The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Ronald L. Meyer - One of the best experts on this subject based on the ideXlab platform.
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Normal activity-dependent refinement in a compressed retinotectal projection in goldfish
The Journal of comparative neurology, 1994Co-Authors: Michael D. Olson, Ronald L. MeyerAbstract:When the optic nerve in a goldfish is crushed, regenerating fibers can reform a normal retinotopic projection. Two processes are thought to generate this retinotopic order. One is an activity-independent process, presumed to be some form of substrate-directed growth, which generates rough Retinotopy as seen in the early formed projection. The other is an activity-dependent process that generates fine Retinotopy during a protracted period of refinement. This projection also displays two other behaviors. One is retinotopic plasticity, in which optic fibers can compensate for retinal or tectal ablations by expanding or compressing into the available tectal space while preserving retinotopic order. These plasticities can dramatically alter the scale of the projection. The other behavior is the formation of fixed synaptic sites in tectum. Optic fibers make a characteristic number of synaptic connectionsin tectum, which is not changed by increasing the number of invading optic, fibers. This has been interpreted to mean that fibers compete for limited synaptic sites. How the two processes that generate order, substrate-directed growth, and activity-dependent refinement might each be affected by the expression of retinotopic plasticity and altered synaptic competition is largely unknown. In particular, it is not known how fine retinotopic order (activity-dependent refinement) might be affected by altering the scale of the projection. Would optic fibers from neighboring ganglion cells converge into the same-sized area of tectum, or would they expand or compress in proportion to the altered scale of the overall map? To explore this issue, the posterior half of tectum of goldfish was removed, and the optic nerve was crushed, thereby forcing regenerating fibers to form a compressed retinotopic projection onto the anterior half of tectum. Under these conditions, optic fibers are also forced to compete for half the normal number of synaptic sites. The effect on Retinotopy was monitored at various times during regeneration by making a small spot injection of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) into nasal retina corresponding to fibers that would normally terminate in the missing posterior half of tectum. To distinguish between activity-dependent and activity-independent processes, retinal impulse activity was blocked in some animals by repeated intraocular injections of tetrodotoxin. The initial projection was found to be unaffected by impulse activity. Regardless of activity, nasal fibers failed initially to grow to the most posterior available regions, but instead were the “incorrect” anterior half of tectum at 30 days. Under activity dispersed across much of the blockade, compressed Retinotopy was subsequently generated by a progressive improvement of this initially dispersed projection over the next 2 months, but this Retinotopy was impaired compared to that formed during regeneration into an intact tectum under activity blockade. Surprisingly, with impulse activity, the amount of refinement was normal in that fibers labelled by the retinal spot injections eventually formed a projection that was the same size and shape as that seen in a normal tectum. Fine Retinotopy was not obviously compressed, even though the map as a whole was. This indicates that fine retinotopic order, as measured by the convergence of neighboring retinal ganglion cells, is relatively constant in spite of large changes in the scale of the overall projection. © 1994 Wiley-Liss, Inc.
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Activity and excitatory amino acid receptors.
Progress in neuro-psychopharmacology & biological psychiatry, 1993Co-Authors: Ronald L. MeyerAbstract:1. In lower vertebrates, optic fibers form a highly ordered retinotopic projection to the contralateral midbrain. 2. The formation of fine Retinotopy during development or regeneration requires patterned impulse activity in optic fibers. 3. The transmitter used by optic fibers is probably glutamate. 4. Blockade of NMDA receptors prevents the formation of fine Retinotopy. 5. The available evidence leaves open several different interpretations for these NMDA effects.
Michael B Reiser - One of the best experts on this subject based on the ideXlab platform.
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Spatial readout of visual looming in the central brain of Drosophila
eLife, 2020Co-Authors: Mai M Morimoto, Arthur Zhao, Edward M Rogers, Allan M Wong, Mathew D Isaacson, Aljoscha Nern, Gerald M. Rubin, Davi D. Bock, Michael B ReiserAbstract:Visual systems can exploit spatial correlations in the visual scene by using Retinotopy. However, Retinotopy is often lost, such as when visual pathways are integrated with other sensory modalities. How is spatial information processed outside of strictly visual brain areas? Here, we focused on visual looming responsive LC6 cells in Drosophila, a population whose dendrites collectively cover the visual field, but whose axons form a single glomerulus-a structure without obvious retinotopic organization-in the central brain. We identified multiple cell types downstream of LC6 in the glomerulus and found that they more strongly respond to looming in different portions of the visual field, unexpectedly preserving spatial information. Through EM reconstruction of all LC6 synaptic inputs to the glomerulus, we found that LC6 and downstream cell types form circuits within the glomerulus that enable spatial readout of visual features and contralateral suppression-mechanisms that transform visual information for behavioral control.
