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PubMed2006

Convergence substitution in pontine tegmental hemorrhage: an observation with Frenzel goggles.

We report a case in which convergence movement was substituted for bilateral horizontal gaze palsy due to a pontine tegmental hemorrhage. When visual fixation was suppressed with Frenzel goggles (FG), substituted convergence movements were prominent in our patient. The observation suggests that both vergence eye movements and horizontal gaze movements act synergistically and lesioning of the version system results in overactivity of the convergence system after a pontine hemorrhage. Furthermore, it may be worth using FG in the observation of substituted eye movements in patients with horizontal gaze palsy due to a pontine tegmental injury.

Adult↗
PubMed2001

[A case of convergence spasm in hysteria improved with a brief psychiatric assessment].

We report a 16-year-old female who developed double vision. The diplopia was in the horizontal plane and persisted for 3 weeks. She also complained of headache and nausea. She kept her eyes closed unless she was told to open. When eyelids were passively open, both eyes deviated inward in an adducted position. The pupil size and the reaction to light were normal. No weakness was noted in the extraocular muscles when each eye was examined individually. The rest of the neurologic examinations were normal. We thought that she had a convergence spasm. Brain CT and MRI were normal. The CSF and blood chemistries were also normal. We treated her with supportive psychotherapy and her convergence spasm disappeared. We concluded that her convergence spasm was a manifestation of conversion hysteria.

Adolescent↗
PubMed2006

[Effects of visual optical stimuli for accommodation-convergence system on asthenopia].

PURPOSE: We investigated the effect on eyestrain of optical stimuli that we designed for accommodation and convergence systems. METHODS: Eight female students were given optical stimuli for accommodation and convergence systems for 1.5 min immediately after 20 min of a sustained task on a 3-D display. Before and after the trial, their ocular functions were measured and their symptoms were assessed. The optical stimuli were applied by moving targets of scenery images far and near around the far point position of both eyes on a horizonal place, which induced divergence in the direction of the eye position of rest. In a control group, subjects rested with closed eyes for 1.5 min instead of applying the optical stimuli. RESULTS: There were significant changes in the accommodative contraction time (from far to near) and the accommodative relaxation time (from near to far) and the lag of accommodation at near target, from 1.26 s to 1.62 s and from 1.49 s to 1.63 s and from 0.5 D to 0.65 D, respectively, and in the symptoms in the control group after the duration of closed-eye rest. In the stimulus group, however, the changes of those functions were smaller than in the control group. CONCLUSION: From these results, we suggest that our designed optical stimuli for accommodation and convergence systems are effective on asthenopia following accommodative dysfunction.

Accommodation, Ocular↗
PubMedDate not supplied

Study of primary convergence insufficiency.

The present study was done to find out the incidence of primary insufficiency of involuntary convergence and evaluate the relative efficacy of synoptophore treatment against home exercise in its management. During the period of study, 2162 cases in the age group 15 to 35 years were studied for convergence in detail. It was found out that the incidence of primary convergence insufficiency is quite high (7.7% of total orthoptic clinic attendance). It commonly affects those who are constantly engaged in near work. Response to synoptophore exercises and home exercises is comparably equal. Recurrence of the ailment after stopping the exercises is not uncommon.

Adolescent↗
PubMed1991

Convergence accommodation: laboratory and clinical evaluation.

The accommodation stimulated by convergence, CA/C, was measured under laboratory and clinical conditions. There was a small nonlinearity to the CA/C ratios measured under laboratory conditions for three of six subjects. We found that convergence accommodation decreases with decreasing accommodative amplitude but not as rapidly as has been reported in the literature. Our results suggest that convergence accommodation can contribute substantially to the near accommodative response for many patients.

Accommodation, Ocular↗
PubMed1995

Accommodation-convergence relationships and age.

