The Experts below are selected from a list of 90 Experts worldwide ranked by ideXlab platform
E. J. Chichilnisky - One of the best experts on this subject based on the ideXlab platform.
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Neurobiology of Disease High-Resolution Electrical Stimulation of Primate Retina for Epiretinal Implant Design
2013Co-Authors: Chris Sekirnjak, Pawel Hottowy, Er Sher, Wladyslaw Dabrowski, Alan M. Litke, E. J. ChichilniskyAbstract:The development of retinal implants for the blind depends crucially on understanding how neurons in the retina respond to electrical stimulation. This study used multielectrode arrays to stimulate ganglion Cells in the peripheral macaque retina, which is very similar to the human retina. Analysis was restricted to Parasol Cells, which form one of the major high-resolution visual pathways in primates. Individual Cells were characterized using visual stimuli, and subsequently targeted for electrical stimulation using electrodes 9–15 �m in diameter. Results were accumulated across 16 ON and 9 OFF Parasol Cells. At threshold, all Cells responded to biphasic electrical pulses 0.05–0.1 ms in duration by firing a single spike with latency lower than 0.35 ms. The average threshold charge density was 0.050 � 0.005 mC/cm 2, significantly below established safety limits for platinum electrodes. ON and OFF ganglion Cells were stimulated with similar efficacy. Repetitive stimulation elicited spikes within a 0.1 ms time window, indicating that the high temporal precision necessary for spike-by-spike stimulation can be achieved in primate retina. Spatial analysis of observed thresholds suggests that electrical activation occurred near the axon hillock, and that dendrites contributed little. Finally, stimulation of a single Parasol Cell produced little or no activation of other Cells in the ON and OFF Parasol Cell mosaics. The low-threshold, temporally precise, and spatially specific response
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Modeling the impact of common noise inputs on the network activity of retinal ganglion Cells
Journal of Computational Neuroscience, 2012Co-Authors: Michael Vidne, Alan M. Litke, E. J. Chichilnisky, Jonathon Shlens, Yashar Ahmadian, Jonathan W. Pillow, Jayant Kulkarni, Eero Simoncelli, Liam PaninskiAbstract:Synchronized spontaneous firing among retinal ganglion Cells (RGCs), on timescales faster than visual responses, has been reported in many studies. Two candidate mechanisms of synchronized firing include direct coupling and shared noisy inputs. In neighboring Parasol Cells of primate retina, which exhibit rapid synchronized firing that has been studied extensively, recent experimental work indicates that direct electrical or synaptic coupling is weak, but shared synaptic input in the absence of modulated stimuli is strong. However, previous modeling efforts have not accounted for this aspect of firing in the Parasol Cell population. Here we develop a new model that incorporates the effects of common noise, and apply it to analyze the light responses and synchronized firing of a large, densely-sampled network of over 250 simultaneously recorded Parasol Cells. We use a generalized linear model in which the spike rate in each Cell is determined by the linear combination of the spatio-temporally filtered visual input, the temporally filtered prior spikes of that Cell, and unobserved sources representing common noise. The model accurately captures the statistical structure of the spike trains and the encoding of the visual stimulus, without the direct coupling assumption present in previous modeling work. Finally, we examined the problem of decoding the visual stimulus from the spike train given the estimated parameters. The common-noise model produces Bayesian decoding performance as accurate as that of a model with direct coupling, but with significantly more robustness to spike timing perturbations.
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Synchronized firing in the retina.
Current opinion in neurobiology, 2008Co-Authors: Jonathon Shlens, Fred Rieke, E. J. ChichilniskyAbstract:Synchronized firing in neural populations has been proposed to constitute an elementary aspect of the neural code, but a complete understanding of its origins and significance has been elusive. Synchronized firing has been extensively documented in retinal ganglion Cells, the output neurons of the retina. However, differences in synchronized firing across species and Cell types have led to varied conclusions about its mechanisms and role in visual signaling. Recent work on two identified Cell populations in the primate retina, the ON-Parasol and OFF-Parasol Cells, permits a more unified understanding. IntraCellular recordings reveal that synchronized firing in these Cell types arises primarily from common synaptic input to adjacent pairs of Cells. Statistical analysis indicates that local pairwise interactions can explain the pattern of synchronized firing in the entire Parasol Cell population. Computational analysis reveals that the aggregate impact of synchronized firing on the visual signal is substantial. Thus, in the Parasol Cells, the origin and impact of synchronized firing on the neural code may be understood as locally shared input which influences the visual signals transmitted from eye to brain.
