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Kerschensteiner D, Feller MB. Mapping the Retina onto the Brain. Cold Spring Harb Perspect Biol 2024; 16:a041512. [PMID: 38052498 PMCID: PMC10835620 DOI: 10.1101/cshperspect.a041512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Vision begins in the retina, which extracts salient features from the environment and encodes them in the spike trains of retinal ganglion cells (RGCs), the output neurons of the eye. RGC axons innervate diverse brain areas (>50 in mice) to support perception, guide behavior, and mediate influences of light on physiology and internal states. In recent years, complete lists of RGC types (∼45 in mice) have been compiled, detailed maps of their dendritic connections drawn, and their light responses surveyed at scale. We know less about the RGCs' axonal projection patterns, which map retinal information onto the brain. However, some organizing principles have emerged. Here, we review the strategies and mechanisms that govern developing RGC axons and organize their innervation of retinorecipient brain areas.
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Affiliation(s)
- Daniel Kerschensteiner
- Department of Ophthalmology and Visual Sciences
- Department of Neuroscience
- Department of Biomedical Engineering, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Marla B Feller
- Department of Molecular and Cell Biology
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California 94720, USA
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2
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Molotkov D, Ferrarese L, Boissonnet T, Asari H. Topographic axonal projection at single-cell precision supports local retinotopy in the mouse superior colliculus. Nat Commun 2023; 14:7418. [PMID: 37973798 PMCID: PMC10654506 DOI: 10.1038/s41467-023-43218-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Accepted: 11/03/2023] [Indexed: 11/19/2023] Open
Abstract
Retinotopy, like all long-range projections, can arise from the axons themselves or their targets. The underlying connectivity pattern, however, remains elusive at the fine scale in the mammalian brain. To address this question, we functionally mapped the spatial organization of the input axons and target neurons in the female mouse retinocollicular pathway at single-cell resolution using in vivo two-photon calcium imaging. We found a near-perfect retinotopic tiling of retinal ganglion cell axon terminals, with an average error below 30 μm or 2° of visual angle. The precision of retinotopy was relatively lower for local neurons in the superior colliculus. Subsequent data-driven modeling ascribed it to a low input convergence, on average 5.5 retinal ganglion cell inputs per postsynaptic cell in the superior colliculus. These results indicate that retinotopy arises largely from topographically precise input from presynaptic cells, rather than elaborating local circuitry to reconstruct the topography by postsynaptic cells.
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Affiliation(s)
- Dmitry Molotkov
- Epigenetics and Neurobiology Unit, EMBL Rome, European Molecular Biology Laboratory, Monterotondo, 00015, Italy
| | - Leiron Ferrarese
- Epigenetics and Neurobiology Unit, EMBL Rome, European Molecular Biology Laboratory, Monterotondo, 00015, Italy
| | - Tom Boissonnet
- Epigenetics and Neurobiology Unit, EMBL Rome, European Molecular Biology Laboratory, Monterotondo, 00015, Italy
- Collaboration for joint PhD degree between EMBL and Université Grenoble Alpes, Grenoble Institut des Neurosciences, La Tronche, 38700, France
- Center for Advanced Imaging, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, 40225, Germany
| | - Hiroki Asari
- Epigenetics and Neurobiology Unit, EMBL Rome, European Molecular Biology Laboratory, Monterotondo, 00015, Italy.
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3
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Gehr C, Sibille J, Kremkow J. Retinal input integration in excitatory and inhibitory neurons in the mouse superior colliculus in vivo. eLife 2023; 12:RP88289. [PMID: 37682267 PMCID: PMC10491433 DOI: 10.7554/elife.88289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/09/2023] Open
Abstract
The superior colliculus (SC) is a midbrain structure that receives inputs from retinal ganglion cells (RGCs). The SC contains one of the highest densities of inhibitory neurons in the brain but whether excitatory and inhibitory SC neurons differentially integrate retinal activity in vivo is still largely unknown. We recently established a recording approach to measure the activity of RGCs simultaneously with their postsynaptic SC targets in vivo, to study how SC neurons integrate RGC activity. Here, we employ this method to investigate the functional properties that govern retinocollicular signaling in a cell type-specific manner by identifying GABAergic SC neurons using optotagging in VGAT-ChR2 mice. Our results demonstrate that both excitatory and inhibitory SC neurons receive comparably strong RGC inputs and similar wiring rules apply for RGCs innervation of both SC cell types, unlike the cell type-specific connectivity in the thalamocortical system. Moreover, retinal activity contributed more to the spiking activity of postsynaptic excitatory compared to inhibitory SC neurons. This study deepens our understanding of cell type-specific retinocollicular functional connectivity and emphasizes that the two major brain areas for visual processing, the visual cortex and the SC, differently integrate sensory afferent inputs.
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Affiliation(s)
- Carolin Gehr
- Neuroscience Research Center, Charité-Universitätsmedizin BerlinBerlinGermany
- Bernstein Center for Computational Neuroscience BerlinBerlinGermany
- Institute for Theoretical Biology, Humboldt-Universität zu BerlinBerlinGermany
- Einstein Center for Neurosciences BerlinBerlinGermany
| | - Jeremie Sibille
- Neuroscience Research Center, Charité-Universitätsmedizin BerlinBerlinGermany
- Bernstein Center for Computational Neuroscience BerlinBerlinGermany
- Institute for Theoretical Biology, Humboldt-Universität zu BerlinBerlinGermany
- Einstein Center for Neurosciences BerlinBerlinGermany
| | - Jens Kremkow
- Neuroscience Research Center, Charité-Universitätsmedizin BerlinBerlinGermany
- Bernstein Center for Computational Neuroscience BerlinBerlinGermany
- Institute for Theoretical Biology, Humboldt-Universität zu BerlinBerlinGermany
- Einstein Center for Neurosciences BerlinBerlinGermany
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4
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Teh KL, Sibille J, Gehr C, Kremkow J. Retinal waves align the concentric orientation map in mouse superior colliculus to the center of vision. SCIENCE ADVANCES 2023; 9:eadf4240. [PMID: 37172095 PMCID: PMC10181181 DOI: 10.1126/sciadv.adf4240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Neurons in the mouse superior colliculus (SC) are arranged in a concentric orientation map, which is aligned to the center of vision and the optic flow experienced by the mouse. The origin of this map remains unclear. Here, we propose that spontaneous retinal waves during development provide a scaffold to establish the concentric orientation map within the SC and its alignment to the optic flow. We test this hypothesis by modeling the orientation-tuned SC neurons that receive ON/OFF retinal inputs. Our model suggests that the propagation direction bias of stage III retinal waves, together with OFF-delayed responses, shapes the spatial organization of the orientation map. The OFF delay establishes orientation-tuned neurons by segregating their ON/OFF receptive subfields, the wave-like activities form the concentric pattern, and the direction biases align the map to the center of vision. Together, retinal waves may play an instructive role in establishing functional properties of single SC neurons and their spatial organization within maps.
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Affiliation(s)
- Kai Lun Teh
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Charitéplatz 1, Berlin 10117, Germany
- Bernstein Center for Computational Neuroscience Berlin, Philippstraße 13, Berlin 10115, Germany
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Philippstraße 13, Berlin 10115, Germany
- Einstein Center for Neurosciences Berlin, Charitéplatz 1, Berlin, Germany
| | - Jérémie Sibille
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Charitéplatz 1, Berlin 10117, Germany
- Bernstein Center for Computational Neuroscience Berlin, Philippstraße 13, Berlin 10115, Germany
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Philippstraße 13, Berlin 10115, Germany
- Einstein Center for Neurosciences Berlin, Charitéplatz 1, Berlin, Germany
| | - Carolin Gehr
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Charitéplatz 1, Berlin 10117, Germany
- Bernstein Center for Computational Neuroscience Berlin, Philippstraße 13, Berlin 10115, Germany
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Philippstraße 13, Berlin 10115, Germany
- Einstein Center for Neurosciences Berlin, Charitéplatz 1, Berlin, Germany
| | - Jens Kremkow
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Charitéplatz 1, Berlin 10117, Germany
- Bernstein Center for Computational Neuroscience Berlin, Philippstraße 13, Berlin 10115, Germany
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Philippstraße 13, Berlin 10115, Germany
- Einstein Center for Neurosciences Berlin, Charitéplatz 1, Berlin, Germany
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5
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Zhang C, Yadav S, Speer CM. The synaptic basis of activity-dependent eye-specific competition. Cell Rep 2023; 42:112085. [PMID: 36753422 PMCID: PMC10404640 DOI: 10.1016/j.celrep.2023.112085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 12/23/2022] [Accepted: 01/24/2023] [Indexed: 02/09/2023] Open
Abstract
Binocular vision requires proper developmental wiring of eye-specific inputs to the brain. In the thalamus, axons from the two eyes initially overlap in the dorsal lateral geniculate nucleus and undergo activity-dependent competition to segregate into target domains. Here, we combine eye-specific tract tracing with volumetric super-resolution imaging to measure the nanoscale molecular reorganization of developing retinogeniculate eye-specific synapses in the mouse brain. We show there are eye-specific differences in presynaptic vesicle pool size and vesicle association with the active zone at the earliest stages of retinogeniculate refinement but find no evidence of eye-specific differences in subsynaptic domain number, size, or transsynaptic alignment across development. Genetic disruption of spontaneous retinal activity decreases retinogeniculate synapse density, delays the emergence eye-specific differences in vesicle organization, and disrupts subsynaptic domain maturation. These results suggest that activity-dependent eye-specific presynaptic maturation underlies synaptic competition in the mammalian visual system.
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Affiliation(s)
- Chenghang Zhang
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Swapnil Yadav
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Colenso M Speer
- Department of Biology, University of Maryland, College Park, MD 20742, USA.
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Sibille J, Gehr C, Benichov JI, Balasubramanian H, Teh KL, Lupashina T, Vallentin D, Kremkow J. High-density electrode recordings reveal strong and specific connections between retinal ganglion cells and midbrain neurons. Nat Commun 2022; 13:5218. [PMID: 36064789 PMCID: PMC9445019 DOI: 10.1038/s41467-022-32775-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 08/16/2022] [Indexed: 11/29/2022] Open
Abstract
The superior colliculus is a midbrain structure that plays important roles in visually guided behaviors in mammals. Neurons in the superior colliculus receive inputs from retinal ganglion cells but how these inputs are integrated in vivo is unknown. Here, we discovered that high-density electrodes simultaneously capture the activity of retinal axons and their postsynaptic target neurons in the superior colliculus, in vivo. We show that retinal ganglion cell axons in the mouse provide a single cell precise representation of the retina as input to superior colliculus. This isomorphic mapping builds the scaffold for precise retinotopic wiring and functionally specific connection strength. Our methods are broadly applicable, which we demonstrate by recording retinal inputs in the optic tectum in zebra finches. We find common wiring rules in mice and zebra finches that provide a precise representation of the visual world encoded in retinal ganglion cells connections to neurons in retinorecipient areas.
