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PubMedDate not supplied

Redundancy and synergy arising from pairwise correlations in neuronal ensembles.

Multielectrode arrays allow recording of the activity of many single neurons, from which correlations can be calculated. The functional roles of correlations can be revealed by measures of the information conveyed by neuronal activity; a simple formula has been shown to discriminate the information transmitted by individual spikes from the positive or negative contributions due to correlations (Panzeri et al., 1999). Here, this analysis, previously applied to recordings from small ensembles, is developed further by considering a model of a large ensemble, in which correlations among the signal and noise components of neuronal firing are small in absolute value and entirely random in origin. Even such small random correlations are shown to lead to large possible synergy or redundancy, whenever the time window for extracting information from neuronal firing extends to the order of the mean interspike interval. In addition, a sample of recordings from rat barrel cortex illustrates the mean time window at which such "corrections" dominate when correlations are, as often in the real brain, neither random nor small. The presence of this kind of correlations for a large ensemble of cells restricts further the time of validity of the expansion.

Action Potentials↗
PubMed1996

The analysis of complex motion patterns by form/cue invariant MSTd neurons.

Several groups have proposed that area MSTd of the macaque monkey has a role in processing optical flow information used in the analysis of self motion, based on its neurons' selectivity for large-field motion patterns such as expansion, contraction, and rotation. It has also been suggested that this cortical region may be important in analyzing the complex motions of objects. More generally, MSTd could be involved in the generic function of complex motion pattern representation, with its cells responsible for integrating local motion signals sent forward from area MT into a more unified representation. If MSTd is extracting generic motion pattern signals, it would be important that the preferred tuning of MSTd neurons not depend on the particular features and cues that allow these motions to be represented. To test this idea, we examined the diversity of stimulus features and cues over which MSTd cells can extract information about motion patterns such as expansion, contraction, rotation, and spirals. The different classes of stimuli included: coherently moving random dot patterns, solid squares, outlines of squares, a square aperture moving in front of an underlying stationary pattern of random dots, a square composed entirely of flicker, and a square of nonFourier motion. When a unit was tuned with respect to motion pattern producing the most vigorous response in a neuron was nearly the same for each class. Although preferred tuning was invariant, the magnitude and width of the tuning curves often varied between classes. Thus, MSTd is form/cue invariant for complex motions, making it an appropriate candidate for analysis of object motion as well as motion introduced by observer translation.

Animals↗
PubMed2005

On the relationships between kinetic schemes and two-state single molecule trajectories.

Trajectories of a signal that fluctuates between two states which originate from single molecule activities have become ubiquitous. Common examples are trajectories of ionic flux through individual membrane channels and of photon counts collected from diffusion, activity, and conformational changes of biopolymers. By analyzing the trajectory, one wishes to deduce the underlying mechanism, which is usually described by a multisubstate kinetic scheme. In previous works [O. Flomenborn, J. Klafter, and A. Szabo, Biophys. J. 88, 3780 (2005); O. Flomenbom and J. Klafter, Acta Phys. Pol. B 36, 1527 (2005)], we divided kinetic schemes that generate two-state trajectories into two types: reducible schemes and irreducible schemes. A full characterization of the reducible ones was given. We showed that all the information in trajectories generated from reducible schemes is contained in the waiting time probability density functions (PDFs) of the two states. It follows that reducible schemes with the same waiting time PDFs are not distinguishable; namely, such schemes lead to identical two-state trajectories in the statistical sense. In this work, we further characterize the topologies of kinetic schemes, now of irreducible schemes, and further study two-state trajectories from the two types of scheme. We suggest various methods for extracting information about the underlying kinetic scheme from the trajectory (e.g., calculate the binned successive waiting times PDFs and analyze the ordered waiting time trajectories), and point out the advantages and disadvantages of each. We show that the binned successive waiting times PDFs are not only more robust than other functions when analyzing finite trajectories, but contain, in most cases, more information about the underlying kinetic scheme than other functions in the limit of infinitely long trajectories. For some cases, however, analyzing the ordered waiting times trajectory may supply unique information about the underlying kinetic scheme.

Journal Article↗
PubMed2005

From single genes to co-expression networks: extracting knowledge from barley functional genomics.

The paper reports an 'in silico' approach to gene expression analysis based on a barley gene co-expression network resulting from the study of several publicly available cDNA libraries. The work is an application of Systems Biology to plant science: at the end of the computational step we identified groups of potentially related genes. The communities of co-expressed genes constructed from the network are remarkably characterized from the functional point of view, as shown by the statistical analysis of the Gene Ontology annotations of their members. Experimental, lab-based testing has been carried out to check the relationship between network and biological properties and to identify and suggest effective strategies of information extraction from the network-derived data.