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high resolution electrical stimulation of primate retina for epiretinal implant design
The Journal of Neuroscience, 2008Co-Authors: Chris Sekirnjak, Pawel Hottowy, Wladyslaw Dabrowski, Alan M. Litke, Alexander Sher, E. J. ChichilniskyAbstract:The development of retinal implants for the blind depends crucially on understanding how neurons in the retina respond to electrical stimulation. This study used multielectrode arrays to stimulate ganglion Cells in the peripheral macaque retina, which is very similar to the human retina. Analysis was restricted to Parasol Cells, which form one of the major high-resolution visual pathways in primates. Individual Cells were characterized using visual stimuli, and subsequently targeted for electrical stimulation using electrodes 9–15 μm in diameter. Results were accumulated across 16 ON and 9 OFF Parasol Cells. At threshold, all Cells responded to biphasic electrical pulses 0.05–0.1 ms in duration by firing a single spike with latency lower than 0.35 ms. The average threshold charge density was 0.050 ± 0.005 mC/cm2, significantly below established safety limits for platinum electrodes. ON and OFF ganglion Cells were stimulated with similar efficacy. Repetitive stimulation elicited spikes within a 0.1 ms time window, indicating that the high temporal precision necessary for spike-by-spike stimulation can be achieved in primate retina. Spatial analysis of observed thresholds suggests that electrical activation occurred near the axon hillock, and that dendrites contributed little. Finally, stimulation of a single Parasol Cell produced little or no activation of other Cells in the ON and OFF Parasol Cell mosaics. The low-threshold, temporally precise, and spatially specific responses hold promise for the application of high-density arrays of small electrodes in epiretinal implants.
David W. Marshak - One of the best experts on this subject based on the ideXlab platform.
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Synaptic input to OFF Parasol ganglion Cells in macaque retina
The Journal of comparative neurology, 2006Co-Authors: Andrea S. Bordt, Elizabeth S. Yamada, Hideo Hoshi, Wendy C. Perryman-stout, David W. MarshakAbstract:A Neurobiotin-injected OFF Parasol Cell from midperipheral macaque retina was studied by reconstruction of serial ultrathin sections and compared with ON Parasol Cells studied previously. In most respects, the synaptic inputs to the two subtypes were similar. Only a few of the amacrine Cell processes that provided input to the labeled OFF Parasol ganglion Cell dendrites made or received inputs within the series, and none of these interactions were with the bipolar Cells or other amacrine Cells presynaptic to the OFF Parasol Cell. These findings suggest that the direct inhibitory input to OFF Parasol Cells originates from other areas of the retina. OFF Parasol Cells were known to receive inputs from two types of diffuse bipolar Cells. To identify candidates for the presynaptic amacrine Cells, OFF Parasol Cells were labeled with Lucifer yellow by using a juxtaCellular labeling technique, and amacrine Cells known to costratify with them were labeled via immunofluorescent methods. Appositions were observed with amacrine Cells containing immunoreactive calretinin, parvalbumin, choline acetylatransferase, and G6-Gly, a cholecystokinin precursor. These findings suggest that the inhibitory input to Parasol Cells conveys information about several different attributes of visual stimuli and, particularly, about their global properties.
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Synaptic input to an ON Parasol ganglion Cell in the macaque retina: a serial section analysis.
Visual Neuroscience, 2002Co-Authors: David W. Marshak, Elizabeth S. Yamada, Andrea S. Bordt, Wendy C. PerrymanAbstract:: A labeled ON Parasol ganglion Cell from a macaque retina was analyzed in serial, ultrathin sections. It received 13% of its input from diffuse bipolar Cells. These directed a large proportion of their output to amacrine Cells but received a relatively small proportion of their amacrine Cell input via feedback synapses. In these respects, they were similar to the DB3 bipolar Cells that make synapses onto OFF Parasol Cells. Bipolar Cell axons that contacted the ON Parasol Cell in stratum 4 of the inner plexiform layer always made synapses onto the dendrite, and therefore, the number of bipolar Cell synapses onto these ganglion Cells could be estimated reliably by light microscopy in the future. Amacrine Cells provided the majority of inputs to the ON Parasol Cell. Only a few of the presynaptic amacrine Cell processes received inputs from the same bipolar Cells as the Parasol Cells, and most of the presynaptic amacrine Cell processes did not receive any inputs at all within the series. These findings suggest that most of the inhibitory input to the ON Parasol Cell originates from other areas of the retina. Amacrine Cells presynaptic to the Parasol ganglion Cell interacted very infrequently with other neurons in the circuit, and therefore, they would be expected to act independently, for the most part.
