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PubMed1993

Epithelial cell detachment in the nephrotic glomerulus: a receptor co-operativity model.

Detachment of epithelial cells from the glomerular capillary wall correlates with the massive increase in protein leakage across the capillary wall that is characteristic of many renal diseases. We introduce the hypothesis that this detachment process involves three classes of physical events acting at the subcellular level: the receptor-mediated binding of epithelial cells to basement membrane, the transglomerular hydraulic pressure gradient acting to lift the cells off the basement membrane, and a receptor-receptor co-operativity induced by mechanical deformations of the epithelial cell surface. After presenting the available evidence, we explore the hypothesis by means of a simplified, quantitative model of the detachment process. The model is developed by mapping between the stochastic events of cell adhesion receptor binding and the equilibrium statistical mechanics of the Ising model. Monte Carlo simulations predict cell attachment under normal conditions, as expected from experimental data, and detachment at lower receptor binding affinity and/or increased pressure gradient. The normal attached state in the model is found to be particularly sensitive to changes in the receptor-binding affinity. The amount of resistance the cell surface offers to deformation forces is a key determinant of whether the detachment of small clusters of receptors spreads to involve large areas of the plasma membrane, precipitating bulk detachment.

Cell Adhesion↗
PubMedDate not supplied

Human cone receptor activity: the leading edge of the a-wave and models of receptor activity.

The leading edge of the a-wave of the electroretinogram (ERG) was evaluated as a measure of human cone photoreceptor activity. The amplitude of the cone a-wave elicited by flashes of different energy was compared to the predictions of a class of models from in vitro studies of cone photoreceptors. These models successfully describe the leading edge of the a-wave. Thus, the human cone a-wave can be used to test hypotheses about normal and abnormal cone receptors. The ability of the human cone to adjust its sensitivity in the presence of steady adapting lights was assessed by recording cone a-waves to flashes on adapting fields up to 3.9 log td in intensity and by comparing these responses to quantitative models of adaptation. The first 10 ms of the cone's response is little affected by field intensities up to 2.9 log td. The 3.9 log td field reduced the response to weak flashes by about a factor of 2.5 (0.4 log unit). This relatively small reduction in sensitivity can be attributed to a combination of response compression, pigment bleaching, and an adaptation mechanism that changes the gain without changing the time course. We conclude that either the human cones show relatively little adaptation or that they have an adaptation mechanism that involves a time-course change. That is, as we are limited with the a-wave to the first 10 ms or so of the cone's response, we cannot rule out a gain mechanism linked to a time-course change.

Adaptation, Ocular↗
PubMed1999

Perception of temporally filtered X-ray fluoroscopy images.

For noisy X-ray fluoroscopy image sequences we quantitatively evaluated image quality after digital temporal filtering to reduce noise. Using an experimental paradigm called a reference/test adaptive forced-choice method we compared detectability of stationary low-contrast disks in filtered and unfiltered, computer-generated image sequences. In the first experiment, a low-pass first-order recursive filter used in X-ray fluoroscopy was found to be much less effective at enhancing detectability than predicted from the reduction of display noise variance, a common measurement of filter effectiveness. Detectability was reasonably predicted by a nonprewhitening human-observer model (NPW-HVS) that included an independently determined human temporal-contrast-sensitivity function. In another experiment, designed to test models over a range of temporal frequencies, we used paired high-pass and low-pass temporal filters that both reduced noise variance by 25%. The high-pass filter was artificially applied to the noise only and greatly improved detectability, while the low-pass filter had little effect. The human-observer model quantitatively described the measurements, but classical prewhitening and nonprewhitening signal detectors did not. As compared to the nonprewhitening, spatio-temporal matched filter, human-observer efficiency was low and variable at 2.1%, 2.9%, and 0.06% for 60 frames of unfiltered low-pass and high-pass noise, respectively. As compared to this detector, humans were not very effective at combining information across frames. On the other hand, signal to noise ratios (SNR's) from the human-observer model were comparable to human performance, and efficiencies were reasonably constant at 40%, 52%, and 32%, respectively. We conclude that it is imperative to include human-observer models and experiments in the analysis of noise-reduction filtering of noisy image sequences, such as X-ray fluoroscopy.

Adult↗
PubMed2006

A reliable morphological method to assess the age of male Anopheles gambiae.