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Affiliation(s)
- Jérémie Sibille
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany
- Bernstein Center for Computational Neuroscience Berlin, Philippstraße 13, 10115, Berlin, Germany
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Philippstraße 13, 10115, Berlin, Germany
- Einstein Center for Neurosciences Berlin, Charitéplatz 1, 10117, Berlin, Germany
| | - Carolin Gehr
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany
- Bernstein Center for Computational Neuroscience Berlin, Philippstraße 13, 10115, Berlin, Germany
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Philippstraße 13, 10115, Berlin, Germany
- Einstein Center for Neurosciences Berlin, Charitéplatz 1, 10117, Berlin, Germany
| | - Jonathan I Benichov
- Max Planck Institute for Ornithology, Eberhard-Gwinner Straße, 82319, Seewiesen, Germany
- Max Planck Institute for Biological Intelligence (in foundation), Eberhard-Gwinner Straße, 82319, Seewiesen, Germany
| | - Hymavathy Balasubramanian
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany
- Bernstein Center for Computational Neuroscience Berlin, Philippstraße 13, 10115, Berlin, Germany
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Philippstraße 13, 10115, Berlin, Germany
- Einstein Center for Neurosciences Berlin, Charitéplatz 1, 10117, Berlin, Germany
| | - Kai Lun Teh
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany
- Bernstein Center for Computational Neuroscience Berlin, Philippstraße 13, 10115, Berlin, Germany
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Philippstraße 13, 10115, Berlin, Germany
- Einstein Center for Neurosciences Berlin, Charitéplatz 1, 10117, Berlin, Germany
| | - Tatiana Lupashina
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany
- Bernstein Center for Computational Neuroscience Berlin, Philippstraße 13, 10115, Berlin, Germany
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Philippstraße 13, 10115, Berlin, Germany
- Einstein Center for Neurosciences Berlin, Charitéplatz 1, 10117, Berlin, Germany
| | - Daniela Vallentin
- Max Planck Institute for Ornithology, Eberhard-Gwinner Straße, 82319, Seewiesen, Germany
- Max Planck Institute for Biological Intelligence (in foundation), Eberhard-Gwinner Straße, 82319, Seewiesen, Germany
| | - Jens Kremkow
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany.
- Bernstein Center for Computational Neuroscience Berlin, Philippstraße 13, 10115, Berlin, Germany.
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Philippstraße 13, 10115, Berlin, Germany.
- Einstein Center for Neurosciences Berlin, Charitéplatz 1, 10117, Berlin, Germany.
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7
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Abstract
Retinal circuits transform the pixel representation of photoreceptors into the feature representations of ganglion cells, whose axons transmit these representations to the brain. Functional, morphological, and transcriptomic surveys have identified more than 40 retinal ganglion cell (RGC) types in mice. RGCs extract features of varying complexity; some simply signal local differences in brightness (i.e., luminance contrast), whereas others detect specific motion trajectories. To understand the retina, we need to know how retinal circuits give rise to the diverse RGC feature representations. A catalog of the RGC feature set, in turn, is fundamental to understanding visual processing in the brain. Anterograde tracing indicates that RGCs innervate more than 50 areas in the mouse brain. Current maps connecting RGC types to brain areas are rudimentary, as is our understanding of how retinal signals are transformed downstream to guide behavior. In this article, I review the feature selectivities of mouse RGCs, how they arise, and how they are utilized downstream. Not only is knowledge of the behavioral purpose of RGC signals critical for understanding the retinal contributions to vision; it can also guide us to the most relevant areas of visual feature space. Expected final online publication date for the Annual Review of Vision Science, Volume 8 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Daniel Kerschensteiner
- John F. Hardesty, MD, Department of Ophthalmology and Visual Sciences; Department of Neuroscience; Department of Biomedical Engineering; and Hope Center for Neurological Disorders, Washington University School of Medicine, Saint Louis, Missouri, USA;
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8
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Topographic map formation and the effects of NMDA receptor blockade in the developing visual system. Proc Natl Acad Sci U S A 2022; 119:2107899119. [PMID: 35193956 PMCID: PMC8872792 DOI: 10.1073/pnas.2107899119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/13/2022] [Indexed: 11/18/2022] Open
Abstract
Studying the emergence of topographic organization in sensory maps has been constrained by spatial limitations of traditional anatomical and physiological techniques early in development in many animal models. Here, we have applied a high-resolution, noninvasive, in vivo calcium imaging approach to study the nascent retinotopic map in the larval Xenopus laevis retinotectal system. We performed longitudinal functional imaging of the three-dimensional organization of emerging retinotopic maps and assessed the effects of N-methyl-D-aspartate (NMDA) receptor blockade on map formation. Our results provide insights into early retinotopic map emergence and the role of NMDA receptors in the refinement of topographic gradients. The development of functional topography in the developing brain follows a progression from initially coarse to more precisely organized maps. To examine the emergence of topographically organized maps in the retinotectal system, we performed longitudinal visual receptive field mapping by calcium imaging in the optic tectum of GCaMP6-expressing transgenic Xenopus laevis tadpoles. At stage 42, just 1 d after retinal axons arrived in the optic tectum, a clear retinotopic azimuth map was evident. Animals were imaged over the following week at stages 45 and 48, over which time the tectal neuropil nearly doubled in length and exhibited more precise retinotopic organization. By microinjecting GCaMP6s messenger ribonucleic acid (mRNA) into one blastomere of two-cell stage embryos, we acquired bilateral mosaic tadpoles with GCaMP6s expression in postsynaptic tectal neurons on one side of the animal and in retinal ganglion cell axons crossing to the tectum on the opposite side. Longitudinal observation of retinotopic map emergence revealed the presence of orderly representations of azimuth and elevation as early as stage 42, although presynaptic inputs exhibited relatively less topographic organization than the postsynaptic component for the azimuth axis. Retinotopic gradients in the tectum became smoother between stages 42 and 45. Blocking N-methyl-D-aspartate (NMDA) receptor conductance by rearing tadpoles in MK-801 did not prevent the emergence of retinotopic maps, but it produced more discontinuous topographic gradients and altered receptive field characteristics. These results provide evidence that current through NMDA receptors is dispensable for coarse topographic ordering of retinotectal inputs but does contribute to the fine-scale organization of the retinotectal projection.
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9
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Ichinose T, Habib S. ON and OFF Signaling Pathways in the Retina and the Visual System. FRONTIERS IN OPHTHALMOLOGY 2022; 2:989002. [PMID: 36926308 PMCID: PMC10016624 DOI: 10.3389/fopht.2022.989002] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Visual processing starts at the retina of the eye, and signals are then transferred primarily to the visual cortex and the tectum. In the retina, multiple neural networks encode different aspects of visual input, such as color and motion. Subsequently, multiple neural streams in parallel convey unique aspects of visual information to cortical and subcortical regions. Bipolar cells, which are the second order neurons of the retina, separate visual signals evoked by light and dark contrasts and encode them to ON and OFF pathways, respectively. The interplay between ON and OFF neural signals is the foundation for visual processing for object contrast which underlies higher order stimulus processing. ON and OFF pathways have been classically thought to signal in a mirror-symmetric manner. However, while these two pathways contribute synergistically to visual perception in some instances, they have pronounced asymmetries suggesting independent operation in other cases. In this review, we summarize the role of the ON-OFF dichotomy in visual signaling, aiming to contribute to the understanding of visual recognition.
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Affiliation(s)
- Tomomi Ichinose
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, USA
- Correspondence: Tomomi Ichinose, MD, PhD,
| | - Samar Habib
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, USA
- Department of Medical Parasitology, Mansoura Faculty of Medicine, Mansoura University, Mansoura, Egypt
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10
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Johnson KO, Smith NA, Goldstein EZ, Gallo V, Triplett JW. NMDA Receptor Expression by Retinal Ganglion Cells Is Not Required for Retinofugal Map Formation nor Eye-Specific Segregation in the Mouse. eNeuro 2021; 8:ENEURO.0115-20.2021. [PMID: 34193509 PMCID: PMC8287875 DOI: 10.1523/eneuro.0115-20.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 05/19/2021] [Accepted: 05/21/2021] [Indexed: 12/01/2022] Open
Abstract
Retinal ganglion cells (RGCs) project topographically to the superior colliculus (SC) and dorsal lateral geniculate nucleus (dLGN). Spontaneous activity plays a critical role in retinotopic mapping in both regions; however, the molecular mechanisms underlying activity-dependent refinement remain unclear. Previous pharmacologic studies implicate NMDA receptors (NMDARs) in the establishment of retinotopy. In other brain regions, NMDARs are expressed on both the presynaptic and postsynaptic side of the synapse, and recent work suggests that presynaptic and postsynaptic NMDARs play distinct roles in retinotectal developmental dynamics. To directly test the role of NMDARs expressed by RGCs in retinofugal map formation, we took a conditional genetic knock-out approach to delete the obligate GluN1 subunit of NMDARs in RGCs. Here, we demonstrate reduced GluN1 expression in the retina of Chrnb3-Cre;GluN1flox/flox (pre-cKO) mice without altered expression in the SC. Anatomical tracing experiments revealed no significant changes in termination zone size in the SC and dLGN of pre-cKO mice, suggesting NMDAR function in RGCs is not an absolute requirement for topographic refinement. Further, we observed no change in the eye-specific organization of retinal inputs to the SC nor dLGN. To verify that NMDA induces activity in RGC terminals, we restricted GCaMP5 expression to RGCs and confirmed induction of calcium transients in RGC terminals. Together, these findings demonstrate that NMDARs expressed by RGCs are not required for retinofugal topographic map formation nor eye-specific segregation in the mouse.
