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Results for “functional connectivity”

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At least 469 records · Page 26Linked to original sources
PubMed2004

A 4.0-T fMRI study of brain connectivity during word fluency in first-episode schizophrenia.

OBJECTIVE: To use functional magnetic resonance imaging (fMRI) to investigate functional connectivity, and hence, underlying neural networks, in never-treated, first-episode patients with schizophrenia using a word fluency paradigm known to activate prefrontal, anterior cingulate, and thalamic regions. Abnormal connectivity between the prefrontal cortex (PFC) and other brain regions has been demonstrated in chronic, medicated patients in previous positron emission tomography (PET) studies, but has not to our knowledge, previously been demonstrated using both first-episode, drug-naïve patients and fMRI technology. METHODS: A 4.0-Tesla (T) fMRI was used to examine activation and functional connectivity [psychophysiological interactions (PPIs)] during a word fluency task compared to silent reading in 10 never-treated, first-episode patients with schizophrenia and 10 healthy volunteers of comparable age, sex, handedness, and parental education. RESULTS: Compared to healthy volunteers, the schizophrenia patient group exhibited less activation during the word fluency task, mostly in the right anterior cingulate and prefrontal regions. Psychophysiological interactions between right anterior cingulate and other parts of the brain revealed a localized interaction with the left temporal lobe in healthy volunteers during the task and a widespread unfocussed interaction in patients. CONCLUSION: These findings suggest anterior cingulate involvement in the neuronal circuitry underlying schizophrenia.

Adult↗
PubMed2007

Functional disconnections in the direct and indirect amygdala pathways for fear processing in schizophrenia.

BACKGROUND: Schizophrenia patients show reduced neural activity, relative to controls, in the amygdala and its projection to the medial prefrontal cortex (MPFC) in response to fear perception. In this study we tested the hypothesis that schizophrenia is characterized by abnormal functional connectivity in the amygdala network underlying fear perception. METHODS: Functional MRI images were acquired from 14 schizophrenia patients and 14 matched healthy control subjects during an emotion perception task, in which fearful and neutral facial expression stimuli were presented pseudorandomly under nonconscious (using masking) and conscious conditions. Both subtraction and functional connectivity analyses were undertaken using a region of interest approach. RESULTS: In response to fearful facial expressions, schizophrenia patients displayed reduced amygdala activity, compared to controls, in both the conscious and nonconscious conditions. The amygdala displayed a reversal of the normal pattern of connectivity with the brainstem, visual cortex, and also with the dorsal and ventral divisions of the MPFC in the schizophrenia patients. CONCLUSIONS: The presence of functional disconnections in amygdala pathways suggests that schizophrenia patients have a failure in coordinating their automatic orienting to salient signals and the associated prefrontal monitoring of these signals.

Adult↗
PubMed2004

Characterizing the dynamic connectivity between genes by variable parameter regression and Kalman filtering based on temporal gene expression data.

MOTIVATION: One popular method for analyzing functional connectivity between genes is to cluster genes with similar expression profiles. The most popular metrics measuring the similarity (or dissimilarity) among genes include Pearson's correlation, linear regression coefficient and Euclidean distance. As these metrics only give some constant values, they can only depict a stationary connectivity between genes. However, the functional connectivity between genes usually changes with time. Here, we introduce a novel insight for characterizing the relationship between genes and find out a proper mathematical model, variable parameter regression and Kalman filtering to model it. RESULTS: We applied our algorithm to some simulated data and two pairs of real gene expression data. The changes of connectivity in simulated data are closely identical with the truth and the results of two pairs of gene expression data show that our method has successfully demonstrated the dynamic connectivity between genes. CONTACT: jiangtz@nlpr.ia.ac.cn.

Computer Simulation↗
PubMed2005

Investigating the neural basis for functional and effective connectivity. Application to fMRI.

Viewing cognitive functions as mediated by networks has begun to play a central role in interpreting neuroscientific data, and studies evaluating interregional functional and effective connectivity have become staples of the neuroimaging literature. The neurobiological substrates of functional and effective connectivity are, however, uncertain. We have constructed neurobiologically realistic models for visual and auditory object processing with multiple interconnected brain regions that perform delayed match-to-sample (DMS) tasks. We used these models to investigate how neurobiological parameters affect the interregional functional connectivity between functional magnetic resonance imaging (fMRI) time-series. Variability is included in the models as subject-to-subject differences in the strengths of anatomical connections, scan-to-scan changes in the level of attention, and trial-to-trial interactions with non-specific neurons processing noise stimuli. We find that time-series correlations between integrated synaptic activities between the anterior temporal and the prefrontal cortex were larger during the DMS task than during a control task. These results were less clear when the integrated synaptic activity was haemodynamically convolved to generate simulated fMRI activity. As the strength of the model anatomical connectivity between temporal and frontal cortex was weakened, so too was the strength of the corresponding functional connectivity. These results provide a partial validation for using fMRI functional connectivity to assess brain interregional relations.