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diffuse bipolar Cells provide input to off Parasol ganglion Cells in the macaque retina
The Journal of Comparative Neurology, 2000Co-Authors: Roy A. Jacoby, Allan F Wiechmann, Susan G Amara, Barbara H Leighton, David W. MarshakAbstract:Parasol retinal ganglion Cells are more sensitive to luminance contrast and respond more transiently at all levels of adaptation than midget ganglion Cells. This may be due, in part, to differences between bipolar Cells that provide their input, and the goal of these experiments was to study these differences. Midget bipolar Cells are known to be presynaptic to midget ganglion Cells. To identify the bipolar Cells presynaptic to Parasol Cells, these ganglion Cells were intraCellularly injected with Neurobiotin, cone bipolar Cells were immunolabeled, and the double-labeled material was analyzed. In the electron microscope, we found that DB3 diffuse bipolar Cells labeled by using antiserum to calbindin D-28k were presynaptic to OFF Parasol Cells. In the confocal microscope, DB3 bipolars costratified with OFF Parasol Cell dendrites and made significantly more appositions with them than expected due to chance. Flat midget bipolar Cells were labeled with antiserum to recoverin. Although they made a few appositions with Parasol Cells, the number was no greater than would be expected when two sets of processes have overlapping distributions in the inner plexiform layer. DB2 diffuse bipolar Cells were labeled with antibodies to excitatory amino acid transporter 2, and they also made appositions with OFF Parasol Cells. These results suggest that DB2 bipolar Cells are also presynaptic to OFF Parasol ganglion Cells, but midget bipolar Cells are not. We estimate that midperipheral OFF Parasol Cells receive ≈500 synapses from 50 DB3 bipolar Cells that, in turn, receive input from 250 cones.
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Gap junctions with amacrine Cells provide a feedback pathway for ganglion Cells within the retina
Proceedings. Biological sciences, 1998Co-Authors: Garrett T. Kenyon, David W. MarshakAbstract:In primates, one type of retinal ganglion Cell, the Parasol Cell, makes gap junctions with amacrine Cells, the inhibitory, local circuit neurons. To study the effects of these gap junctions, we developed a linear, mathematical model of the retinal circuitry providing input to Parasol Cells. Electrophysiological studies have indicated that gap junctions do not enlarge the receptive field centres of Parasol Cells, but our results suggest that they make other contributions to their light responses. According to our model, the coupled amacrine Cells enhance the responses of Parasol Cells to luminance contrast by disinhibition. We also show how a mixed chemical and electrical synapse between two sets of amacrine Cells presynaptic to the Parasol Cells might make the responses of Parasol Cells more transient and, therefore, more sensitive to motion. Finally, we show how coupling via amacrine Cells can synchronize the firing of Parasol Cells. An action potential in a model Parasol Cell can excite neighbouring Parasol Cells, but only when the coupled amacrine Cells also fire action potentials. Passive conduction was ineffective due to low–pass temporal filtering. Inhibition from the axons of the coupled amacrine Cells also produced oscillations that might synchronize the firing of more distant ganglion Cells.