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connectivity establishes spatial readout of visual looming in a glomerulus lacking Retinotopy
bioRxiv, 2020Co-Authors: Mai M Morimoto, Arthur Zhao, Edward M Rogers, Allan M Wong, Mathew D Isaacson, Davi Bock, Aljoscha Nern, Gerald M. Rubin, Michael B ReiserAbstract:Visual systems can exploit spatial correlations in the visual scene by using Retinotopy, the organizing principle by which neighboring cells encode neighboring spatial locations. However, Retinotopy is often lost, such as when visual pathways are integrated with other sensory modalities. How is spatial information processed in the absence of Retinotopy? Here, we focused on visual looming responsive LC6 cells in Drosophila, a population whose dendrites collectively tile the visual field, but whose axons form a single glomerulus--a structure lacking retinotopic organization--in the central brain. We identified multiple glomerulus neurons and found that they respond to looming in different portions of the visual field, unexpectedly preserving spatial information. Through EM reconstruction of all LC6 synaptic inputs to the glomerulus, we found that LC6 and downstream cell types form circuits within the glomerulus that establish spatial readout of visual features and contralateral suppression--mechanisms that transform visual information for behavioral control.
Lauren R. Marotte - One of the best experts on this subject based on the ideXlab platform.
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Location of retinal ganglion cells contributing to the early imprecision in the retinotopic order of the developing projection to the superior colliculus of the wallaby (Macropus eugenii).
The Journal of comparative neurology, 1993Co-Authors: Lauren R. MarotteAbstract:The position of ganglion cells contributing to the early imprecision in retinotopic order in the developing retinocollicular projection in the wallaby (Macropus eugenii) has been determined. Deposits of horseradish peroxidase conjugated to wheat germ agglutinin (WGA-HRP) were made in the caudal pole of the superior colliculus (SC) at ages ranging from 22 days after birth, when sparse retinal axons have only just reached the caudal pole of the SC and are yet to cover its surface completely, to 96 days when the Retinotopy of ganglion cell terminals in the SC is precise (Marotte, '90). From 30 days onwards, the deposit of WGA-HRP resulted in a dense patch of retrogradely labelled retinal ganglion cells that could be seen to be appropriately positioned in nasal retina. However, at all ages prior to 92 days, there were inappropriately positioned labelled cells between the densely labelled patch and the central retina and both dorsal and ventral to the patch. They were not found in far distant regions of retina and composed a relatively small proportion of labelled cells. They reached a peak at 45 days, had decreased to low levels by 63 days, were rare by 81 days, and by 92 days were absent. This latter age fits with the time when Retinotopy was judged to be precise in a previous study (Marotte, '90). Inappropriately projecting cells never originate from the entire retina but only from regions adjacent to the appropriate region. Thus, during development there are no gross projection errors. Initially, ganglion cell axons are distributed on the colliculus in a coarse Retinotopy. Refinement of the projection then follows, revealed by this technique as a loss of inappropriately projecting ganglion cells. This is complete by 92 days well before eye opening at around 140 days.
Mai M Morimoto - One of the best experts on this subject based on the ideXlab platform.
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Spatial readout of visual looming in the central brain of Drosophila
eLife, 2020Co-Authors: Mai M Morimoto, Arthur Zhao, Edward M Rogers, Allan M Wong, Mathew D Isaacson, Aljoscha Nern, Gerald M. Rubin, Davi D. Bock, Michael B ReiserAbstract:Visual systems can exploit spatial correlations in the visual scene by using Retinotopy. However, Retinotopy is often lost, such as when visual pathways are integrated with other sensory modalities. How is spatial information processed outside of strictly visual brain areas? Here, we focused on visual looming responsive LC6 cells in Drosophila, a population whose dendrites collectively cover the visual field, but whose axons form a single glomerulus-a structure without obvious retinotopic organization-in the central brain. We identified multiple cell types downstream of LC6 in the glomerulus and found that they more strongly respond to looming in different portions of the visual field, unexpectedly preserving spatial information. Through EM reconstruction of all LC6 synaptic inputs to the glomerulus, we found that LC6 and downstream cell types form circuits within the glomerulus that enable spatial readout of visual features and contralateral suppression-mechanisms that transform visual information for behavioral control.
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connectivity establishes spatial readout of visual looming in a glomerulus lacking Retinotopy
bioRxiv, 2020Co-Authors: Mai M Morimoto, Arthur Zhao, Edward M Rogers, Allan M Wong, Mathew D Isaacson, Davi Bock, Aljoscha Nern, Gerald M. Rubin, Michael B ReiserAbstract:Visual systems can exploit spatial correlations in the visual scene by using Retinotopy, the organizing principle by which neighboring cells encode neighboring spatial locations. However, Retinotopy is often lost, such as when visual pathways are integrated with other sensory modalities. How is spatial information processed in the absence of Retinotopy? Here, we focused on visual looming responsive LC6 cells in Drosophila, a population whose dendrites collectively tile the visual field, but whose axons form a single glomerulus--a structure lacking retinotopic organization--in the central brain. We identified multiple glomerulus neurons and found that they respond to looming in different portions of the visual field, unexpectedly preserving spatial information. Through EM reconstruction of all LC6 synaptic inputs to the glomerulus, we found that LC6 and downstream cell types form circuits within the glomerulus that establish spatial readout of visual features and contralateral suppression--mechanisms that transform visual information for behavioral control.
