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At least 649 records · Page 36Linked to original sources
PubMed2006

Functional and effective connectivity in an fMRI study of an auditory-related task.

This study investigates the sets of brain areas that are functionally connected during an auditory goal-directed task. We used a paradigm including a resting state condition and an active condition, which consisted in active listening to the footsteps of walking humans. The regional brain activity was measured using fMRI and the adjusted values of activity in brain regions involved in the task were analysed using both principal component analysis and structural equation modelling. A first set of connected areas includes regions located in Heschl's gyrus, planum temporale, posterior superior temporal sulcus (in the so-called 'social cognition' area), and parietal lobe. This network could be responsible for the perceptual integration of the auditory signal. A second set encompassing frontal regions is related to attentional control. Dorsolateral- and medial-prefrontal cortex have mutual negative influences which are similar to those described during a visual goal-directed task [T. Chaminade & P. Fonlupt (2003) Eur. J. Neurosci., 18, 675-679.]. Moreover, the dorsolateral prefrontal cortex (DLPFC) exerts a positive influence on the auditory areas during the task, as well as a strong negative influence on the visual areas. These results show that: (i) the negative influence between the medial and lateral parts of the frontal cortex during a goal-directed task is not dependent on the input modality (visual or auditory), and (ii) the DLPFC activates the pathway of the relevant sensory modality and inhibits the nonrelevant sensory modality pathway.

Acoustic Stimulation↗
PubMed2006

Integrin-binding RGD peptides induce rapid intracellular calcium increases and MAPK signaling in cortical neurons.

Integrins mediate cell adhesion to the extracellular matrix and initiate intracellular signaling. They play key roles in the central nervous system (CNS), participating in synaptogenesis, synaptic transmission and memory formation, but their precise mechanism of action remains unknown. Here we show that the integrin ligand-mimetic peptide GRGDSP induced NMDA receptor-dependent increases in intracellular calcium levels within seconds of presentation to primary cortical neurons. These were followed by transient activation and nuclear translocation of the ERK1/2 mitogen-activated protein kinase. RGD-induced effects were reduced by the NMDA receptor antagonist MK801, and ERK1/2 signaling was specifically inhibited by ifenprodil and PP2, indicating a functional connection between integrins, Src and NR2B-containing NMDA receptors. GRGDSP peptides were not significantly neuroprotective against excitotoxic insults. These results demonstrate a previously undescribed, extremely rapid effect of RGD peptide binding to integrins on cortical neurons that implies a close, functionally relevant connection between adhesion receptors and synaptic transmission.

Analysis of Variance↗
PubMed1997

Immune network at the edge of chaos.

Some time ago Jerne proposed a new theory to explain the basis of the immune system. He suggested the existence of a functional connected network, based on pattern recognition of the idiotypes carried by the lymphocytes, which is responsible for the self regulation of the immune system. Only 15-20% of the lymphocytes available in the immune repertoire will participate in this functional network, while the rest of the lymphocytes will be free to respond to any foreign antigen. Each individual immune repertoire will be different depending on the lymphocytes that participate in the connected network. Using a very simple cellular automata model of the immune repertoire dynamics we show that, although the usual regimes (stable and chaotic) attained by this automata, are not interesting from the biological point of view, the transition region, at the edge of chaos, is very appropriate to describe such dynamics. In this region we have obtained a functional connected network involving 10-20% of the lymphocytes available in the repertoire, as suggested by Jerne and others. The model also reproduces the immune system signature, the ensemble of different lymphocytes that each individual expresses in his immune repertoire, which varies from one individual to another. We show how the immune memory comes out as a consequence of the dynamics of the system. From our results we confirm and present evidence that the chaotic regime corresponds to a sort of non-healthy state, as has been suggested previously.

Antigen Presentation↗
PubMed1997

Nip and tuck at the neuromuscular junction: a role for proteases in developmental synapse elimination.

