Detection and correction of erroneous eye movements by the brain error detector while tracking moving object

The models for research of function of the brain error detector of eye movements are described. The quantitative estimation of temporary parameters of erroneous eye saccades detection and correction of the healthy people is given. The data on distinctions in duration of the latency, speed and other parameters of erroneous and correctional saccades, are used for discussion on types of sensory signals used by the brain detector for revealing and correction of erroneous eye movements.     

Correlation of genetic and demographic differences between populations of indigenous inhabitants of the Northeastern USSR

Correlative analysis is given for some demographic characteristics in populations of asiatic eskimos, coastal and reindeer chuckchies, Kamchatka koryaks and Chukotka evens. Summarized estimation of population differences for 7 demographic parameters is presented. Highly reliable correlation of genetic distinctions as defined for 17 polymorphic loci, and demographic differences between populations estimated for 7 parameters (r = 0.868, P less than 0.001) was found. The role of ecological factors in formation of genetic structure features and application of demographic characteristics, as possible indicator of ecological particularities of the given populations, is considered.     

Comparative analysis of methods for estimating arm segment parameters and joint torques from inverse dynamics

A common problem in the analyses of upper limb unfettered reaching movements is the estimation of joint torques using inverse dynamics. The inaccuracy in the estimation of joint torques can be caused by the inaccuracy in the acquisition of kinematic variables, body segment parameters (BSPs), and approximation in the biomechanical models. The effect of uncertainty in the estimation of body segment parameters can be especially important in the analysis of movements with high acceleration. A sensitivity analysis was performed to assess the relevance of different sources of inaccuracy in inverse dynamics analysis of a planar arm movement. Eight regression models and one water immersion method for the estimation of BSPs were used to quantify the influence of inertial models on the calculation of joint torques during numerical analysis of unfettered forward arm reaching movements. Thirteen subjects performed 72 forward planar reaches between two targets located on the horizontal plane and aligned with the median plane. Using a planar, double link model for the arm with a floating shoulder, we calculated the normalized joint torque peak and a normalized root mean square (rms) of torque at the shoulder and elbow joints. Statistical analyses quantified the influence of different BSP models on the kinetic variable variance for given uncertainty on the estimation of joint kinematics and biomechanical modeling errors. Our analysis revealed that the choice of BSP estimation method had a particular influence on the normalized rms of joint torques. Moreover, the normalization of kinetic variables to BSPs for a comparison among subjects showed that the interaction between the BSP estimation method and the subject specific somatotype and movement kinematics was a significant source of variance in the kinetic variables. The normalized joint torque peak and the normalized root mean square of joint torque represented valuable parameters to compare the effect of BSP estimation methods on the variance in the population of kinetic variables calculated across a group of subjects with different body types. We found that the variance of the arm segment parameter estimation had more influence on the calculated joint torques than the variance of the kinematics variables. This is due to the low moments of inertia of the upper limb, especially when compared with the leg. Therefore, the results of the inverse dynamics of arm movements are influenced by the choice of BSP estimation method to a greater extent than the results of gait analysis.     

Spatio-temporal parameters of gait measured by an ambulatory system using miniature gyroscopes

In this study we describe an ambulatory system for estimation of spatio-temporal parameters during long periods of walking. This original method based on wavelet analysis is proposed to compute the values of temporal gait parameters from the angular velocity of lower limbs. Based on a mechanical model, the medio-lateral rotation of the lower limbs during stance and swing, the stride length and velocity are estimated by integration of the angular velocity. Measurement's accuracy was assessed using as a criterion standard the information provided by foot pressure sensors. To assess the accuracy of the method on a broad range of performance for each gait parameter, we gathered data from young and elderly subjects. No significant error was observed for toe-off detection, while a slight systematic delay (10 ms on average) existed between heelstrike obtained from gyroscopes and footswitch. There was no significant difference between actual spatial parameters (stride length and velocity) and their estimated values. Errors for velocity and stride length estimations were 0.06 m/s and 0.07 m, respectively. This system is light, portable, inexpensive and does not provoke any discomfort to subjects. It can be carried for long periods of time, thus providing new longitudinal information such as stride-to-stride variability of gait. Several clinical applications can be proposed such as outcome evaluation after total knee or hip replacement, external prosthesis adjustment for amputees, monitoring of rehabilitation progress, gait analysis in neurological diseases, and fall risk estimation in elderly.     