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Affiliation(s)
- Kristy O Johnson
- Center for Neuroscience Research, Children's National Research Institute, Washington, DC 20010
- Institute for Biomedical Sciences, The George Washington University School of Medicine and Health Sciences, Washington, DC 20052
| | - Nathan A Smith
- Center for Neuroscience Research, Children's National Research Institute, Washington, DC 20010
- Department of Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, DC 20052
- Department of Pharmacology and Physiology, The George Washington University School of Medicine and Health Sciences, Washington, DC 20052
| | - Evan Z Goldstein
- Center for Neuroscience Research, Children's National Research Institute, Washington, DC 20010
| | - Vittorio Gallo
- Center for Neuroscience Research, Children's National Research Institute, Washington, DC 20010
- Institute for Biomedical Sciences, The George Washington University School of Medicine and Health Sciences, Washington, DC 20052
- Department of Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, DC 20052
- Department of Pharmacology and Physiology, The George Washington University School of Medicine and Health Sciences, Washington, DC 20052
| | - Jason W Triplett
- Center for Neuroscience Research, Children's National Research Institute, Washington, DC 20010
- Institute for Biomedical Sciences, The George Washington University School of Medicine and Health Sciences, Washington, DC 20052
- Department of Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, DC 20052
- Department of Pharmacology and Physiology, The George Washington University School of Medicine and Health Sciences, Washington, DC 20052
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11
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Differential Distribution of Ca 2+ Channel Subtypes at Retinofugal Synapses. eNeuro 2020; 7:ENEURO.0293-20.2020. [PMID: 33097488 PMCID: PMC7768275 DOI: 10.1523/eneuro.0293-20.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 10/06/2020] [Accepted: 10/20/2020] [Indexed: 02/06/2023] Open
Abstract
Retinofugal synapses serve as models for understanding how sensory signals from the periphery are relayed to the brain. Past studies have focused primarily on understanding the postsynaptic glutamatergic receptor subtypes involved in signal transmission, but the mechanisms underlying glutamate release at presynaptic retinal terminals remains largely unknown. Here we explored how different calcium (Ca2+) channel subtypes regulate glutamatergic excitatory synaptic transmission in two principal retinorecipient targets, the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SC) of the mouse. We used an in vitro slice preparation to record the synaptic responses of dLGN and SC neurons evoked by the electrical stimulation of optic tract (OT) fibers before and during the application of selective Ca2+ channel blockers. We found that synaptic responses to paired or repetitive OT stimulation were highly sensitive to extracellular levels of Ca2+ and to selective antagonists of voltage gated Ca2+ channels, indicating that these channels regulate the presynaptic release of glutamate at retinal synapses in both dLGN and SC. Bath application of selective Ca2+ channel blockers revealed that P/Q-type Ca2+ channels primarily operate to regulate glutamate release at retinal synapses in dLGN, while N-type Ca2+ channels dominate release in the SC.
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12
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Al-Chami A, Ross A, Hayley S, Sun H. Early life stress facilitates synapse premature unsilencing to enhance AMPA receptor function in the developing hippocampus. J Neurophysiol 2020; 124:815-821. [PMID: 32783592 DOI: 10.1152/jn.00339.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chronic early life stress (ELS) increases vulnerability to psychopathologies and cognitive deficits in adulthood by disrupting the function of related neural circuits. However, whether this disruption emerges early in the developing brain remains largely unexplored. In the current study, using an established limited-bedding and nesting model of ELS in postnatal day (P)2-10 mice, we provide direct evidence that ELS caused early modification of hippocampal glutamatergic synapses in the developing brain. We demonstrated that ELS induced rapid enhancement of AMPA receptor function in hippocampal CA1 pyramidal neurons through a postsynaptic mechanism, and importantly, this was associated with premature unsilencing of NMDA receptor-only silent hippocampal synapses. These results suggest that potentiation of AMPAR function may represent an early mediator of ELS-induced alterations of neural networks in the developing brain and may potentially contribute to subsequent cognitive impairments later in life.NEW & NOTEWORTHY Early life stress (ELS) is known to increase the risk of later life cognitive deficits by disrupting neural circuit function. However, whether this disruption emerges early in the developing brain remains largely unexplored. The current study presents direct evidence that ELS prematurely unsilences hippocampal synapses to enhance AMPA receptor functions in a limited-bedding and nesting model, revealing an early mediator of ELS-induced neural circuit reorganizations.
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Affiliation(s)
- Aycheh Al-Chami
- Department of Neuroscience, Carleton University, Ottawa, Ontario, Canada
| | - Alysia Ross
- Department of Neuroscience, Carleton University, Ottawa, Ontario, Canada
| | - Shawn Hayley
- Department of Neuroscience, Carleton University, Ottawa, Ontario, Canada
| | - Hongyu Sun
- Department of Neuroscience, Carleton University, Ottawa, Ontario, Canada
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13
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López DE, Ballaz SJ. The Role of Brain Cyclooxygenase-2 (Cox-2) Beyond Neuroinflammation: Neuronal Homeostasis in Memory and Anxiety. Mol Neurobiol 2020; 57:5167-5176. [PMID: 32860157 DOI: 10.1007/s12035-020-02087-x] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 08/24/2020] [Indexed: 12/13/2022]
Abstract
Cyclooxygenases are a group of heme-containing isozymes (namely Cox-1 and Cox-2) that catalyze the conversion of arachidonic acid to largely bioactive prostaglandins (PGs). Cox-1 is the ubiquitous housekeeping enzyme, and the mitogen-inducible Cox-2 is activated to cause inflammation. Interestingly, Cox-2 is constitutively expressed in the brain at the postsynaptic dendrites and excitatory terminals of the cortical and spinal cord neurons. Neuronal Cox-2 is activated in response to synaptic excitation to yield PGE2, the predominant Cox-2 metabolite in the brain, which in turn stimulates the release of glutamate and neuronal firing in a retrograde fashion. Cox-2 is also engaged in the metabolism of new endocannabinoids from 2-arachidonoyl-glycerol to modulate their actions at presynaptic terminals. In addition to these interactions, the induction of neuronal Cox-2 is coupled to the trans-synaptic activation of the dopaminergic mesolimbic system and some serotoninergic receptors, which might contribute to the development of emotional behavior. Although much of the focus regarding the induction of Cox-2 in the brain has been centered on neuroinflammation-related neurodegenerative and psychiatric disorders, some evidence also suggests that Cox-2 release during neuronal signaling may be pivotal for the fine tuning of cortical networks to regulate behavior. This review compiles the evidence supporting the homeostatic role of neuronal Cox-2 in synaptic transmission and plasticity, since neuroinflammation is originally triggered by the induction of glial Cox-2 expression. The goal is to provide perspective on the roles of Cox-2 beyond neuroinflammation, such as those played in memory and anxiety, and whose evidence is still scant.
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Affiliation(s)
- Diana E López
- Biomedical Sciences Graduate Program, Yachay Tech University, Urcuquí, Ecuador
| | - Santiago J Ballaz
- School of Biological Sciences and Engineering, Yachay Tech University, Hacienda San José s/n, San Miguel de Urcuquí, Ecuador.
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14
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Rasmussen R, Yonehara K. Contributions of Retinal Direction Selectivity to Central Visual Processing. Curr Biol 2020; 30:R897-R903. [DOI: 10.1016/j.cub.2020.06.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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15
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Reinhard K, Li C, Do Q, Burke EG, Heynderickx S, Farrow K. A projection specific logic to sampling visual inputs in mouse superior colliculus. eLife 2019; 8:e50697. [PMID: 31750831 PMCID: PMC6872211 DOI: 10.7554/elife.50697] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 11/02/2019] [Indexed: 02/07/2023] Open
Abstract
Using sensory information to trigger different behaviors relies on circuits that pass through brain regions. The rules by which parallel inputs are routed to downstream targets are poorly understood. The superior colliculus mediates a set of innate behaviors, receiving input from >30 retinal ganglion cell types and projecting to behaviorally important targets including the pulvinar and parabigeminal nucleus. Combining transsynaptic circuit tracing with in vivo and ex vivo electrophysiological recordings, we observed a projection-specific logic where each collicular output pathway sampled a distinct set of retinal inputs. Neurons projecting to the pulvinar or the parabigeminal nucleus showed strongly biased sampling from four cell types each, while six others innervated both pathways. The visual response properties of retinal ganglion cells correlated well with those of their disynaptic targets. These findings open the possibility that projection-specific sampling of retinal inputs forms a basis for the selective triggering of behaviors by the superior colliculus.
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Affiliation(s)
- Katja Reinhard
- Neuro-Electronics Research FlandersLeuvenBelgium
- VIBLeuvenBelgium
- Department of BiologyKU LeuvenLeuvenBelgium
| | - Chen Li
- Neuro-Electronics Research FlandersLeuvenBelgium
- VIBLeuvenBelgium
- Department of BiologyKU LeuvenLeuvenBelgium
| | - Quan Do
- Neuro-Electronics Research FlandersLeuvenBelgium
- Northeastern UniversityBostonUnited States
| | - Emily G Burke
- Neuro-Electronics Research FlandersLeuvenBelgium
- Northeastern UniversityBostonUnited States
| | | | - Karl Farrow
- Neuro-Electronics Research FlandersLeuvenBelgium
- VIBLeuvenBelgium
- Department of BiologyKU LeuvenLeuvenBelgium
- IMECLeuvenBelgium
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16
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Sun H, Takesian AE, Wang TT, Lippman-Bell JJ, Hensch TK, Jensen FE. Early Seizures Prematurely Unsilence Auditory Synapses to Disrupt Thalamocortical Critical Period Plasticity. Cell Rep 2019; 23:2533-2540. [PMID: 29847785 PMCID: PMC6446922 DOI: 10.1016/j.celrep.2018.04.108] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 01/02/2018] [Accepted: 04/25/2018] [Indexed: 12/31/2022] Open
Abstract
Heightened neural excitability in infancy and childhood results in increased susceptibility to seizures. Such early-life seizures are associated with language deficits and autism that can result from aberrant development of the auditory cortex. Here, we show that early-life seizures disrupt a critical period (CP) for tonotopic map plasticity in primary auditory cortex (A1). We show that this CP is characterized by a prevalence of “silent,” NMDA-receptor (NMDAR)-only, glutamate receptor synapses in auditory cortex that become “unsilenced” due to activity-dependent AMPA receptor (AMPAR) insertion. Induction of seizures prior to this CP occludes tonotopic map plasticity by prematurely unsilencing NMDAR-only synapses. Further, brief treatment with the AMPAR antagonist NBQX following seizures, prior to the CP, prevents synapse unsilencing and permits subsequent A1 plasticity. These findings reveal that early-life seizures modify CP regulators and suggest that therapeutic targets for early post-seizure treatment can rescue CP plasticity.