Computational Biology↗
PubMed2026

The reporting and handling of missing data in genetic epidemiological studies of mental health in childhood and adolescence: A systematic review.

BACKGROUND: Genetic epidemiological analyses of child and adolescent mental health often use data from prospective longitudinal cohorts. Missingness due to selective attrition is therefore an important potential source of bias in such analyses. Informatively reporting on missingness and taking appropriate steps to handle it in analyses can mitigate this potential bias. Here, we aim to systematically assess how researchers report and address missingness in genetic epidemiological studies of child and adolescent mental health-related outcomes using cohort data. METHODS: We systematically searched the Ovid Medline database for studies published between August 2012 and August 2025, reporting polygenic score, genome-wide association, or Mendelian randomization analyses, of data on children or adolescents participating in cohort studies. We extracted information from eligible studies based on criteria adapted from the strengthening and reporting of observational studies in epidemiology (STROBE) guidelines. RESULTS: A total of 133 eligible studies were included, of which 125 (93.98%) reported the number of complete cases in all waves, while 84 (63.16%) detailed the amount of missingness on all key variables. Most studies used complete case analysis, while 39 studies explicitly reported applying other methods to handle missingness, with multiple imputation (n = 20, 15.04%) being the most common, followed by full information maximum likelihood 10 (8.1%). Only 18 studies (13.53%) reported an assumed missing mechanism along with the method used to address missingness. Full reporting of both the extent and handling of missingness at the item level was rare, occurring in only 5 (3.76%) and 15 (11.28%) studies, respectively, among the 123 studies that used multi-item instruments. CONCLUSION: Best practice recommendations for reporting on missing data handling emphasize the importance of detailing the proportion of missingness, types of mechanisms underpinning missingness, and details of approaches used. Based on this review, these recommendations for proper reporting of missing data are rarely followed in full.

children and adolescents↗
PubMed1998

Semiparametric linkage analysis using pseudolikelihoods on neighbouring sets.

For many complex diseases, study has suggested that the disease genes influence not only the occurrence of the disease, but also the age of onset. Current methods in linkage analysis are mainly concentrated on affected relative pairs or affected family members, and age of onset information is either ignored or is taken into account by specifying age-dependent penetrances for liability classes. In fact, affected relatives with different ages of onset may be the result of different genetic aetiologies and unaffected relatives are censored at the study time. Therefore, incorporation of age of onset and including contrasts between affected and unaffected pedigree members are important components of effective analysis for the detection of linkage with genetic markers. We use multiple markers to infer the inheritance vector in order to extract information about the inheritance pattern of the disease allele in a pedigree. For a given inheritance vector, we define two neighbour sets for each individual based on allele identical by descent (IBD). We then use the within-set and between-sets conditional hazard ratios to characterize the dependence of age of onset among relatives. A pseudolikelihood ratio test is proposed for testing linkage. Simulated and real data sets are used to illustrate these new statistical methods.

Age of Onset↗
PubMed1989

Disparity curvature and the perception of three-dimensional surfaces.

BINOCULAR stereopsis provides information about the relative distance of objects from the differences in the horizontal position of their images on the two retinas. Because the size of the disparity between two points is inversely related to the square of the viewing distance, it is usually assumed that disparities have to be scaled according to distance using the vergence angle of the eyes, or by using the small vertical disparities that also exist between corresponding points of the two images. Here we present evidence that the visual system could extract information about the shapes of surfaces (without the need for scaling) by using the second spatial derivative of disparity--disparity curvature--which remains invariant with viewing distance. Rather than computing the second derivative, we suggest that an approximation to disparity curvature could be derived from the differences in curvature of corresponding line elements in the two eyes.

Discrimination, Psychological↗
PubMedDate not supplied

Desktop image analysis: workstations of the future.

We report the use of an interactive graphics-oriented workstation to explore quantitative information extracted from medical images. At the University of California at Los Angeles, a Macintosh II personal computer operates as a stand-alone system and images are imported from a central PACS (picture archiving and communication system) server through an Ethernet network. The image-analysis program contains a complete set of general-purpose tools for image manipulation and processing, as well as specific tools for clinical analysis of cardiac and vascular images obtained by various techniques. Most of these features were designed to communicate information through color-coded graphic displays. Ten novice users were given a brief introduction to the program and asked to perform eight analytic tasks. The overall success rate was 95%, and the subjects considered the program easy to use without a manual or formal training. We conclude that with a well-designed graphic interface, physicians without training in the use of computers can easily learn to manipulate and analyze medical images.

