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Query: UMLS:C0038379 (strabismus)
 9,317 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have studied the effects of surgically induced convergent strabismus (esotropia) on the morphological development of retinogeniculate X and Y axon arbors in cats. Single axons were recorded in the lateral geniculate nucleus or in the optic tract adjacent to the nucleus, classified physiologically, and injected intracellularly with horseradish peroxidase. The arbors of recovered axons were compared with X and Y axon arbors from normally reared adult cats. Our data demonstrate that while X axon arbors are relatively normal, the arbors of Y axons are profoundly affected by rearing with strabismus. Y axons, whether originating from the deviated or the nondeviated eye, have substantially smaller arbors and fewer boutons in the A-laminae of the lateral geniculate nucleus compared to Y axons in normal cats. The C-lamina terminations of contralaterally projecting Y axons in the strabismic cats are unaffected. These results suggest that the postnatal development of retinogeniculate Y axon arbors in the A-laminae is strongly influenced by abnormalities in postnatal visual experience. Furthermore, the present data suggest that, in addition to intraocular competitive interactions between X and Y axons previously proposed to account for the effects of other rearing conditions, interactions between afferents from the two eyes must also be involved in the development of at least Y axons.
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PMID:Effects of convergent strabismus on the development of physiologically identified retinogeniculate axons in cats. 280 63

The cat's distribution of claustral cells that project to the contralateral visual cortex via the corpus callosum was examined. Horseradish peroxidase (HRP) was applied to severed callosal axons to label a heterogeneous population of callosal connections. Cats reared with optically induced strabismus, and Siamese cats, had HRP-filled cells extending more ventrally in the claustrum than in controls. In these groups the compaction of labeled cells was higher than in controls and the amount of increased labeled area was not dependent on the resulting eye alignment. This indicates possible plasticity of visual claustrocallosal connectivity in cats.
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PMID:Plasticity of claustroneocortical connections via the corpus callosum in the cat. 334 Mar 19

The number of callosally projecting neurons (callosal neurons) which can be labeled in cortical areas 17 and 18 by horseradish peroxidase (HRP), injected in the contralateral visual cortex, is reduced to about 50% of normal in cats reared with their eyelids bilaterally sutured. In the same animals the density of HRP anterogradely transported to areas 17 and 18 is also decreased. The apparent loss of callosal neurons is limited to layers III and IV (subzone a), whereas layer VI (subzone c) is unaffected. The effect is obtained after 3 months or more but not after 1 month of deprivation. Two months of visual experience following deprivation do not restitute a normal number of callosal neurons. However, 10 days of normal visual experience preceding the deprivation are sufficient to prevent the effects of the latter. Animals deprived of vision after a short period of normal visual experience and animals allowed normal vision after 1 month of visual deprivation have a more widespread distribution of callosal neurons than do normal animals; in this way they are similar to previously described cats reared with convergent or divergent strabismus, monocular enucleation, or monocular eyelid suture. The results suggest that: vision is actively responsible for both the maintenance and the elimination of fractions of the juvenile callosal connections; the elimination which normally takes place during the second postnatal month requires normal binocular vision; and activity-dependent competition between callosal and other axons can explain the role of vision.
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PMID:Maturation of visual callosal connections in visually deprived kittens: a challenging critical period. 397 65

The connectivity of the corpus callosum in visual cortical areas 17 and 18 was studied in normal cats, in cats reared with unilateral convergent or divergent surgically-induced strabismus, and in a Siamese cat. The extents of the callosal cell and terminal zones were determined following multiple injections of horseradish peroxidase and tritiated amino-acids into one hemisphere. Following surgically-induced strabismus, abnormally wide callosal cell zones were seen in both the left and the right hemisphere irrespective of the direction of eye misalignment. Abnormally wide callosal terminal zones were seen in the hemisphere ipsilateral to the deviating eye in cats reared with unilateral convergent and divergent strabismus. Abnormally wide callosal zones were seen in cats which had strabismus induced as late as postnatal day 36. In a Siamese cat with a naturally-occurring convergent strabismus, callosal cells had a different distribution and were fewer in number compared to normal cats or cats with surgically induced strabismus. This implies that the abnormal callosal connectivity of Siamese cats is not a simple result of strabismus.
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PMID:Alterations in connections of the corpus callosum following convergent and divergent strabismus. 662 49

The distribution of the origin of corpus callosum neurons was investigated in cats reared with an optically induced strabismus by applying horseradish peroxidase (HRP) to severed callosal axons. These animals demonstrated an enlargement of the region of callosal connectivity compared to normal cats. Bilaterally there was an expanded efferent zone, with callosal cell bodies widely distributed in area 17, extending down the medial bank of the lateral gyrus halfway to the fundus of the splenial sulcus. This suggests that rearing a cat with visual spatial dissociation requires additional communication between the hemispheres in the form of increased callosal connections between cortical regions representing more peripheral portions of the visual field.
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PMID:Spatial dissociation of visual inputs alters the origin of the corpus callosum. 684 87