BACKGROUND: Release of genetically-modified (GM) or sterile male mosquitoes for malaria control is hampered by inability to assess the age and mating history of free-living male Anopheles. METHODS: Age and mating-related changes in the reproductive system of male Anopheles gambiae were quantified and used to fit predictive statistical models. These models, based on numbers of spermatocysts, relative size of sperm reservoir and presence/absence of a clear area around the accessory gland, were evaluated using an independent sample of mosquitoes whose status was blinded during the experiment. RESULTS: The number of spermatocysts in male testes decreased with age, and the relative size of their sperm reservoir increased. The presence of a clear area around accessory glands was also linked to age and mating status. A quantitative model was able to categorize males from the blind trial into age groups of young (< or = 4 days) and old (> 4 days) with an overall efficiency of 89%. Using the parameters of this model, a simple table was compiled that can be used to predict male age. In contrast, mating history could not be reliably assessed as virgins could not be distinguished from mated males. CONCLUSION: Simple assessment of a few morphological traits which are easily collected in the field allows accurate age-grading of male An. gambiae. This simple, yet robust, model enables evaluation of demographic patterns and mortality in wild and released males in populations targeted by GM or sterile male-based control programmes.

Age Factors↗
PubMed1993

Prions and molecular chaperones.

Molecular chaperones are proteins involved in the folding of other proteins. Among these chaperones, some are involved in their own folding (auto-chaperones). A question arises: what is the mechanism of the chaperone folding catalysis? A model for protein folding that uses the thermodynamics of irreversible processes and statistical mechanics to describe the phenomenon is proposed; the analysis presents a clear link between these two aspects. A consequence of this model is the possible existence of misfolded proteins. This point is discussed and some experimental results arguing in this direction detailed. This thermo-kinetic model is applied to protein folding driven by a molecular chaperone. Analysis of folding shows that a misfolded chaperone can induce misfolding in protein and, in the case of autofolding (auto-chaperone), may lead to new misfolded chaperones. The consequences are explored by computer simulations. They show that such an auto-chaperone could behave as a new kind of informative molecule and replicate a misfolded structure by a process similar to infection. A quantitative model, displaying the epidemiologic characters of prion infections, is derived from this hypothesis. This hypothesis satisfactorily explains the three manifestations (infectious, genetic and sporadic) that are the characteristic features of all prion diseases. Are prions really molecular chaperones required for their own assembly? Analysis of the structure of prions revealed some features shared by true molecular chaperones. This analysis suggests the positions of the mutations likely to lead to the characteristic early onset of encephalopathy. They are in good agreement with experimental results.

Amino Acid Sequence↗
PubMed2006

Quantitative analysis of multi-component spherical virus assembly: scaffolding protein contributes to the global stability of phage P22 procapsids.

Assembly of the hundreds of subunits required to form an icosahedral virus must proceed with exquisite fidelity, and is a paradigm for the self-organization of complex macromolecular structures. However, the mechanism for capsid assembly is not completely understood for any virus. Here we have investigated the in vitro assembly of phage P22 procapsids using a quantitative model specifically developed to analyze assembly of spherical viruses. Phage P22 procapsids are the product of the co-assembly of 420 molecules of coat protein and approximately 100-300 molecules of scaffolding protein. Scaffolding protein serves as an assembly chaperone and is not part of the final mature capsid, but is essential for proper procapsid assembly. Here we show that scaffolding protein also affects the thermodynamics of assembly, and for the first time this quantitative analysis has been performed on a virus composed of more than one type of protein subunit. Purified coat and scaffolding proteins were mixed in varying ratios in vitro to form procapsids. The reactions were allowed to reach equilibrium and the proportion of the input protein assembled into procapsids or remaining as free subunits was determined by size exclusion chromatography and SDS-PAGE. The results were used to calculate the free energy contributions for individual coat and scaffolding proteins. Each coat protein subunit was found to contribute -7.2(+/-0.1)kcal/mol and each scaffolding protein -6.1(+/-0.2)kcal/mol to the stability of the procapsid. Because each protein interacts with two or more neighbors, the pair-wise energies are even less. The weak protein interactions observed in the assembly of procapsids are likely important in the control of nucleation, since an increase in affinity between coat and scaffolding proteins can lead to kinetic traps caused by the formation of too many nuclei. In addition, we find that adjusting the molar ratio of scaffolding to coat protein can alter the assembly product. When the scaffolding protein concentration is low relative to coat protein, there is a correspondingly low yield of proper procapsids. When the relative concentration is very high, too many nuclei form, leading to kinetically trapped assembly intermediates.