PURPOSE: The objective of this study was to determine if there are differences in accommodative-convergence/accommodation (AC/A) and convergence-accommodation/convergence (CA/C) ratios in subjects with increasing age. The authors aimed to relate the findings to the present theories of the development of presbyopia. METHODS: Using a Canon AutoRef R-1 to measure accommodation and an IRIS eye movement monitor to measure eye movements, the authors determined objective AC/A and CA/C ratios for 23 subjects between 17 and 42 years of age with normal binocular vision. Changes in accommodation and convergence responses were stimulated by lenses (-1.00 DS and -2.00 DS) and prisms (4 and 8 prism diopters), respectively. Measures were made at two visits on consecutive days. RESULTS: A moderate linear relationship was found between AC/A ratio and age (P < .002), and a strong linear relationship was found between CA/C ratio and age (P < .0001). The decrease in CA/C ratio with age was due to a decreased accommodative response to prisms (P = .0001). Measurements were reliable, with 95% confidence intervals at +/- 1.28 delta/D and +/- 0.02 D/delta for AC/A and CA/C ratios, respectively. A reciprocal relationship existed between the AC/A and CA/C ratios. CONCLUSION: The AC/A ratio increases, and the CA/C ratio decreases, in persons between 20 and 40 years of age. This may be because increasing ciliary muscle contraction is required to produce a given change in accommodation with increasing age or because of changes in the adaptability of the tonic accommodation and vergence systems with age.

Accommodation, Ocular↗
PubMed1994

Natural strabismus in monkeys: accommodative errors assessed by photorefraction and their relationship to convergence errors.

PURPOSE: To examine accommodation and accommodative convergence relationships in naturally strabismic monkeys. METHODS: Photorefraction was used to measure accommodative responses of each eye under monocular and binocular viewing conditions. These accommodative results were then compared to assessments of vergence state made under monocular viewing conditions using methods previously described. RESULTS: Accommodation was always accurate under monocular viewing conditions, with the exception of the inability of one myopic eye to focus distant targets. The accommodative response in the two eyes was always consensual. In animals with an anisometropia, the fixating eye was focused accurately on the target, and the fellow eye was in error by an amount predicted by the magnitude of the anisometropia. Some animals alternated fixation, and, under these conditions, control of accommodation and fixation switched in tandem. Accommodative convergence ratios (AC:A) were abnormally low in animals with strabismus syndromes, similar to human essential infantile esotropia, and were excessively high in animals with syndromes, similar to human early onset accommodative esotropia. CONCLUSIONS: There was no evidence that the strabismus seen in any of the monkeys was related to errors in accommodation. However, the crosslink gain between accommodation and vergence was abnormal in some of the animals. These abnormalities have the effect of driving vergence toward a misalignment that can only be overcome by other factors, such as fusional vergence. Thus, the authors speculate that these abnormalities in synkinesis between accommodation and convergence were present during early postnatal development when fusional vergence is weak, and that they acted as predisposing factors for the development of strabismus.

Accommodation, Ocular↗
PubMed1997

The efficacy of vision therapy for convergence excess.

BACKGROUND: Convergence excess is a commonly encountered non-strabismic ocular motility disorder. There are, however, very few research data that evaluate the effect of vision therapy for this condition in a clinical population. METHODS: The records of 83 consecutive patients with convergence excess who were treated with vision therapy were reviewed to assess the impact of treatment on clinical findings and patient symptoms. RESULTS: Statistically and clinically significant changes in direct and indirect measures of negative fusional vergence were seen, with 84% of patients reporting a total elimination of initial symptoms. Larger increases in negative fusional vergence were found than those previously reported. This may be a result of the more extensive and better controlled in-office treatment used in this study. CONCLUSIONS: Vision therapy was successful in enhancing negative fusional vergence and eliminating symptoms in the vast majority of patients with convergence excess and should be considered an effective treatment for this condition.

Adolescent↗
PubMed1998

Gradient in convergent cell movement during Fundulus gastrulation.

This contribution represents a continuation of our studies of a gradient in convergent cell movement in the germ ring (GR) during Fundulus gastrulation (Trinkaus et al. [1992] J. Exp. Zool., 261:40-61). In our previous study, we discovered that cells in the dorsal GR nearest the embryonic shield (ES) move toward the ES at a net faster rate than those farther away and that this is due to less meandering. Those farther away meander more. These data suggest the hypothesis that there is a gradient of cues that direct cells to the ES. If so, cells in the ventral GR, farthest from the ES, should meander even more and hence show little or no convergence toward the ES. To test this hypothesis, we have traced the trajectories of individual cells in the midventral GR during midepiboly and have found that, although the general motile behavior of ventral GR cells is the same as that of dorsal cells, they do indeed meander much more and, as a result, show little or no directional movement toward the ES. Taken together, these results indicate that cells of the germ ring move up a gradient in directionality as they converge toward their target, the embryonic shield. One possible explanation for this is that the embryonic shield attracts cells to itself.

Animals↗
PubMed1997

Epidermal ectoderm is required for full elevation and for convergence during bending of the avian neural plate.

