The Ornstein-Uhlenbeck neuronal model is specified by two types of parameters. One type corresponds to the properties of the neuronal membrane, whereas the second type (local average rate of the membrane depolarization and its variability) corresponds to the input of the neuron. In this article, we estimate the parameters of the second type from an intracellular record during neuronal firing caused by stimulation (audio signal). We compare the obtained estimates with those from the spontaneous part of the record. As predicted from the model construction, the values of the input parameters are larger for the periods when neuron is stimulated than for the spontaneous ones. Finally, the firing regimen of the model is checked. It is confirmed that the neuron is in the suprathreshold regimen during the stimulation.

• MeSH
• akční potenciály fyziologie   MeSH
• akustická stimulace metody   MeSH
• časové faktory MeSH
• elektroencefalografie MeSH
• membránové potenciály fyziologie   MeSH
• modely neurologické MeSH
• morčata MeSH
• nervové dráhy fyziologie   MeSH
• neurony klasifikace   fyziologie   MeSH
• počítačové zpracování signálu MeSH
• reakční čas fyziologie   MeSH
• stochastické procesy MeSH
• zvířata MeSH
• Check Tag
• morčata MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Stimulus response latency is the time period between the presentation of a stimulus and the occurrence of a change in the neural firing evoked by the stimulation. The response latency has been explored and estimation methods proposed mostly for excitatory stimuli, which means that the neuron reacts to the stimulus by an increase in the firing rate. We focus on the estimation of the response latency in the case of inhibitory stimuli. Models used in this paper represent two different descriptions of response latency. We consider either the latency to be constant across trials or to be a random variable. In the case of random latency, special attention is given to models with selective interaction. The aim is to propose methods for estimation of the latency or the parameters of its distribution. Parameters are estimated by four different methods: method of moments, maximum-likelihood method, a method comparing an empirical and a theoretical cumulative distribution function and a method based on the Laplace transform of a probability density function. All four methods are applied on simulated data and compared.

• MeSH
• aferentní nervové dráhy fyziologie   MeSH
• akční potenciály fyziologie   MeSH
• časové faktory MeSH
• fyzikální stimulace MeSH
• lidé MeSH
• modely neurologické * MeSH
• nervový útlum fyziologie   MeSH
• neurony fyziologie   MeSH
• počítačová simulace MeSH
• reakční čas fyziologie   MeSH
• statistické modely MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

• MeSH
• Bayesova věta MeSH
• membránové potenciály MeSH
• modely neurologické MeSH
• neurony fyziologie   MeSH

PURPOSE: One of the main obstacles for reliable quantitative dynamic contrast-enhanced (DCE) MRI is the need for accurate knowledge of the arterial input function (AIF). This is a special challenge for preclinical small animal applications where it is very difficult to measure the AIF without partial volume and flow artifacts. Furthermore, using advanced pharmacokinetic models (allowing estimation of blood flow and permeability-surface area product in addition to the classical perfusion parameters) poses stricter requirements on the accuracy and precision of AIF estimation. This paper addresses small animal DCE-MRI with advanced pharmacokinetic models and presents a method for estimation of the AIF based on blind deconvolution. METHODS: A parametric AIF model designed for small animal physiology and use of advanced pharmacokinetic models is proposed. The parameters of the AIF are estimated using multichannel blind deconvolution. RESULTS: Evaluation on simulated data show that for realistic signal to noise ratios blind deconvolution AIF estimation leads to comparable results as the use of the true AIF. Evaluation on real data based on DCE-MRI with two contrast agents of different molecular weights showed a consistence with the known effects of the molecular weight. CONCLUSION: Multi-channel blind deconvolution using the proposed AIF model specific for small animal DCE-MRI provides reliable perfusion parameter estimates under realistic signal to noise conditions.

