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ROYER, AUDREY S., i ROBERT F. MILLER. "Dendritic impulse collisions and shifting sites of action potential initiation contract and extend the receptive field of an amacrine cell". Visual Neuroscience 24, nr 4 (lipiec 2007): 619–34. http://dx.doi.org/10.1017/s0952523807070617.
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We evaluated the contributions of somatic and dendritic impulses to the receptive field dimensions of amacrine cells in the amphibian retina. For this analysis, we used the NEURON simulation program with a multicompartmental, multichannel model of an On-Off amacrine cell with a three-dimensional structure obtained through computer tracing techniques. Simulated synaptic inputs were evenly spaced along the dendritic branches and organized into eight annuli of increasing radius. The first set of simulations activated each ring progressively to simulate an area summation experiment, while a second approach activated each annulus individually. Both sets of simulations were done with and without the presence of Na channels in the dendrites and soma. Unexpectedly, the receptive field dimensions observed in the area summation simulations was often smaller than that predicted from the summation of the annular simulations. Collisions of action potentials moving in opposite directions in the dendrites largely accounted for this contraction in receptive field size for the area summation studies. The presence of dendritic Na channels increased the size of the receptive field beyond that achieved in their absence and allowed the physiological size of the receptive field to approximate the physical dimensions of the dendritic tree. This receptive field augmentation was the result of impulse generating ability in the dendrites which enhanced the signal observed at the soma. These simulations provide a plausible mechanistic explanation for physiological recordings from amacrine cells that show similar phenomena.
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DAVENPORT, CHRISTOPHER M., PETER B. DETWILER i DENNIS M. DACEY. "Functional polarity of dendrites and axons of primate A1 amacrine cells". Visual Neuroscience 24, nr 4 (29.05.2007): 449–57. http://dx.doi.org/10.1017/s0952523807070010.
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The A1 cell is an axon-bearing amacrine cell of the primate retina with a diffusely stratified, moderately branched dendritic tree (∼400 μm diameter). Axons arise from proximal dendrites forming a second concentric, larger arborization (>4 mm diameter) of thin processes with bouton-like swellings along their length. A1 cells are ON-OFF transient cells that fire a brief high frequency burst of action potentials in response to light (Stafford & Dacey, 1997). It has been hypothesized that A1 cells receive local input to their dendrites, with action potentials propagating output via the axons across the retina, serving a global inhibitory function. To explore this hypothesis we recorded intracellularly from A1 cells in an in vitro macaque monkey retina preparation. A1 cells have an antagonistic center-surround receptive field structure for the ON and OFF components of the light response. Blocking the ON pathway with L-AP4 eliminated ON center responses but not OFF center responses or ON or OFF surround responses. Blocking GABAergic inhibition with picrotoxin increased response amplitudes without affecting receptive field structure. TTX abolished action potentials, with little effect on the sub-threshold light response or basic receptive field structure. We also used multi-photon laser scanning microscopy to record light-induced calcium transients in morphologically identified dendrites and axons of A1 cells. TTX completely abolished such calcium transients in the axons but not in the dendrites. Together these results support the current model of A1 function, whereby the dendritic tree receives synaptic input that determines the center-surround receptive field; and action potentials arise in the axons, which propagate away from the dendritic field across the retina.
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Poe, Amy R., Lingfeng Tang, Bei Wang, Yun Li, Maria L. Sapar i Chun Han. "Dendritic space-filling requires a neuronal type-specific extracellular permissive signal inDrosophila". Proceedings of the National Academy of Sciences 114, nr 38 (5.09.2017): E8062—E8071. http://dx.doi.org/10.1073/pnas.1707467114.
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Neurons sometimes completely fill available space in their receptive fields with evenly spaced dendrites to uniformly sample sensory or synaptic information. The mechanisms that enable neurons to sense and innervate all space in their target tissues are poorly understood. UsingDrosophilasomatosensory neurons as a model, we show that heparan sulfate proteoglycans (HSPGs) Dally and Syndecan on the surface of epidermal cells act as local permissive signals for the dendritic growth and maintenance of space-filling nociceptive C4da neurons, allowing them to innervate the entire skin. Using long-term time-lapse imaging with intactDrosophilalarvae, we found that dendrites grow into HSPG-deficient areas but fail to stay there. HSPGs are necessary to stabilize microtubules in newly formed high-order dendrites. In contrast to C4da neurons, non–space-filling sensory neurons that develop in the same microenvironment do not rely on HSPGs for their dendritic growth. Furthermore, HSPGs do not act by transporting extracellular diffusible ligands or require leukocyte antigen-related (Lar), a receptor protein tyrosine phosphatase (RPTP) and the only knownDrosophilaHSPG receptor, for promoting dendritic growth of space-filling neurons. Interestingly, another RPTP, Ptp69D, promotes dendritic growth of C4da neurons in parallel to HSPGs. Together, our data reveal an HSPG-dependent pathway that specifically allows dendrites of space-filling neurons to innervate all target tissues inDrosophila.