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Affiliation(s)
- Hongyu Sun
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Neuroscience, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Anne E Takesian
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Ave., Boston, MA 02115, USA
| | - Ting Ting Wang
- Department of Neuroscience, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Jocelyn J Lippman-Bell
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Takao K Hensch
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Ave., Boston, MA 02115, USA; Center for Brain Science, Department of Molecular & Cellular Biology, Harvard University, 52 Oxford St., Cambridge, MA 02138, USA.
| | - Frances E Jensen
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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17
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Ito S, Feldheim DA. The Mouse Superior Colliculus: An Emerging Model for Studying Circuit Formation and Function. Front Neural Circuits 2018; 12:10. [PMID: 29487505 PMCID: PMC5816945 DOI: 10.3389/fncir.2018.00010] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 01/22/2018] [Indexed: 11/30/2022] Open
Abstract
The superior colliculus (SC) is a midbrain area where visual, auditory and somatosensory information are integrated to initiate motor commands. The SC plays a central role in visual information processing in the mouse; it receives projections from 85% to 90% of the retinal ganglion cells (RGCs). While the mouse SC has been a long-standing model used to study retinotopic map formation, a number of technological advances in mouse molecular genetic techniques, large-scale physiological recordings and SC-dependent visual behavioral assays have made the mouse an even more ideal model to understand the relationship between circuitry and behavior.
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Affiliation(s)
- Shinya Ito
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - David A Feldheim
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA, United States
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18
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Seabrook TA, Burbridge TJ, Crair MC, Huberman AD. Architecture, Function, and Assembly of the Mouse Visual System. Annu Rev Neurosci 2018; 40:499-538. [PMID: 28772103 DOI: 10.1146/annurev-neuro-071714-033842] [Citation(s) in RCA: 165] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Vision is the sense humans rely on most to navigate the world, make decisions, and perform complex tasks. Understanding how humans see thus represents one of the most fundamental and important goals of neuroscience. The use of the mouse as a model for parsing how vision works at a fundamental level started approximately a decade ago, ushered in by the mouse's convenient size, relatively low cost, and, above all, amenability to genetic perturbations. In the course of that effort, a large cadre of new and powerful tools for in vivo labeling, monitoring, and manipulation of neurons were applied to this species. As a consequence, a significant body of work now exists on the architecture, function, and development of mouse central visual pathways. Excitingly, much of that work includes causal testing of the role of specific cell types and circuits in visual perception and behavior-something rare to find in studies of the visual system of other species. Indeed, one could argue that more information is now available about the mouse visual system than any other sensory system, in any species, including humans. As such, the mouse visual system has become a platform for multilevel analysis of the mammalian central nervous system generally. Here we review the mouse visual system structure, function, and development literature and comment on the similarities and differences between the visual system of this and other model species. We also make it a point to highlight the aspects of mouse visual circuitry that remain opaque and that are in need of additional experimentation to enrich our understanding of how vision works on a broad scale.
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Affiliation(s)
- Tania A Seabrook
- Department of Neurobiology, Stanford University School of Medicine, Stanford, California 94305
| | - Timothy J Burbridge
- Department of Neuroscience, Yale University School of Medicine, New Haven, Connecticut 06520;
| | - Michael C Crair
- Department of Neuroscience, Yale University School of Medicine, New Haven, Connecticut 06520;
| | - Andrew D Huberman
- Department of Neurobiology, Stanford University School of Medicine, Stanford, California 94305.,Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, California 94303; .,Bio-X, Stanford University, Stanford, California 94305
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19
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Corticothalamic Axons Are Essential for Retinal Ganglion Cell Axon Targeting to the Mouse Dorsal Lateral Geniculate Nucleus. J Neurosci 2017; 36:5252-63. [PMID: 27170123 DOI: 10.1523/jneurosci.4599-15.2016] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 03/25/2016] [Indexed: 01/21/2023] Open
Abstract
UNLABELLED Retinal ganglion cells (RGCs) relay information about the outside world to multiple subcortical targets within the brain. This information is either used to dictate reflexive behaviors or relayed to the visual cortex for further processing. Many subcortical visual nuclei also receive descending inputs from projection neurons in the visual cortex. Most areas receive inputs from layer 5 cortical neurons in the visual cortex but one exception is the dorsal lateral geniculate nucleus (dLGN), which receives layer 6 inputs and is also the only RGC target that sends direct projections to the cortex. Here we ask how visual system development and function changes in mice that develop without a cortex. We find that the development of a cortex is essential for RGC axons to terminate in the dLGN, but is not required for targeting RGC axons to other subcortical nuclei. RGC axons also fail to target to the dLGN in mice that specifically lack cortical layer 6 projections to the dLGN. Finally, we show that when mice develop without a cortex they can still perform a number of vision-dependent tasks. SIGNIFICANCE STATEMENT The dorsal lateral geniculate nucleus (dLGN) is a sensory thalamic relay area that receives feedforward inputs from retinal ganglion cells (RGCs) in the retina, and feed back inputs from layer 6 neurons in the visual cortex. In this study we examined genetically manipulated mice that develop without a cortex or without cortical layer 6 axonal projections, and find that RGC axons fail to project to the dLGN. Other RGC recipient areas, such as the superior colliculus and suprachiasmatic nucleus, are targeted normally. These results provide support for a new mechanism of target selection that may be specific to the thalamus, whereby descending cortical axons provide an activity that promotes feedforward targeting of RGC axons to the dLGN.
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20
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Shi X, Barchini J, Ledesma HA, Koren D, Jin Y, Liu X, Wei W, Cang J. Retinal origin of direction selectivity in the superior colliculus. Nat Neurosci 2017; 20:550-558. [PMID: 28192394 PMCID: PMC5374021 DOI: 10.1038/nn.4498] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 01/11/2017] [Indexed: 12/12/2022]
Abstract
Detecting visual features in the environment such as motion direction is crucial for survival. The circuit mechanisms that give rise to direction selectivity in a major visual center, the superior colliculus (SC), are entirely unknown. Here, we optogenetically isolate the retinal inputs that individual direction-selective SC neurons receive and find that they are already selective as a result of precisely converging inputs from similarly-tuned retinal ganglion cells. The direction selective retinal input is linearly amplified by the intracollicular circuits without changing its preferred direction or level of selectivity. Finally, using 2-photon calcium imaging, we show that SC direction selectivity is dramatically reduced in transgenic mice that have decreased retinal selectivity. Together, our studies demonstrate a retinal origin of direction selectivity in the SC, and reveal a central visual deficit as a consequence of altered feature selectivity in the retina.
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Affiliation(s)
- Xuefeng Shi
- Department of Neurobiology, Northwestern University, Evanston, Illinois, USA.,Tianjin Eye Hospital, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Institute, Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
| | - Jad Barchini
- Department of Neurobiology, Northwestern University, Evanston, Illinois, USA.,Interdepartmental Neuroscience Program, Northwestern University, Evanston, Illinois, USA
| | | | - David Koren
- Department of Neurobiology, The University of Chicago, Chicago, Illinois, USA
| | - Yanjiao Jin
- Department of Neurobiology, Northwestern University, Evanston, Illinois, USA.,General Hospital, Tianjin Medical University, Tianjin, China
| | - Xiaorong Liu
- Department of Neurobiology, Northwestern University, Evanston, Illinois, USA.,Department of Ophthalmology, Northwestern University, Chicago, Illinois, USA
| | - Wei Wei
- Department of Neurobiology, The University of Chicago, Chicago, Illinois, USA
| | - Jianhua Cang
- Department of Neurobiology, Northwestern University, Evanston, Illinois, USA
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21
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Fernandes D, Carvalho AL. Mechanisms of homeostatic plasticity in the excitatory synapse. J Neurochem 2016; 139:973-996. [PMID: 27241695 DOI: 10.1111/jnc.13687] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 05/25/2016] [Accepted: 05/27/2016] [Indexed: 11/30/2022]
Abstract
Brain development, sensory information processing, and learning and memory processes depend on Hebbian forms of synaptic plasticity, and on the remodeling and pruning of synaptic connections. Neurons in networks implicated in these processes carry out their functions while facing constant perturbation; homeostatic responses are therefore required to maintain neuronal activity within functional ranges for proper brain function. Here, we will review in vitro and in vivo studies demonstrating that several mechanisms underlie homeostatic plasticity of excitatory synapses, and identifying participant molecular players. Emerging evidence suggests a link between disrupted homeostatic synaptic plasticity and neuropsychiatric and neurologic disorders. Hebbian forms of synaptic plasticity, such as long-term potentiation (LTP), induce long-lasting changes in synaptic strength, which can be destabilizing and drive activity to saturation. Conversely, homeostatic plasticity operates to compensate for prolonged activity changes, stabilizing neuronal firing within a dynamic physiological range. We review mechanisms underlying homeostatic plasticity, and address how neurons integrate distinct forms of plasticity for proper brain function. This article is part of a mini review series: "Synaptic Function and Dysfunction in Brain Diseases".
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Affiliation(s)
- Dominique Fernandes
- CNC-Centre for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,PDBEB-Doctoral Program in Experimental Biology and Biomedicine, Interdisciplinary Research Institute (III-UC), University of Coimbra, Coimbra, Portugal
| | - Ana Luísa Carvalho
- CNC-Centre for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Department of Life Sciences, University of Coimbra, Coimbra, Portugal
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22
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Shanks JA, Ito S, Schaevitz L, Yamada J, Chen B, Litke A, Feldheim DA. Corticothalamic Axons Are Essential for Retinal Ganglion Cell Axon Targeting to the Mouse Dorsal Lateral Geniculate Nucleus. J Neurosci 2016. [PMID: 27170123 DOI: 10.6080/k07d2s2f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/26/2023] Open
Abstract
UNLABELLED Retinal ganglion cells (RGCs) relay information about the outside world to multiple subcortical targets within the brain. This information is either used to dictate reflexive behaviors or relayed to the visual cortex for further processing. Many subcortical visual nuclei also receive descending inputs from projection neurons in the visual cortex. Most areas receive inputs from layer 5 cortical neurons in the visual cortex but one exception is the dorsal lateral geniculate nucleus (dLGN), which receives layer 6 inputs and is also the only RGC target that sends direct projections to the cortex. Here we ask how visual system development and function changes in mice that develop without a cortex. We find that the development of a cortex is essential for RGC axons to terminate in the dLGN, but is not required for targeting RGC axons to other subcortical nuclei. RGC axons also fail to target to the dLGN in mice that specifically lack cortical layer 6 projections to the dLGN. Finally, we show that when mice develop without a cortex they can still perform a number of vision-dependent tasks. SIGNIFICANCE STATEMENT The dorsal lateral geniculate nucleus (dLGN) is a sensory thalamic relay area that receives feedforward inputs from retinal ganglion cells (RGCs) in the retina, and feed back inputs from layer 6 neurons in the visual cortex. In this study we examined genetically manipulated mice that develop without a cortex or without cortical layer 6 axonal projections, and find that RGC axons fail to project to the dLGN. Other RGC recipient areas, such as the superior colliculus and suprachiasmatic nucleus, are targeted normally. These results provide support for a new mechanism of target selection that may be specific to the thalamus, whereby descending cortical axons provide an activity that promotes feedforward targeting of RGC axons to the dLGN.