During late embryonic and early postnatal development, synaptic connections are extensively modified so that some functional connections are weakened and eliminated from a neural circuit while others are strengthened and maintained. The mechanisms that underlie synapse elimination are beginning to be understood from studies of the neuromuscular junction. A recent paper provides some intriguing insights into the role proteases may play in the developmental disassembly of neuromuscular synapses.

Endopeptidases↗
PubMed2005

A new device and protocol for combining TMS and online recordings of EEG and evoked potentials.

We describe an electroencephalographic (EEG) device and protocol that allows recording of electrophysiological signals generated by the human brain during transcranial magnetic stimulation (TMS) despite the TMS-induced high-voltage artifacts. The key hardware components include slew-rate limited preamplifiers to prevent saturation of the EEG system due to TMS. The protocol involves artifact subtraction to isolate the electrophysiological signals from residual TMS-induced contaminations. The TMS compatibility of the protocol is illustrated with examples of two data sets demonstrating the feasibility of the approach in the single-pulse TMS design, as well as during repetitive TMS. Our data show that both high-amplitude potentials evoked by visual checkerboard stimulation and low-amplitude steady-state oscillations induced by auditory click-trains can be retrieved with the present protocol. The signals recorded during TMS perfectly matched control EEG responses to the same visual and auditory stimuli. The main field of application of the present protocol is in cognitive neuroscience complementing behavioral studies that use TMS to induce transient, 'virtual lesions'. Combined EEG-TMS techniques provide neuroscientists with a unique method to test hypothesis on functional connectivity, as well as on mechanisms of functional orchestration, reorganization, and plasticity.

Adult↗
PubMed2005

Measuring temporal dynamics of functional networks using phase spectrum of fMRI data.

We present a novel method to measure relative latencies between functionally connected regions using phase-delay of functional magnetic resonance imaging data. Derived from the phase component of coherency, this quantity estimates the linear delay between two time-series. In conjunction with coherence, derived from the magnitude component of coherency, phase-delay can be used to examine the temporal properties of functional networks. In this paper, we apply coherence and phase-delay methods to fMRI data in order to investigate dynamics of the motor network during task and rest periods. Using the supplementary motor area (SMA) as a reference region, we calculated relative latencies between the SMA and other regions within the motor network including the dorsal premotor cortex (PMd), primary motor cortex (M1), and posterior parietal cortex (PPC). During both the task and rest periods, we measured significant delays that were consistent across subjects. Specifically, we found significant delays between the SMA and the bilateral PMd, bilateral M1, and bilateral PPC during the task condition. During the rest condition, we found that the temporal dynamics of the network changed relative to the task period. No significant delays were measured between the SMA and the left PM and left M1; however, the right PM, right M1, and bilateral PPC were significantly delayed with respect to the SMA. Additionally, we observed significant map-wise differences in the dynamics of the network at task compared to the network at rest. These differences were observed in the interaction between the SMA and the left M1, left superior frontal gyrus, and left middle frontal gyrus. These temporal measurements are important in determining how regions within a network interact and provide valuable information about the sequence of cognitive processes within a network.

Adult↗
PubMed1999

Parabolic quantitative structure-activity relationships and photodynamic therapy: application of a three-compartment model with clearance to the in vivo quantitative structure-activity relationships of a congeneric series of pyropheophorbide derivatives used as photosensitizers for photodynamic therapy.