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Synaptic Inputs to ON Parasol Ganglion Cells in the Primate Retina
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1996Co-Authors: Roy A. Jacoby, Donna Stafford, Nobuo Kouyama, David W. MarshakAbstract:In primates, the retinal ganglion Cells that project to the magnoCellular layers of the lateral geniculate nucleus have distinctive responses to light, and one of these has been identified morphologically as the Parasol ganglion Cell. To investigate their synaptic connections, we injected Parasol Cells with Neurobiotin in lightly fixed baboon retinas. The five ON-center Cells we analyzed by electron microscopy received approximately 20% of their input from bipolar Cells. The major synaptic input to Parasol Cells was from amacrine Cells via conventional synapses and, in this respect, they resembled alpha ganglion Cells of the cat retina. We also found the gap junctions between amacrine Cells and Parasol ganglion Cells that had been predicted from tracer-coupling experiments. To identify the presynaptic amacrine Cells, ON-center Parasol Cells were injected with Neurobiotin and Lucifer yellow in living macaque retinas, which were then fixed and labeled by immunofluorescence. Two kinds of amacrine Cells were filled with Neurobiotin via gap junctions: a large, polyaxonal Cell containing cholecystokinin and a smaller one without cholecystokinin. There were also appositions between cholecystokinin-containing amacrine Cell processes and Parasol Cell dendrites. Cholinergic amacrine Cell processes often followed Parasol Cell dendrites and made extensive contacts. In other mammals, the light responses of polyaxonal amacrine Cells like these and cholinergic amacrine Cells have been recorded, and the effects of acetylcholine and cholecystokinin on ganglion Cells are known. Using this information, we developed a model of Parasol Cells that accounts for some properties of their light responses.
Deforest Mellon - One of the best experts on this subject based on the ideXlab platform.
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Parasol Cell responses to hyperpolarizing current.
2016Co-Authors: Deforest MellonAbstract:A1, voltage sag and post-hyperpolarizing discharge produced in a crayfish Parasol Cell by a 10 sec pulse of hyperpolarizing current during background activity in normal saline. A2, sag produced by an identical current injection in the same neuron after treating the preparation with 5 x 10−7 M TTX. B, response of a TTX-treated crayfish Parasol Cell to a series of 0.2 nA steps of hyperpolarizing current. The threshold for onset of the voltage sag in this neuron was approximately 25 mV hyperpolarized to the resting potential. C, effect of the addition of 10 mM CsCl to the perfusate saline in a TTX-treated parsol Cell. The voltage sag and depolarizing overshoot present in the response to a five second rectangular pulse of hyperpolarizing current in normal saline were reduced or eliminated in the saline containing Cs+ ions, and the recovery to resting potential level from the hyperpolarization took approximately one second longer. Broken lines in all records indicate zero membrane potential.
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Background synaptic activity in lobster and crayfish Parasol Cells.
2016Co-Authors: Deforest MellonAbstract:A, spontaneous bursting during background activity in a Parasol Cell from Homarus americanus, recurring at approximately 4-second intervals. B, irregular, occasional spontaneous bursting during background activity in a Parasol Cell of P. clarkii imaged on a similar time base. Note pause in background activity following the bursts in A and B. C, repetitive bursting in the same Parasol Cell as in B in response to a light pulse to the ipsilateral compound eye, the duration of which is approximated by the time marker below the electrical trace.
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Experimental protocol to reveal IA.
2016Co-Authors: Deforest MellonAbstract:Stimulation paradigm used to reveal the presence of IA. A, response of a Parasol Cell to a 4-sec rectangular pulse of depolarizing current. After a period of no current injection, a two-second pulse of hyperpolarizing current (0.2 nA) was injected into the neuron (bottom traces), followed immediately by the previous depolarizing current injection. As discussed in the text, the hyperpolarizing prepulse delayed the onset of the spike response to the depolarization. B, treatment of the Cell with 1 mM 4-AP reduced the prepulse delay and promoted bursting in the Parasol Cell. Zero membrane potential is indicated by the dashed lines.
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Increased spontaneous bursting in saline with 4-AP.
2016Co-Authors: Deforest MellonAbstract:Effects of 4-AP upon background activity in two Parasol Cells. A1, background activity in normal saline. A2, spontaneous bursting (*) in the presence of 1 mM 4-AP. A3, recovery in normal saline. B1, different Parasol Cell in normal saline. B2, following exposure to saline plus 1mM 4-AP. Bursts indicated by (*). Recording situation was lost immediately following return to normal saline. Dashed lines indicate zero membrane potential.
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Responses of Parasol Cells to Cesium saline.
2016Co-Authors: Deforest MellonAbstract:Effects of 10 mM CsCl on the background activity of a crayfish Parasol Cell. A, preparation perfused with normal saline prior to application of 10 mM CsCl saline. B, after 15' in saline with Cs + ions. The maximum levels achieved by the resting membrane potential increased by 6 mV to –76 mV, and the frequency of background bursts was reduced by approximately 50%. C, recovery in normal saline after 55', by which time the resting potential had fallen to –74 mV.
Dennis M. Dacey - One of the best experts on this subject based on the ideXlab platform.