• MeSH
• algoritmy MeSH
• arterie diagnostické zobrazování   MeSH
• farmakokinetika MeSH
• kontrastní látky farmakokinetika   MeSH
• lidé MeSH
• magnetická rezonanční tomografie * MeSH
• myši inbrední BALB C MeSH
• myši MeSH
• nekróza patologie   MeSH
• perfuze MeSH
• počítačová simulace MeSH
• počítačové zpracování obrazu metody   MeSH
• poměr signál - šum MeSH
• regresní analýza MeSH
• reprodukovatelnost výsledků MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

• MeSH
• látky znečišťující půdu analýza   chemie   MeSH
• riziko MeSH
• zdraví MeSH

OBJECTIVE: An extension of single- and multi-channel blind deconvolution is presented to improve the estimation of the arterial input function (AIF) in quantitative dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). METHODS: The Lucy-Richardson expectation-maximization algorithm is used to obtain estimates of the AIF and the tissue residue function (TRF). In the first part of the algorithm, nonparametric estimates of the AIF and TRF are obtained. In the second part, the decaying part of the AIF is approximated by three decaying exponential functions with the same delay, giving an almost noise free semi-parametric AIF. Simultaneously, the TRF is approximated using the adiabatic approximation of the Johnson-Wilson (aaJW) pharmacokinetic model. RESULTS: In simulations and tests on real data, use of this AIF gave perfusion values close to those obtained with the corresponding previously published nonparametric AIF, and are more noise robust. CONCLUSION: When used subsequently in voxelwise perfusion analysis, these semi-parametric AIFs should give more correct perfusion analysis maps less affected by recording noise than the corresponding nonparametric AIFs, and AIFs obtained from arteries. SIGNIFICANCE: This paper presents a method to increase the noise robustness in the estimation of the perfusion parameter values in DCE-MRI.

• MeSH
• algoritmy MeSH
• arterie patologie   MeSH
• kontrastní látky chemie   farmakokinetika   MeSH
• magnetická rezonanční tomografie * MeSH
• myši inbrední C57BL MeSH
• myši MeSH
• perfuze MeSH
• počítačová simulace MeSH
• počítačové zpracování obrazu * MeSH
• reprodukovatelnost výsledků MeSH
• vylepšení obrazu * MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

PURPOSE: The composite vascular transport function of a brain voxel consists of one convolutional component for the arteries, one for the capillaries and one for the veins in the voxel of interest. Here, the goal is to find each of these three convolutional components and the associated arterial input function. PHARMACOKINETIC MODELLING: The single voxel vascular transport functions for arteries, capillaries and veins were all modelled as causal exponential functions. Each observed multipass tissue contrast function was as a first approximation modelled as the resulting parametric composite vascular transport function convolved with a nonparametric and voxel specific multipass arterial input function. Subsequently, the residue function was used in the true perfusion equation to optimize the three parameters of the exponential functions. DECONVOLUTION METHODS: For each voxel, the parameters of the three exponential functions were estimated by successive iterative blind deconvolutions using versions of the Lucy-Richardson algorithm. The final multipass arterial input function was then computed by nonblind deconvolution using the Lucy-Richardson algorithm and the estimated composite vascular transport function. RESULTS: Simulations showed that the algorithm worked. The estimated mean transit time of arteries, capillaries and veins of the simulated data agreed with the known input values. For real data, the estimated capillary mean transit times agreed with known values for this parameter. The nonparametric multipass arterial input functions were used to derive the associated map of the arrival time. The arrival time map of a healthy volunteer agreed with known arterial anatomy and physiology. CONCLUSION: Clinically important new voxelwise hemodynamic information for arteries, capillaries and veins separately can be estimated using multipass tissue contrast functions and the iterative blind Lucy-Richardson deconvolution algorithm.

• MeSH
• algoritmy MeSH
• arterie patologie   MeSH
• kapiláry * diagnostické zobrazování   MeSH
• kontrastní látky * farmakokinetika   MeSH
• lidé MeSH
• magnetická rezonanční spektroskopie MeSH
• magnetická rezonanční tomografie metody   MeSH
• mozek diagnostické zobrazování   MeSH
• mozkový krevní oběh MeSH
• perfuzní zobrazování MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Five parameters of one of the most common neuronal models, the diffusion leaky integrate-and-fire model, also known as the Ornstein-Uhlenbeck neuronal model, were estimated on the basis of intracellular recording. These parameters can be classified into two categories. Three of them (the membrane time constant, the resting potential and the firing threshold) characterize the neuron itself. The remaining two characterize the neuronal input. The intracellular data were collected during spontaneous firing, which in this case is characterized by a Poisson process of interspike intervals. Two methods for the estimation were applied, the regression method and the maximum-likelihood method. Both methods permit to estimate the input parameters and the membrane time constant in a short time window (a single interspike interval). We found that, at least in our example, the regression method gave more consistent results than the maximum-likelihood method. The estimates of the input parameters show the asymptotical normality, which can be further used for statistical testing, under the condition that the data are collected in different experimental situations. The model neuron, as deduced from the determined parameters, works in a subthreshold regimen. This result was confirmed by both applied methods. The subthreshold regimen for this model is characterized by the Poissonian firing. This is in a complete agreement with the observed interspike interval data.