An open three-compartment pharmacokinetic model was applied to the in vivo quantitative structure-activity relationship (QSAR) data of a homologous series of pyropheophorbide photosensitizers for photodynamic therapy (PDT). The physical model was a lipid compartment sandwiched between two identical aqueous compartments. The first compartment was assumed to clear irreversibly at a rate K0. The measured octanol-water partition coefficients, P(i) (where i is the number of carbons in the alkyl chain) and the clearance rate K0 determined the clearance kinetics of the drugs. Solving the coupled differential equations of the three-compartment model produced clearance kinetics for each of the sensitizers in each of the compartments. The third compartment was found to contain the target of PDT. This series of compounds is quite lipophilic. Therefore these drugs are found mainly in the second compartment. The drug level in the third compartment represents a small fraction of the tissue level and is thus not accessible to direct measurement by extraction. The second compartment of the model accurately predicted the clearance from the serum of mice of the hexyl ether of pyropheophorbide a, one member of this series of compounds. The diffusion and clearance rate constants were those found by fitting the pharmacokinetics of the third compartment to the QSAR data. This result validated the magnitude and mechanistic significance of the rate constants used to model the QSAR data. The PDT response to dose theory was applied to the kinetic behavior of the target compartment drug concentration. This produced a pharmacokinetic-based function connecting PDT response to dose as a function of time postinjection. This mechanistic dose-response function was fitted to published, single time point QSAR data for the pheophorbides. As a result, the PDT target threshold dose together with the predicted QSAR as a function of time postinjection was found.

Animals↗
PubMed2004

Sutter Connect beefs up back-office functions.

Sutter Connect, an administrative services organization, uses a variety of information technology methods to reduce PMPM costs. Find out what back office functions are used to manage more than dollars 504 million in capitation dollars for about 415,000 commercial and Medicare Advantage managed care lives.

California↗
PubMed2026

Schizophrenia and bipolar disorder: a comparative analysis of genetic and brain network connectivity.

BACKGROUND: Schizophrenia (SCZ) and bipolar disorder (BD) are severe psychiatric conditions with overlapping clinical presentations, genetic risk factors, and brain network dysfunction. Whether alterations in large-scale intrinsic brain networks reflect shared or disorder-specific genetic influences remains poorly understood. Clarifying this distinction is essential for refining etiological models and improving diagnostic precision. METHODS: Genome-wide inferred statistics (GWIS) were applied to decompose the genetic architecture of SCZ and BD into shared and unique components. Using resting-state network (RSN) data from the UK Biobank, functional connectivity (FC) and structural connectivity (SC) were extracted as neuroimaging phenotypes. Causal inference approaches were subsequently employed to infer potential directional relationships between brain network connectivity and each disorder. RESULTS: Analyses revealed both common and distinct patterns of brain network connectivity associated with SCZ and BD. Notably, SC within the default mode network (DMN) exhibited opposing effects across the two disorders, suggesting divergent structural underpinnings despite clinical overlap. Additionally, SC within the limbic network (LN) and frontotemporal control network demonstrated potential causal relationships with both conditions, implicating these circuits astransdiagnostic neural substrates. CONCLUSION: These findings illuminate the shared and disorder-specific genetic and neural architecture underlying SCZ and BD. Integrating genome-wide genetic methods with large-scale neuroimaging data offers a powerful framework for disentangling psychiatric comorbidity and may inform more targeted diagnostic criteria and individualized treatment strategies.

Humans↗
PubMed1988

Regenerated fibers of the lamprey spinal cord can coordinate fictive swimming in the presence of curare.

Recently evidence was presented that, following transection, spinal cords of larval lampreys could regenerate functional connections. The demonstration in isolated spinal cord-notochord preparations consisted of fictive swimming coordinated across the lesion site. In the study reported here curare was added to the bath to eliminate the possible contribution from reflexes mediated by contractions from any remaining muscle fibers attached to the notochord. Coordination remained in the presence of curare, adding further evidence that indeed the regenerated fibers formed functionally appropriate connections.

Animals↗
PubMedDate not supplied

[The pharmacological testing of intracortical interneuronal connections].

