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PubMed1984

An electrophysiological study of canine, premolar and molar tooth pulp afferents and their convergence on medullary trigeminal neurons.

The two main aims of this study were (1) to compare the conduction velocities of tooth pulp (TP) afferents innervating the cat canine, premolar and molar teeth and (2) to determine the degree of convergence of afferent input originating in these different teeth on medullary dorsal horn (MDH) neurons. Experiments were conducted on 10 cats anesthetized with chloralose. Single unit extracellular recordings were obtained from the tooth pulp or the MDH. The distribution of conduction velocities of afferents originating in the mandibular and maxillary canines, premolars and mandibular molar were all found to be similar except that the mean conduction velocity of canine afferents was slightly higher than the means for the other teeth. A total of 48 MDH neurons excited by TP stimulation was studied. Most MDH neurons activated by electrical stimulation of one of the TPs could also be activated by stimulation of one or more of the other TPs. In addition to the marked convergence from different teeth, most of the TP-activated neurons also had convergent inputs from facial skin and/or intraoral mucosa.

Animals↗

PubMed1995

Dorsal horn convergent neurones: negative feedback triggered by spatial summation of nociceptive afferents.

In order to investigate the effects of spatial summation on the spinal transmission of nociceptive information, we compared in intact and spinal anaesthetized rats, responses of lumbar convergent neurones elicited by noxious heat stimuli applied to areas of the body much greater in size than their individual excitatory receptive fields, located distally on the hindpaw. Twenty-four neurones were recorded in each group of animals. For each neurone, 4 successive immersions of increasing areas (1.9-18 cm2) of the ipsilateral hindpaw in a 48 degrees C water bath (15-sec duration) were performed with 10-min intervals in a randomized and balanced order. In intact animals, the responses of convergent neurones progressively decreased when the area of noxious thermal stimulation reached and then exceeded approximately twice the area of their individual excitatory receptive fields. This decrease was highly significant for 18 cm2 which represents approximately 10-fold the mean of the receptive field areas. Such a phenomenon was not observed for neurones recorded in spinal animals although their excitatory receptive field areas were not significantly different. These results suggest that the activation of a large population of nociceptive afferents triggers supraspinally mediated negative feed-back loop modulating the responses of convergent neurones.

Analysis of Variance↗

PubMed1984

Convergence and interaction of neck and macular vestibular inputs on reticulospinal neurons.

Extracellular recordings were obtained in decerebrate cats from neurons located in the inhibitory area of the medullary reticular formation, namely in the medial aspects of the nucleus reticularis gigantocellularis, magnocellularis and ventralis. Of 127 medullary reticular units examined, 77 were reticulospinal neurons antidromically identified following stimulation of the spinal cord at T12-L1; the remaining 50 neurons were not activated antidromically. Unit firing rate was analyzed under separate stimulation of macular vestibular, neck, or combined receptors by using sinusoidal rotations about the longitudinal axis at 0.026 Hz, 10 peak amplitude. Among the 127 reticular units, 84 (66.1%) responded with a periodic modulation of their firing rate to roll tilt of the animal and 93 (73.2%) responded to neck rotation. Convergence of macular and neck inputs was found in 71/127 (55.9%) reticular neurons; in these units, the gain as well as the sensitivity of the first harmonic of response corresponded on the average to 0.49 +/- 0.41, SD imp/s/deg and 5.10 +/- 4.27, SD %/deg for the neck responses and to 0.40 +/- 0.39, SD imp/s/deg and 3.90 +/- 3.80, SD %/deg for the macular responses, respectively. Most of the convergent reticular units were maximally excited by the direction of stimulus orientation, the first hormonic or responses showing an average phase lead of about +42.7 with respect to neck position and +24.9 with respect to animal position. Two populations of convergent neurons were observed. The first group of units (58/71, i.e. 81.7%) showed reciprocal ("out of phase") responses to the two inputs in that they were mainly excited during side-down neck rotation, but inhibited during side-down animal tilt. The remaining group of units (13/71, i.e. 18.3%) showed parallel ("in phase") responses to the two inputs and they were mainly excited by side-down neck rotation and animal tilt. The response characteristics of medullary reticular neurons to the combined neck and macular inputs, elicited during head rotation, closely corresponded to those predicted by a vectorial summation of the individual neck and macular responses. In particular, "out of phase" units displayed small amplitudes and large phase leads of the responses with respect to head position, when both types of receptors were costimulated. In contrast, "in phase" units displayed large amplitude and small phase leads during head rotation.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗

PubMed1983

Convergence of basolateral amygdaloid and mediodorsal thalamic projections in different areas of the frontal cortex in the rat.

