaches have considerably broadened our understanding of the role of baroreflex modulation of the heart and peripheral circulation in a number of pathological and physiological conditions.

Animals↗
PubMed1997

Computerized method of lesion volume quantitation in multiple sclerosis: error of serial studies.

This study was designed to evaluate a potentially important source of error in T2-hyperintense lesion measurement unique to longitudinal multiple sclerosis treatment trials that would not be detected by the standard intraobserver and interobserver error analyses. The effect of this "error of serial studies" was tested by using the standard-of-reference manual-outlining approach and a modified bi-feature space (statistical) approach applied to a database of five consecutive patients. To simulate the conditions of a longitudinal treatment trial, each patient had immediate repeat MR studies of the brain with imperfect head repositioning. The study hypothesis was confirmed that with an improved quantitative methodology, the "error of serial studies" (interseries error) would exceed the intraobserver error.

Brain↗
PubMedDate not supplied

Empirical decompositions of overall AIDS epidemics in local epidemics using generalized neural networks.

A generalized neural network was adapted for the simulation of processes strongly dependent upon the history, imposed by the inner own history of an individual neuronal activation. This involves the dependence of the neural network parameters upon the cumulated values of the corresponding neuron activations. When in the neural network weakly coupled blocks with strong inner couplings can be identified, the activation wave on the entire network (associated with the overall epidemic) can be decomposed into quasi-independent intra-block local activation waves, with characteristic delays between them (corresponding to the simultaneous and successive local epidemics). Special simulations on strongly connex neural network determine the typical local activation waves for various block parameters and the mentioned delays between two such successive activation waves in two coupled blocks. Another type of neural network is used to achieve the empirical decomposition of the overall epidemic into simultaneous (corresponding to a layer) and successive local epidemics (corresponding to the various epidemic waves, associated with different layers). A simpler approximative algorithm for the estimation of the number of the mentioned simultaneous local typical epidemics is also presented.

Acquired Immunodeficiency Syndrome↗
PubMed1998

A technique to take leave into account in shift-rota design.

Sick leave, vacations, and the like lead to substantial leave factors. Rota design techniques for covering leave are not always feasible. A small company was helped to develop a new rota. The main requirements were an ergonomically better rota, less overtime caused by leave, and a rota that lets employees take their vacation during the summer. The internal evaluation was unanimously positive after 1 year. A prospective leave coverage was used, with different workhours during summer and spring and with a mixture of shift work and flexible day work. Later the rota was further refined, and broader qualifications of the workers made a much simpler rota possible. The experiences of this study indicate that problems with leave can be reduced if expected variations in leave are considered in the rota design by including variations in workhours. A further promising strategy is to mix shift work with other types of work when time is not a critical factor.

Austria↗
PubMed1988

BASIC programs to compute source densities from autoradiographic cross-fire matrices.

Two different mathematical procedures to compute source densities from cross-fire matrices in quantitative EM autoradiography are reported. BASIC programs for a desk-top microcomputer were written to fit the hypothetical silver grain distribution to the observed real silver grain distribution using a non-iterative linear process (least-squares procedure) and an iterative method, which minimizes the chi-square component between the observed and computed silver grain distributions. The latter procedure uses a Gauss-Newton algorithm.

Autoradiography↗
PubMed1997

Matrix multiplication with DNA.

A DNA-based method for calculating the product of Boolean matrices or matrices containing positive, real numbers is presented. In the case of matrices containing real numbers, the manipulation of reaction conditions allows a quantitative calculation to be performed. The use of DNA to perform an analog calculation illustrates a new approach to computing with DNA.

DNA↗
PubMed2002

[Determination of the coordinates in the stereotactic computed tomography: simplification of the conventional method].

A simplification of the graphic and arithmetical method traditionally used for determination of the target stereotactic coordinates in the computed tomography is presented. The arithmetical calculation, besides simpler, is theoretically more accurate for using a real point of the stereotactic space. The proposed diagram (graphic method) presents the advantage of allowing the determination of the target stereotactic coordinates independently of the computed tomographic image size.

Mathematical Computing↗