Computer Graphics↗
PubMed2003

Revealing system dynamics through decomposition of the perturbation domain in two-dimensional correlation spectroscopy.

A technique is presented to simply and effectively decompose the perturbation domain in two-dimensional (2D) correlation maps calculated on a given set of vibrational spectra. Decomposition of the perturbation domain exposes a wealth of kinetic information complementary to the information extracted from conventional 2D correlation spectroscopy. It is shown that the technique produces "perturbation profile maps" that can be utilized in both the interpretation of the conventional 2D correlation maps and the independent kinetic analysis of the given system. Discrimination between spectral features exhibiting similar, but not identical, dynamics is facilitated by the decomposition, and spectral features exhibiting identical dynamics over the perturbation interval are quickly identified. Spectral features exhibiting similar dynamics over only a sub-range of the full perturbation are also identifiable. Interpretation of phase information illuminated in synchronous and asynchronous maps is simplified. Comparison between similar spectral features present in different samples is facilitated with the technique. The simplicity and ease of implementation of the technique make decomposition of the perturbation domain a valuable addition to the tools available in 2D correlation analysis.

Journal Article↗
PubMed1997

Zafirlukast: the first leukotriene-receptor antagonist approved for the treatment of asthma.

OBJECTIVE: To review the pharmacology, pharmacokinetics, clinical efficacy, and adverse effects of zafirlukast. Therapeutic issues regarding the use of a leukotriene-receptor antagonist as prophylactic antiinflammatory therapy for asthma are also discussed. DATA SOURCES: A MEDLINE search was conducted to identify pertinent literature, including preclinical trials, clinical trials, and reviews. Pharmacokinetic and dosing information were abstracted from the product labeling. STUDY SELECTION: All available published articles describing double-blind, placebo-controlled trials of both oral and aerosol zafirlukast in patients with asthma or rhinitis were reviewed. These included single-dose studies with zafirlukast against exercise, allergen, leukotriene D4 (LTD4), and platelet-activating factor (PAF) challenges, and 6- and 13-week trials in patients with asthma. Studies describing clinical trials with long-term use or comparisons with other asthma medications as reported in abstracts are also included. DATA EXTRACTION: Information on the safety and efficacy of zafirlukast from single- and multiple-dose studies was evaluated on the basis of statistical significance relative to placebo treatment. DATA SYNTHESIS: Zafirlukast, a potent and selective antagonist of the cysteinyl leukotriene receptor, blocks leukotriene-mediated pathologic events in both experimental animal and clinical disease models. Zafirlukast antagonizes LTD4-, PAF-, and exercise-induced bronchoconstriction, and blocks both early- and late-phase responses following allergen provocation in patients with atopic asthma. Greater efficacy is noted following oral administration than with aerosol dosing, presumably because of the enhanced delivery of drug when ingested rather than inhaled. CONCLUSIONS: Zafirlukast is the first orally active leukotriene-receptor antagonist approved by the Food and Drug Administration for the prophylactic and chronic treatment of asthma. Since the leukotrienes play an important role in the underlying inflammatory processes of asthma, zafirlukast represents a new antiinflammatory option available in an oral dosage form. It is clear that this agent has therapeutic activity in patients with asthma, but its effectiveness relative to other antiasthma medications still needs confirmation. Data from clinical studies support the use of zafirlukast as first-line therapy in patients with mild-to-moderate asthma. Further research is needed to establish its role as an add-on agent for patients with severe asthma, aspirin-sensitive asthma, and both allergies and asthma. In addition to having a favorable safety and efficacy profile, zafirlukast has the advantage of being an oral agent with twice-daily dosing; these attributes offer the potential for greater patient adherence to pharmacotherapy and, thereby, improved control of asthma symptoms.

Animals↗
PubMed2006

[The secondary prevention of ischaemic heart disease in Spain. A systematic review of observational studies].

OBJECTIVE: To describe the use of ischaemic heart disease (IHD) secondary prevention measures in the Spanish National Health System. DESIGN: Systematic review of observational studies with information on the use of preventive treatment and measures in the prevention of secondary IHD. SETTING: Primary care and specialised out-patient clinics. DATA SOURCES: Medline search and complementary searches of studies published between 1995 and 2004 with a description of the use secondary prevention measures on hospital discharge or in the follow up after discharge. SELECTION OF STUDIES: A total of 125 references were found after the MEDLINE search, 13 of which were selected after an independent review by 2 researchers. The complementary sources provided 9 more studies giving a total of 22. DATA EXTRACTION: One researcher extracted information on the characteristics of the study and the results variables, which were independently verified by a second evaluator. RESULTS. In the 22 studies found, a high level of variation was shown in the different treatment rates: anti-aggregants (at discharge, 72%-97.1%; follow-up, 46.4%-93.8%); beta-blockers (at discharge, 29%-68.3%; follow-up, 22.4%-59.0%); drugs with action on the renin-angiotensin system (at discharge, 16.2%-52.2%; follow-up, 6.1%-53.1%); lipid lowering drugs (at discharge, 6.7%-88.7%; follow-up, 24.5%-89.5%). The treatment rates showed a progressive improvement over time during the period studied. CONCLUSIONS: In the period 1994-2003 treatment rates in the secondary prevention of IHD have increased, although there is still much room for improvement.