Auditory Perception↗
PubMed1992

Monosynaptic EPSPs elicited by single interneurones and spindle afferents in trigeminal motoneurones of anaesthetized rats.

1. Our aim has been to quantify the monosynaptic connections of trigeminal interneurones and spindle afferents onto jaw-elevator motoneurones as a step towards identifying common features in organization of monosynaptic inputs onto motoneurones. We have used the intracellular variant of the spike-triggered averaging method to examine the connections of single identified trigeminal interneurones and jaw-elevator muscle spindle afferents onto single jaw-elevator motoneurones. The interneurones examined lay in the region immediately caudal to the trigeminal motor nucleus. The experiments were performed on rats anaesthetized with pentobarbitone, paralysed and artificially ventilated. 2. Ten EPSPs and eight IPSPs were obtained from examining the connections of seventeen interneurones to thirty-six motoneurones, suggesting a functional connectivity of 50% for individual interneurones onto elevator motoneurones. Fourteen EPSPs were obtained from examining the connections of thirteen spindle afferents onto twenty-seven motoneurones, giving a functional connectivity of 52% for individual spindle afferents onto elevator motoneurones. The amplitudes of the EPSPs elicited by interneurones ranged from 7-48 microV (mean = 17, S.D. = 12.5, n = 10) and from 7 to 289 microV (mean = 64, S.D. = 76.0, n = 14) for the spindle-mediated EPSPs; the difference in the two means was not significant (P = 0.07). 3. However, the amplitude of averaged responses obtained by signal averaging methods are dependent on the assumption that the postsynaptic response occurs following every impulse in the presynaptic neurone. We therefore estimated the percentage of sweeps which contained EPSPs triggered by the presynaptic neurone under study. In essence the method used consisted of visual inspection of the individual sweeps comprising an average in order to assess the occurrence of EPSPs within six separate time windows, each of duration +/- 0.3 ms. Five windows were placed at randomly selected times on average and were used to provide an estimate of the frequency of occurrence of randomly triggered EPSPs. The sixth window was centred on the start of the averaged EPSP and the frequency of occurrence of randomly triggered EPSPs was subtracted from the frequency of occurrence of EPSPs in this window to produce an estimate of the incidence of EPSPs triggered by the presynaptic neurone under study. 4. Values of the incidence of occurrence of EPSPs triggered by the presynaptic neurones ranged from 4.3 to 92% for the fifteen averaged EPSPs which could be analysed in this manner (two elicited by interneurones and thirteen by spindle afferents).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2005

EEG coherence analysis in never-medicated patients with panic disorder.

To investigate the functional abnormalities in the central nervous system (CNS) of patients with panic disorder (PD), we compared the electroencephalography (EEG) coherence values in 18 never-medicated PD patients with those in age-matched normal control subjects, and examined the relationships between EEG coherence values and both the duration of disease and the severity of panic attacks. EEG data were recorded in the resting state. The PD patients had lower coherence values with significant differences in F3-F4, C3-C4, P3-P4, F7-T5, and F8-T6. There were positive correlations for the higher alpha band between coherence values and both the duration of disease and the severity of panic attacks. These findings provide further evidence that PD patients have a lower degree of inter-hemispheric functional connectivity in the frontal region and intra-hemispheric functional connectivity in the bilateral temporal region, and that chronic condition or frequent panic attacks in PD patients may be related to the pathophysiological CNS changes.

Adult↗
PubMed1998

Restitution of functional neural connections in chick embryos assessed in vitro after spinal cord transection in Ovo.

Functional neural reconnection is not common after spinal cord transection in the CNS of adult higher vertebrates but has been demonstrated in embryonic avian and neonatal mammalian CNS. Chick brainstem spinal cord preparations from nontransected controls and embryos transected at the cervical level on embryonic days (E) 8, 9, or 10 in ovo were assessed in vitro between E12 and E20 for their ability to produce and maintain episodic motor activity (EMA) using electrophysiological, voltage sensitive dye and anatomical tract-tracing techniques. After 3 to 4 days recovery, cycle-by-cycle coupling of EMA between segments separated by a transection was absent or inconsistent, although otherwise normal bouts of locally stimulated and spontaneous EMA were routinely observed restricted to segments of a cord separated by a transection site. After 5-7 days recovery in ovo the cross-transection coordination during bouts of EMA approached that of nontransected controls. The delay between the initiation of EMA in cervical segments to its initiation in lumbosacral segments caudal to a transection was an indicator of reconnection strength. The delay shortened from 0.5 to a few seconds after 3 days of recovery to around 150 ms (i.e., normal) after 5 days of recovery. We conclude that the reconnection of spinal central pattern generators for EMA across the transection was served mainly by axons which established connections with local circuits after extending 1-3 segments through a transection. Propriospinal axons that originated within 1-3 segments rostral to the transection then served to serially initiate EMA in distal caudal segments.

