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PubMed2006

Cortical and thalamic coherence during spike-wave seizures in WAG/Rij rats.

The study examines cortico-cortical and cortico-thalamic network synchronization at the onset of spike-wave discharges (SWD) in a genetic model of absence epilepsy, WAG/Rij rats. Coherence was measured between multiple cortical areas (intracortical), reticular and rely thalamic nuclei (intrathalamic) and between the cortex and the thalamus. SWD-related increase of coherence (5-60 Hz) was found in all investigated pairs. The highest increase of coherence was around the mean frequency of SWD (8-11.5 Hz) and in the harmonic band 16-21.5 Hz with two central maxima around 10 and 20 Hz. The frequency profile of coherence was different in different intracortical networks, therefore latter were divided into local, global and transhemispheric networks. The presumable source of SWD in the somatosensory cortex and its closest surroundings formed a minimal (local) circuit, in which occurrence of SWD was facilitated by a consistent shift of network synchrony from delta to alpha/beta frequencies. Transhemispheric coherence revealed the largest increase with an additional 16 Hz peak, suggesting a crucial involvement of the corpus callosum in the pathophysiology of absence seizures. The increase in interhemispheric coherence was largest between relatively remote somatosensory or frontal areas, supporting the assumption that SWD originate from the lateral fronto-parietal cortical area.

Analysis of Variance↗
PubMed2001

[Local and distributed neuronal networks and individuality].

To estimate stable behavioural peculiarities, an individual varying choice of greater or better appetite reinforcement depending on the time of instrumental motor response was used with cats. A decisive role in realisation of the response choice is played by the influence of motivational structures of hypothalamus and amygdala on formal areas of neocortex typical for "impulsive" (fast reacting) cats, and interaction of the frontal cortex--hippocampus system for the animals with delayed pressing of the lever to obtain their preferred food, i.e. manifesting the ability of "self-control".

Animals↗
PubMed2002

Automatic recognition of cortical sulci of the human brain using a congregation of neural networks.

This paper describes a complete system allowing automatic recognition of the main sulci of the human cortex. This system relies on a preprocessing of magnetic resonance images leading to abstract structural representations of the cortical folding patterns. The representation nodes are cortical folds, which are given a sulcus name by a contextual pattern recognition method. This method can be interpreted as a graph matching approach, which is driven by the minimization of a global function made up of local potentials. Each potential is a measure of the likelihood of the labelling of a restricted area. This potential is given by a multi-layer perceptron trained on a learning database. A base of 26 brains manually labelled by a neuroanatomist is used to validate our approach. The whole system developed for the right hemisphere is made up of 265 neural networks. The mean recognition rate is 86% for the learning base and 76% for a generalization base, which is very satisfying considering the current weak understanding of the variability of the cortical folding patterns.

Artificial Intelligence↗
PubMed1998

Early motor influences on visuomotor transformations for reaching: a positive image of optic ataxia.

Coding of reaching in the cerebral cortex is based on the operation of distributed populations of parietal and frontal neurons, whose main functional characteristics reside in their combinatorial power, i.e., in the capacity for combining different information related to the spatial aspects of reaching. The tangential distribution of reach-related neurons endowed with different functional properties changes gradually in the cortex and defines, in the parieto-frontal network, trends of functional properties. These visual-to-somatic gradients imply the existence of cortical regions of functional overlaps, i.e., of combinatorial domains, where the integration of different reach-related signals occurs. Studies of early coding of reaching in the mesial parietal areas show how somatomotor information, such as that related to arm posture and movement, influences neuronal activity in the very early stages of the visuomotor transformation underlying the composition of the motor command and is not added "downstream" in the frontal cortex. This influence is probably due to re-entrant signals traveling through fronto-parietal-association connections. Together with the gradient architecture of the network and the reciprocity of cortico-cortical connections, this implies that coding of reaching cannot be regarded as a top-down, serial sequence of coordinate transformation, each performed by a given cortical area, but as a recursive process, where different signals are progressively matched and further elaborated locally, due to intrinsic cortical connections. This model of reaching is also supported by psychophysical studies stressing the parallel processing of the different relevant parameters and the "hybrid" nature of the reference frame where they are combined. The theoretical frame presented here can also offer a background for a new interpretation of a well-known visuomotor disorder, due to superior parietal lesions, i.e., optic ataxia. More than a disconnection syndrome, this can now be interpreted as the consequence of the breakdown of the operations occurring in the combinatorial domains of the superior parietal segment of the parieto-frontal network.