Cardiovascular Agents↗
PubMed1997

HLA-B27-associated cardiac disease.

PURPOSE: To review the available information about cardiac disease in relation to the immunogenetic marker HLA-B27 and the inflammatory disorders associated with it (seronegative spondyloarthropathies). DATA SOURCES: English-language clinical studies, case reports, and reviews published in 1995 or earlier were identified from a search of the MEDLINE database. These papers, textbooks, and other bibliographic sources were used to identify other relevant publications, enabling collection of references from 1936 through 1995 in a stepwise manner. STUDY SELECTION: Clinical studies, case reports, and topical reviews on the HLA-B27 histocompatibility locus, seronegative spondyloarthropathies, and cardiac disease were selected. DATA EXTRACTION: Information from systemic or hypothesis-driven studies, including those showing clinically and statistically meaningful associations between disorders, and additional relevant information from case reports and reviews is presented. DATA SYNTHESIS: Immunogenetic, histopathologic, clinical, and electrophysiologic evidence was examined to explore the concept of HLA-B27-associated cardiac disease. RESULTS: Relative to the general population (in which the frequency is 6% to 8%), men (but not women) with pacemakers have a significantly increased frequency of HLA-B27. Furthermore, a cardiac syndrome that consists of severe conduction system abnormalities plus aortic regurgitation is associated with HLA-B27, which was present in 67% to 88% of the patients with both of these clinical findings. This proportion of HLA-B27 is similar to that found in patients with ankylosing spondylitis and Reiter disease. Cardiac and aortic tissue both show intimal proliferation of small arteries (obliterative endarteritis) and fibrosis, as seen in tissues adjacent to afflicted joints. Both cardiac conduction abnormalities and aortic regurgitation occur in patients with various HLA-B27-related extracardiac disorders, regardless of the severity of the latter; in about 50% of patients with these cardiac findings, a diagnosis of an HLA-B57-related rheumatic disease has not previously been made. Third-degree (complete) atrioventricular block related to HLA-B57 is located within the atrioventricular node in 95% rather than the expected 20% of cases. CONCLUSIONS: The heart and the joints are both of major importance as targets for the HLA-B57-associated disease process. HLA-B57-related cardiac lesions may be found in the absence of other rheumatologic manifestations. Furthermore, a genetically linked cardiac syndrome has been defined: the combination of conduction system abnormalities and aortic regurgitation.

Arrhythmias, Cardiac↗
PubMed2004

Second-order motion conveys depth-order information.

Psychophysical and neurophysiological studies have revealed that the visual system is sensitive to both "first-order" motion, in which moving features are defined by luminance cues, and "second-order" motion, in which motion is defined by nonluminance cues, such as contrast or flicker. Here we show psychophysically that common types of second-order stimuli provide potent cues to depth order. Although motion defined exclusively by nonluminance cues may be relatively rare in natural scenes, the depth-order cues offered by second-order stimuli arise ubiquitously as a result of occlusion of one moving object by another. Our results thus shed new light on the ecological importance of second-order motion. Furthermore, our results imply that visual cortical areas that have been shown to be responsive to second-order motion may be extracting information not just about object motion as has been assumed, but also about the relative depth of objects.

Cues↗
PubMed2005

Does the acoustic waveform mirror the voice?

Over recent decades, much effort has been invested in the search for acoustic correlates of vocal function and dysfunction. The convenience of non-invasive voice measurements has been a major incentive for this effort. The acoustic signal is a rich but also very diversified source of information. Computer literacy and technical curiosity in the voice care and voice performance communities are now higher than ever, and tools for voice analysis are proliferating. On such a busy scene, a review may be useful of some basic principles for what we can and cannot hope to determine from non-invasive acoustic analysis. One way of doing this is to consider communication by voice as though it were engineered, with layered protocols. This results in a scheme for systematizing the many sources of variation that are present in the acoustic signal, that can complement other strategies for extracting information.

Humans↗
PubMed2005

Resolving abbreviations to their senses in Medline.