The extent of convergence of mediodorsal thalamic and amygdalar afferents on the rat's frontal cortex was studied by tracing retrogradely labeled cells following injections of horseradish peroxidase (HRP). HRP was applied iontophoretically in extremely small injections throughout all areas of the frontal cortex. The following organization was revealed: Converging inputs from the mediodorsal nucleus and the amygdala are observed in the posterior parts of the pre- and infralimbic areas, in the posterior half of the dorsal and ventral agranular insular areas and in the lateral and dorsal precentral areas. Both mediodorsal and amygdaloid afferents reach the dorsal tip of the frontal cortex. Only the mediodorsal afferents were found to terminate in the anterior parts of the pre- and infralimbic areas and in the anterior part of the dorsal division of the anterior cingulate area and in the medial precentral area. On the lateral side of the hemisphere the anterior halves of the dorsal and ventral agranular insular areas receive mediodorsal afferents. Amygdaloid, but not mediodorsal afferents, were found following injections into the more posterior parts of the lateral precentral area. These results are discussed with respect to the extent of the prefrontal cortex in the rat and its definability as a target area of subcortical nuclei. Functional aspects of the anatomical convergence of connections within the so-called basolateral limbic circuit are outlined.

Afferent Pathways↗

PubMed1993

Convergence of gastric and hepatic information in brain stem neurons of the rat.

Convergence of gastric and hepatic information in the nucleus of the solitary tract (NTS) was investigated by single-pulse electrical stimulation of the hepatic and the gastric branches of the vagus. Facilitation induced by both stimuli occurred most often in responses of neurons in the NTS, indicating convergence of information there. In a second experiment using gastric distension and portal infusion of glucose to analyze such convergence, activation by gastric distension and suppression by portal glucose was the most prominent combination of responses to both stimuli. This confirmed the results of electrical stimulation, because distension increases the firing rate of gastric afferents and glucose infusion decreases the firing rate of hepatic afferents. Analysis of the responses to varying degrees of gastric distension revealed that some NTS neurons are activated by weak distension, but inhibited by strong distensions.

Animals↗

PubMed1991

A new method for noninvasive estimation of ventricular septal defect shunt flow by Doppler color flow mapping: imaging of the laminar flow convergence region on the left septal surface.

An accurate but simple and noninvasive method for quantifying flow across a ventricular septal defect has yet to be implemented for routine clinical use. A region of flow convergence is commonly imaged by Doppler color flow mapping on the left septal surface of the ventricular septal defect, appearing as a narrowed region of laminar flow with aliased flow velocities entering the orifice. If the first aliasing region represents a hemispheric isovelocity boundary of a surface of flow convergence and all flow at this surface crosses the ventricular septal defect, the flow through the defect can be estimated by using the radius (R), measured from the first alias to the orifice, and the Nyquist limit (NL) velocity (the flow velocity at the first alias). Doppler color flow imaging was performed in 18 children with a single membranous ventricular septal defect undergoing cardiac catheterization at a mean age of 29.8 months (Group I). Indexes of maximal flow rate across the defect were developed from either the radius or the area, obtained by planimetry, of the first alias, based on Doppler color flow images. All indexes were corrected for body surface area and compared with shunt flow (Qp-Qs) and pulmonary to systemic flow ratio (Qp/Qs) determined at cardiac catheterization. Doppler color flow indexes derived from images of flow convergence in both the long-axis (n = 15) and oblique four-chamber (n = 10) views correlated closely with Qp/Qs (r = 0.71 to 0.92) and Qp - Qs (r = 0.69 to 0.97).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗

PubMed1995

Nature of flow acceleration into a finite-sized orifice: steady and pulsatile flow studies on the flow convergence region using simultaneous ultrasound Doppler flow mapping and laser Doppler velocimetry.

OBJECTIVES: This study investigated the proximal centerline flow convergence region simultaneously by both color Doppler and laser Doppler velocimetry. BACKGROUND: Although numerous investigations have been performed to test the flow convergence method, to our knowledge there has yet been no experimental study using reference standard velocimetric techniques to define precisely the hydrodynamic factors involved in the accelerating flow region during steady and pulsatile flow. METHODS: Using an in vitro model that allows velocity measurements by laser Doppler velocimetry with simultaneous comparison with color Doppler results, we studied the centerline flow acceleration region proximal to orifices of various sizes (0.08 to 2.0 cm2). RESULTS: Agreement between theory and experimental velocities was good for large flow rates through small orifices only, and only at distances > 1.2 cm from the orifice. Changing the orifice shape from circular to slitlike produced no significant changes in velocity profiles. Constraining the proximal side walls caused a significant increase in proximal velocities at distances > 0.7 cm for the largest orifice only (2.0 cm2). Calculated flow rates agreed well with actual flow rates, with functional dependence on proximal distance and orifice size. Velocity profiles for pulsatile flow were similar to steady state flow profiles and could be integrated to calculate stroke volumes, which followed actual flow volumes well, although with general overestimation (y = 1.22x + 0.164, r = 0.92), most likely due to the use of all available proximal velocities. CONCLUSIONS: The accelerating proximal flow region responds to several hydrodynamic factors that can affect flow quantitation using the flow convergence method in the clinical situation.