Physiological Mechanisms of Respiratory Phenomena in Anxiety and Depressive Disorders

An analysis is presented of the current views on the functional respiratory disorders associated with depressive and panic disorders. The following subjects are discussed: the phenomenology of the problem, modern diagnostic methods, the role of hypocapnia in the symptomatological development of panic disorders, the relative contributions of psychogenic and biological factors in developing respiratory disorders, and the distinctions between dyspnea and the hyperventilation syndrome.     

Synchronization of calcium channel activity in mollusk neurons after treatment with ferricyanide and barium ions

Using the patch-voltage-clamp method on the isolated membrane patches from molluscan neurons, effects of ferricyanide and barium on fast potassium channels with a priori destroyed synchronism in the transitions between conductance sublevels were studied. Ferricyanide (0.1-0.5 mM) applied at the inner membrane side produced irreversible transformation of occasional transitions of the channel conductance between intermediate states into highly cooperative and potential-dependent process. Barium ions completely or partly reversibly restore synchronism.     

The ontogenetic approach to chlorophyll fluorescence studies of plant photosynthetic apparatus under stressful conditions

Based on the analysis of reasons limiting the application of the method of chlorophyll fluorescence induction for estimating the state of the leaf photosynthetic apparatus under prolonged stress, the necessity of the ontogenetic approach consisting in a more exact determination of leaf age was substantiated. A comparison of the calendar and ontogenetic ways of determination of age of cucumber leaves under controlled conditions revealed essential distinctions in the estimation of plant leaf photosynthetic apparatus by the method of chlorophyll fluorescence induction for two variants distinguishing by the cultivation light regime ("white", 400-700 nm, and "red", 600-700 nm). It was shown that, in the case of prolonged effect of the stress factor on the plant, the unambiguity of the interpretation of chlorophyll fluorescence induction parameters in the estimation of the state of their photosynthetic apparatus depends essentially on the choice of the ontogenetic period of leaves of plants being compared and the accuracy of determination of leaf age.     

Random-effects models for serial observations with binary response

This paper presents a general mixed model for the analysis of serial dichotomous responses provided by a panel of study participants. Each subject's serial responses are assumed to arise from a logistic model, but with regression coefficients that vary between subjects. The logistic regression parameters are assumed to be normally distributed in the population. Inference is based upon maximum likelihood estimation of fixed effects and variance components, and empirical Bayes estimation of random effects. Exact solutions are analytically and computationally infeasible, but an approximation based on the mode of the posterior distribution of the random parameters is proposed, and is implemented by means of the EM algorithm. This approximate method is compared with a simpler two-step method proposed by Korn and Whittemore (1979, Biometrics 35, 795-804), using data from a panel study of asthmatics originally described in that paper. One advantage of the estimation strategy described here is the ability to use all of the data, including that from subjects with insufficient data to permit fitting of a separate logistic regression model, as required by the Korn and Whittemore method. However, the new method is computationally intensive.     

Data-Mining Discovery of Pattern and Process in Ecological Systems

ABSTRACT Most ecologists use statistical methods as their main analytical tools when analyzing data to identify relationships between a response and a set of predictors; thus, they treat all analyses as hypothesis tests or exercises in parameter estimation. However, little or no prior knowledge about a system can lead to creation of a statistical model or models that do not accurately describe major sources of variation in the response variable. We suggest that under such circumstances data mining is more appropriate for analysis. In this paper we 1) present the distinctions between data-mining (usually exploratory) analyses and parametric statistical (confirmatory) analyses, 2) illustrate 3 strengths of data-mining tools for generating hypotheses from data, and 3) suggest useful ways in which data mining and statistical analyses can be integrated into a thorough analysis of data to facilitate rapid creation of accurate models and to guide further research.     