Animals↗
PubMedDate not supplied

The three networks framework to deal with public health emergencies in Guangxi, China.

OBJECTIVE: To improve the detection and control of infectious diseases in Guangxi, China. SETTING/PARTICIPANTS: Guangxi province in southwest China has almost 50 million people, of whom approximately 30% reside in urban and 70% in rural areas. There are 12 minority nationality groups living in the region. INTERVENTION: A village doctor reports any infectious disease outbreak to the Reporting Network, which notifies the Service Network to organize the clinical response. This is supported by the Government Network that coordinates the response among the multiple layers of local governments. OUTCOMES: Since 2002 when the Three Networks system was first started, the time from incidence to report has been shortened on average from 30.6 to 7.6 days and the number of cases has increased from slightly less than 5000 cases/year (4965) to almost 10,000 cases/year (9873). Average mortality has decreased from 3.23% to 0.74%. The Three Networks system has been successful in controlling measles outbreaks; and during SARS, when 11 cases came to Guangxi from the neighbouring Guangdong province, there were only 11 additional new cases with no community spread and no spread to medical staff. CONCLUSION: The Three Networks system has played an important role in infectious disease prevention and control in Guangxi province, and may be applicable to other areas with a similar situation.

China↗
PubMed2006

Local and global motion after-effects are both enhanced in migraine, and the underlying mechanisms differ across cortical areas.

Visual after-effects are illusions that occur after prolonged viewing of visual displays (pattern adaptation). The motion after-effect (MAE), for example, is an illusory impression of motion that is seen after viewing moving displays. After-effects have been used extensively in basic vision research as well as in clinical settings, and have been reported to be enhanced in migraine. Pattern adaptation is a cortical phenomenon that reflects both cellular mechanisms acting within individual neurons and specific interactions between groups of neurons activated by the adapting display. A remarkable feature of the MAE is that its duration is only slightly reduced if a delay is inserted between the end of the adaptation and the test display ('storage'). The reduction is consistent with recovery of the cellular component, and the residual with network changes that are maintained during the delay. This study aimed (i) to assess explanations for prolonged MAEs in migraine by teasing apart the proposed cellular and network components of adaptation using storage; (ii) to determine the extent of cortical abnormality in migraine using local and global MAEs, which reflect adaptation at different stages of the visual system. Fifty migraine (22 with, 28 without aura) and 50 control participants adapted to motion before viewing a stationary or dynamic (random motion) test, which consequently appeared to move in the opposite direction (local and global MAEs, respectively). Half of the trials included a delay between the adapting and test displays. The results extend those reported previously, as both local and global MAEs lasted longer in migraine compared with the control group. Global MAEs survived delays almost completely for both groups, whereas local MAEs were reduced to a greater extent in migraine. There were no significant differences between migraine subgroups classified according to the presence or absence of visual aura. These results suggest that cellular recovery is slowed in migraine for early but not later visual cortical areas. Sustained network changes following adaptation are implicated across cortical areas. Differences between people with and without migraine on various measures of visual perception have been attributed to abnormal cortical processing in migraine, variously described by hyperexcitability, heightened responsiveness and/or a lack of intra-cortical inhibition. The results are not consistent with hyperexcitability resulting from a lack of inhibition in migraine, but are consistent with extended suppression of intra-cortical excitation. The implications of these results for alternative models of hyperexcitability are discussed.

Adaptation, Physiological↗
PubMed1999

MT neurons in the macaque exhibited two types of bimodal direction tuning as predicted by a model for visual motion detection.

