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PubMed2003

Stability analysis of spatiotemporal cnoidal waves in cubic nonlinear media.

We analyze numerically the modulational instability of spatiotemporal cnoidal waves of cn, dn, and sn types that are periodic along a single space coordinate and are uniform in time. The band of possible increments is calculated for all three types of cnoidal waves as a function of parameter describing the degree of localization of the wave field energy. It is shown that this band transforms into a set of discrete values for waves of cn and dn types in the limit of strong spatial localization. Simulation of perturbed cnoidal-wave propagation revealed suppression of collapse and multiple-wave filamentation on the developed stage of instability. Different instability scenarios are considered in detail.

Journal Article↗
PubMed2002

Spatiotemporal independent component analysis of event-related fMRI data using skewed probability density functions.

We introduce two independent component analysis (ICA) methods, spatiotemporal ICA (stICA) and skew-ICA, and demonstrate the utility of these methods in analyzing synthetic and event-related fMRI data. First, stICA simultaneously maximizes statistical independence over both time and space. This contrasts with conventional ICA methods, which maximize independence either over time only or over space only; these methods often yield physically improbable solutions. Second, skew-ICA is based on the assumption that images have skewed probability density functions (pdfs), an assumption consistent with spatially localized regions of activity. In contrast, conventional ICA is based on the physiologically unrealistic assumption that images have symmetric pdfs. We combine stICA and skew-ICA, to form skew-stICA, and use it to analyze synthetic data and data from an event-related, left-right visual hemifield fMRI experiment. Results obtained with skew-stICA are superior to those of principal component analysis, spatial ICA (sICA), temporal ICA, stICA, and skew-sICA. We argue that skew-stICA works because it is based on physically realistic assumptions and that the potential of ICA can only be realized if such prior knowledge is incorporated into ICA methods.

Evoked Potentials↗
PubMed2006

Improving source detection and separation in a spatiotemporal Bayesian inference dipole analysis.

Most existing spatiotemporal multi-dipole approaches for MEG/EEG source localization assume that the dipoles are active for the full time range being analysed. If the actual time range of activity of sources is significantly shorter than the time range being analysed, the detectability, localization and time-course determination of such sources may be adversely affected, especially for weak sources. In order to improve detectability and reconstruction of such sources, it is natural to add active time range information (starting time point and ending time point of source activation) for each candidate source as unknown parameters in the analysis. However, this adds additional nonlinear free parameters that could burden the analysis and could be unfeasible for some methods. Recently, we described a spatiotemporal Bayesian inference multi-dipole analysis for the MEG/EEG inverse problem. This approach treated the number of dipoles as a free parameter, produced realistic uncertainty estimates using a Markov chain Monte Carlo numerical sampling of the posterior distribution and included a method to reduce the unwanted effects of local minima. In this paper, our spatiotemporal Bayesian inference multi-dipole analysis is extended to incorporate active time range parameters of starting and stopping time points. The properties of this analysis in comparison to the previous one without active time range parameters are demonstrated through extensive studies using both simulated and empirical MEG data.

Action Potentials↗
PubMed2005

Spatiotemporal chaos in excised larynx vibrations.

Spatiotemporal chaos in excised larynx vibrations is reported using high-speed digital imaging. Spatiotemporal correlation and eigenmode analyses are applied to describe the spatiotemporal dynamics of the vocal fold vibrations and to investigate the effects of subglottal pressure. High subglottal pressures cause spatiotemporal chaos with decreased spatiotemporal correlation and increased entropy in the vocal fold vibrations. Spatiotemporal analysis shows a valuable biomedical application in investigating the spatiotemporal chaotic dynamics of the vocal fold system.

Animals↗
PubMed1991

Analysis of EEG changes between the frontal and occipital cortex during speech.

A method of spatiotemporal analysis, using time series analysis techniques to represent activity in multiple brain regions, was applied to the interpretation of EEG information changes between the frontal and occipital areas during speech. This paper proposes and discusses a bidirectional communication model between the frontal and occipital cortices. Entropy analysis was introduced and used to simplify the calculation of transinformation in two dimensions. In this work, transinformation with direction between the frontal and occipital cortices before and during speech was investigated quantitatively for 11 subjects. The dominant information flow in the occipital-frontal direction was found immediately before speech in the right hemisphere. During speech, the dominant information flow was found in the occipital-frontal direction in both the right and left hemispheres. These results suggest that the method used in our work is feasible to analyze EEG signals in language processes.