Previous studies suggest that bending of the neural plate requires the juxtaposition of neural plate and non-neuroepithelial tissues. The current study examines the role of one of these tissues, the epidermal ectoderm, in bending. Chick blastoderms were harvested from fertile eggs incubated for 24 hr and cultured dorsal-side-up on agar-albumen substrates. In one experiment, a rectangular flap of epidermal ectoderm on one side of each blastoderm was separated from underlying layers and gently reflected onto the area opaca; a fragment of tungsten wire was placed on top of the flap to hold it down and to prevent healing. Embryos were then allowed to develop in a humidified incubator for 2-18 hr. Asymmetric neurulation was observed between the operated and control sides as early as 2 hr after surgery. The amount of asymmetry was quantified in serial transverse sections from embryos collected 8 hr after surgery. Elevation of the lateral edge of the neural plate on the operated side averaged one half to two thirds of that on the control side, and convergence of the operated side around the dorsolateral hinge point toward the dorsal midline did not occur. These results demonstrate that epidermal ectoderm is required for full elevation and for convergence during bending. In another experiment, lateral epidermal ectoderm was removed, leaving only a medial strip consisting of both the epidermal component of the future neural fold and flanking future epidermis. This experiment revealed that although epidermal ectoderm is necessary for full elevation and for convergence of the neural folds, a medial strip of epidermal ectoderm is sufficient to drive bending. Collectively, these results further support the idea that neurulation is a multifactorial process driven by both intrinsic and extrinsic factors acting in concert.

Animals↗
PubMed1994

Convergent validity of the eating disorder inventory and the anorexia nervosa inventory for self-rating in an Austrian nonclinical population.

This study assesses the convergent and divergent validity of the Eating Disorder Inventory (EDI--German version) and the Anorexia Nervosa Inventory for Self-Rating (ANIS) in a German-speaking nonclinical population. One hundred fifty-five female and 224 male Austrian medical students were surveyed. Validity was studied at a dimensional level, separately for both sexes, by correlating with conceptually related as well as distinct scales. These instruments included the General Health Questionnaire (GHQ). The intercorrelation coefficients of the EDI and the ANIS were similar to the original samples. In women, the convergent validity of the EDI and the ANIS was confirmed, especially for the subscales measuring the specific psychopathology (r = .43 to .84) and for ineffectiveness/feelings of inadequacy (r = .63). The EDI subscales Maturity Fears and Interpersonal Distrust and the ANIS subscales Obsessive-Compulsive Traits and Sexual Anxiety address traits not included in the other test and these showed divergent validity. Divergent validity of the ANIS and to a lesser degree the EDI with the GHQ was established. Both tests can be equally recommended for female subjects. In males however, the validity indices of both tests were generally lower and convergent and divergent validity was not established.

Adult↗
PubMed1986

Convergence of genetic distances in a migration matrix model.

A recurring problem with the use of migration matrix models of genetic differentiation has to do with their convergence properties. In practice, predictions can be drawn from these models only at equilibrium; but in the case of the standard predictors (most of which are modifications of Wright's FST), it can take an unrealistically large number of generations to approach equilibrium. An alternative set of predictors, the set of all pairwise genetic distances among the populations that define the rows and columns of the migration matrix, is investigated here. These distances are shown analytically to converge much more rapidly than the more commonly used predictors. In an application of the model to migration data on a human population from Papua New Guinea, it takes only about three to four generations for the pairwise distances to converge, in contrast to more than 100 generations for one of the standard predictors. In this case, moreover, the distances predicted by the model at equilibrium are similar to those calculated from the available genetic data.

Alleles↗
PubMed2002

Quantification of mitral regurgitation by the proximal flow convergence method--comparison of transthoracic and transesophageal echocardiography.