We previously proposed a model for detecting local image velocity on the magnocellular visual pathway (Kawakami & Okamoto (1996) Vision Research, 36, 117-147). The model detects visual motion in two stages using the hierarchical network that includes component and pattern cells in area MT. To validate the model, we predicted two types of bimodal direction tuning for MT neurons. The first type is characteristic of component cells. The tuning is bimodal when stimulated with high-speed spots, but unimodal for low-speed spots or for bars. The interval between the two peaks widens as the spot's speed increases. The second type is characteristic of pattern cells. The tuning is bimodal when stimulated with low-speed bars, but unimodal for high-speed bars or for spots. The interval widens as the bar's speed decreases. To confirm this prediction, we studied the change of direction tuning curves for moving spots and bars in area MT of macaque monkeys. Out of 35 neurons measured at various speeds, six component cells and four pattern cells revealed the predicted bimodal tunings. This result provided neurophysiological support for the validity of the model. We believe ours is the first systematic study that records the two types of bimodality in MT neurons.

Animals↗
PubMed2006

Crystallization of zeolites from organo-silicic colloids.

As shown recently, the networks of mesoporous high-surface-area silicates and zeolites undergo a deep depolymerization process in glycerol, near 200 degrees C. Within 1 h, X-ray diffraction analysis amorphous gels are obtained. However, some local ordering subsists as demonstrated by a striking similarity between the silicon and aluminum high-resolution solid-state NMR spectra before and after the reaction. The residual organization could be investigated indirectly in studying the recrystallization of these gels in the presence or absence of structure-directing agents. Were this attempt successful, the way should be opened for the synthesis of molecular sieves starting from gels obtained from naturally occurring zeolites. Here, it will be shown that an amorphous gel obtained from HZSM-5 recovers the initial long-range structure of the parent material in a few hours at 85 degrees C in the presence of an aqueous solution of tetrapropyl ammonium (TPA) or NH3. The recrystallization of HY requires the presence of tetramethylammonium, but about 25% of the crystallization is obtained rapidly (approximately = 1 day) at 80 degrees C with ammonia. Hypotheses about the preorganized structural units are presented. The value of the Si-O-Si angle in the silica cluster seems to be of paramount importance.

Journal Article↗
PubMed2007

Beta/gamma oscillatory activity in the CA3 hippocampal area is depressed by aberrant GABAergic transmission from the dentate gyrus after seizures.

Oscillatory activity in the CA3 region is thought to be involved in the encoding and retrieval of information. These oscillations originate from the recurrent excitation between pyramidal cells that are entrained by the synchronous rhythmic inhibition of local interneurons. We show here that, after seizures, the dentate gyrus (DG) tonically inhibits beta/gamma (20-24 Hz) field oscillations in the CA3 area through GABA-mediated signaling. These oscillations originate in the interneuron network because they are maintained in the presence of ionotropic glutamate receptor antagonists, and they can be blocked by GABA(A) receptor antagonists or by perfusion of a calcium-free extracellular medium. Inhibition of this oscillatory activity requires intact DG-to-CA3 connections, and it is suppressed by the activation of metabotropic glutamate receptors (mGluR). The influence of mGluR activation was reflected in the spontaneous subthreshold membrane oscillations of CA3 interneurons after one seizure but could also be observed in pyramidal cells after several seizures. Coincident stimulation of the DG at and beta/gamma frequencies produced a frequency-dependent excitation of interneurons and the inhibition of pyramidal cells. Indeed, these effects were maximal at the frequency that matched the mGluR-sensitive spontaneous field oscillations, suggesting a resonance phenomenon. Our results shed light on the mechanisms that may underlie the deficits in memory and cognition observed after epileptic seizures.

Animals↗
PubMed2000

[Impact of the daily variations of the air pollution on the ambulatory emergency health services activity. Study in the urban area of Rouen (France)].