Brain↗
PubMed1999

Highly reproducible spatiotemporal patterns of mammalian embryonic movements at the developmental stage of the earliest spontaneous motility.

The principles underlying the variations in patterns of mammalian embryonic movements have not been established. In an attempt to clarify the mechanism that is responsible for the variations in motor patterns, we carried out a precise quantitative spatiotemporal analysis of movements in mouse embryos, using a transplacental perfusion method for the in vitro maintenance of live mammalian embryos. Episodes of spontaneous movements at the inception of motility, at embryonic day 12.5, occurred once every few minutes, lasted for several seconds and consisted of successive movements of body regions, the spatiotemporal patterns of which varied from episode to episode. By analysing and categorizing the patterns of these movements, we found that embryonic movements follow relatively few restricted patterns with respect to the order of the movements of body regions. A further analysis of episodes at high spatiotemporal resolution revealed that most of the episodes in a major category could be classified into two distinct subtypes. Each of these subtypes had its own highly reproducible spatiotemporal patterns of movement. Overall, these results show that early embryonic movements follow relatively few rather stereotyped patterns, and random local fluctuations have little effect on such movement patterns. The appearance of one pattern out of several rather stereotyped patterns may be the main cause of apparent variations in patterns of early embryonic movements. The stereotyped patterns may represent important orderly characteristics of spontaneous embryonic activities that may be involved in the development of orderly structures and functions in higher animals.

Animals↗
PubMed2005

Multiscale multifractality analysis of a 12-lead electrocardiogram.

This paper proposes that a multiscale multifractality (MSMF) method be adopted for the spatiotemporal analysis of 12-lead ECG. By using this method, the authors find that, in some frequency range, 12-lead ECG has a more complex fractal structure, and the position of the largest singularity strength range delta alpha is not relying on the data length but on the scale factor. By determining the inflexion, the MSMF proves to be more sensitive in displaying the trend that the singularity strength range delta alpha of human ECG decreases with human aging.

Algorithms↗
PubMed2025

Cilia in the brain display region-dependent oscillations of length and orientation.

In this study, we conducted high-throughput spatiotemporal analysis of primary cilia length and orientation across 22 mouse brain regions. We developed automated image analysis algorithms, which enabled us to examine over 10 million individual cilia, generating the largest spatiotemporal atlas of cilia. We found that cilia length and orientation display substantial variations across different brain regions and exhibit fluctuations over a 24-h period, with region-specific peaks during light-dark phases. Our analysis revealed unique orientation patterns of cilia, suggesting that cilia orientation within the brain is not random but follows specific patterns. Using BioCycle, we identified rhythmic fluctuations in cilia length across five brain regions: the nucleus accumbens core, somatosensory cortex, and the dorsomedial, ventromedial, and arcuate hypothalamic nuclei. Our findings present novel insights into the brain cilia dynamics, and highlight the need for further investigation into cilia's role in the brain's response to environmental changes and regulation of oscillatory physiological processes.

Animals↗
PubMed2006

Analysis of Ras activation in living cells with GFP-RBD.

Several genetically encoded fluorescent biosensors for Ras family GTPases have been developed that permit spatiotemporal analysis of the activation of these signaling molecules in living cells. We describe here the use of the simplest of these probes, the Ras binding domain (RBD) of selected effectors fused with green fluorescent protein (GFP) or one of its spectral mutants. When expressed in quiescent cells, these probes are distributed homogeneously through the cytosol and nucleoplasm. On activation of their cognate GTPases on membranes, they are recruited to these compartments, and activation can be scored by redistribution of the probe. The advantage of this system is its simplicity: the probes are genetically encoded and can easily be constructed with standard cloning techniques, and the readout of activation requires only standard epifluorescence or confocal microscopy. The disadvantage of the system is that only rarely are Ras-related GTPases expressed at high enough levels to permit detection of the activation of the endogenous proteins. In general, the method requires overexpressing untagged, wild-type versions of the GTPase of interest. However, we describe a FRET-based method called bystander FRET developed to detect endogenous proteins that can be used to validate the results obtained by overexpressing Ras proteins. By use of this technique, we and others have uncovered important new features of the spatiotemporal regulation of Ras and related GTPases.