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A synaptic signature for ON- and OFF-center Parasol ganglion Cells of the primate retina
Visual neuroscience, 2013Co-Authors: Joanna D. Crook, Orin S. Packer, Dennis M. DaceyAbstract:In the primate retina, Parasol ganglion Cells contribute to the primary visual pathway via the magnoCellular division of the lateral geniculate nucleus, display ON and OFF concentric receptive field structure, nonlinear spatial summation, and high achromatic temporal–contrast sensitivity. Parasol Cells may be homologous to the alpha-Y Cells of nonprimate mammals where evidence suggests that N-methyl-D-aspartate (NMDA) receptor-mediated synaptic excitation as well as glycinergic disinhibition play critical roles in contrast sensitivity, acting asymmetrically in OFF- but not ON-pathways. Here, light-evoked synaptic currents were recorded in the macaque monkey retina in vitro to examine the circuitry underlying Parasol Cell receptive field properties. Synaptic excitation in both ON and OFF types was mediated by NMDA as well as α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate glutamate receptors. The NMDA-mediated current–voltage relationship suggested high Mg2+ affinity such that at physiological potentials, NMDA receptors contributed ~20% of the total excitatory conductance evoked by moderate stimulus contrasts and temporal frequencies. Postsynaptic inhibition in both ON and OFF Cells was dominated by a large glycinergic “crossover” conductance, with a relatively small contribution from GABAergic feedforward inhibition. However, crossover inhibition was largely rectified, greatly diminished at low stimulus contrasts, and did not contribute, via disinhibition, to contrast sensitivity. In addition, attenuation of GABAergic and glycinergic synaptic inhibition left center–surround and Y-type receptive field structure and high temporal sensitivity fundamentally intact and clearly derived from modulation of excitatory bipolar Cell output. Thus, the characteristic spatial and temporal–contrast sensitivity of the primate Parasol Cell arises presynaptically and is governed primarily by modulation of the large AMPA/kainate receptor-mediated excitatory conductance. Moreover, the negative feedback responsible for the receptive field surround must derive from a nonGABAergic mechanism.
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effects of ph buffering on horizontal and ganglion Cell light responses in primate retina evidence for the proton hypothesis of surround formation
The Journal of Neuroscience, 2008Co-Authors: Christopher M Davenport, Peter B Detwiler, Dennis M. DaceyAbstract:Negative feedback from horizontal Cells to cone photoreceptors is regarded as the critical pathway for the formation of the antagonistic surround of retinal neurons, yet the mechanism by which horizontal Cells accomplish negative feedback has been difficult to determine. Recent evidence suggests that feedback uses a novel, non-GABAergic pathway that directly modulates the calcium current in cones. In non-mammalian vertebrates, enrichment of retinal pH buffering capacity attenuates horizontal Cell feedback, supporting one model in which feedback occurs by horizontal Cell modulation of the extraCellular pH in the cone synaptic cleft. Here we test the effect of exogenous pH buffering on the response dynamics of H1 horizontal Cells and the center-surround receptive field structure of Parasol ganglion Cells in the macaque monkey retina. Enrichment of the extraCellular buffering capacity with HEPES selectively attenuates surround antagonism in Parasol ganglion Cells. The H1 horizontal Cell light response includes a slow, depolarizing component that is attributed to negative feedback to cones. This part of the response is attenuated by HEPES and other pH buffers in a dose-dependent manner that is correlated with predicted buffering capacity. The selective effects of pH buffering on the Parasol Cell surround and H1 Cell light response suggests that, in primate retina, horizontal Cell feedback to cones is mediated via a pH-dependent mechanism and is a major determinant of the ganglion Cell receptive field surround.
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A coupled network for Parasol but not midget ganglion Cells in the primate retina.