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Affiliation(s)
- James A Shanks
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Shinya Ito
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, Santa Cruz, California 95064, and
| | - Laura Schaevitz
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064, Department of Biology, Trinity College, Hartford, Connecticut 06106
| | - Jena Yamada
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Bin Chen
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Alan Litke
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, Santa Cruz, California 95064, and
| | - David A Feldheim
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064,
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23
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Neurons in the most superficial lamina of the mouse superior colliculus are highly selective for stimulus direction. J Neurosci 2015; 35:7992-8003. [PMID: 25995482 DOI: 10.1523/jneurosci.0173-15.2015] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The superior colliculus (SC) is a layered midbrain structure important for multimodal integration and sensorimotor transformation. Its superficial layers are purely visual and receive depth-specific projections from distinct subtypes of retinal ganglion cells. Here we use two-photon calcium imaging to characterize the response properties of neurons in the most superficial lamina of the mouse SC, an undersampled population with electrophysiology. We find that these neurons have compact receptive fields with primarily overlapping ON and OFF subregions and are highly direction selective. The high selectivity is observed in both excitatory and inhibitory neurons. These neurons do not cluster according to their direction preference and lack orientation selectivity. In addition, we perform single-unit recordings and show that direction selectivity declines with depth in the SC. Together, our experiments reveal for the first time a highly specialized lamina in the most superficial SC for movement direction, a finding that has important implications for understanding signal transformation in the early visual system.
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24
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Rosa Salva O, Mayer U, Vallortigara G. Roots of a social brain: Developmental models of emerging animacy-detection mechanisms. Neurosci Biobehav Rev 2015; 50:150-68. [DOI: 10.1016/j.neubiorev.2014.12.015] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Revised: 12/16/2014] [Accepted: 12/18/2014] [Indexed: 10/24/2022]
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25
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Chen H, Zhao Y, Liu M, Feng L, Puyang Z, Yi J, Liang P, Zhang HF, Cang J, Troy JB, Liu X. Progressive degeneration of retinal and superior collicular functions in mice with sustained ocular hypertension. Invest Ophthalmol Vis Sci 2015; 56:1971-84. [PMID: 25722210 DOI: 10.1167/iovs.14-15691] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
PURPOSE We investigated the progressive degeneration of retinal and superior collicular functions in a mouse model of sustained ocular hypertension. METHODS Focal laser illumination and injection of polystyrene microbeads were used to induce chronic ocular hypertension. Retinal ganglion cell (RGC) loss was characterized by in vivo optical coherence tomography (OCT) and immunohistochemistry. Retinal dysfunction was also monitored by the full-field ERG. Retinal ganglion cell light responses were recorded using a 256-channel multielectrode array (MEA), and RGC subtypes were characterized by noncentered spike-triggered covariance (STC-NC) analysis. Single-unit extracellular recordings from superficial layers of the superior colliculus (SC) were performed to examine the receptive field (RF) properties of SC neurons. RESULTS The elevation of intraocular pressure (IOP) lasted 4 months in mice treated with a combination of laser photocoagulation and microbead injection. Progressive RGC loss and functional degeneration were confirmed in ocular hypertensive (OHT) mice. These mice had fewer visually responsive RGCs than controls. Using the STC-NC analysis, we classified RGCs into ON, OFF, and ON-OFF functional subtypes. We showed that ON and OFF RGCs were more susceptible to the IOP elevation than ON-OFF RGCs. Furthermore, SC neurons of OHT mice had weakened responses to visual stimulation and exhibited mismatched ON and OFF subfields and irregular RF structure. CONCLUSIONS We demonstrated that the functional degeneration of RGCs is subtype-dependent and that the ON and OFF pathways from the retina to the SC were disrupted. Our study provides a foundation to investigate the mechanisms underlying the progressive vision loss in experimental glaucoma.
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Affiliation(s)
- Hui Chen
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
| | - Yan Zhao
- Department of Biomedical Engineering, Robert R. McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois, United States
| | - Mingna Liu
- Department of Neurobiology, Weinberg College of Arts and Sciences, Northwestern University, Evanston, Illinois, United States
| | - Liang Feng
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
| | - Zhen Puyang
- Department of Biomedical Engineering, Robert R. McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois, United States School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Ji Yi
- Department of Biomedical Engineering, Robert R. McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois, United States
| | - Peiji Liang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Hao F Zhang
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States Department of Biomedical Engineering, Robert R. McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois, United States
| | - Jianhua Cang
- Department of Neurobiology, Weinberg College of Arts and Sciences, Northwestern University, Evanston, Illinois, United States
| | - John B Troy
- Department of Biomedical Engineering, Robert R. McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois, United States
| | - Xiaorong Liu
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States Department of Neurobiology, Weinberg College of Arts and Sciences, Northwestern University, Evanston, Illinois, United States
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26
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Lansdell B, Ford K, Kutz JN. A reaction-diffusion model of cholinergic retinal waves. PLoS Comput Biol 2014; 10:e1003953. [PMID: 25474327 PMCID: PMC4256014 DOI: 10.1371/journal.pcbi.1003953] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 10/01/2014] [Indexed: 01/21/2023] Open
Abstract
Prior to receiving visual stimuli, spontaneous, correlated activity in the retina, called retinal waves, drives activity-dependent developmental programs. Early-stage waves mediated by acetylcholine (ACh) manifest as slow, spreading bursts of action potentials. They are believed to be initiated by the spontaneous firing of Starburst Amacrine Cells (SACs), whose dense, recurrent connectivity then propagates this activity laterally. Their inter-wave interval and shifting wave boundaries are the result of the slow after-hyperpolarization of the SACs creating an evolving mosaic of recruitable and refractory cells, which can and cannot participate in waves, respectively. Recent evidence suggests that cholinergic waves may be modulated by the extracellular concentration of ACh. Here, we construct a simplified, biophysically consistent, reaction-diffusion model of cholinergic retinal waves capable of recapitulating wave dynamics observed in mice retina recordings. The dense, recurrent connectivity of SACs is modeled through local, excitatory coupling occurring via the volume release and diffusion of ACh. In addition to simulation, we are thus able to use non-linear wave theory to connect wave features to underlying physiological parameters, making the model useful in determining appropriate pharmacological manipulations to experimentally produce waves of a prescribed spatiotemporal character. The model is used to determine how ACh mediated connectivity may modulate wave activity, and how parameters such as the spontaneous activation rate and sAHP refractory period contribute to critical wave size variability.
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Affiliation(s)
- Benjamin Lansdell
- Department of Applied Mathematics, University of Washington, Seattle, Washington, United States of America
| | - Kevin Ford
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
| | - J. Nathan Kutz
- Department of Applied Mathematics, University of Washington, Seattle, Washington, United States of America
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27
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Speer CM, Sun C, Liets LC, Stafford BK, Chapman B, Cheng HJ. Eye-specific retinogeniculate segregation proceeds normally following disruption of patterned spontaneous retinal activity. Neural Dev 2014; 9:25. [PMID: 25377639 PMCID: PMC4289266 DOI: 10.1186/1749-8104-9-25] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 10/20/2014] [Indexed: 11/10/2022] Open
Abstract
Background Spontaneous retinal activity (SRA) is important during eye-specific segregation within the dorsal lateral geniculate nucleus (dLGN), but the feature(s) of activity critical for retinogeniculate refinement are controversial. Pharmacologically or genetically manipulating cholinergic signaling during SRA perturbs correlated retinal ganglion cell (RGC) spiking and disrupts eye-specific retinofugal refinement in vivo, consistent with an instructive role for SRA during visual system development. Paradoxically, ablating the starburst amacrine cells (SACs) that generate cholinergic spontaneous activity disrupts correlated RGC firing without impacting retinal activity levels or eye-specific segregation in the dLGN. Such experiments suggest that patterned SRA during retinal waves is not critical for eye-specific refinement and instead, normal activity levels are permissive for retinogeniculate development. Here we revisit the effects of ablating the cholinergic network during eye-specific segregation and show that SAC ablation disrupts, but does not eliminate, retinal waves with no concomitant impact on normal eye-specific segregation in the dLGN. Results We induced SAC ablation in postnatal ferret pups beginning at birth by intraocular injection of a novel immunotoxin selective for the ferret vesicular acetylcholine transporter (Ferret VAChT-Sap). Through dual-patch whole-cell and multi-electrode array recording we found that SAC ablation altered SRA patterns and led to significantly smaller retinal waves compared with controls. Despite these defects, eye-specific segregation was normal. Further, interocular competition for target territory in the dLGN proceeded in cases where SAC ablation was asymmetric in the two eyes. Conclusions Our data demonstrate normal eye-specific retinogeniculate development despite significant abnormalities in patterned SRA. Comparing our current results with earlier studies suggests that defects in retinal wave size, absolute levels of SRA, correlations between RGC pairs, RGC burst frequency, high frequency RGC firing during bursts, and the number of spikes per RGC burst are each uncorrelated with abnormalities in eye-specific segregation in the dLGN. An increase in the fraction of asynchronous spikes occurring outside of bursts and waves correlates with eye-specific segregation defects in studies reported to date. These findings highlight the relative importance of different features of SRA while providing additional constraints for computational models of Hebbian plasticity mechanisms in the developing visual system. Electronic supplementary material The online version of this article (doi:10.1186/1749-8104-9-25) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | - Hwai-Jong Cheng
- Center for Neuroscience, University of California, Davis, 1544 Newton Court, Davis, CA 95618, USA.
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Louros SR, Hooks BM, Litvina L, Carvalho AL, Chen C. A role for stargazin in experience-dependent plasticity. Cell Rep 2014; 7:1614-1625. [PMID: 24882000 DOI: 10.1016/j.celrep.2014.04.054] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 01/19/2014] [Accepted: 04/24/2014] [Indexed: 01/08/2023] Open
Abstract
During development, neurons are constantly refining their connections in response to changes in activity. Experience-dependent plasticity is a key form of synaptic plasticity, involving changes in α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) accumulation at synapses. Here, we report a critical role for the AMPAR auxiliary subunit stargazin in this plasticity. We show that stargazin is functional at the retinogeniculate synapse and that in the absence of stargazin, the refinement of the retinogeniculate synapse is specifically disrupted during the experience-dependent phase. Importantly, we found that stargazin expression and phosphorylation increased with visual deprivation and led to reduced AMPAR rectification at the retinogeniculate synapse. To test whether stargazin plays a role in homeostatic plasticity, we turned to cultured neurons and found that stargazin phosphorylation is essential for synaptic scaling. Overall, our data reveal an important role for stargazin in regulating AMPAR abundance and composition at glutamatergic synapses during homeostatic and experience-dependent plasticity.