BACKGROUND: The aim of this study was to evaluate feasibility of using both the emergency phone calls (SAMU) and medical interventions (SMUR) related to ambulatory emergency services for local epidemiological surveillance of health impact of air pollution. METHODS: A temporal ecological study was performed at Rouen area (France) (380,000 inhabitants) for 1990-1997 (SAMU) and 1990-1996 (SMUR). The pollutants tested were: Sulphur dioxide (SO(2)), Particles (PM13), and Nitrogen dioxide (NO(2)), as collected routinely by a local automated network. For each phone call (SAMU) or emergency interventions (SMUR), the date, medical reason for calling (SAMU) or diagnosis after interventions (SMUR) (classified as respiratory, cardiovascular or other diseases) have been extracted from a specific information system. A statistical analysis based on time series analysis associated to a Poisson regression was conducted, taking into account temporal trend, seasonal variations, influenza, days of the week, holiday and meteorological data. RESULTS: An association was observed between ambulatory emergency services activity for cardiovascular diseases, and the daily variations of both SO(2) (relative risk=1.008 [1.001-1.016] for SAMU with an increase of 10 microg/m(3)) and NO(2) (relative risk=1.018 [1.008-1. 030] for SAMU, relative risk=1.016 [1.001-1.032] for SMUR with an increase of 10 microg/m(3)). No association could be observed with the respiratory diseases for these pollutants. CONCLUSION: The ambulatory emergency services activity data could contribute to an epidemiological surveillance of the health impact of the air pollution, but a better quality of data collected (concerning both procedures and codification) is requested. The interest of an epidemiological surveillance, rather than usual pollutant monitoring, remains to evaluate.

Air Pollutants↗
PubMed1980

Redistribution of contractile and cytoskeletal components induced by cytochalasin. I. In Hmf cells, a nontransformed fibroblastoid line.

Hmf cells are normal rat fibroblastoid cells of large size having an extensive stress fiber (cable) system. On exposure to cytochalasin D (CD), shortening and segmentation of the actin-based cables and diffusion of the normal periodic distribution of tropomyosin and myosin occur, concomitant with generalized cell retraction. During retraction, areas of extended cytoplasm may be pulled apart and torn. The actin, tropomyosin, and myosin of the stress fibers become localized in dispersed masses represented in the electron microscope as compact filamentous felt-like networks. Many of these are derived from shortening of stress fibers at their insertions into the persisting attachment plaques. In a few cells, rod-like elements of variable length remain; these are CD-resistant segments of uncontracted stress fibers. Inhibitors of energy metabolism prevent these changes. Microtubules remain unaltered but are passively displaced in the CD-deformed cells. Bundles of 10 nm filaments maintain close relations with the actomyosin masses resulting from CD-treatment. Evidence is considered for the hypothesis that cellular retraction, the apparent disorganization of stress fibers, and the redistribution of contractile proteins result from unremittent energy-dependent contraction induced by CD, and that the compact forms may be analogous to rigor complexes. A mechanism for these actions of cytochalasin is proposed.

Animals↗
PubMed2006

Pediatric spinal cord injury in a subset of European countries.

STUDY DESIGN: Postal survey. SETTING: A total of 19 countries in Europe. OBJECTIVES: Firstly, to collect information about incidence and systems of care for pediatric spinal cord injury (pedSCI); including prevention, initial care and follow-up in a subset of European countries. Secondly, to initiate a network of involved professionals for exchange of information and development of research and care programs. METHODS: A short semi-structured questionnaire was sent to respondents working with spinal cord injury (SCI) in 19 countries in Europe. RESULTS: Only in Portugal and Sweden, is the incidence of pedSCI (fatal injuries included) established, that is 27 children/million children/year and 4.6 children/million children/year, respectively. For the other countries, the estimated incidence of pedSCI (nonfatal injuries) varied from 0.9 to 21.2 children/million children/year in the age group of 0-14 years. Although the incidence varies considerably, pedSCI is rare throughout Europe. The management differs between the countries depending on the age of the child and the local organization of health care. CONCLUSIONS: The survey confirms that pedSCI is rare. In order to establish high-quality standardized care, further integration of knowledge in this area is needed throughout Europe. The contacts initiated by this survey may be used to create an international network serving as a reference for health professionals, researchers and families, thereby possibly alleviating some of the unwanted variations of care identified in this study.