Animals↗
PubMed2007

Connections of functional areas in the mustached bat's auditory cortex with the auditory thalamus.

The auditory thalamus is the major target of the inferior colliculus and connects in turn with the auditory cortex. In the mustached bat, biosonar information is represented according to frequency in the central nucleus of the inferior colliculus (ICc) but according to response type in the cortex. In addition, the cortex has multiple areas with neurons of similar response type compared to the single tonotopic representation in the ICc. To investigate whether these transformations occur at the level of the thalamus, we injected anatomical tracers into physiologically defined locations in the mustached bat's auditory cortex. Injections in areas used for target ranging labeled contiguous regions of the auditory thalamus rather than separate patches corresponding to regions that respond to the different harmonic frequencies used for ranging. Injections in the two largest ranging areas produced labeling in separate locations. These results indicate that the thalamus is organized according to response type rather than frequency and that multiple mappings of response types exist. Injections in areas used for target detection labeled thalamic regions that were largely separate from those that interconnect with ranging areas. However, injections in an area used for determining target velocity overlapped with the areas connected to ranging areas and areas involved in target detection. Thus, separation by functional type and multiplication of areas with similar response type occurs by the thalamic level, but connections with the cortex segregate the functional types more completely than occurs in the thalamus.

Acoustic Stimulation↗
PubMed1976

Regulation of neuronal properties by afferent connections. I. Functional changes in snail neurons following section of presysnaptic nerve fibers.

The left cerebral connective of snail ganglia containing afferent inputs to a particular neuron was sectioned. One week after the operation synaptic potentials were not obtained when the connective was stimulated, and they had not reappeared after 60 days. The current-voltage relationship of denervated cells showed a rectification in the hyperpolarizing direction, whereas that of control cells had an ohmic behavior. Depolarization or conductance changes produced by ACh or carbachol showed a supersensitivity in denervated cells, evidenced by a shift to the left of the dose-response curve and an increase of the maximal responses obtained. The reversal potential of ACh shifted from--22 mV in the control to--8 mV in denervated cells. Depolarization produced by serotonin was similar in control and denervated cells.

Acetylcholine↗
PubMed2000

Diversity and cell type specificity of local excitatory connections to neurons in layer 3B of monkey primary visual cortex.

In the primary visual cortex of macaque monkeys, laminar and columnar axonal specificity are correlated with functional differences between locations. We describe evidence that embedded within this anatomical framework is finer specificity of functional connections. Photostimulation-based mapping of functional input to 31 layer 3B neurons revealed that input sources to individual cells were highly diverse. Although some input differences were correlated with neuronal anatomy, no 2 neurons received excitatory input from the same cortical layers. Thus, input diversity reveals far more cell types than does anatomical diversity. This implies relatively little functional redundancy; despite trends related to laminar or columnar position, pools of neurons contributing uniquely to visual processing are likely relatively small. These results also imply that similarities in the anatomy of circuits in different cortical areas or species may not indicate similar functional connectivity.

Animals↗
PubMed2000

Touch feel illusion in schizophrenic patients.

BACKGROUND: The rubber hand illusion is a tactile sensation referred to as an alien limb. The illusion has been explained by a spurious reconciliation of visual and tactile inputs reflecting functional connectivity in the brain and was used to explore alterations of functional connectivity in schizophrenia. METHODS: The rubber hand illusion was achieved when two paintbrushes simultaneously stroke the hand of the subject hidden from vision by a screen, as well as an artificial hand placed in view of the subject. The rubber hand illusion was assessed with a questionnaire affirming or denying the occurrence of the illusion. RESULTS: Schizophrenic subjects felt the illusion stronger and faster then did normal control subjects. Some rubber hand illusion effects correlated with positive symptoms of schizophrenia but not with negative symptoms. CONCLUSIONS: Altered functional integration of environmental inputs could constitute the basis for erroneous interpretations of reality, such as delusions and hallucinations.

Adult↗
PubMed2006

Function and connectivity in human primary auditory cortex: a combined fMRI and DTI study at 3 Tesla.