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Affiliation(s)
- Susana R Louros
- PhD Program in Experimental Biology and Biomedicine, Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; F.M. Kirby Neurobiology Center, Children's Hospital, Boston, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Bryan M Hooks
- F.M. Kirby Neurobiology Center, Children's Hospital, Boston, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Liza Litvina
- F.M. Kirby Neurobiology Center, Children's Hospital, Boston, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Ana Luisa Carvalho
- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Department of Life Sciences, University of Coimbra, 3001-401 Coimbra, Portugal.
| | - Chinfei Chen
- F.M. Kirby Neurobiology Center, Children's Hospital, Boston, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA.
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Lin DJ, Kang E, Chen C. Changes in input strength and number are driven by distinct mechanisms at the retinogeniculate synapse. J Neurophysiol 2014; 112:942-50. [PMID: 24848465 DOI: 10.1152/jn.00175.2014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recent studies have demonstrated that vision influences the functional remodeling of the mouse retinogeniculate synapse, the connection between retinal ganglion cells and thalamic relay neurons in the dorsal lateral geniculate nucleus (LGN). Initially, each relay neuron receives a large number of weak retinal inputs. Over a 2- to 3-wk developmental window, the majority of these inputs are eliminated, and the remaining inputs are strengthened. This period of refinement is followed by a critical period when visual experience changes the strength and connectivity of the retinogeniculate synapse. Visual deprivation of mice by dark rearing from postnatal day (P)20 results in a dramatic weakening of synaptic strength and recruitment of additional inputs. In the present study we asked whether experience-dependent plasticity at the retinogeniculate synapse represents a homeostatic response to changing visual environment. We found that visual experience starting at P20 following visual deprivation from birth results in weakening of existing retinal inputs onto relay neurons without significant changes in input number, consistent with homeostatic synaptic scaling of retinal inputs. On the other hand, the recruitment of new inputs to the retinogeniculate synapse requires previous visual experience prior to the critical period. Taken together, these findings suggest that diverse forms of homeostatic plasticity drive experience-dependent remodeling at the retinogeniculate synapse.
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Affiliation(s)
- David J Lin
- Department of Neurology, F.M. Kirby Neurobiology Center, Children's Hospital, Boston, Massachusetts; and Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology, Harvard Medical School, Boston, Massachusetts
| | - Erin Kang
- Department of Neurology, F.M. Kirby Neurobiology Center, Children's Hospital, Boston, Massachusetts; and
| | - Chinfei Chen
- Department of Neurology, F.M. Kirby Neurobiology Center, Children's Hospital, Boston, Massachusetts; and
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30
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Ackman JB, Crair MC. Role of emergent neural activity in visual map development. Curr Opin Neurobiol 2013; 24:166-75. [PMID: 24492092 DOI: 10.1016/j.conb.2013.11.011] [Citation(s) in RCA: 135] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 11/12/2013] [Accepted: 11/22/2013] [Indexed: 11/24/2022]
Abstract
The initial structural and functional development of visual circuits in reptiles, birds, and mammals happens independent of sensory experience. After eye opening, visual experience further refines and elaborates circuits that are critical for normal visual function. Innate genetic programs that code for gradients of molecules provide gross positional information for developing nerve cells, yet much of the cytoarchitectural complexity and synaptogenesis of neurons depends on calcium influx, neurotransmitter release, and neural activity before the onset of vision. In fact, specific spatiotemporal patterns of neural activity, or 'retinal waves', emerge amidst the development of the earliest connections made between excitable cells in the developing eye. These patterns of spontaneous activity, which have been observed in all amniote retinae examined to date, may be an evolved adaptation for species with long gestational periods before the onset of functional vision, imparting an informational robustness and redundancy to guide development of visual maps across the nervous system. Recent experiments indicate that retinal waves play a crucial role in the development of interconnections between different parts of the visual system, suggesting that these spontaneous patterns serve as a template-matching mechanism to prepare higher-order visually associative circuits for the onset of visuomotor learning and behavior. Key questions for future studies include determining the exact sources and nature of spontaneous activity during development, characterizing the interactions between neural activity and transcriptional gene regulation, and understanding the extent of circuit connectivity governed by retinal waves within and between sensory-motor systems.
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Affiliation(s)
- James B Ackman
- Department of Neurobiology, Yale University School of Medicine, New Haven, CT 06510, United States
| | - Michael C Crair
- Department of Neurobiology, Yale University School of Medicine, New Haven, CT 06510, United States; Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, CT 06510, United States; Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT 06510, United States.
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31
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Abstract
Throughout development, the nervous system produces patterned spontaneous activity. Research over the past two decades has revealed a core group of mechanisms that mediate spontaneous activity in diverse circuits. Many circuits engage several of these mechanisms sequentially to accommodate developmental changes in connectivity. In addition to shared mechanisms, activity propagates through developing circuits and neuronal pathways (i.e., linked circuits in different brain areas) in stereotypic patterns. Increasing evidence suggests that spontaneous network activity shapes synaptic development in vivo Variations in activity-dependent plasticity may explain how similar mechanisms and patterns of activity can be employed to establish diverse circuits. Here, I will review common mechanisms and patterns of spontaneous activity in emerging neural networks and discuss recent insights into their contribution to synaptic development.
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Affiliation(s)
- Daniel Kerschensteiner
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, MO, USA Department of Anatomy and Neurobiology, Washington University School of Medicine, Saint Louis, MO, USA Hope Center for Neurological Disorders, Washington University School of Medicine, Saint Louis, MO, USA
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32
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Retinal ganglion cell maps in the brain: implications for visual processing. Curr Opin Neurobiol 2013; 24:133-42. [PMID: 24492089 DOI: 10.1016/j.conb.2013.08.006] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 08/05/2013] [Indexed: 11/23/2022]
Abstract
Everything the brain knows about the content of the visual world is built from the spiking activity of retinal ganglion cells (RGCs). As the output neurons of the eye, RGCs include ∼20 different subtypes, each responding best to a specific feature in the visual scene. Here we discuss recent advances in identifying where different RGC subtypes route visual information in the brain, including which targets they connect to and how their organization within those targets influences visual processing. We also highlight examples where causal links have been established between specific RGC subtypes, their maps of central connections and defined aspects of light-mediated behavior and we suggest the use of techniques that stand to extend these sorts of analyses to circuits underlying visual perception.
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33
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Abstract
The dorsal lateral geniculate nucleus (dLGN) receives visual information from the retina and transmits it to the cortex. In this study, we made extracellular recordings in the dLGN of both anesthetized and awake mice, and found that a surprisingly high proportion of cells were selective for stimulus orientation. The orientation selectivity of dLGN cells was unchanged after silencing the visual cortex pharmacologically, indicating that it is not due to cortical feedback. The orientation tuning of some dLGN cells correlated with their elongated receptive fields, while in others orientation selectivity was observed despite the fact that their receptive fields were circular, suggesting that their retinal input might already be orientation selective. Consistently, we revealed orientation/axis-selective ganglion cells in the mouse retina using multielectrode arrays in an in vitro preparation. Furthermore, the orientation tuning of dLGN cells was largely maintained at different stimulus contrasts, which could be sufficiently explained by a simple linear feedforward model. We also compared the degree of orientation selectivity in different visual structures under the same recording condition. Compared with the dLGN, orientation selectivity is greatly improved in the visual cortex, but is similar in the superior colliculus, another major retinal target. Together, our results demonstrate prominent orientation selectivity in the mouse dLGN, which may potentially contribute to visual processing in the cortex.
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34
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Furman M, Xu HP, Crair MC. Competition driven by retinal waves promotes morphological and functional synaptic development of neurons in the superior colliculus. J Neurophysiol 2013; 110:1441-54. [PMID: 23741047 PMCID: PMC3763158 DOI: 10.1152/jn.01066.2012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 06/03/2013] [Indexed: 11/22/2022] Open
Abstract
Prior to eye opening, waves of spontaneous activity sweep across the developing retina. These "retinal waves," together with genetically encoded molecular mechanisms, mediate the formation of visual maps in the brain. However, the specific role of wave activity in synapse development in retino-recipient brain regions is unclear. Here we compare the functional development of synapses and the morphological development of neurons in the superior colliculus (SC) of wild-type (WT) and transgenic (β2-TG) mice in which retinal wave propagation is spatially truncated (Xu HP, Furman M, Mineur YS, Chen H, King SL, Zenisek D, Zhou ZJ, Butts DA, Tian N, Picciotto MR, Crair MC. Neuron 70: 1115-1127, 2011). We use two recently developed brain slice preparations to examine neurons and synapses in the binocular vs. mainly monocular SC. We find that retinocollicular synaptic strength is reduced whereas the number of retinal inputs is increased in the binocular SC of β2-TG mice compared with WT mice. In contrast, in the mainly monocular SC the number of retinal inputs is normal in β2-TG mice, but, transiently, synapses are abnormally strong, possibly because of enhanced activity-dependent competition between local, "small" retinal wave domains. These findings demonstrate that retinal wave size plays an instructive role in the synaptic and morphological development of SC neurons, possibly through a competitive process among retinofugal axons.
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Affiliation(s)
- Moran Furman
- Department of Neurobiology, Yale University School of Medicine, New Haven, Connecticut
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35
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RNA-binding protein Hermes/RBPMS inversely affects synapse density and axon arbor formation in retinal ganglion cells in vivo. J Neurosci 2013; 33:10384-95. [PMID: 23785151 DOI: 10.1523/jneurosci.5858-12.2013] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The RNA-binding protein Hermes [RNA-binding protein with multiple splicing (RBPMS)] is expressed exclusively in retinal ganglion cells (RGCs) in the CNS, but its function in these cells is not known. Here we show that Hermes protein translocates in granules from RGC bodies down the growing axons. Hermes loss of function in both Xenopus laevis and zebrafish embryos leads to a significant reduction in retinal axon arbor complexity in the optic tectum, and expression of a dominant acting mutant Hermes protein, defective in RNA-granule localization, causes similar defects in arborization. Time-lapse analysis of branch dynamics reveals that the decrease in arbor complexity is caused by a reduction in new branches rather than a decrease in branch stability. Surprisingly, Hermes depletion also leads to enhanced early visual behavior and an increase in the density of presynaptic puncta, suggesting that reduced arborization is accompanied by increased synaptogenesis to maintain synapse number.