Determination of DNA polymerase and nuclease activities of DNA-dependent polymerases using fluorescence detection under real-time conditions

A new method is proposed for estimation of polymerase activities using fluorescence detection during isothermal reaction. The method allows simultaneous determination of DNA-dependent DNA polymerase and 5'-3'-exonuclease activities using amplifiers supplied with an optical module for fluorescence detection under real-time conditions. Different primer-template combinations used as polymerase substrates were compared. Primer elongation (polymerase reaction) is detected by changes in SYBR Green I fluorescence upon binding to dsDNA during reaction; nuclease activities are detected by changes in fluorescence due to cleavage of the probe, containing the reporter fluorophore and fluorescence quencher, and hybridized in advance to the template single-stranded region. It was also shown that the method can be used for determination of relative activities of DNA polymerase preparations, estimation of temperature-time dissociation parameters of polymerase complexes with specific antibodies to its active center, and analysis of effects of inhibitors and activators of different nature on reaction rates of dsDNA polymerization and 5'-3'-exonuclease cleavage by polymerase. The method can be also used for estimation of endonuclease activities of DNA polymerases.     

Experience in using correlation analysis for evaluating the synchronism of the fluctuations in the level of infectious morbidity in individual areas

The possibility of using correlation analysis for evaluating the synchronism of changes in infectious morbidity rate on different territories was studied. The study demonstrated that the intensity of correlative relationships was mainly influenced by the degree of manifestation and the direction of prolonged tendencies in the changes of infectious morbidity on the territories under study. The presence of prolonged pronounced tendencies towards growth or decrease in the compared curves characterizing prolonged morbidity dynamics was found to limit the use of correlation analysis for the evaluation of synchronism of changes in morbidity rate.     

Cardiorespiratory Synchronism in Humans

Cardiorespiratory synchronism manifests itself (generally at respiratory rates higher than the corresponding baseline heart rates) when the heart adjusts itself to the respiratory rhythm and eventually beats at rate equal to the rate of respiration. Its characteristic parameters are the width of the synchronization range, the time needed for its development (measured from the onset of tachypnea), and the difference between the baseline heart rate and the lower and upper limits of the synchronization range. These parameters were determined for 5- to 65-year-old subjects.     

Metabolomic analysis of bronchoalveolar lavage fluid from cystic fibrosis patients

Metabolite profiles of bronchoalveolar lavage fluid (BALF) from pediatric patients with cystic fibrosis (CF) were correlated to the degree of airway inflammation using nuclear magnetic resonance spectroscopy-based metabolomics. BALF was collected from 11 children with CF during clinically indicated bronchoscopy. The spectra from BALF with high levels of neutrophilic airway inflammation displayed signals from numerous metabolites, whereas the spectra from subjects with low levels of inflammation were very sparse. The metabolites identified in samples taken from subjects with high inflammation include known markers of inflammation such as amino acids and lactate, as well as many novel signals. Statistical analysis highlighted the most important metabolites that distinguished the high- from the low-inflammation groups. This first demonstration of metabolomics of human BALF shows that clear distinctions in the metabolic profiles can be observed between subjects experiencing high versus low inflammation and is a first step toward the goal of discovering novel biomarkers of airway inflammation.     