MOTIVATION: Biological literature contains many abbreviations with one particular sense in each document. However, most abbreviations do not have a unique sense across the literature. Furthermore, many documents do not contain the long forms of the abbreviations. Resolving an abbreviation in a document consists of retrieving its sense in use. Abbreviation resolution improves accuracy of document retrieval engines and of information extraction systems. RESULTS: We combine an automatic analysis of Medline abstracts and linguistic methods to build a dictionary of abbreviation/sense pairs. The dictionary is used for the resolution of abbreviations occurring with their long forms. Ambiguous global abbreviations are resolved using support vector machines that have been trained on the context of each instance of the abbreviation/sense pairs, previously extracted for the dictionary set-up. The system disambiguates abbreviations with a precision of 98.9% for a recall of 98.2% (98.5% accuracy). This performance is superior in comparison with previously reported research work. AVAILABILITY: The abbreviation resolution module is available at http://www.ebi.ac.uk/Rebholz/software.html.

Abbreviations as Topic↗
PubMed2004

Robust neurofuzzy rule base knowledge extraction and estimation using subspace decomposition combined with regularization and D-optimality.

A new robust neurofuzzy model construction algorithm has been introduced for the modeling of a priori unknown dynamical systems from observed finite data sets in the form of a set of fuzzy rules. Based on a Takagi-Sugeno (T-S) inference mechanism a one to one mapping between a fuzzy rule base and a model matrix feature subspace is established. This link enables rule based knowledge to be extracted from matrix subspace to enhance model transparency. In order to achieve maximized model robustness and sparsity, a new robust extended Gram-Schmidt (G-S) method has been introduced via two effective and complementary approaches of regularization and D-optimality experimental design. Model rule bases are decomposed into orthogonal subspaces, so as to enhance model transparency with the capability of interpreting the derived rule base energy level. A locally regularized orthogonal least squares algorithm, combined with a D-optimality used for subspace based rule selection, has been extended for fuzzy rule regularization and subspace based information extraction. By using a weighting for the D-optimality cost function, the entire model construction procedure becomes automatic. Numerical examples are included to demonstrate the effectiveness of the proposed new algorithm.

Journal Article↗
PubMedDate not supplied

Diffusion-weighted NMR imaging: application to experimental focal cerebral ischemia.

Changes in diffusion NMR imaging are believed to be based on intra/extracellular water homeostasis and will therefore reflect early disturbances of ion and water homeostasis after the onset of an ischemic event. Diffusion-weighted NMR imaging (DWI) thus has the potential to be a sensitive tool for the observation of stroke evolution. The present state of information extracted from diffusion-weighted NMR imaging for the understanding of cerebral focal ischemia in experimental research has been compiled in this review. The emphasis was set on three essential aspects of the technique in relation to focal ischemia. Firstly, the sensitivity of diffusion-weighted imaging for ischemic alterations is described. A comparison with conventional NMR imaging using relaxation time changes is included. Secondly, the comparison of the diffusion-weighted imaging with invasive techniques is discussed. Here, interpretation of the physiological, metabolic and hemodynamic alterations reflected in the observed diffusion changes is presented. The importance of regionally resolved information for a meaningful assignment of DWI changes to pathophysiological alterations is demonstrated for the differentiation between ischemic core and penumbra from DWI and quantitative diffusion coefficient data. The time dependence of correlations with physiological, biochemical and hemodynamic variables as a further important aspect is stressed. Thirdly, the potential of the technique for the assessment of development and effectiveness of new therapeutical strategies against stroke is demonstrated.

Animals↗
PubMed2002

Eye movements in iconic visual search.

Visual cognition depends critically on the moment-to-moment orientation of gaze. To change the gaze to a new location in space, that location must be computed and used by the oculomotor system. One of the most common sources of information for this computation is the visual appearance of an object. A crucial question is: How is the appearance information contained in the photometric array is converted into a target position? This paper proposes a such a model that accomplishes this calculation. The model uses iconic scene representations derived from oriented spatiochromatic filters at multiple scales. Visual search for a target object proceeds in a coarse-to-fine fashion with the target's largest scale filter responses being compared first. Task-relevant target locations are represented as saliency maps which are used to program eye movements. A central feature of the model is that it separates the targeting process, which changes gaze, from the decision process, which extracts information at or near the new gaze point to guide behavior. The model provides a detailed explanation for center-of-gravity saccades that have been observed in many previous experiments. In addition, the model's targeting performance has been compared with the eye movements of human subjects under identical conditions in natural visual search tasks. The results show good agreement both quantitatively (the search paths are strikingly similar) and qualitatively (the fixations of false targets are comparable).

Attention↗