An attempt is made to study the influence of acetylcholine on functional connections of cortical neurons and their frequency characteristics. Multiunit activity was recorded in the sensorimotor cortex of immobilized and freely moving rats. Crosscorrelation analysis was used. Influence of acetylcholine (Ach) and Ca chelator ethyleneglicoltetraacetat (EGTA) on the functional characteristics of the neighbouring neurons was studied in the first series of experiments. The substances were iontophoretically applied to the sensorimotor cortex neurons of the immobilized unanesthetized rats. Application of Ach led to variation in the frequency characteristics of single neurons and in the majority cases did not affect the neuronal interrelations. EGTA application, independently on the background frequency of the neuronal activity, resulted in disappearance of interneuronal connections which recovered after the end of EGTA effect. The second series of experiments was carried out in freely moving rats. System injection of galantamine essentially increased the frequency of activity of the cortical neurons not affecting their network activity. We suppose that intracortical relations can be realized independently on the extracortical influences which are manifested in variations in the background impulsation of the single neurons. Qualitative estimation of Ach influence on the functional characteristics of the cortical neurons do not reveal Ach effects on formation of intracortical connections. The technique used by us may be applied in further studies of intracortical neurons connections.

Acetylcholine↗
PubMed2003

Two-dimensional gap analysis: a tool for efficient conservation planning and biodiversity policy implementation.

The maintenance of biodiversity by securing representative and well-connected habitat networks in managed landscapes requires a wise combination of protection, management, and restoration of habitats at several scales. We suggest that the integration of natural and social sciences in the form of "Two-dimensional gap analysis" is an efficient tool for the implementation of biodiversity policies. The tool links biologically relevant "horizontal" ecological issues with "vertical" issues related to institutions and other societal issues. Using forest biodiversity as an example, we illustrate how one can combine ecological and institutional aspects of biodiversity conservation, thus facilitating environmentally sustainable regional development. In particular, we use regional gap analysis for identification of focal forest types, habitat modelling for ascertaining the functional connectivity of "green infrastructures", as tools for the horizontal gap analysis. For the vertical dimension we suggest how the social sciences can be used for assessing the success in the implementation of biodiversity policies in real landscapes by identifying institutional obstacles while implementing policies. We argue that this interdisciplinary approach could be applied in a whole range of other environments including other terrestrial biota and aquatic ecosystems where functional habitat connectivity, nonlinear response to habitat loss and a multitude of economic and social interests co-occur in the same landscape.

Conservation of Natural Resources↗
PubMed2026

Cerebellar iTBS enhances gait adaptation by modulating cortical sensorimotor network dynamics: a randomized controlled trial.

Gait adaptation enables individuals to maintain locomotor stability under persistent perturbations. Although the cerebellum is critical for sensory prediction error-based (SPE) adaptation, how cerebellar neuromodulation reshapes cortical sensorimotor networks to enhance gait adaptation remains unclear. This study investigated the behavioral effects and underlying cortical neurodynamic mechanisms of cerebellar intermittent theta-burst stimulation (iTBS) on gait adaptation. Thirty-two healthy adults received either active or sham cerebellar iTBS. Participants performed a split-belt treadmill adaptation task before and after intervention. Cortical responsiveness was evaluated using TMS-evoked EEG over primary motor cortex (M1), while resting-state EEG was analyzed to assess spectral power and directional functional connectivity. Compared to sham, cerebellar iTBS significantly enhanced gait adaptation, evidenced by a faster adaptation rate (p = 0.035) and enhanced Early Adaptation SLS (p = 0.011), without altering initial perturbation responses or post-adaptation outcomes. The iTBS increased TMS-evoked α (p = 0.031) and γ (p = 0.022) power in M1, while the α power was correlated with faster adaptation (r = 0.526, p = 0.002). Furthermore, iTBS strengthened PPC-to-M1 directed connectivity in the β (p = 0.025) and γ (p = 0.013) bands. Enhanced parieto-motor directionality were positively associated with adaptation rate (β: r = 0.515, p = 0.003; γ: r = 0.463, p = 0.009). These findings suggest that cerebellar iTBS facilitates gait adaptation by modulating cortical responsiveness and directional sensorimotor network connectivity, providing multi-level neurodynamic evidence for the cerebello-cortical modulation during gait adaptation and offering a strong physiological rationale for targeted neuromodulation in gait rehabilitation strategies.