The squirrel monkey is the only primate reported to lack ocular dominance columns. Nothing anomalous about the visual capacity of squirrel monkeys has been found to explain their missing columns, leading to the suggestion that ocular dominance columns might be "an epiphenomenon, not serving any purpose" (Livingstone et al., 1995). Puzzled by the apparent lack of ocular dominance columns in squirrel monkeys, we made eye injections with transneuronal tracers in four normal squirrel monkeys. An irregular mosaic of columns, averaging 225 microns in width, was found throughout striate cortex. They were double-labeled by placing wheat germ agglutinin-horseradish peroxidase into the left eye and [3H]proline into the right eye. The tracers labeled opposite sets of interdigitating columns, proving they represent ocular dominance columns. The columns were much clearer in layer IVc alpha (magno-receiving) than IVc beta (parvo-receiving). In the lateral geniculate body, the parvo laminae showed extensive mixing of ocular inputs, suggesting that increased label spillover contributes to the blurred columns in layer IVc beta. The cytochrome oxidase (CO) patches were organized into distinct rows, but they bore no consistent relationship to the ocular dominance columns. These experiments indicate that ocular dominance columns are less well segregated in squirrel monkeys than macaques, but they are present. This fact is pertinent to a recent study reporting that ocular dominance columns are absent in normal squirrel monkeys, but induced to form by strabismus (Livingstone, 1996).
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PMID:Anatomical demonstration of ocular dominance columns in striate cortex of the squirrel monkey. 875 63

Previous studies have shown that the distribution of callosal connections in the 17/18 callosal zone of the cat is patchy at a small scale, but the mechanisms that determine this periodic pattern remain unclear. The present study investigated this issue by correlating the distribution of retrogradely labeled callosal cells with the underlying patterns of ocular dominance columns (ODCs) revealed transneuronally after intraocular injections of wheat germ agglutinin-horseradish peroxidase. The density of labeled callosal cells was found to vary significantly between adjacent territories dominated by different eyes, indicating that the distribution of callosal cells is significantly biased toward domains that are eye specific. Moreover, callosal connections relate to the pattern of ODCs in a rather unique way: callosal cells correlate preferentially with contralateral ODCs within the 17/18 transition zone (TZ), and with ipsilateral ODCs in regions of areas 17 and 18 located outside the TZ. Similar results were obtained in cats raised with strabismus, indicating that the overlap between right and left ODCs present in normal cats does not influence the correlation between callosal neurons and ODCs. The results are consistent with the hypothesis that callosal linkages are stabilized during development by interhemispheric correlated activity driven by bilateral projections from temporal retina. It is proposed that developmental constraints imposed by both this retinally driven mechanism and the pattern of ODCs are likely to determine not only the association of callosal clusters with specific sets of ODCs, but also important aspects of the functional characteristics of the callosal pathway in cat striate cortex.
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PMID:Callosal connections correlate preferentially with ipsilateral cortical domains in cat areas 17 and 18, and with contralateral domains in the 17/18 transition zone. 1130 9

The interhemispheric connections of areas 17 and 18 of the cerebral cortex were investigated in cats with experimental unilateral strabismus. Single cortical columns were microiontophoretically injected with horseradish peroxidase, and retrogradelly labeled cells were demonstrated in the opposite brain hemisphere. After tracer injection in area 18 columns, the labeled callosal cells were located in area 17/18 transitional zone, similar to what was found in normal cats. However, in some cases the expansion of the region of callosally labeled cells distribution, was found. It is proposed that the extent of the region of callosally-connected cells may vary depending on whether the cells receive their input from intact or strabismic eye.
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PMID:[Interhemispheric connections of areas 17 and 18 in the cortical columns of cats with unilateral strabismus]. 1535 98

In six cats with experimental unilateral or bilateral strabismus, surgically induced early in postnatal life, torsion eye rotation with a deviation angle of 10 to 20 degrees was also detected. Spatial distribution of retrogradely labeled neurons in area 17 was studied following microiontophoretic injection of horseradish peroxidase in area 17 or 18 cortical columns. Eye rotation was shown to cause the increase of the length of horizontal neuronal connections in area 17 along the projection of visual field vertical meridian. The reorganization of neuronal connections, detected in this work, may promote the functional changes, described in the literature, that compensate for the eye rotation.
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PMID:[Spatial reorganization of horizontal connections of cat cortical area 17 induced by eye rotation]. 1620 39

We have determined the spatial distribution of retrograde labelled callosal cells after microiontophoretic horseradish peroxidase injections into the single cortical columns of area 17, 18 in cats reared with bilateral convergent strabismus. The obtained strabismus angle was in the range 10-35 degrees. The zone of labelled cells was located asymmetrically in respect to location of injected column in opposite hemisphere. Some cells were revealed in the transition zone 17/18 and their retinotopic coordinates corresponded to the injected column, as was shown in intact cats. Other labelled cells were located in areas 17, 18, in clusters approximately in 1000 mkm from marginal clusters of transition zone. Analysis of labeling in lateral geniculate nucleus has shown that most of the injected columns were driven by ipsilateral eye. The data obtained may be interpreted as evidence of eye-specificity of monosynaptic callosal connections. The functional role in such connections changes in cats with bilateral strabismus is discussed.
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PMID:[Interhemispheric connections in the visual cortex of cats reared with bilateral strabismus]. 1625 91


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