Comparison of two methods for in vivo estimation of the glenohumeral joint rotation center (GH-JRC) of the patients with shoulder hemiarthroplasty

Determination of an accurate glenohumeral-joint rotation center (GH-JRC) from marker data is essential for kinematic and dynamic analysis of shoulder motions. Previous studies have focused on the evaluation of the different functional methods for the estimation of the GH-JRC for healthy subjects. The goal of this paper is to compare two widely used functional methods, namely the instantaneous helical axis (IHA) and symmetrical center of rotation (SCoRE) methods, for estimating the GH-JRC in vivo for patients with implanted shoulder hemiarthroplasty. The motion data of five patients were recorded while performing three different dynamic motions (circumduction, abduction, and forward flexion). The GH-JRC was determined using the CT-images of the subjects (geometric GH-JRC) and was also estimated using the two IHA and SCoRE methods. The rotation centers determined using the IHA and SCoRE methods were on average 1.47±0.62 cm and 2.07±0.55 cm away from geometric GH-JRC, respectively. The two methods differed significantly (two-tailed p-value from paired t-Test ～0.02, post-hoc power ～0.30). The SCoRE method showed a significant lower (two-tailed p-value from paired t-Test ～0.03, post-hoc power ～0.68) repeatability error calculated between the different trials of each motion and each subject and averaged across all measured subjects (0.62±0.10 cm for IHA vs. 0.43±0.12 cm for SCoRE). It is concluded that the SCoRE appeared to be a more repeatable method whereas the IHA method resulted in a more accurate estimation of the GH-JRC for patients with endoprostheses.     

Improving the Accuracy and Efficiency of Respiratory Rate Measurements in Children Using Mobile Devices

The recommended method for measuring respiratory rate (RR) is counting breaths for 60 s using a timer. This method is not efficient in a busy clinical setting. There is an urgent need for a robust, low-cost method that can help front-line health care workers to measure RR quickly and accurately. Our aim was to develop a more efficient RR assessment method. RR was estimated by measuring the median time interval between breaths obtained from tapping on the touch screen of a mobile device. The estimation was continuously validated by measuring consistency (% deviation from the median) of each interval. Data from 30 subjects estimating RR from 10 standard videos with a mobile phone application were collected. A sensitivity analysis and an optimization experiment were performed to verify that a RR could be obtained in less than 60 s; that the accuracy improves when more taps are included into the calculation; and that accuracy improves when inconsistent taps are excluded. The sensitivity analysis showed that excluding inconsistent tapping and increasing the number of tap intervals improved the RR estimation. Efficiency (time to complete measurement) was significantly improved compared to traditional methods that require counting for 60 s. There was a trade-off between accuracy and efficiency. The most balanced optimization result provided a mean efficiency of 9.9 s and a normalized root mean square error of 5.6%, corresponding to 2.2 breaths/min at a respiratory rate of 40 breaths/min. The obtained 6-fold increase in mean efficiency combined with a clinically acceptable error makes this approach a viable solution for further clinical testing. The sensitivity analysis illustrating the trade-off between accuracy and efficiency will be a useful tool to define a target product profile for any novel RR estimation device.     

Joint modeling and analysis of longitudinal data with informative observation times

Summary .  In analysis of longitudinal data, it is often assumed that observation times are predetermined and are the same across study subjects. Such an assumption, however, is often violated in practice. As a result, the observation times may be highly irregular. It is well known that if the sampling scheme is correlated with the outcome values, the usual statistical analysis may yield bias. In this article, we propose joint modeling and analysis of longitudinal data with possibly informative observation times via latent variables. A two-step estimation procedure is developed for parameter estimation. We show that the resulting estimators are consistent and asymptotically normal, and that the asymptotic variance can be consistently estimated using the bootstrap method. Simulation studies and a real data analysis demonstrate that our method performs well with realistic sample sizes and is appropriate for practical use.     

Comparative analysis of changes in short EEG segments during music perception based on event-related synchronization/desynchronization and wavelet synchronicity