Blood Flow Velocity↗

PubMed1989

A prospective study of the reliability and convergent validity of three physical activity measures in a field research trial.

This investigation sought to determine the test-retest reliability and convergent validity of three commonly used physical activity measures. The Stanford Physical Activity Recall, the Caltrac Activity Monitor, and a daily physical activity log were administered to 45 subjects over a 3-week period. The results indicated high levels of test-retest reliability for the Stanford and the daily log; low test-retest reliability was obtained for the Caltrac. Convergent validity was also high between the Stanford and daily log but was low for both of these measures with the Caltrac. These results suggest that the Stanford Physical Activity Recall may be the self-report measure of choice for large studies due to its high reliability and convergent validity with a more time-consuming daily log, as well as its cost- and time-efficiency. Based on the results, it is recommended that the Caltrac activity sensors not be used for field studies of physical activity until the logistical problems of their use in clinical trials are solved.

Adult↗

PubMed2004

Reproducibility of the proximal flow convergence method in mitral and tricuspid regurgitation.

BACKGROUND: The follow-up of patients with mitral and tricuspid regurgitation is important for their clinical treatment. We aimed to evaluate the reproducibility of the flow convergence method in mitral and tricuspid regurgitation. METHODS: The proximal flow convergence region was imaged with color Doppler ultrasound scanning echocardiography in 83 patients with mitral regurgitation, tricuspid regurgitation, or both. Proximal isovelocity surface area radii for aliasing velocities of 27 to 29 cm/s and 41 to 43 cm/s were repeatedly measured by the same experienced investigator on different days and by experienced and less experienced investigators at 1 day. RESULTS: In mitral regurgitation, the intraobserver variability rate was 0.2% +/- 13.5% (2.8% +/- 13.3%) and the interobserver variability was 0.1% +/- 13.8% (1.7% +/- 18.0%) for an aliasing velocity of 27 to 29 cm/s (41-43 cm/s). For the aliasing velocity of 27 to 29 cm/s (41-43 cm/s), the 95% ranges for change of the proximal isovelocity surface area radii were +/- 2.7 mm (+/- 1.8 mm) for measurements repeated by the same investigator and +/- 2.7 mm ( +/- 2.4 mm) for different investigators. Interobserver variability was independent of the investigators' experience. Similar data were achieved in tricuspid regurgitation. CONCLUSIONS: The proximal flow convergence method is acceptably reproducible in mitral and tricuspid regurgitation independent of the investigators experience. For the aliasing velocity of 27 to 29 cm/s (41-43 cm/s), the proximal isovelocity surface area radius has to change for >2.7 (2.4) mm before an altered severity of mitral or tricuspid regurgitation in a single patient can be assumed.

Adult↗

PubMedDate not supplied

Convergence of techniques for the evaluation of discrepant data.

The problem of evaluating discrepant data has been addressed by several authors over the previous 20 yr. More recently some attention has been given to the use of the median, which is expected to have better statistical 'robustness'. The various evaluation techniques should converge towards the 'true' value as the number of data in a data set increases, and the 'robustness' of each evaluation technique can then be tested by the rate at which that technique converges. Several evaluation techniques have been applied to discrepant data sets, and the results are shown to converge as the size of the data set grows. The discrepant data sets used as examples are the measured half-lives of 90Sr and 137Cs. Differences in the behaviour of the evaluation techniques are discussed, as applied to these data sets. The half-lives deduced from this study are: 90Sr 10,551+/-14 days; 137Cs 10,981+/-11 days.

Cesium Radioisotopes↗

PubMed2004

The convergence of cancer prevention and therapy in early-phase clinical drug development.

After decades of separate but not equal drug development, prevention and therapy are beginning to converge at the level of early-phase clinical testing. This highly beneficial convergence is due to spectacular molecular advances in our understanding of neoplasia (both cancer and precancer), cancer risk and prognosis, and the mechanisms by which novel drugs with less toxicity and more cytostatic activity profiles target specific molecular events to suppress malignant and premalignant cells. The future full convergence of prevention-therapy drug development (aided by technological advances, such as in molecular imaging) promises to hasten the progress of oncology in reducing the public health impact of the major cancers.