Animals↗
PubMed2002

Spatiotemporal EEG/MEG source analysis based on a parametric noise covariance model.

A method is described to incorporate the spatiotemporal noise covariance matrix into a spatiotemporal source analysis. The essential feature is that the estimation problem is split into two parts. First, a model is fitted to the observed noise covariance matrix. This model is a Kronecker product of a spatial and a temporal matrix. The spatial matrix models the spatial covariances by a function dependent on sensor distance. The temporal matrix models the temporal covariances as lag dependent. In the second part, sources are estimated given this noise model, which can be done very efficiently due to the Kronecker formulation. An application to real electroencephalogram (EEG) data shows that the noise model fits the data very well. Simulation results show that the resulting source estimates are more precise than those obtained from a standard analysis neglecting the noise covariance. In addition, the estimated standard errors of the source parameter estimates are far more precise than those obtained from a standard analysis. Finally, the source parameter standard errors are used to investigate the effects of temporal sampling. It is shown that increasing the sampling by a factor x, decreases the standard errors of all source parameters with the square root of x.

Computer Simulation↗
PubMed2000

Internally driven spatiotemporal irregularity in a dc glow discharge

Spatiotemporal dynamics of an undriven dc glow discharge at intermediate pressures (p(0)r(0)=6.2 Torr cm, i<50 mA) is investigated experimentally. Spatiotemporal irregularity and windows of regular nonlinear waves occur and are found to depend on the discharge current. Above a threshold current column head oscillations arise and inject high-frequency ionization waves into the positive column that decay towards the anode through nonlinear wave coupling with a discrete eigenmode of the positive column. Regularity was found to be a result of commensuration of both waves and obeys a devil's staircase. Since column head oscillations occur in the transition region from cathode fall to positive column as result of discharge formation, the irregularities were internally driven. Spatiotemporal analysis by means of biorthogonal decomposition gives insights into the mechanism of irregularity and can be employed for characterization of spatiotemporal complexity.

Journal Article↗
PubMed1995

Comparison of evoked potentials and high-frequency (gamma-band) oscillating potentials in rat auditory cortex.

1. Transient and steady-state (40 Hz) evoked potentials, as well as spontaneous and click-evoked gamma-band oscillations, were recorded from 15 lightly anesthetized rats using an 8 x 8 electrode epipial array covering auditory cortex and adjacent areas to determine and compare the spatiotemporal distributions of these four phenomena. 2. The transient evoked response replicated earlier findings in our laboratory, consisting of an initial biphasic sharp wave in area 41, a similar but delayed biphasic sharp wave in area 36, and more widely distributed slow-wave components. Spatiotemporal analysis supported a model of parallel and asynchronous activation of distinct groups of thalamocortical projections underlying the neurogenesis of these temporal components of the middle-latency auditory evoked potential (MAEP) complex. 3. The 40-Hz response to click trains was superimposed on a steady potential shift (SP), both of which were localized within primary auditory cortex. Epipial distributions of the SP were similar to those of the shortest-latency negative peak in area 41 recorded in the same animals, suggesting similar neural generators. The 40-Hz response was more focal and dissimilar from the SP and any other temporal components of the MAEP complex, suggesting that a unique subpopulation of cells underlies its neurogenesis. 4. Spontaneous gamma-band activity, as assessed by power spectrum analysis, was localized to primary and secondary auditory cortex but had a variable distribution between rats that did not conform to the cytoarchitectonic boundaries within subdivisions of this region. Digital movies computed for individual bursts of gamma-activity indicated a high degree of spatiotemporal variability within and between bursts. 5. Single-trial spectral analysis of click responses indicated an inhibition of gamma-band oscillations during most of the MAEP complex, with subsequent enhanced gamma-activity during the 300- to 350-ms slow-wave component that outlasted the MAEP by approximately 500 ms. The epipial distributions of prestimulus and enhanced poststimulus gamma-oscillations were the same. In contrast to the 40-Hz response to click trains, phase-locking of gamma-oscillations by the single click stimulus was not observed. 6. These results suggest that both the MAEP complex and the steady-state 40-Hz response with its associated SP are highly stereotyped in lightly anesthetized rodent cortex. Their spatiotemporal distributions are probably determined in large part by asynchronous activation of parallel thalamocortical projection systems. Our data suggest no direct link between either the MAEP or the steady-state 40-Hz response to spontaneous or evoked gamma-band oscillations in auditory cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1997