Humans↗
PubMed2006

A comprehensive study of the spatial and temporal expression of the col5a1 gene in mouse embryos: a clue for understanding collagen V function in developing connective tissues.

Collagen V is a quantitatively minor component of collagen I fibrils and the defective product of classic Ehlers-Danlos syndrome (EDS). To provide new insights into its embryonic function, a continuous evaluation of the expression pattern of proalpha1(V), a chain common to all collagen V molecular forms, was performed by in situ hybridization of developing mouse from 7.5 days after conception (dpc) to birth. Proalpha1(V) transcripts were first detected at 8.5 dpc, signals being considerably augmented at 16.5 dpc and declining at birth. Hybridization signals were, at first, exclusively detected in the dorsal aorta wall, heart, and adnexa. At 10.5 dpc, col5a1 expression was found in the heart, dorsal aorta wall, branchial arches, mesonephrotic tubules, and intestinal mesenchyme and coincided with proalpha1(I) developmental expression. Later stages exhibited an intense signal in more restricted regions, notably the skin, the bones and vertebral column, the cornea, the tendons and ligaments, the peritoneal membranes, the umbilical cord, and the salivary gland. The data revealed the important contribution of collagen V to the development of functional connective tissues. Proalpha1(V) signals were exclusively detected in the flattened cells of the surface ectoderm at 10.5 dpc. By 12.5 dpc, when cells had become cuboidal, the signal switched to the dermal fibroblasts. Thus, type V collagen appears to contribute to epidermis differentiation. Our data also suggest that collagen V participates in bone formation and/or mineralization and in the renewal of stromal cells in the cornea. The results underscore the role of collagen V in developing embryos and provide important clues for analyzing the phenotype of mouse models for EDS.

Animals↗
PubMed2026

Infra-low-frequency neurofeedback alters EEG network efficiency: exploratory evidence from healthy volunteers.

Infra-Low-Frequency Neurofeedback (ILF-NFB) combines classic frequency-band (FB) and infra-low-frequency (ILF) EEG components in implicit training protocols and is increasingly applied in clinical contexts. Yet, the neurophysiological mechanisms underlying ILF-NFB remain to be further elucidated. In this randomized, sham-controlled and double-blind study, we explored the online impact of a one-session ILF-NFB application on EEG correlates in healthy participants (39 analyzed datasets). Continuous 31-channel EEG was recorded during verum and sham feedback in a double-blind, randomized crossover design. In this exploratory analysis approach, functional connectivity was estimated using the debiased weighted phase-lag index (dwPLI) and analyzed with graph-theoretical measures. The results revealed higher global efficiency during verum compared to sham in the Beta1 band (12-15 Hz), reaching significance in the primary comparison but not surviving Bonferroni correction across the five tested bands; block-wise follow-ups showed a significant verum-sham difference in the first half of the neurofeedback session and a directionally consistent pattern in the second half. The Condition × Block interaction was not significant. No consistent differences were observed in other frequency bands, nor for betweenness centrality. While preliminary, these exploratory results point to possible network-level effects during ILF-NFB and motivate further confirmatory work in extended training protocols and clinical populations.

Humans↗
PubMed1999

Direct connection of the nucleus reticularis gigantocellularis neurons with neck motoneurons in cats.