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36
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Akrouh A, Kerschensteiner D. Intersecting circuits generate precisely patterned retinal waves. Neuron 2013; 79:322-34. [PMID: 23830830 DOI: 10.1016/j.neuron.2013.05.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/30/2013] [Indexed: 11/29/2022]
Abstract
The developing retina generates spontaneous glutamatergic (stage III) waves of activity that sequentially recruit neighboring ganglion cells with opposite light responses (ON and OFF RGCs). This activity pattern is thought to help establish parallel ON and OFF pathways in downstream visual areas. The circuits that produce stage III waves and desynchronize ON and OFF RGC firing remain obscure. Using dual patch-clamp recordings, we find that ON and OFF RGCs receive sequential excitatory input from ON and OFF cone bipolar cells (CBCs), respectively. This input sequence is generated by crossover circuits, in which ON CBCs control glutamate release from OFF CBCs via diffusely stratified inhibitory amacrine cells. In addition, neighboring ON CBCs communicate directly and indirectly through lateral glutamatergic transmission and gap junctions, both of which are required for wave initiation and propagation. Thus, intersecting lateral excitatory and vertical inhibitory circuits give rise to precisely patterned stage III retinal waves.
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Affiliation(s)
- Alejandro Akrouh
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, 660 S. Euclid Avenue, Saint Louis, MO 63110, USA
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37
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On the Importance of Countergradients for the Development of Retinotopy: Insights from a Generalised Gierer Model. PLoS One 2013; 8:e67096. [PMID: 23826201 PMCID: PMC3694955 DOI: 10.1371/journal.pone.0067096] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Accepted: 05/14/2013] [Indexed: 11/19/2022] Open
Abstract
During the development of the topographic map from vertebrate retina to superior colliculus (SC), EphA receptors are expressed in a gradient along the nasotemporal retinal axis. Their ligands, ephrin-As, are expressed in a gradient along the rostrocaudal axis of the SC. Countergradients of ephrin-As in the retina and EphAs in the SC are also expressed. Disruption of any of these gradients leads to mapping errors. Gierer's (1981) model, which uses well-matched pairs of gradients and countergradients to establish the mapping, can account for the formation of wild type maps, but not the double maps found in EphA knock-in experiments. I show that these maps can be explained by models, such as Gierer's (1983), which have gradients and no countergradients, together with a powerful compensatory mechanism that helps to distribute connections evenly over the target region. However, this type of model cannot explain mapping errors found when the countergradients are knocked out partially. I examine the relative importance of countergradients as against compensatory mechanisms by generalising Gierer's (1983) model so that the strength of compensation is adjustable. Either matching gradients and countergradients alone or poorly matching gradients and countergradients together with a strong compensatory mechanism are sufficient to establish an ordered mapping. With a weaker compensatory mechanism, gradients without countergradients lead to a poorer map, but the addition of countergradients improves the mapping. This model produces the double maps in simulated EphA knock-in experiments and a map consistent with the Math5 knock-out phenotype. Simulations of a set of phenotypes from the literature substantiate the finding that countergradients and compensation can be traded off against each other to give similar maps. I conclude that a successful model of retinotopy should contain countergradients and some form of compensation mechanism, but not in the strong form put forward by Gierer.
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38
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A competition-based mechanism mediates developmental refinement of tectal neuron receptive fields. J Neurosci 2013; 32:16872-9. [PMID: 23175839 DOI: 10.1523/jneurosci.2372-12.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Neural activity plays an important role in development and maturation of visual circuits in the brain. Activity can be instructive in refining visual projections by directly mediating formation and elimination of specific synaptic contacts through competition-based mechanisms. Alternatively, activity could be permissive-regulating production of factors that create a favorable environment for circuit refinement. Here we used the Xenopus laevis tadpole visual system to test whether activity is instructive or permissive for shaping development of the retinotectal circuit. In vivo spike output was dampened in a small subgroup of tectal neurons, starting from developmental stages 44-46, by overexpressing Shaker-like Xenopus Kv1.1 potassium channels using electroporation. Tadpoles were then reared until stage 49, a time period when significant refinement of the retinotectal map occurs. Kv1.1-expressing neurons had significantly decreased spike output in response to both current injection and visual stimuli compared to untransfected controls, with spiking occurring during a more limited time interval. We found that Kv1.1-expressing neurons had larger visual receptive fields, decreased receptive field sharpness, and more persistent recurrent excitation than control neurons, all of which are characteristics of immature neurons. Transfected cells, however, had normal spontaneous excitatory synaptic currents and dendritic arbors. These results suggest that spike output of a tectal neuron plays an important instructive role in development of its receptive field properties and refinement of local circuits. However, other activity-dependent processes, such as synaptogenesis and dendritic growth, remain unaffected due to the permissive environment created by otherwise normal network activity.
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Furman M, Crair MC. Synapse maturation is enhanced in the binocular region of the retinocollicular map prior to eye opening. J Neurophysiol 2012; 107:3200-16. [PMID: 22402661 PMCID: PMC3774562 DOI: 10.1152/jn.00943.2011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 03/07/2012] [Indexed: 02/08/2023] Open
Abstract
In the developing visual system of mammals, retinal axons from the two eyes compete for postsynaptic partners. After eye opening, this process is regulated in part by homeostatically constrained competition for synaptic connectivity with target neurons. However, prior to eye opening, the functional and synaptic basis of binocular map development is unclear. To examine the role of binocular interactions during early stages of visual map development, we performed in vitro patch-clamp recordings from the superior colliculus (SC) of neonatal mice. Using newly designed slice preparations, we compared retinocollicular synapse development in the medial SC, which receives binocular input, and the lateral SC, which is predominantly monocular. Surprisingly, we found that at P6-7, when eye-specific segregation has just emerged, retinocollicular synapses were stronger and more mature and dendritic arbors were more elaborate in the medial than the lateral SC. Furthermore, monocular enucleation of the ipsilateral eye at P0 selectively reduced synaptic strength and dendritic branching in the medial SC and abolished the differences normally observed between the two slices at P6-7. This specifically implicates binocular interactions in the development of retinocollicular connectivity prior to eye opening. Our findings contrast with the predictions of a constrained-connectivity model of binocular map development and suggest instead that binocular competition prior to eye opening enhances retinocollicular synaptic strength and the morphological development of retino-recipient neurons.
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Affiliation(s)
- Moran Furman
- Dept. of Neurobiology, Yale Univ. School of Medicine, New Haven, CT 06510, USA
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40
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Suppression of a MEF2-KLF6 survival pathway by PKA signaling promotes apoptosis in embryonic hippocampal neurons. J Neurosci 2012; 32:2790-803. [PMID: 22357862 DOI: 10.1523/jneurosci.3609-11.2012] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In the mammalian nervous system, regulation of transcription factor activity is a crucial determinant of neuronal cell survival, differentiation, and death. The myocyte enhancer factor 2 (MEF2) transcription factors have been implicated in cellular processes underlying neuronal survival and differentiation. A core component of the MEF2 complex is the MEF2D subunit. Recently, we reported that cAMP-dependent protein kinase (cAMP/PKA) signaling negatively regulates MEF2D function in myogenic cells. Here, we assessed whether cAMP signaling converges on the prosurvival role of MEF2D in Sprague Dawley rat embryonic (E18) hippocampal neurons. Initially, we observed that experimental induction of cAMP/PKA signaling promotes apoptosis in primary hippocampal neurons as indicated by TUNEL and FACS analysis. Luciferase reporter gene assays revealed that PKA potently represses MEF2D trans-activation properties in neurons. This effect was largely reversed by engineered neutralizing mutations of PKA phospho-acceptor sites on MEF2D (S121/190A). Krüppel-like factor 6 (KLF6) was identified as a key transcriptional target of MEF2 in hippocampal neurons, and siRNA-mediated knockdown of KLF6 expression promotes neuronal cell death and also antagonizes the prosurvival role of MEF2D. These observations have important implications for understanding the pathways controlling cell survival and death in the mammalian nervous system.
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Turrigiano G. Homeostatic synaptic plasticity: local and global mechanisms for stabilizing neuronal function. Cold Spring Harb Perspect Biol 2012; 4:a005736. [PMID: 22086977 DOI: 10.1101/cshperspect.a005736] [Citation(s) in RCA: 711] [Impact Index Per Article: 59.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Neural circuits must maintain stable function in the face of many plastic challenges, including changes in synapse number and strength, during learning and development. Recent work has shown that these destabilizing influences are counterbalanced by homeostatic plasticity mechanisms that act to stabilize neuronal and circuit activity. One such mechanism is synaptic scaling, which allows neurons to detect changes in their own firing rates through a set of calcium-dependent sensors that then regulate receptor trafficking to increase or decrease the accumulation of glutamate receptors at synaptic sites. Additional homeostatic mechanisms may allow local changes in synaptic activation to generate local synaptic adaptations, and network-wide changes in activity to generate network-wide adjustments in the balance between excitation and inhibition. The signaling pathways underlying these various forms of homeostatic plasticity are currently under intense scrutiny, and although dozens of molecular pathways have now been implicated in homeostatic plasticity, a clear picture of how homeostatic feedback is structured at the molecular level has not yet emerged. On a functional level, neuronal networks likely use this complex set of regulatory mechanisms to achieve homeostasis over a wide range of temporal and spatial scales.
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Affiliation(s)
- Gina Turrigiano
- Department of Biology and Center for Behavioral Genomics, Brandeis University, Waltham, Massachusetts 02493, USA.
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42
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McGregor S, Polani D, Dautenhahn K. Generation of tactile maps for artificial skin. PLoS One 2011; 6:e26561. [PMID: 22102863 PMCID: PMC3213097 DOI: 10.1371/journal.pone.0026561] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Accepted: 09/29/2011] [Indexed: 11/19/2022] Open
Abstract
Prior research has shown that representations of retinal surfaces can be learned from the intrinsic structure of visual sensory data in neural simulations, in robots, as well as by animals. Furthermore, representations of cochlear (frequency) surfaces can be learned from auditory data in neural simulations. Advances in hardware technology have allowed the development of artificial skin for robots, realising a new sensory modality which differs in important respects from vision and audition in its sensorimotor characteristics. This provides an opportunity to further investigate ordered sensory map formation using computational tools. We show that it is possible to learn representations of non-trivial tactile surfaces, which require topologically and geometrically involved three-dimensional embeddings. Our method automatically constructs a somatotopic map corresponding to the configuration of tactile sensors on a rigid body, using only intrinsic properties of the tactile data. The additional complexities involved in processing the tactile modality require the development of a novel multi-dimensional scaling algorithm. This algorithm, ANISOMAP, extends previous methods and outperforms them, producing high-quality reconstructions of tactile surfaces in both simulation and hardware tests. In addition, the reconstruction turns out to be robust to unanticipated hardware failure.