The goal of the pilot study was to analyze the characteristics of changes in short EEG segments recorded from 32 sites during perception of musical melodies by healthy subjects depending on logical (recognition) and emotional (pleasant/unpleasant) estimation of the melody. For this purpose, the changes in event-related synchronization/desynchronization and the indices of wavelet synchrony of EEG responses were compared in 31 healthy subjects (18 to 60 years old). It has been shown that melody recognition during logical estimation of music is accompanied by event-related desynchronization in the left frontal-parietal-temporal area. Emotional estimation of a melody is characterized by event-related synchronization in the left frontal-temporal area for pleasant melodies, desynchronization in the temporal area for unpleasant melodies, and desynchronization in the occipital area for melodies inducing no emotional response. The analysis of EEG wavelet synchronization characterizing reactive changes in the interaction between cortical areas shows that the most distinct topographic differences are associated with the type of music processing: logical (familiar/unfamiliar) or emotional (pleasant/unpleasant). The changes in interhemispheric connections between the associative cortical areas (central, frontal, temporal) are greater during emotional estimation, while the changes in inter- and intrahemispheric connections between the projection areas of the acoustic analyzer (temporal area) are greater during logical estimation. It is assumed that the revealed event-related synchronization/desynchronization is most likely to reflect the activation component of musical fragment estimation, whereas wavelet analysis provides insight into the character of musical stimulus processing.     

An image analysis morphometric method for the study of myelinated nerve fibers from mouse trigeminal root

For the morphometric light microscopic study of myelinated fibers in mouse trigeminal root, it was necessary to write: (1) an entirely automatic analysis program for the myelinated axons inside the myelin sheath, based on the detection of the myelin sheaths, and (2) an interactive analysis program for the myelinated fibers outside the myelin sheath, due to the high density of compactness of the myelinated fibers based on an indirect fiber individualization by reconstructing them from their axons. In the latter, a semiautomatic correction method (drawing the profile contours with a light pen) allowed compensation for the failures of the automatic method, except for the smallest fibers, which represented 8% of the total. Using these programs, 95% of the axons could be measured and 92% of the myelinated fibers whose axons were analyzed could be measured. The area-equivalent diameter was independent of the detection method; it is a correct-size measurement parameter for axons and fibers that is unrelated to their shape. The projected diameter, an estimation of the perimeter obtained by measurement of the profile projections, depended upon the detection method because the profile contour was influenced by the detection method; it thus takes into account the profile shape. For myelinated fibers, whose analysis program used two detection methods (automatic and semiautomatic), there was an average difference of 16% between the projected diameters obtained with these two methods, whereas the equivalent diameter value was the same. The fiber circularity factor could not be precisely estimated because of the detection error; the axon circularity factor was more reliable since the axon detection was completely automatic.     

Relations between two types of the spatial-temporal organization of the human brain potentials during formation and actualization of set to a visual nonverbal stimulus

The functional state of the brain cortex estimated by the dynamic changes in the global spatio-temporal organization of brain potentials (STOP) was studied at different stages of the cognitive set formed on the basis of the image of two circles of different diameter. Thirty five subjects (predominantly, right-handed) were examined. The method of quantitative estimation of successive topograms was used for the analysis of the STOP. Two coexisting types of the STOP were described. The relations between them define the functional state of the brain. Quantitative characteristic of these relations is reflected in the value of the coefficient of dynamic variation (CDV). Group of subjects with the stable and unstable set had significantly different values of CDV during the experiment. These groups of subjects also had different topographic characteristics of the CDV.     

Comparison of three multitrait methods for QTL detection

A comparison of power and accuracy of estimation of position and QTL effects of three multitrait methods and one single trait method for QTL detection was carried out on simulated data, taking into account the mixture of full and half-sib families. One multitrait method was based on a multivariate function as the penetrance function (MV). The two other multitrait methods were based on univariate analysis of linear combination(s) (LC) of the traits. One was obtained by a principal component analysis (PCA) performed on the phenotypic data. The second was based on a discriminate analysis (DA). It calculates a LC of the traits at each position, maximising the ratio between the genetic and the residual variabilities due to the putative QTL. Due to its number of parameters, MV was less powerful and accurate than the other methods. In general, DA better detected QTL, but it had lower accuracy for the QTL effect estimation when the detection power was low, due to higher bias than the other methods. In this case, PCA was better. Otherwise, PCA was slightly less powerful and accurate than DA. Compared to the single trait method, power can be improved by 30% to 100% with multitrait methods.