Yasuo Tano - One of the best experts on this subject based on the ideXlab platform.
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Successful photodynamic therapy with verteporfin for recurrent choroidal neovascularization beneath the new fovea after macular translocation surgery with 360-degree retinotomy.
American journal of ophthalmology, 2003Co-Authors: Miki Sawa, Masahito Ohji, Takashi Fujikado, Yasuo Tano, Wai-man Chan, Kazuyuki Imai, Andrew P. SchachatAbstract:Abstract Purpose To report a case of successfully treated recurrent choroidal neovascularization after macular translocation surgery with 360-degree retinotomy by photodynamic therapy with verteporfin. Design Interventional case report Methods A 76-year-old man developed recurrent choroidal neovascularization at the new fovea after macular translocation surgery with 360-degree retinotomy. Results Two sessions of photodynamic therapy were applied, which resolved the choroidal neovascularization. Best-corrected visual acuity improved to 20/50 at the 6 and 12 months follow-up. Conclusion Photodynamic therapy may be an option for treatment of recurrent choroidal neovascularization in the new subfoveal region after macular translocation surgery with 360-degree retinotomy.
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Comparison of three techniques of foveal translocation in patients with subfoveal choroidal neovascularization resulting from age-related macular degeneration.
American journal of ophthalmology, 2001Co-Authors: Masahito Ohji, Takashi Fujikado, Shunji Kusaka, Atsushi Hayashi, Jun Hosohata, Yasushi Ikuno, Miki Sawa, Akira Kubota, Noriyasu Hashida, Yasuo TanoAbstract:Abstract PURPOSE: To report the results of three methods of foveal translocation in the presence of subfoveal choroidal neovascular membrane resulting from age-related macular degeneration. METHODS: We treated 51 eyes of 51 consecutive patients with subfoveal choroidal neovascular membranes resulting from age-related macular degeneration with one of three techniques of foveal translocation surgery: foveal translocation with partial retinotomy (n = 6), limited translocation (n = 9), and translocation with 360-degree retinotomy (n = 36). All patients were followed for at least 6 months postoperatively. The size of the choroidal neovascular membrane and the amount of foveal displacement, the best-corrected visual acuity, and complications were recorded preoperatively and postoperatively. RESULTS: The mean distance of the foveal translocation was greater in the 360-degree retinotomy group (3340 μm) than in the partial retinotomy (1060 μm, P P CONCLUSIONS: A significant number of patients improved or maintained best-corrected visual acuity after translocation with 360-degree retinotomy, and limited translocation, whereas translocation with 360-degree retinotomy is suitable for larger choroidal neovascular membranes because it resulted in the greatest foveal displacement among the three translocation procedures.
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comparison of visual function after foveal translocation with 360 retinotomy and with scleral shortening in a patient with bilateral myopic neovascular maculopathy
American Journal of Ophthalmology, 2000Co-Authors: Takashi Fujikado, Masahito Ohji, Atsushi Hayashi, Jun Hosohata, Koichi Oda, Yasuo TanoAbstract:Abstract PURPOSE: To compare the visual outcome after foveal translocation by scleral shortening and that after 360° retinotomy with extraocular muscle surgery in a patient with bilateral myopic neovascular maculopathy. METHODS: Case report. RESULTS: A 52-year-old woman with bilateral myopic neovascular maculopathy underwent foveal translocation with scleral shortening in the left eye, and visual acuity improved from 20/70 to 20/30. However, choroidal neovascularization recurred, and the final visual acuity was 20/40 after excision of the choroidal neovascularization. Foveal translocation with 360° retinotomy was performed on the right eye, and visual acuity improved from 20/150 to 20/30. The critical print size was better, and the retinal sensitive area was larger in the right eye. CONCLUSION: The better reading ability shown by foveal translocation by a 360° retinotomy compared with scleral shortening may stem from a larger retinal sensitive area obtained by this method.
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Comparison of visual function after foveal translocation with 360° retinotomy and with scleral shortening in a patient with bilateral myopic neovascular maculopathy
American journal of ophthalmology, 2000Co-Authors: Takashi Fujikado, Masahito Ohji, Atsushi Hayashi, Jun Hosohata, Koichi Oda, Yasuo TanoAbstract:Abstract PURPOSE: To compare the visual outcome after foveal translocation by scleral shortening and that after 360° retinotomy with extraocular muscle surgery in a patient with bilateral myopic neovascular maculopathy. METHODS: Case report. RESULTS: A 52-year-old woman with bilateral myopic neovascular maculopathy underwent foveal translocation with scleral shortening in the left eye, and visual acuity improved from 20/70 to 20/30. However, choroidal neovascularization recurred, and the final visual acuity was 20/40 after excision of the choroidal neovascularization. Foveal translocation with 360° retinotomy was performed on the right eye, and visual acuity improved from 20/150 to 20/30. The critical print size was better, and the retinal sensitive area was larger in the right eye. CONCLUSION: The better reading ability shown by foveal translocation by a 360° retinotomy compared with scleral shortening may stem from a larger retinal sensitive area obtained by this method.