Child↗
PubMed2006

Network analysis of single-subject fMRI during a finger opposition task.

The analysis of functional magnetic resonance imaging (fMRI) data has typically relied on univariate methods to identify areas of brain activity related to cognitive and behavioral task performance. We investigated the ability of multivariate network analysis using a modified form of principal component analysis, the Scaled Subprofile Model (SSM), applied to single-subject fMRI data to identify patterns of interactions among brain regions over time during an anatomically well-characterized simple motor task. We hypothesized that each subject would exhibit correlated patterns of brain activation in several regions known to participate in the regulation of movement including the contralateral motor cortex and the ipsilateral cerebellum. EPI BOLD images were acquired in six healthy participants as they performed a visually and auditorally paced finger opposition task. SSM analysis was applied to the fMR time series on a single-subject basis. Linear combinations of the major principal components that predicted the expected hemodynamic response to the order of experimental conditions were identified for each participant. These combinations of SSM patterns were highly associated with the expected hemodynamic response, an indicator of local neuronal activity, in each participant (0.84 </= R(2) </= 0.97, all P's < 0.0001). As predicted, the combined pattern in each subject was characterized most prominently by relatively increased activations in contralateral sensorimotor cortex and ipsilateral cerebellum. Additionally, all subjects showed areas of relatively decreased activation in the ipsilateral sensorimotor cortex and contralateral cerebellum. The application of network analysis methods, such as SSM, to single-subject fMRI data can identify patterns of task-specific, functionally interacting brain areas in individual subjects. This approach may help identify individual differences in the task-related functional connectivity, track changes in task-related patterns of activity within or between fMRI sessions, and provide a method to identify individual differences in response to treatment.

Acoustic Stimulation↗
PubMed1989

Differential expression and subcellular localization for subunits of cAMP-dependent protein kinase during ram spermatogenesis.

The expression of mRNAs for the RI alpha, RII alpha, and C alpha subunits of cAMP-dependent protein kinase has been studied in different ram germ cells. The sizes of the specific RI alpha, RII alpha, and C alpha mRNAs, observed in germ cells were 1.6, 2.0, and 2.6 kb, respectively. RI alpha and C alpha mRNAs were mainly expressed in primary spermatocytes. A postmeiotic expression predominating in early spermatids was unique to RII alpha mRNA. The location of RI, RII alpha, and C subunits in well-defined organelles of ram spermatids and epididymal sperm was assessed by immunogold electron microscopy. In spermatids, RI, RII alpha, and C were essentially present in the forming acrosome and, to a lesser extent, in the nucleus. During sperm epididymal maturation, the protein kinases disappeared from the acrosome and were detected in a variety of sperm functional areas, such as the tip of the acrosome, the motility apparatus, and the membrane network. The present study on subunits of cAMP-dependent protein kinase supports the concept that specific functions are attached to the different subunits in that it shows differential expression and differential subcellular localization in germ cells.

Animals↗
PubMed2003

Integrating air pollution modelling with scenario testing in road transport planning: the TRAEMS approach.

Transport add-on environmental modelling system (TRAEMS) is a GIS-based environmental modelling system designed to evaluate the environmental consequences of road traffic in urban areas. Its development has been underpinned by the premises that the evaluation of road traffic impacts is best undertaken during the early planning stages of road networks, and that this can utilise much of the data generated by the transport planners themselves as they apply their travel demand models as to planning of road networks. The system integrates information about traffic-usually from travel-forecasting models-with information about land use, to provide the input data to a range of commonly used models that estimate pollution from a road traffic system, and the energy consumption of that system. TRAEMS facilitates this integration and allows land use, transport and environmental planners to have rapid feedback on the environmental effects of road transport network scenarios that are being developed and tested. Its purpose is to aid in the selection of environmentally-preferred road networks and to highlight where management of pollution levels on future road networks will be required. TRAEMS has a modular structure. This paper describes the main features of the air pollution and fuel consumption modules of the system and illustrates the system's utility through case studies at both metropolitan-wide- and local-area scales.