• MeSH
• akční potenciály fyziologie   MeSH
• buněčná membrána fyziologie   MeSH
• financování organizované MeSH
• lidé MeSH
• mozek fyziologie   MeSH
• nervové dráhy fyziologie   MeSH
• nervový přenos fyziologie   MeSH
• neuronové sítě MeSH
• neurony fyziologie   MeSH
• počítačové zpracování signálu MeSH
• Poissonovo rozdělení MeSH
• stochastické procesy MeSH
• synapse fyziologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH

Service life assessment of three historical building envelopes constructed using different types of sandstone is presented. At first, experimental measurements of material parameters of sandstones are performed to provide the necessary input data for a subsequent computational analysis. In the second step, the moisture and temperature fields across the studied envelopes are calculated for a representative period of time. The computations are performed using dynamic climatic data as the boundary conditions on the exterior side of building envelope. The climatic data for three characteristic localities are experimentally determined by the Czech Hydrometeorological Institute and contain hourly values of temperature, relative humidity, rainfalls, wind velocity and direction, and sun radiation. Using the measured durability properties of the analyzed sandstones and the calculated numbers of freeze/thaw cycles under different climatic conditions, the service life of the investigated building envelopes is assessed. The obtained results show that the climatic conditions can play a very significant role in the service life assessment of historical buildings, even in the conditions of such a small country as the Czech Republic. In addition, the investigations reveal the importance of the material characteristics of sandstones, in particular the hygric properties, on their service life in a structure.

• MeSH
• konstrukční materiály analýza   MeSH
• lidé MeSH
• mechanické jevy MeSH
• teoretické modely MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

V práci sme sa pokúsili objektívne zhodnotiť vplyv 8-týždňového tréningu na balančných podložkách na parametre rovnováhy u športovcov 12 týždňov po rekonštrukcii predného skríženého väzu (LCA). 12 probandov z experimentálnej skupiny absolvovalo tréning na nestabilných podložkách, 12 probandov z kontrolnej skupiny absolvovalo identický tréning na pevnej podložke. V oboch skupinách boli vykonané vstupné a výstupné merania statickej a dynamickej rovnováhy. Výsledky preukázali, že tréning na nestabilných podložkách má vplyv na parametre rovnováhy hlavne na operovanej dolnej končatine.

In our thesis we have attempted to evaluate the effect of eight-week training on balance mats has on parameters of stability of athletes twelve weeks after a plastic surgery of the anterior cruciate ligament. Twelve probands of the experimental groups were subjected to sports practice on unstable mats, and twelve probands of the control group participated in identical practice on stable mats. We have measured the input and the output static and dynamic balance in both groups. The results have shown that training on unstable mats effects the parameters of stability, mainly as to the lower limb after a surgery.

• Klíčová slova
• statická rovnováha, dynamická rovnováha, balanční podložky,
• MeSH
• dospělí MeSH
• lidé MeSH
• ligamentum cruciatum anterius MeSH
• mladý dospělý MeSH
• motorické dovednosti fyziologie   MeSH
• následné studie MeSH
• odporový trénink MeSH
• poranění kolena rehabilitace   MeSH
• poranění předního zkříženého vazu MeSH
• posturální rovnováha * fyziologie   MeSH
• propriocepce MeSH
• rehabilitace metody   MeSH
• rekonstrukce předního zkříženého vazu * rehabilitace   MeSH
• svalová síla fyziologie   MeSH
• techniky cvičení a pohybu MeSH
• tělesná výkonnost fyziologie   MeSH
• terapie cvičením * MeSH
• výsledek terapie MeSH
• zatížení muskuloskeletálního systému MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• přehledy MeSH
• srovnávací studie MeSH