Visual neuroscience, 1992Co-Authors: Dennis M. Dacey, Sarah T. BraceAbstract:IntraCellular injections of Neurobiotin were used to determine whether the major ganglion Cell classes of the macaque monkey retina, the magnoCellular-projecting Parasol, and the parvoCellular-projecting midget Cells showed evidence of Cellular coupling similar to that recently described for cat retinal ganglion Cells. Ganglion Cells were labeled with the fluorescent dye acridine orange in an in vitro , isolated retina preparation and were selectively targeted for intraCellular injection under direct microscopic control. The macaque midget Cells, like the beta Cells of the cat's retina, showed no evidence of tracer coupling when injected with Neurobiotin. By contrast, Neurobiotin-filled Parasol Cells, like cat alpha Cells, showed a distinct pattern of tracer coupling to each other (homotypic coupling) and to amacrine Cells (heterotypic coupling). In instances of homotypic coupling, the injected Parasol Cell was surrounded by a regular array of 3–6 neighboring Parasol Cells. The somata and proximal dendrites of these tracer-coupled Cells were lightly labeled and appeared to costratify with the injected Cell. Analysis of the nearest-neighbor distances for the Parasol Cell clusters showed that dendritic-field overlap remained constant as dendritic-field size increased from 100–400 μm in diameter. At least two amacrine Cell types showed tracer coupling to Parasol Cells. One amacrine type had a small soma and thin, sparsely branching dendrites that extended for 1–2 mm in the inner plexiform layer. A second amacrine type had a relatively large soma, thick main dendrites, and distinct, axon-like processes that extended for at least 2–3 mm in the inner plexiform layer. The main dendrites of the large amacrine Cells were closely apposed to the dendrites of Parasol Cells and may be the site of Neurobiotin transfer between the two Cell types. We suggest that the tracer coupling between neighboring Parasol Cells takes place indirectly via the dendrites of the large amacrine Cells and provides a mechanism, absent in midget Cells, for increasing Parasol Cell receptive-field size and luminance contrast sensitivity.
Andrea S. Bordt - One of the best experts on this subject based on the ideXlab platform.
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Synaptic input to OFF Parasol ganglion Cells in macaque retina
The Journal of comparative neurology, 2006Co-Authors: Andrea S. Bordt, Elizabeth S. Yamada, Hideo Hoshi, Wendy C. Perryman-stout, David W. MarshakAbstract:A Neurobiotin-injected OFF Parasol Cell from midperipheral macaque retina was studied by reconstruction of serial ultrathin sections and compared with ON Parasol Cells studied previously. In most respects, the synaptic inputs to the two subtypes were similar. Only a few of the amacrine Cell processes that provided input to the labeled OFF Parasol ganglion Cell dendrites made or received inputs within the series, and none of these interactions were with the bipolar Cells or other amacrine Cells presynaptic to the OFF Parasol Cell. These findings suggest that the direct inhibitory input to OFF Parasol Cells originates from other areas of the retina. OFF Parasol Cells were known to receive inputs from two types of diffuse bipolar Cells. To identify candidates for the presynaptic amacrine Cells, OFF Parasol Cells were labeled with Lucifer yellow by using a juxtaCellular labeling technique, and amacrine Cells known to costratify with them were labeled via immunofluorescent methods. Appositions were observed with amacrine Cells containing immunoreactive calretinin, parvalbumin, choline acetylatransferase, and G6-Gly, a cholecystokinin precursor. These findings suggest that the inhibitory input to Parasol Cells conveys information about several different attributes of visual stimuli and, particularly, about their global properties.
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Synaptic input to an ON Parasol ganglion Cell in the macaque retina: a serial section analysis.
Visual Neuroscience, 2002Co-Authors: David W. Marshak, Elizabeth S. Yamada, Andrea S. Bordt, Wendy C. PerrymanAbstract:: A labeled ON Parasol ganglion Cell from a macaque retina was analyzed in serial, ultrathin sections. It received 13% of its input from diffuse bipolar Cells. These directed a large proportion of their output to amacrine Cells but received a relatively small proportion of their amacrine Cell input via feedback synapses. In these respects, they were similar to the DB3 bipolar Cells that make synapses onto OFF Parasol Cells. Bipolar Cell axons that contacted the ON Parasol Cell in stratum 4 of the inner plexiform layer always made synapses onto the dendrite, and therefore, the number of bipolar Cell synapses onto these ganglion Cells could be estimated reliably by light microscopy in the future. Amacrine Cells provided the majority of inputs to the ON Parasol Cell. Only a few of the presynaptic amacrine Cell processes received inputs from the same bipolar Cells as the Parasol Cells, and most of the presynaptic amacrine Cell processes did not receive any inputs at all within the series. These findings suggest that most of the inhibitory input to the ON Parasol Cell originates from other areas of the retina. Amacrine Cells presynaptic to the Parasol ganglion Cell interacted very infrequently with other neurons in the circuit, and therefore, they would be expected to act independently, for the most part.