Sample and probe: a novel approach for identifying development-specific cis-elements of the enkephalin gene.

We have developed a novel 'sample and probe' approach as a means to identifying specific DNA elements of the enkephalin gene that control differentiation of the enkephalinergic phenotype during neurodevelopment. The approach is a systematic spatiotemporal analysis of protein-DNA interactions; soluble nuclear proteins ('samples') prepared from microdissected regions of the developing brain are 'probed' with radiolabeled DNA fragments representing various regulatory regions of the enkephalin gene. The resulting spatiotemporal 'molecular maps', i.e. characteristic patterns of protein-DNA complexes showed DNA regions that harbor potential cis-elements regulating differentiation of the enkephalin phenotype at various stages of neurodevelopment. DNase I footprint analysis of such a DNA region identified a binding site (GACGGGAGATCGCTCGT) which is similar to the motif for a lymphoid-specific, developmentally regulated transcription factor, Ikaros, suggesting that the developing brain expresses Ikaros-like transcription factor(s) in a spatiotemporally defined manner. In summary, our approach offers a unique view into the chronology of coordinated protein-DNA interactions and will greatly facilitate identifying DNA elements and isolating development-specific transcription factors.

Animals↗
PubMedDate not supplied

Regional analysis of climate, primary production, and livestock density in inner Mongolia.

Overstocking is believed to be one of the principal causes for grassland degradation in northern China. For this reason, quantification of overstocking and spatiotemporal analysis are needed for this area. In this study, the relationship between annual rainfall and grassland aboveground net primary production (ANPP) was analyzed using data from 1982 to 1991 in the Inner Mongolia Autonomous Region (IMAR), China. Subsequently, rainfall-based livestock carrying capacity was estimated and combined with livestock density calculated from county-level livestock data from 1982 to 1991 to determine spatial and temporal patterns of a stocking rate index and its relationship with climatic factors. The results indicate the following. First, there was a significant linear relationship between annual rainfall and ANPP in IMAR and the slope of ANPP versus rainfall was greater than those found in South America and Africa, indicating higher rain-use efficiency. Second, temporally averaged livestock density showed overstocking in most of the rural counties except for those in the cold north, where human populations are low and transportation systems are poor. Third, the stocking rate index increased with temperature, from less than 1.0 in the north, to greater than 2.0 in most of the southern IMAR. Within the central IMAR, the index increased from west to east, along the gradient of increasing rainfall. Fourth, long-term dynamics of livestock density depicted continuous overstocking, more than 20%, from 1982 to 1991 along the western part of the NorthEast China Transect (NECT) within IMAR. Spatial planning of livestock densities according to carrying capacities and improved pastoral management are needed in this area.

Animals↗
PubMed1997

Experimental analysis of neuronal dynamics in cultured cortical networks and transitions between different patterns of activity.

Experimental investigation of the dynamics of biological networks is a fundamental step towards understanding how the nervous system works. Spontaneous activity in cultured networks of cortical neurons has been investigated by using a multisite recording technique with planar electrode arrays. In these networks, the spatiotemporal firing patterns were studied in the presence of different extracellular solutions. Transitions from asynchronous firing dynamics to synchronous firing dynamics were observed when the extracellular Ca2+ concentration was increased from 0.1 mM to 1 mM. Addition of extracellular Mg2+ reduced the spontaneous activity at any Ca2+ concentration, and an increase in the extracellular K+ concentration enhanced the frequency of periodical synchronous bursts. N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptor antagonists inhibited synchronous activity. A spatiotemporal analysis of the data has been performed, and the properties of the network such as the synchronization and the periodicity have been quantified in order to clarify how variations of intrinsic parameters of the network can induce structural transitions in the neural dynamics. This experimental study is a possible approach to investigate the computational properties of a neuronal network.