Bacteriophage P22↗
PubMed2004

Regeneration of defects in articular cartilage in rat knee joints by CCN2 (connective tissue growth factor).

UNLABELLED: CTGF/CCN2, a hypertrophic chondrocyte-specific gene product, possessed the ability to repair damaged articular cartilage in two animal models, which were experimental osteoarthritis and full-thickness defects of articular cartilage. These findings suggest that CTGF/CCN2 may be useful in regeneration of articular cartilage. INTRODUCTION: Connective tissue growth factor (CTGF)/CCN2 is a unique growth factor that stimulates the proliferation and differentiation, but not hypertrophy, of articular chondrocytes in vitro. The objective of this study was to investigate the therapeutic use of CTGF/CCN2. MATERIALS AND METHODS: The effects of recombinant CTGF/CCN2 (rCTGF/CCN2) on repair of damaged cartilage were evaluated by using both the monoiodoacetic acid (MIA)-induced experimental rat osteoarthritis (OA) model and full-thickness defects of rat articular cartilage in vivo. RESULTS: In the MIA-induced OA model, quantitative real-time RT-PCR assays showed a significant increase in the level of CTGF/CCN2 mRNA, and immunohistochemical analysis and in situ hybridization revealed that the clustered chondrocytes, in which clustering indicates an attempt to repair the damaged cartilage, produced CTGF/CCN2. Therefore, CTGF/CCN2 was suspected to play critical roles in cartilage repair. In fact, a single injection of rCTGF/CCN2 incorporated in gelatin hydrogel (rCTGF/CCN2-hydrogel) into the joint cavity of MIA-induced OA model rats repaired their articular cartilage to the extent that it became histologically similar to normal articular cartilage. Next, to examine the effect of rCTGF/CCN2 on the repair of articular cartilage, we created defects (2 mm in diameter) on the surface of articular cartilage in situ and implanted rCTGF/CCN2-hydrogel or PBS-hydrogel therein with collagen sponge. In the group implanted with rCTGF/CCN2-hydrogel collagen, new cartilage filled the defect 4 weeks postoperatively. In contrast, only soft tissue repair occurred when the PBS-hydrogel collagen was implanted. Consistent with these in vivo effects, rCTGF/CCN2 enhanced type II collagen and aggrecan mRNA expression in mouse bone marrow-derived stromal cells and induced chondrogenesis in vitro. CONCLUSION: These findings suggest the utility of CTGF/CCN2 in the regeneration of articular cartilage.

Aggrecans↗
PubMed1995

Mental scanning of visual images generated from verbal descriptions: towards a model of image accuracy.

Recent mental scanning experiments have shown that subjects are not only able to construct mental images from verbal descriptions, but that these images have structural properties similar to those of images derived from perception. In addition, the specific sequencing of a description can affect the internal structure of images of described objects, in particular their metric properties. Discontinuous descriptions require additional exposure to achieve the structural coherence of images constructed from continuous descriptions. Thus, the capacity of images to reflect accurately the objects they refer to is not an all-or-nothing property, but rather results from stepwise elaboration. This study describes a quantitative model designed to account for the gradual process of image elaboration and the progressive increase in image accuracy. The model posits that the location of a landmark mentioned in a description is not represented as a sharp point in the mental image, but is instead associated with a region around this point. Learning the description essentially consists of progressively narrowing each 'region of uncertainty' associated with a landmark to its exact location. Additional experimental data were collected to provide a more finegrained understanding of image elaboration. Computations of the regions of uncertainty associated with each landmark were used to develop a computer program simulating the whole mental scanning protocol, which provided support for our account of image accuracy.

Adult↗
PubMed2003

A neural model of how the brain represents and compares multi-digit numbers: spatial and categorical processes.