Antineoplastic Agents↗

PubMed2006

Pulmonary nodule detection in CT images with quantized convergence index filter.

A novel filter termed quantized convergence index filter (QCI filter) that is capable of enhancing the conspicuity of rounded lesions is proposed as part of a CAD (computer-aided diagnosis) scheme for detecting pulmonary nodules in computed tomography (CT) images. In this filter and its predecessor, the convergence index filter (CI filter), the output at a pixel represents the degree of convergence toward the pixel shown by the directions of gray-level gradients at surrounding pixels. The QCI filter and the CAD scheme were evaluated using five clinical datasets containing 50 nodules. With the support region of 9 x 9 pixels, the QCI filter showed more selective response to the nodules than the CI filter. In the CAD scheme, intermediate nodule candidates are generated based on the QCI filter output and then classified using linear discriminant analysis of eight features that are attributed to each intermediate nodule candidate. The QCI filter output level itself was used as one of the features. The scheme achieved a sensitivity of 90% with 1.67 false positives per slice. The QCI filter output level was most effective among the features in correctly classifying intermediate nodule candidates. The QCI filter is promising as a tool of preprocessing for automated pulmonary nodule detection in CT images.

Algorithms↗

PubMed2004

Cerebellar interpositus nuclear and gastric vagal afferent inputs reach and converge onto glycemia-sensitive neurons of the ventromedial hypothalamic nucleus in rats.

The glycemia-sensitive neurons of the ventromedial hypothalamic nucleus (VMN) have traditionally been implicated in feeding regulation. Some studies reported that the neuronal activity of the VMN could be modulated by inputs from the gastric vagal afferent, and the cerebellum might participate in regulating non-somatic visceral activities via the cerebellohypothalamic projections. The present study was therefore undertaken to investigate whether the inputs from the gastric vagal nerves and the cerebellar interpositus nucleus (IN) could reach and converge onto single VMN neurons, especially those glycemia-sensitive ones. Among recorded 283 VMN neurons, 187 (66.1%) and 139 (49.1%) responded to the gastric vagal and the cerebellar IN stimulations, respectively. Within the VMN neurons that were responsive to either of the gastric vagal or cerebellar IN stimulation, 91 responded to both of the stimuli, suggesting a convergence of gastric vagal and cerebellar inputs on the cells. When the gastric vagal nerves and cerebellar IN were stimulated simultaneously, a summation of the responses could be observed (n = 22). Moreover, of the 91 cells that responded to both of the gastric vagal and cerebellar IN stimuli, 61 (67.0%) were identified to be glycemia-sensitive neurons. These results demonstrate that the visceral signals conveyed by the gastric vagal afferents and the somatic information forwarded by the cerebellar IN could converge onto single VMN neurons, especially the glycemia-sensitive neurons. And the findings suggest that an integration of the somatic-visceral response related to the food intake could take place in the VMN and the cerebellum might actively participate in the short-term feeding regulation through the cerebellohypothalamic projections.

Action Potentials↗

PubMed2005

Dissociation between emotion and personality judgments: convergent evidence from functional neuroimaging.

Cognitive neuroscientists widely agree on the importance of providing convergent evidence from neuroimaging and lesion studies to establish structure-function relationships. However, such convergent evidence is, in practice, rarely provided. A previous lesion study found a striking double dissociation between two superficially similar social judgment processes, emotion recognition and personality attribution, based on the same body movement stimuli (point-light walkers). Damage to left frontal opercular (LFO) cortices was associated with impairments in personality trait attribution, whereas damage to right postcentral/supramarginal cortices was associated with impairments in emotional state attribution. Here, we present convergent evidence from fMRI in support of this double dissociation, with regions of interest (ROIs) defined by the regions of maximal lesion overlap from the previous study. Subjects learned four emotion words and four trait words, then watched a series of short point-light walker body movement stimuli. After each stimulus, subjects saw either an emotion word or a trait word and rated how well the word described the stimulus. The LFO ROI exhibited greater activity during personality judgments than during emotion judgments. In contrast, the right postcentral/supramarginal ROI exhibited greater activity during emotion judgments than during personality judgments. Follow-up experiments ruled out the possibility that the LFO activation difference was due to word frequency differences. Additionally, we found greater activity in a region of the medial prefrontal cortex previously associated with "theory of mind" tasks when subjects made personality, as compared to emotion judgments.

Adult↗

PubMed2006

Presynaptic inhibition by kainate receptors converges mechanistically with presynaptic inhibition by adenosine and GABAB receptors.