Functional connections of single reticulospinal neurons (RSNs) in the nucleus reticularis gigantocellularis (NRG) with ipsilateral dorsal neck motoneurons were examined with the spike-triggered averaging technique. Extracellular spikes of single NRG-RSNs activated antidromically from the C6, but not from the L1 segment (C-RSNs) were used as the trigger. These neurons were monosynaptically activated from the superior colliculus and the cerebral peduncle. Single-RSN PSPs were recorded in 43 dorsal neck motoneurons [biventer cervicis and complexus (BCC) and splenius (SPL)] for 21 NRG-RSNs and 135 motoneurons tested. All synaptic potentials were EPSPs, and most of their latencies, measured from the triggering spikes, were 0.8-1.5 ms, which is in a monosynaptic range. The amplitudes of single-RSN EPSPs were 10-360 microV. Spike-triggered averaging revealed single-RSN EPSPs in multiple motoneurons of the same species (SPL or BCC), their locations extending up to nearly 1 mm rostrocaudally. Synaptic connections of single RSNs with both SPL and BCC motoneurons were also found with some predominance for one of them. The results provide direct evidence that NRG-RSNs make monosynaptic excitatory connections with SPL and BCC motoneurons. It appears that some NRG-RSNs connect predominantly with SPL motoneurons and others with BCC motoneurons.

Animals↗
PubMedDate not supplied

Pharmacological testing of intracortical interneuronal connections.

The present study comprises an attempt to investigate the influence of acetylcholine on the functional connections of the cortical cells and their frequency characteristics. The multineuronal activity was recorded in the sensorimotor cortex of immobilized and freely moving rats, and was subsequently analyzed using the method of cross-correlational analysis. In the first series of experiments, the influence of the neuromediator, acetylcholine (ACh), and calcium chelation, ethyleneglycol tetraacetate (EGTA), on the functional characteristics of adjacent neurons during the iontophoretic application of these substances to cells of the sensorimotor cortex of unanesthetized immobilized rats was investigated. In this case, the iontophoretic application of ACh led to a change in the frequency characteristics of individual neurons, and in the majority of cases did not influence the character of the interneuronal interactions. The application of EGTA led to a decrease in the average frequency of impulse activity for the majority of the neurons, as well as to the disappearance, independent of the running frequency, of excitatory connections in the cross-correlograms, with their subsequent recovery following the termination of exposure to the EGTA. In the second series of experiments, carried out in freely moving rats with a chronically implanted recording electrode, the systemic administration of the acetylcholinesterase blocker, galantamine, led to a substantial intensification of the impulse activity of the cortical neurons, and at the same time did not exert a substantial influence on the network activity of the same neurons. The hypothesis is advanced that the intracortical neuronal interactions may be accomplished independently of extracortical influences that are expressed in the fluctuations of the baseline impulse activity of individual cells. The qualitative assessment that was carried out of the influence of ACh on the functional characteristics of the cortical neurons does not make it possible to identify an influence of ACh (including a modulatory influence) on the formation of intracortical connections. The methods used in this investigation may be used for a further study of the influence of various mediator systems of the brain on the functioning of intracortical interneuronal connections.

Acetylcholine↗
PubMed2002

Multidimensional scaling of integrated neurocognitive function and schizophrenia as a disconnexion disorder.

Multidimensional scaling (MDS) is a multivariate statistical technique that can be used to define subsystems of functionally connected brain regions based on the analysis of functional magnetic resonance imaging (fMRI) data. Here we introduce three-way multidimensional scaling as a method for the analysis of a group of fMRI data, which yields both a generic interregional configuration in low-dimensional space and a measure of each individual's deviation from the generic configuration. The distance between two generic interregional configurations obtained by MDS of two groups of data can be minimized by generalized Procrustes analysis, and the probability under the null hypothesis (that the two groups are sampled from the same population) of any residual group difference in interregional configurations can be assessed by a permutation test. These methods are developed and applied to activated fMRI time series acquired from 19 patients with schizophrenia and 20 normal comparison subjects during the performance of a semantic categorization and subvocal rehearsal task. The first three scaling dimensions are interpretable in terms of the major anatomical or functional subsystems of the activated system: "left-right," "input processing-other," and "subvocal output-other". We found no significant global or local differences between groups in interregional configurations in this 3D space. However, there was significantly greater variability of interregional configurations within the group of patients with schizophrenia. The implications for schizophrenia as a disconnexion disorder are discussed.

Adult↗