Both animals and humans represent and compare numerical quantities, but only humans have evolved multi-digit place-value number systems. This article develops a Spatial Number Network, or SpaN, model to explain how these shared numerical capabilities are computed using a spatial representation of number quantities in the Where cortical processing stream, notably the inferior parietal cortex. Multi-digit numerical representations that obey a place-value principle are proposed to arise through learned interactions between categorical language representations in the What cortical processing stream and the Where spatial representation. Learned semantic categories that symbolize separate digits, as well as place markers like 'ty,' 'hundred,' and 'thousand,' are associated through learning with the corresponding spatial locations of the Where representation. Such What-to-Where auditory-to-visual learning generates place-value numbers as an emergent property, and may be compared with other examples of multi-modal cross-modality learning, including synesthesia. The model quantitatively simulates error rates in quantification and numerical comparison tasks, and reaction times for number priming and numerical assessment and comparison tasks. In the Where cortical process, transient responses to inputs are integrated before they activate an ordered spatial map that selectively responds to the number of events in a sequence and exhibits Weber law properties. Numerical comparison arises from activity pattern changes across the spatial map that define a 'directional comparison wave.' Variants of these model mechanisms have elsewhere been used to explain data about other Where stream phenomena, such as motion perception, spatial attention, and target tracking. The model is compared with other models of numerical representation.

Animals↗
PubMedDate not supplied

The trough effect: implications for speech motor programming.

While the existence of the trough effect is unquestioned, its theoretical significance is unknown. A multifaceted instrumental approach - spectrographic, cineradiographic, and vocal tract modeling - was used to document the trough effect in open (V.CV) and closed (VC.V) syllable forms using a symmetrical vowel context surrounding labial stops. Collectively, the results document the trough phenomenon as a momentary deactivation of tongue and/or lip movement after V1 and continuing into the stop closure. This empirical event suggests a segment-by-segment activation pattern as opposed to a diphthongal vowel-to-vowel trajectory with an independent and superimposed consonantal gesture. Quantitative models of VCV coarticulation must incorporate the trough effect in order to more effectively capture the kinematic properties of speech.

Humans↗
PubMed1996

Quantitative assessment of the efficacy of amorphous calcium phosphate/methacrylate composites in remineralizing caries-like lesions artificially produced in bovine enamel.

Recent studies show that methacrylate-based composites with amorphous calcium phosphate (ACP) as a filler can release supersaturating levels of calcium and phosphate ions in proportions favorable for apatite formation. These findings suggest that such composites could be effectively used as coatings for remineralizing teeth damaged by tooth decay. To examine this hypothesis, we tested composites in vitro for their efficacy to remineralize artificially formed caries-like lesions in extracted bovine incisors. Single 120-microns-thick sagittal tooth sections were placed in holders that exposed only the carious enamel surface. The exposed surfaces were coated with a 1-mm- to 1.5-mm-thick layer of the composite containing, by mass, 40% apatite, silica, or P2O7(-4)-stabilized ACP and 60% photoactivated resin comprised of Bis-GMA, TEGDMA, HEMA, and ZrM. The photocured composite-coated sections were immersed either in a remineralizing solution for 4 weeks at 37 degrees C (static model) or cyclically immersed in demineralizing (0.5 h) and remineralizing solutions (11.5 h) for 2 weeks (dynamic model). Quantitative digital image analysis of matched 102 microns x 220 microns areas from contact microradiographs taken of the sections before and after immersion showed that lesions coated with ACP-filled composites fractionally recovered 71% +/- 33% of their lost mineral compared with 14% +/- 13% for apatite controls in the static model and 38% +/- 16% compared with -6% +/- 24% in the dynamic model. The results suggest that sealants based on ACP-filled methacrylate composites have the potential to remineralize carious enamel lesions.

Animals↗
PubMed2004

Current comprehensive assessment and management of women at increased risk for breast cancer.

The potential for reducing the risk of breast cancer through selective estrogen receptor modulators, aromatase inhibitors, and surgery has generated interest in the use of quantitative models of risk assessment. With the addition of ductal lavage cytology to traditional epidemiologic risk factors, a discovery of cellular atypia can result in refinement of assigned risk values, while simultaneously optimizing patient selection for selective estrogen receptor modulators utilization. In view of increasing complexity in this arena, a Risk Assessment Working Group was formed to outline management strategies for the patient at an elevated risk for the development of breast cancer. No longer a statistical exercise, quantitative risk assessment is part of basic breast care and comprehensive management includes a discussion of the following: ductal lavage for improved risk stratification, multiple options for risk reduction, and high risk surveillance strategies that might incorporate investigational imaging protocols.

Adult↗
PubMed2006

Multimedia and physiology: a new way to ensure the quality of medical education and medical knowledge.