Kainate receptors are widely reported to regulate the release of neurotransmitter in the CNS, but the mechanisms involved remain controversial. Previous studies have found that the kainate receptor agonist ATPA, which selectively activates Glu(K5)-containing kainate receptors, depresses glutamate release at Schaffer-collateral synapses in the hippocampus. In the present study, we provide pharmacological evidence that this depressant effect is mediated by Glu(K5)-containing heteromers, but is distinct from a similar depressant effect engaged by the kainate receptor agonist domoate. The depressant effect of ATPA is insensitive to antagonists for GABA(A), GABA(B), and adenosine receptors, and is also unaffected by lowering the release probability by reducing extracellular calcium. However, the effect of ATPA is partly occluded by prior activation of GABA(B) receptors and completely occluded by prior activation of adenosine receptors, suggesting a mechanistic convergence of heteromeric Glu(K5) kainate receptor signaling with GABA(B) receptors and adenosine receptors. The effects of domoate are partially occluded by both adenosine and GABA(B) receptor agonists, indicating at least a partial convergence of Glu(K5)-lacking kainate receptor signaling with these other pathways. The depressant effect of ATPA is not blocked by inhibition of serine/threonine protein kinases. These results suggest that ATPA and domoate inhibit glutamate release through mechanisms that converge with those of classical metabotropic receptor agonists, although they do so through different receptors.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed2006

Convergent validity of the aberrant behavior checklist and behavior problems inventory with people with complex needs.

The current study aimed to replicate and extend Rojahn et al. [Rojahn, J., Aman, M. G., Matson, J. L., & Mayville, E. (2003). The aberrant behavior checklist and the behavior problems inventory: Convergent and divergent validity. Research in Developmental Disabilities, 24, 391-404] by examining the convergent validity of the behavior problems inventory (BPI) and the aberrant behavior checklist (ABC) for individuals presenting with multiple complex behavior problems. Data were collected from 69 children and adults with severe intellectual disabilities and challenging behavior living in residential establishments. MANCOVA analyses showed that individuals with elevated BPI stereotyped behavior subscale scores had higher scores on ABC lethargy and stereotypy subscales, while those with elevated BPI aggressive/destructive behavior subscale scores obtained higher scores on ABC irritability, stereotypy and hyperactivity subscales. Multiple regression analyses showed a corresponding pattern of results in the prediction of ABC subscale scores by BPI subscale scores. Exploratory factor analysis of the BPI data suggested a six-factor solution with an aggressive/destructive behavior factor, four factors relating to stereotypy, and one related to stereotypy and self-injury. These results, discussed with reference to Rojahn et al. [Rojahn, J., Aman, M. G., Matson, J. L., & Mayville, E. (2003). The aberrant behavior checklist and the behavior problems inventory: Convergent and divergent validity. Research in Developmental Disabilities, 24, 391-404], support the existence of relationships between specific subscales of the two instruments in addition to an overall association between total scores related to general severity of behavioral disturbance.

Adolescent↗

PubMed2006

The changing context of Western European healthcare systems: convergence versus divergence in nursing problematics.

Many countries reorganizing their health services are drawn toward similar reform programs and tend to experience what seem to be similar problems relating to implementation outcomes. One such problem is the major crisis within the nursing profession relating to the labor market, working conditions and level of autonomy. This research examines the thesis that the profile of nursing problems is global (the 'convergence' thesis) by comparing the changing hospital contexts nursing has been confronting in 20 Western European countries between 1990 and 2001. The analysis indicates that in spite of growing convergence, the divergence in patient care processes, workforce composition and resources allocated for care is still rather remarkable and that similarity or divergence between countries changes over time. This contextual variability highlights why problems such as the crisis of the nursing profession must be analysed from a divergent rather than a convergent perspective.

Cluster Analysis↗

PubMed2006

Decentralisation and convergence in health among the provinces of Spain (1980-2001).

This study measures the process of convergence in the state of health among the provinces and regions of Spain during 1980-2001 in order to analyse the possible influence of the decentralisation of healthcare management to the regions in this period. Sigma and beta convergence models, traditionally employed in macroeconomics, have been used, taking Life Expectancy at Birth (LEB) and Infant Mortality (IM) as health indicators. The analysis was carried out at two territorial levels: provinces and regions. The results reveal that the process of decentralisation either does not affect convergence or leads to divergence in health. Indeed, in the case of IM the so-called change of role scenario seems to have occurred. Thus, certain provinces with initially poor indicators have improved, overtaking those that were originally in a better position. The final result, however, is of greater dispersion than initially.

Empirical Research↗