Human primary auditory cortex (PAC) is functionally organized in a tonotopic manner. Past studies have used neuroimaging to characterize tonotopic organization in PAC and found similar organization as that described in mammals. In contrast to what is known about PAC in primates and nonprimates, in humans, the structural connectivity within PAC has not been defined. In this study, stroboscopic event-related functional magnetic resonance imaging (fMRI) was utilized to reveal mirror symmetric tonotopic organization consisting of a high-low-high frequency gradient in PAC. Furthermore, diffusion tensor tractography and probabilistic mapping was used to study projection patterns within tonotopic areas. Based on earlier physiological and histological work in nonhuman PAC, we hypothesized the existence of cross-field isofrequency (homotopic) and within-field non-isofrequency (heterotopic)-specific axonal projections in human PAC. The presence of both projections types was found in all subjects. Specifically, the number of diffusion tensor imaging (DTI) reconstructed fibers projecting between high- and low-frequency regions was greater than those fibers projecting between 2 high-frequency areas, the latter of which are located in distinct auditory fields. The fMRI and DTI results indicate that functional and structural properties within early stages of the auditory processing stream are preserved across multiple mammalian species at distinct evolutionary levels.

Acoustic Stimulation↗
PubMedDate not supplied

Changes in minute waves of superslow brain activity after various methods for electrostimulating two neocortical zones.

Changes in the oscillations of the decasecond and minute waves of superslow activity in the 0 to 1 Hz range were compared using various techniques for electrostimulating neocortical zones in rabbits with gold electrodes chronically implanted in structures of the brain. Successive stimulation of the frontal and motor zones of the cortex with a 2.5-3.0 microA current strength was accompanied by changes of negligible duration and amplitude in the decasecond and minute waves, which were of a more local character primarily in the stimulation zones. Simultaneous synchronous stimulation of two neocortical zones with the same strength evoked considerable shifts in amplitude for a long period in various structural formations of the brain including the dorsal hippocampus. Ethimizole at a dose of 1.5 mg/kg fixed the given changes in the amplitude of the decasecond and minute waves for an extended time. For two weeks the overall level of metabolism of the neocortical zones was altered after the method of artificial stable functional connections (ASFC); for one week, after a shortened reflex. It was shown that the application of a shortened reflex and the application of artificial stable functional connections are of a differing functional organization of intracentral relationships.

Animals↗
PubMedDate not supplied

Pulmonary function tests: the telephone connection.

Pulmonary function tests have been out of reach of many persons living far from medical centers. Now, new techniques are making remote testing by telephone available to larger and larger numbers of people and are proving to be cost-effective for patients and hospitals alike.

Health Services Accessibility↗
PubMed1985

[Connective tissue function and fibril formation processes in fibrous-cavernous pulmonary tuberculosis].

Electronmicroscopic and histochemical examination of connective tissue in the resected lungs of patients with fibrocavernous tuberculosis was carried out. High metabolic activity and developed ultrastructural organization of fibroblasts were observed in the foci of productive tissue response. The stages of cell differentiation and the maturation of collagen fibers resulted in the multilayer structure of both the tuberculosis foci and the cavernous wall. The activation of smooth muscle cells and myofibroblasts facilitated the development of perivascular and peribronchial sclerosis. Fibroblasts were found to be in connection with lymphoid cells and macrophages that influence the intensity of fibrosis. The formation of numerous lymphoid follicles combined with the progression of fibrosis is an unfavourable prognostic symptom as it results in an excessive cirrhosis and fibrosis which inhibits the healing of destructive tuberculosis.

Collagen↗
PubMed2006

Functional MRI evidence for disparate developmental processes underlying intelligence in boys and girls.

Previous research has shown evidence for sex differences in the neuroanatomical bases for intelligence in adults. Possible differences in the neuroanatomical correlates of intelligence and their developmental trajectories between boys and girls were investigated using functional MRI (fMRI). A large cohort of over 300 children, ages 5-18, performed the semantic processing task of silent verb generation. Regions were found in the left hemisphere exhibiting positive correlations of blood-oxygenation-level-dependent (BOLD) activation with IQ, including the middle temporal gyrus, prefrontal cortex (Broca's area), medial frontal gyrus, precuneus, and cingulate gyrus, while the superior temporal gyrus in the right hemisphere displayed a negative correlation of BOLD activation with IQ. Significant sex-X-IQ and sex-X-IQ-X-age interaction effects were also seen in the left middle temporal gyrus and left inferior frontal gyrus. Using a data-driven analysis procedure, a sex-X-IQ-X-age interaction was also demonstrated in the functional connectivity between regions in the left hemisphere, parameterized as a weighted sum of pairwise covariances between fMRI time courses. While young girls (<13 years) exhibited no correlation of connectivity with intelligence, older girls (>13 years) demonstrated a positive association of functional connectivity with intelligence. Boys, however, demonstrated the opposite developmental trajectory, from a positive association of connectivity with intelligence in young boys (ages <9 years), to a negative association in older boys (ages >13 years). Our results provide evidence for disparate neuroanatomical trajectories underlying intelligence in boys and girls.

Adolescent↗