BACKGROUND: since the eighties and the existence of virtual campuses, the value of computers in distance education has been acknowledged. The development of information and communication technologies is driving at discriminating distance education and on-line education. PURPOSE: the aim of the "Campus Numérique de Physiologie" is not to reproduce an on-line copy of classical textbooks but to put at students' and physicians' disposal the huge possibilities of multimedia resources for an active and easier understanding of complex physiopathological phenomena. METHODS: the on-line course materials were created using both original IBC-made and registered trade-mark software tools. Multiscale modelling and corresponding knowledge bases were implemented by mathematicians, biologists and software engineers from Rennes. The website, which is accessible through a server of the French Virtual Medical University, was developed in the language HTML/PHP connected to a MySQL database. RESULTS: the content managing system is consistent with classical home page facilities and multicriteria browser. Interactive resources are freely available for the site's users. Two- and three-dimensional simulations born out of mathematical qualitative and quantitative models at the molecular, cellular or organic level keep students active with regards to fundamental mechanisms by interactively manipulating the simulation environment. CONCLUSION: authors comment the already available course materials which should stimulate the creation of new documents following a validation by a qualified commission of the "Société de Physiologie". Providing evaluation tests, teachers anticipate that the increasing content of this virtual campus will allow users to gain a complete understanding and an integrative view of many physiopathological mechanisms.

Education, Distance↗
PubMed1977

F-bodies as Y chromosome markers in mature human sperm heads: a quantitative approach.

It is generally accepted that at least some Y chromosomes in human mature sperm heads are represented in preparations by fluorescent F-bodies. From data consisting solely of F-body scorings and the visually estimated size of sperm heads from normal donors, a quantitative model is developed which permits simultaneous estimation of six parameters representing biological factors (the proportions of ploidy classes and of their sex-chromosome complements) and biassing factors (not all Y chromosomes represented by F-bodies, not all F-bodies representing Y chromosomes, and error in scoring ploidy from visual size). The analysis is statistically adequate and succeeds in predicting a variety of independently validated phenomena. The work may be regarded as a contribution to the integration of qualitative and quantitative evidence in the study of F-bodies. In all, 21,700 one-headed spermatozoa from 12 donors were scored. A mean of 54% spermatozoa lacking F-bodies was subject to a standard deviation between donors of 4.8, over and above binomial error. Analysis yielded the following estimates: 83.3% of diploid spermatozoa are XY, the remainder XX and YY in assumed equal number (this information assists analysis of the origin of embryonic triploidy); 2.4% of spermatozoa are diploid (this estimate does not compete in accuracy with direct estimates from DNA absorbance); only 83% of Y chromosomes are represented by F-bodies; 7% of haploid heads and 14% of diploids contain one or more "adventitious bodies" indistinguishable from true F-bodies. The visually scored head sizes "Small" and "Medium" correspond approximately with haploidy and diploidy; nearly all haploids are scored as Small, and 72% of the Medium are diploid. F-bodies are not thought at present to give a useful basis for estimating the presumably low incidence of sex-chromosome aneuploidy and nondisjunction. No such estimate has been attempted. The problem is overshadowed by not fully understood complicating factors of greater magnitude, which now appear to be a major subject of enquiry. Some implications and possible future developments are discussed.

Humans↗
PubMed2006

Towards an understanding of lineage specification in hematopoietic stem cells: a mathematical model for the interaction of transcription factors GATA-1 and PU.1.

In addition to their self-renewal capabilities, hematopoietic stem cells guarantee the continuous supply of fully differentiated, functional cells of various types in the peripheral blood. The process which controls differentiation into the different lineages of the hematopoietic system (erythroid, myeloid, lymphoid) is referred to as lineage specification. It requires a potentially multi-step decision sequence which determines the fate of the cells and their successors. It is generally accepted that lineage specification is regulated by a complex system of interacting transcription factors. However, the underlying principles controlling this regulation are currently unknown. Here, we propose a simple quantitative model describing the interaction of two transcription factors. This model is motivated by experimental observations on the transcription factors GATA-1 and PU.1, both known to act as key regulators and potential antagonists in the erythroid vs. myeloid differentiation processes of hematopoietic progenitor cells. We demonstrate the ability of the model to account for the observed switching behavior of a transition from a state of low expression of both factors (undifferentiated state) to the dominance of one factor (differentiated state). Depending on the parameter choice, the model predicts two different possibilities to explain the experimentally suggested, stem cell characterizing priming state of low level co-expression. Whereas increasing transcription rates are sufficient to induce differentiation in one scenario, an additional system perturbation (by stochastic fluctuations or directed impulses) of transcription factor levels is required in the other case.