Air Pollution↗
PubMed1976

Implementing formative health planning under PL 93-641.

The National Health Planning and Resources Development Act of 1974 (PL 93-641) melds the Hill-Burton program, Regional Medical Program and Comprehensive Health Planning into a new network for health planning and resources development. Health-systems agencies will possess broader powers than predecessor agencies, particularly in the areas of regulation, control of federal funds, resources development and implementation. PL 93-641 thus offers the possibility of transforming the basic concept of health planning from reactive to "proactive." Successful legislative implementaion will require each health-systems agency to build local legitimacy, ensure constructive consumer/provider dialogue, and respond to state and national managerial requirements. Many questions about planning implementation, the role of subarea councils, agency co-ordination and local governance remain unresolved. The new health-planning network has the potential to assume the function of active system transformation, but will be critically dependent on adequate program budgeting to fulfill this promise. (N Engl J Med 295:698-703, 1976).

Delivery of Health Care↗
PubMed2005

An inter-centre quality assurance network for IMRT verification: results of the ESTRO QUASIMODO project.

BACKGROUND AND PURPOSE: IMRT necessitates extension of existing inter-centre quality assurance programs due to its increased complexity. We assessed the feasibility of an inter-centre verification method for different IMRT techniques. MATERIALS AND METHODS: Eight European radiotherapy institutions of the QUASIMODO network, have designed an IMRT plan for a horseshoe-shaped PTV surrounding a cylindrical OAR in a simplified pelvic phantom. All centres applied common plan objectives but used their own equipment for planning and delivery. They verified the delivery of this plan according to a common protocol with radiographic film and ionisation chamber measurements. The irradiated films, the results of the ionisation chamber measurements and the computed dose distributions were sent to one analysis centre that compared the measured and computed dose distributions with the gamma method and composite dose-area histograms. RESULTS: 4% (relative to the prescribed dose) and 3mm (distance-to-agreement) were decided feasible gamma criteria. The composite dose-area histograms showed a maximum local deviation of 3.5% in the mean dose of the PTV and 5% in the OAR. Systematic differences could be identified, and in some cases explained. CONCLUSIONS: This multi-centre dosimetric verification study demonstrated both the feasibility of a multi-centre quality assurance network to evaluate any IMRT planning and delivery system combination, as well as the validity of the methodology involved.

Community Networks↗
PubMed2000

Continuum model of mnemonic and amnesic phenomena.

Amnesia in its various forms is characterized by defects in one or more components of a complex system. Implantation of short-term memory occurs in the hippocampus, while long-term memory is essentially located in the neocortex; these regions are interconnected through complex synaptic structures. In the hippocampus, physiological data show that, as predicted by Hebb, excitatory synapses between nearby excitatory cells become strengthened by simultaneous activation. In contrast with this local process, the preponderance of clinical and experimental evidence indicates that cortical recall of a "memory" is the reconstruction of fragments stored in different synaptically distant brain regions. A mathematical model of memory must reconcile this apparent contradiction as well as explain how many different memories and "ideas" can be assembled within a given anatomical area. Continuum theory, which treats an ensemble of "cell assemblies" or neural networks, offers a step in this direction. Linear analysis using this approach shows that it is the nature of the neural continuum to generate activity waves of wavelength greater than synaptic connection ranges. These waves grow under certain circumstances, and their wavelength is controlled by the synaptic parameters. Both hippocampal and cortical tissue are subject to such wave growth. In the hippocampus, the local Hebbian strengthening controls the global wave growth, making the difference between wave decay and growth. The cortical wave structure can become very complex, so that reproducible memory recall as well as "creative thought" can be accommodated in the theory. Deficits in the functioning of the system may also be evaluated potentially by means of "goodness-of-fit" of the clinical and spatially resolved data with the model.

Algorithms↗