Animals↗
PubMed1999

Two-dimensional photon counting imaging and spatiotemporal characterization of ultraweak photon emission from a rat's brain in vivo.

The process of metabolic reactions within living cells leads to spontaneous ultraweak light emission. The development of a system for highly sensitive imaging and spatiotemporal analysis of ultraweak photon emission from a rat's brain is reported in this paper. The equipment used in this experiment consists of a two-dimensional photon-counting tube with a photocathode measuring 40 mm in diameter, a highly efficient lens system, and an electronic device to record time series of a photoelectron train with spatial information. The sensitivity and ability to extract spatiotemporal information from sequential data of a single photoelectron train were examined. The minimum detectable radiant flux density of the system was experimentally estimated to be 9.9 x 10(-17) W/cm2 with a 1-s observation time. Spontaneous photon emission was demonstrated from an exposed rat's cortex in vivo without adding any chemical agent or employing external excitation. An image of ultraweak photon emission was compared with one obtained after cardiac arrest. The intensity after cardiac arrest was depressed to approximately 60% of before that. The regional properties of time courses of emission intensity were also demonstrated, indicating the potential usefulness for spatiotemporal characterization of photon emission with mapping of physiological information such as oxidative stress. This technology constitutes a novel method, with the potential to extract pathophysiological information from the central nervous system.

Animals↗
PubMed2005

Regularized phase tracker with isophase scanning strategy for analysis of dynamic interferograms of nonwetting droplets under excitation.

The surface of a nonwetting droplet is separated from a solid surface by a continuous supply of a lubricating gas film within the apparent contact region. Under certain conditions, e.g., application of an external excitation force, the gas film thickness can decrease to a level where intermolecular forces cause the droplet to wet the surface. The thickness of the lubricating film can be measured by interferometry. Externally imposed oscillations change the shape of the film, leading to dynamic interference fringes that are recorded with a high-speed CCD camera. We propose a spatiotemporal analysis of the interference patterns based on the regularized phase-tracker method. This well-known method minimizes a cost function to estimate the absolute phase of a single element in the interferogram. A proper scanning method along all elements of the interferogram is necessary to avoid phase estimation errors that will propagate throughout the entire continuous phase image of interest. The scanning method we propose traces along contours of constant phase in the interferogram and does not require segmentation of the interferogram in dark and bright fringes. Results in the form of dynamic height profiles of droplets under excitation obtained by this method are presented.

Journal Article↗
PubMed1995

Vestibular evoked responses: a new frontier in equilibriometry.

Modern neurootology has proved that many vertigo patients suffer from central dysequilibrium states. As vertigo patients are very frequent amongst our patient population we have to increase our diagnostic as well as therapeutical efforts. Since 1965, eliciting vestibular evoked cortical potentials has been possible. A method of evoked responses based upon computation of several stimulus responses has been used since then. Besides we are also using the frequency analysis of representative epochs of ongoing vestibular-ocular or retino-ocular reactions has been used since then. For diagnostic purposes we are combining various techniques like systematic history taking, ENG, ECG, CCG and BEAM. Brain electrical activity mapping (BEAM) is a newly developed tool, which we can also use for differentiating central from peripheral vestibular diseases. We are applying this technique for topographic correlates of vertigo related functional changes as well as for spatiotemporal analysis of cerebral evoked potentials due to vestibular stimulation. By means of a specific vestibular evoked potential technique, 6 typical cortical wave patterns can be elicited, which are displayed in the EEG curves as well as in colour maps of the whole scalp. The interactions between the various cortical structures are turning into an image similar to a weather map. BEAM, the fourth plan for projecting vertigo disorders, is now also bound into our concept for planning and monitoring a drug based therapy.

Brain Mapping↗