BACKGROUND: No dataexist to indicate whether transthoracic (TTE) and transesophageal echocardiography (TEE) are of comparable value for the detection and quantification of mitral regurgitation using the proximal flow convergence method. HYPOTHESIS: The study was performed to compare the value of TTE and TEE for the detection and quantification of mitral regurgitation using this method. METHODS: The study included 57 patients with and 11 patients without mitral regurgitation. In all patients, the proximal flow convergence region was imaged by transthoracic and transesophageal color Doppler echocardiography, and proximal isovelocity surface area radii were determined. In 19 patients, monoplane TEE and in 49 patients multiplane TEE was performed. Thirty-one patients with mitral regurgitation underwent cardiac catheterization. RESULTS: Both methods had a comparable sensitivity for the detection of mitral regurgitation. Proximal isovelocity surface area radii derived from TTE and TEE agreed moderately (mean difference -0.5 +/- 1.3 mm). TTE and TEE correlated significantly with the angiographic grade (rank correlation coefficients 0.83 and 0.81), and both differentiated mild to moderate from severe mitral regurgitation with an accuracy of 90%. Regurgitant volumes derived from both echocardiographic techniques and cardiac catheterization correlated moderately (correlation coefficients between 0.67 and 0.81). CONCLUSIONS: TTE and TEE were of comparable value for the detection and quantification of mitral regurgitation using the proximal flow convergence method.

Adult↗
PubMed2002

Hippocampal and prefrontal cortical inputs monosynaptically converge with individual projection neurons of the nucleus accumbens.

Afferents to the nucleus accumbens from different sources innervate specific areas of the central "core" and peripheral "shell" and are related to each other, at the light microscopical level, in an intricate overlapping and nonoverlapping way. This lack of homogeneity suggests that this region consists of circuits involving emsembles of neurons modulated by specific sets of convergent afferent inputs and abnormal regulation of such ensembles has been implicated in mental disorders. Early extracellular studies suggested that individual Acb neurons might respond to activation of afferents from more than one excitatory input: More recent studies of hippocampal and amygdalar or prefrontal cortical afferents suggest that hippocampal afferents gate the input from the prefrontal cortex or amygdala. Electrophysiological evidence for convergence of excitatory afferents in the Acb is strong and suggests that these pathways are monosynaptic. Nevertheless, this convergence has proved difficult to demonstrate anatomically as a result of the spatial distribution of the afferent inputs on the dendritic tree of the target neurons. To establish whether individual accumbens neurons receive monosynaptic input from pairs of afferents, one projection was labelled anterogradely with Phaseolus vulgaris leucoagglutinin and the second with biotinylated dextran amine (BDA) with Vector slate grey and 3,3'-diaminobenzidine tetrahydrochloride as the chromagens. Accumbens neurons possibly postsynaptic to these afferents, labelled by an in vivo focal injection of BDA, were examined using correlated light and electron microscopy to establish the proximal-distal distribution of labelled afferent synaptic inputs on their dendritic arbours. Individual cells were shown to receive monosynaptic afferent input from both ventral subiculum and prefrontal cortex, providing an anatomical framework for the hippocampal gating of other limbic inputs to the accumbens.

Animals↗
PubMed2003

Synaptic density, convergence, and dendritic complexity of prevertebral sympathetic neurons.

Prevertebral sympathetic ganglia contain a unique population of final motor neurons receiving convergent synaptic inputs not only from spinal preganglionic neurons, but also from peripheral intestinofugal neurons projecting from the gut. We used quantitative confocal and ultrastructural immunohistochemistry to determine how this increased synaptic convergence is accommodated by sympathetic final motor neurons in the celiac ganglion of guinea pigs. Terminals of intestinofugal neurons were identified by their immunoreactivity to vasoactive intestinal peptide. Stereologic analyses were based on transects and point counts at confocal and ultrastructural levels. The relative amount of dendritic neuropil in the medial regions of the ganglion was approximately 2.5 times greater than in the lateral regions of the ganglion, consistent with the 2 to 3 times difference in average dendritic field size of neurons in these regions. The total numbers of boutons and synaptic profiles showed significant positive correlations with the relative amount of neuropil in a region. However, the overall density of synaptic boutons was twice as high in the medial region of the ganglion compared with the lateral regions. Because the relative density of preganglionic synapses was similar in each region, this difference was due to the selective projection of intestinofugal inputs to neurons in the medial celiac ganglion, where they provided 45% of synaptic contacts. These results show that, compared with vasoconstrictor neurons, sympathetic neurons regulating gastrointestinal activity support a higher number of convergent inputs in two ways: in addition to having larger dendritic fields, they also have a twofold higher density of synapses.

Animals↗
PubMed1987

Topographic organization of convergent projections to the thalamus from the inferior colliculus and spinal cord in the rat.