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Affiliation(s)
- Simon McGregor
- University of Hertfordshire, Hatfield, Herts, United Kingdom
| | - Daniel Polani
- University of Hertfordshire, Hatfield, Herts, United Kingdom
- * E-mail:
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43
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Turrigiano G. Too Many Cooks? Intrinsic and Synaptic Homeostatic Mechanisms in Cortical Circuit Refinement. Annu Rev Neurosci 2011; 34:89-103. [PMID: 21438687 DOI: 10.1146/annurev-neuro-060909-153238] [Citation(s) in RCA: 485] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Gina Turrigiano
- Department of Biology, Center for Complex Systems, and Center for Behavioral Genomics, Brandeis University, Waltham, Massachusetts 02454;
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Abstract
The maturation of retinal ganglion cell (RGC) axon projections in the dorsal lateral geniculate nucleus (dLGN) and the superior colliculus (SC) relies on both molecular and activity-dependent mechanisms. Despite the increasing popularity of the mouse as a mammalian visual system model, little is known in this species about the normal development of individual RGC axon arbors or the role of activity in this process. We used a novel in vivo single RGC labeling technique to quantitatively characterize the elaboration and refinement of RGC axon arbors in the dLGN and SC in wild-type (WT) and β2-nicotinic acetylcholine receptors mutant (β2(-/-)) mice, which have perturbed retinal waves, during the developmental period when eye-specific lamination and retinotopic refinement occurs. Our results suggest that eye-specific segregation and retinotopic refinement in WT mice are not the result of refinement of richly exuberant arbors but rather the elaboration of arbors prepositioned in the proper location combined with the elimination of inappropriately targeted sparse branches. We found that retinocollicular arbors mature ∼1 week earlier than retinogeniculate arbors, although RGC axons reach the dLGN and SC at roughly the same age. We also observed striking differences between contralateral and ipsilateral RGC axon arbors in the SC but not in the LGN. These data suggest a strong influence of target specific cues during arbor maturation. In β2(-/-) mice, we found that retinofugal single axon arbors are well ramified but enlarged, particularly in the SC, indicating that activity-dependent visual map development occurs through the refinement of individual RGC arbors.
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45
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Visual receptive field properties of neurons in the superficial superior colliculus of the mouse. J Neurosci 2011; 30:16573-84. [PMID: 21147997 DOI: 10.1523/jneurosci.3305-10.2010] [Citation(s) in RCA: 155] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The mouse is a promising model in the study of visual system function and development because of available genetic tools. However, a quantitative analysis of visual receptive field properties had not been performed in the mouse superior colliculus (SC) despite its importance in mouse vision and its usefulness in developmental studies. We have made single-unit extracellular recordings from superficial layers of the SC in urethane-anesthetized C57BL/6 mice. We first map receptive fields with flashing spot stimuli and show that most SC neurons have spatially overlapped ON and OFF subfields. With drifting sinusoidal gratings, we then determine the tuning properties of individual SC neurons, including selectivity for stimulus direction and orientation, spatial frequency tuning, temporal frequency tuning, response linearity, and size preference. A wide range of receptive field sizes and selectivity are observed across the population and in various subtypes of SC neurons identified morphologically. In particular, orientation-selective responses are discovered in the mouse SC, and they are not affected by cortical lesion or long-term visual deprivation. However, ON/OFF characteristics and spatial frequency tuning of SC neurons are influenced by cortical inputs and require visual experience during development. Together, our results provide essential information for future investigations on the functional development of the superior colliculus.
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Carrasco MM, Mao YT, Balmer TS, Pallas SL. Inhibitory plasticity underlies visual deprivation-induced loss of receptive field refinement in the adult superior colliculus. Eur J Neurosci 2010; 33:58-68. [PMID: 21050281 DOI: 10.1111/j.1460-9568.2010.07478.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Increasing evidence shows that sensory experience is not necessary for initial patterning of neural circuitry but is essential for maintenance and plasticity. We have investigated the role of visual experience in development and plasticity of inhibitory synapses in the retinocollicular pathway of an altricial rodent, the Syrian hamster. We reported previously that visual receptive field (RF) refinement in superior colliculus (SC) occurs with the same time course in long-term dark-reared (LTDR) as in normally-reared hamsters, but RFs in LTDR animals become unrefined in adulthood. Here we provide support for the hypothesis that this failure to maintain refined RFs into adulthood results from inhibitory plasticity at both pre- and postsynaptic levels. Iontophoretic application of gabazine, a GABA(A) receptor antagonist, or muscimol, a GABA(A) receptor agonist, had less of an effect on RF size and excitability of adult LTDR animals than in short-term DR animals or normal animals. Consistent with these physiological observations, the percentage of GABA-immunoreactive neurons was significantly decreased in the SC of LTDR animals compared to normal animals and to animals exposed to a normal light cycle early in development, before LTDR. Thus GABAergic inhibition in the SC of LTDR animals is reduced, weakening the inhibitory surround and contributing significantly to the visual deprivation-induced enlargement of RFs seen. Our results argue that early visually-driven activity is necessary to maintain the inhibitory circuitry intrinsic to the adult SC and to protect against the consequences of visual deprivation.
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Affiliation(s)
- María M Carrasco
- Department of Biology, Georgia State University, Atlanta, GA 30302, USA
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47
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Prostaglandin E2-induced synaptic plasticity in neocortical networks of organotypic slice cultures. J Neurosci 2010; 30:11678-87. [PMID: 20810888 DOI: 10.1523/jneurosci.4665-09.2010] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Traumatic brain injury (TBI) is a major cause of epilepsy, yet the mechanisms underlying the progression from TBI to epilepsy are unknown. TBI induces the expression of COX-2 (cyclooxygenase-2) and increases levels of prostaglandin E2 (PGE2). Here, we demonstrate that acutely applied PGE2 (2 mum) decreases neocortical network activity by postsynaptically reducing excitatory synaptic transmission in acute and organotypic neocortical slices of mice. In contrast, long-term exposure to PGE2 (2 mum; 48 h) presynaptically increases excitatory synaptic transmission, leading to a hyperexcitable network state that is characterized by the generation of paroxysmal depolarization shifts (PDSs). PDSs were also evoked as a result of depriving organotypic slices of activity by treating them with tetrodotoxin (TTX, 1 mum; 48 h). This treatment predominantly increased postsynaptically excitatory synaptic transmission. The network and cellular effects of PGE2 and TTX treatments reversed within 1 week. Differences in the underlying mechanisms (presynaptic vs postsynaptic) as well as occlusion experiments in which slices were exposed to TTX plus PGE2 suggest that the two substances evoke distinct forms of homeostatic plasticity, both of which result in a hyperexcitable network state. PGE2 and TTX (alone or together with PGE2) also increased levels of apoptotic cell death in organotypic slices. Thus, we hypothesize that the increase in excitability and apoptosis may constitute the first steps in a cascade of events that eventually lead to epileptogenesis triggered by TBI.
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48
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Butts DA, Kanold PO. The applicability of spike time dependent plasticity to development. Front Synaptic Neurosci 2010; 2:30. [PMID: 21423516 PMCID: PMC3059702 DOI: 10.3389/fnsyn.2010.00030] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Accepted: 06/27/2010] [Indexed: 11/22/2022] Open
Abstract
Spike time dependent plasticity (STDP) has been observed in both developing and adult animals. Theoretical studies suggest that it implicitly leads to both competition and homeostasis in addition to correlation-based plasticity, making it a good candidate to explain developmental refinement and plasticity in a number of systems. However, it has only been observed to play a clear role in development in a small number of cases. Because the fast time scales necessary to elicit STDP, it would likely be inefficient in governing synaptic modifications in the absence of fast correlations in neural activity. In contrast, later stages of development often depend on sensory inputs that can drive activity on much faster time scales, suggesting a role in STDP in many sensory systems after opening of the eyes and ear canals. Correlations on fast time scales can be also be present earlier in developing microcircuits, such as those produced by specific transient “teacher” circuits in the cerebral cortex. By reviewing examples of each case, we suggest that STDP is not a universal rule, but rather might be masked or phased in, depending on the information available to instruct refinement in different developing circuits. Thus, this review describes selected cases where STDP has been studied in developmental contexts, and uses these examples to suggest a more general framework for understanding where it could be playing a role in development.
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Affiliation(s)
- Daniel A Butts
- Department of Biology and Program in Neuroscience and Cognitive Science, University of Maryland College Park, MD, USA
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Pfeiffer BE, Zang T, Wilkerson JR, Taniguchi M, Maksimova MA, Smith LN, Cowan CW, Huber KM. Fragile X mental retardation protein is required for synapse elimination by the activity-dependent transcription factor MEF2. Neuron 2010; 66:191-7. [PMID: 20434996 DOI: 10.1016/j.neuron.2010.03.017] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/05/2010] [Indexed: 11/18/2022]
Abstract
Fragile X syndrome (FXS), the most common genetic form of mental retardation and autism, is caused by loss-of-function mutations in an RNA-binding protein, Fragile X Mental Retardation Protein (FMRP). Neurons from patients and the mouse Fmr1 knockout (KO) model are characterized by an excess of dendritic spines, suggesting a deficit in excitatory synapse elimination. In response to neuronal activity, myocyte enhancer factor 2 (MEF2) transcription factors induce robust synapse elimination. Here, we demonstrate that MEF2 activation fails to eliminate functional or structural excitatory synapses in hippocampal neurons from Fmr1 KO mice. Similarly, inhibition of endogenous MEF2 increases synapse number in wild-type but not Fmr1 KO neurons. MEF2-dependent synapse elimination is rescued in Fmr1 KO neurons by acute postsynaptic expression of wild-type but not RNA-binding mutants of FMRP. Our results reveal that active MEF2 and FMRP function together in an acute, cell-autonomous mechanism to eliminate excitatory synapses.
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Affiliation(s)
- Brad E Pfeiffer
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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50
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Basu A, Graziadio S, Smith M, Clowry GJ, Cioni G, Eyre JA. Developmental plasticity connects visual cortex to motoneurons after stroke. Ann Neurol 2010; 67:132-6. [PMID: 20186850 DOI: 10.1002/ana.21827] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
We report motor cortical function in the left occipital cortex of a subject who suffered a left middle cerebral artery stroke early in development. Transcranial magnetic stimulation of the left occipital cortex evoked contraction of right hand muscles. Electroencephalogram recorded over the left occipital cortex showed: 1) coherence with electromyogram from a right hand muscle; 2) a typical sensorimotor Mu rhythm at rest that was suppressed during contraction of right hand muscles. This is the first evidence that cortical plasticity extends beyond reshaping of primary sensory cortical fields to respecification of the cortical origin of subcortically projecting pathways.
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Affiliation(s)
- Anna Basu
- Developmental Neuroscience, Institute of Neuroscience, Newcastle University, Newcastle Upon Tyne, UK
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