Cell Differentiation↗
PubMed1995

An unexpected effect of ATP on the ratio between activity and phosphoenzyme level of Na+/K(+)-ATPase in steady state.

According to the Albers-Post model the hydrolysis of ATP catalyzed by the Na+/K(+)-ATPase requires the sequential formation of at least two conformers of a phosphoenzyme (E1P and E2P), followed by the K(+)-stimulated hydrolysis of E2P. In this paper we show that this model is a particular case of a more general class of models in all of which the ratio between ATPase activity (v) and total phosphoenzyme level (EP) in steady state is determined solely by the rate constants of interconversion between phosphoconformers and of dephosphorylation. Since these are thought to be unaffected by ATP, the substrate curves for ATPase activity and EP should be identical in shape so that the ratio v/EP ought to be independent of the concentration of ATP. We tested this prediction by parallel measurements of v and EP as a function of [ATP] in the absence or presence of non-limiting concentrations of K+, Rb+ or NH+4. In the absence of K+ or its congeners, both curves followed Michaelis-Menten kinetics, with almost identical Km values (0.16 microM) so that v/EP remained independent of [ATP]. In the presence of either K+, Rb+ or NH+4, v and EP increased with [ATP] along the sum of two Michaelis-Menten equations. The biphasic response of v is well known but, to the best of our knowledge, our results are the first demonstration that the response of EP to [ATP] is also biphasic. Under these conditions, the ratio v/EP increased with [ATP] from 19.8 to 40.1 s-1 along a hyperbola that was half-maximal at 9.5 microM. To preserve the validity of the current model it seems necessary to assume that ATP acts on the E1P <--> E2P transition and/or on the rate of hydrolysis of E2P. The latter possibility was ruled out. We also found that to fit the Albers-Post model to our data, the rate constant for K+ deocclussion from E2 has to be about 10-times higher than that reported from measurements of partial reactions. The results indicate that the Albers-Post model quantitatively predicts the experimental behavior of the Na(+)-ATPase activity but is unable to do this for the Na+/K(+)-ATPase activity, unless additional and yet unproved hypothesis are included.

Adenosine Triphosphatases↗
PubMed2001

Sleep and treatment response in depression: new findings using power spectral analysis.

This study examined quantitative measures of sleep electroencephalogram (EEG) and phasic rapid eye movements (REM) as correlates of remission and recovery in depressed patients. To address correlates of remission, pre-treatment EEG sleep studies were examined in 130 women outpatients with major depressive disorder treated with interpersonal psychotherapy (IPT). To address correlates of recovery, baseline and post-treatment EEG sleep studies were examined in 23 women who recovered with IPT alone and 23 women who recovered with IPT+fluoxetine. Outcomes included EEG power spectra during non-rapid eye movement (NREM) sleep and REM sleep and quantitative REMs. IPT non-remitters had increased phasic REM compared with remitters, but no significant differences in EEG power spectra. IPT+fluoxetine recoverers, but not IPT recoverers, showed increases in phasic REM and REM percentage from baseline to recovery. In NREM sleep, the IPT+fluoxetine group showed a decrease in alpha power from baseline to recovery, while the IPT group showed a slight increase. The number of REMs was a more robust correlate of remission and recovery than modeled quantitative EEG spectra during NREM or REM sleep. Quantitative REMs may provide a more direct measure of brainstem function and dysfunction during REM sleep than quantitative sleep EEG measures.

Arousal↗
PubMed1994

Rasch partial credit analysis of gross motor competence.

The purpose of this study was to introduce a model for measurement of partial credit for the assessment of gross motor competence. Four different striking tasks were administered to a total of 128 children, ages 3 to 9 years, consisting of 64 boys and 64 girls. The partial scores were analyzed using the Rasch Partial Credit model. Satisfactory fit of model and data was obtained for Task 1 and Task 4. Step difficulties estimated for Tasks 1 and 4 ranged from 5.61 to 5.50. The average ability of the children was 0.09 (SD = 2.95). The first and second steps of Tasks 1 and 4 were easy for the children and the fourth step was difficult for them. The major advantage of using the Rasch Partial Credit analysis is that motor process measures can be calibrated and analyzed by a quantitative model with advanced test characteristics.

Child↗