The purpose of this study was to identify thalamic areas receiving convergent sensory inputs from acoustic and spinal projection systems in the rat. The topographic distribution of afferents to the thalamus from the inferior colliculus and spinal cord was examined by using WGA-HRP as an anterograde axonal tracer. Following injections in the inferior colliculus, terminal labeling was present in ventral, medial, and dorsal divisions of the medial genicuate body (MGB) and in adjacent areas of the posterior thalamus, including the posterior limitans nucleus, the posterior intralaminar nucleus, the marginal zone, the peripeduncular region, the lateral or parvicellular part of the subparafascicular nucleus, and a region intercalated between the posterior limitans nucleus and the suprageniculate nucleus. In the caudal thalamus spinal projections remained in the reticular formation medial to the collicular terminal field. At intermediate levels of the MG, however, the spinal projection began to overlap the collicular field, terminating in the medial division of the MG and in the posterior intralaminar nucleus, the marginal zone, the lateral subparafascicular nucleus, and the area between the suprageniculate and posterior limitans nuclei. More rostrally, the convergent field expanded to include aspects of the dorsal MG division. The extent to which afferent projections to the thalamus from the inferior colliculus and spinal cord converge is thus graded in the caudorostral plane, with the greatest overlap occurring at the level of the rostral third of the MGB. These observations identify potential areas of acoustic and somesthetic integration and may account for observations of neuronal plasticity in the thalamus in response to the pairing of acoustic and somesthetic inputs.

Afferent Pathways↗
PubMed1991

Gracile projection to the cat medial accessory olive: ultrastructural termination patterns and convergence with spino-olivary projection.

The caudal medial accessory subdivision of the inferior olive (cMAO) receives information from the hindlimb from both the gracile nucleus and the lumbosacral spinal cord. This study determined which elements in cMAO serve as the postsynaptic targets of the gracile projection and whether these elements also receive input from the lumbosacral spinal cord. Gracile axons were labeled in cats by anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP), visualized with tetramethylbenzidine. Convergence of gracile and lumbosacral axons was evaluated by labeling in the same animal, one pathway by WGA-HRP and the other by degeneration. In cMAO, gracile axons synapse with equal probability on dendritic spines and distal dendritic shafts. This termination pattern contrasts markedly with that of other somatosensory inputs to the inferior olive and may account for the greater heterogeneity in responses to somatosensory stimuli displayed by neurons in cMAO. The distal dendritic shafts receiving gracile input were more likely than dendritic spines to receive convergent input from putative inhibitory synapses. The most likely source of these inhibitory synapses is the parasolitary nucleus, a structure that has been shown by others to receive input from the cerebellum. Thus the parasolitary nucleus may serve as an inhibitory relay between the cerebellum and cMAO. The dendritic spines in cMAO that receive input from the gracile nucleus often receive additional input from the lumbosacral spinal cord. This convergence of somatosensory axons on dendritic spines may provide a mechanism through which the unusually complex receptive fields of neurons in cMAO are generated.

Animals↗
PubMed1994

Glutamatergic hippocampal formation projections to prefrontal cortex in the rat are regulated by GABAergic inhibition and show convergence with glutamatergic projections from the limbic thalamus.

Anatomic and physiologic studies in the rat have shown projections from the hippocampal formation (HF) and mediodorsal (MD) thalamic nucleus to the medial prefrontal cortex (mPFC). The authors used multi-barrel iontophoresis to: confirm the neurotransmitter used in the projection from HF to mPFC; investigate the role of GABAergic inhibition in the regulation of this projection; and examine the functional convergence of projections from HF and MD onto single mPFC neurons. During HF stimulation, nine cells (6%) showed excitation followed by prolonged inhibition, 39 cells (26%) showed prolonged inhibition alone and 100 cells (68%) showed no clear response. In a further 12 cells that showed no predrug excitation to HF stimulation (representing 16% of the cells in this category), iontophoresis of the GABAA antagonist bicuculline methiodide (BMI) revealed excitatory responses. A total of six mPFC cells (38% of the cells showing excitatory responses to HF stimulation) showed convergent excitation to HF and MD thalamic (or adjacent paratenial nucleus) stimulation. Five out of eight (63%) of the predrug or BMI-revealed excitatory responses of mPFC neurons to HF stimulation were selectively decreased after AMPA antagonist iontophoresis (either CNQX or DNQX). These data confirm that the HF projection to prefrontal cortex is, at least in part, glutamatergic; suggest that the responses of mPFC neurons to activity in this HF pathway are regulated by GABAergic inhibition; and indicate that projections from HF and MD converge onto single mPFC neurons.

6-Cyano-7-nitroquinoxaline-2,3-dione↗