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Peters, B. N., i R. H. Masland. "Responses to light of starburst amacrine cells". Journal of Neurophysiology 75, nr 1 (1.01.1996): 469–80. http://dx.doi.org/10.1152/jn.1996.75.1.469.
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1. Starburst amacrine cells were studied using whole cell patch recording. Displaced starburst cells were labeled in rabbit retinas by intraocular injection of 4,6-diamidino-2-phenylindole. The retinas were isolated and maintained in vitro. The inner limiting membrane and Muller cell endfeet were removed mechanically from small areas above the starburst cell bodies, allowing an unimpeded approach under visual control to the cells. A total of 104 cells was studied. 2. In voltage-clamp recordings, the cells responded to light with slow, graded inward and outward currents on which were superimposed smaller, rapid inward currents. The rapid inward currents appeared to be postsynaptic currents. 3. The receptive fields of the cells were mapped using small spots. They had an on-center, off-surround organization. Visualizing the dendrites by including Lucifer yellow in the patch pipette showed that the receptive fields' centers closely approximated the dendritic spread of the neurons. 4. The cells' responses to movement were tested with smooth movements or with two-spot apparent motion. No directional preference was seen for spots swept across the whole receptive field, for centrifugal movements, or for centripetal movements. 5. Bath-applied tetrodotoxin (TTX) or intracellularly applied lidocaine N-ethyl bromide (QX-314) had no effect on any component of the spontaneous or light-evoked activity. Depolarization of the cell bodies by injected current showed evidence of active conductances, but they were unaffected by TTX or QX-314. 6. 6-Cyano-7-nitroquionxyline-2,3-dione eliminated the small rapid currents, indicating that they depend on alpha-amino-3-hydroxy-5-methyl-4- isoxazolepropionic acid/kainate glutamate receptors. 7. Because it is unlikely that we voltage clamped the distalmost dendrites of these wide-field cells, uncertainties remain about rapid electrical events occurring in the dendrites. From a functional point of view, though, the fact that slow responses to distal photic stimulation were recorded at the soma suggests that the starburst cells could in principle integrate inputs across fairly substantial fractions of their total dendritic arbors. The extent to which this actually occurs remains to be learned.
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Swindale, Nicholas V. "Feedback Decoding of Spatially Structured Population Activity in Cortical Maps". Neural Computation 20, nr 1 (styczeń 2008): 176–204. http://dx.doi.org/10.1162/neco.2008.20.1.176.
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A mechanism is proposed by which feedback pathways model spatial patterns of feedforward activity in cortical maps. The mechanism can be viewed equivalently as readout of a content-addressable memory or as decoding of a population code. The model is based on the evidence that cortical receptive fields can often be described as a separable product of functions along several dimensions, each represented in a spatially ordered map. Given this, it is shown that for an N-dimensional map, accurate modeling and decoding of xN feedforward activity patterns can be done with Nx fibers, N of which must be active at any one time. The proposed mechanism explains several known properties of the cortex and pyramidal neurons: (1) the integration of signals by dendrites with a narrow tangential distribution, that is, apical dendrites; (2) the presence of fast-conducting feedback projections with broad tangential distributions; (3) the multiplicative effects of attention on receptive field profiles; and (4) the existence of multiplicative interactions between subthreshold feedforward inputs to basal dendrites and inputs to apical dendrites.
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Wilson, James R., Donna M. Forestner i Ryan P. Cramer. "Quantitative analyses of synaptic contacts of interneurons in the dorsal lateral geniculate nucleus of the squirrel monkey". Visual Neuroscience 13, nr 6 (listopad 1996): 1129–42. http://dx.doi.org/10.1017/s095252380000777x.
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AbstractThree interneurons were recorded from and then injected with horseradish peroxidase in the parvocellular laminae of the squirrel monkey's (Saimiri sciureus) dorsal lateral geniculate nucleus. They were then examined using the electron microscope for their synaptic contacts, both the afferent contacts onto their dendrites and their presynaptic dendritic contacts onto presumptive projection (relay) neuron dendrites. The somata of these interneurons were small (mean = 178 μm2), but the dendritic trees were large compared with those of projection neurons. All three interneurons had similar synaptic patterns onto their dendrites with about equal numbers of retinal, cortical, and GABAergic contacts. The distribution of these contacts was more uniform compared with the same types of contacts made onto projection neurons. The presynaptic dendrites were observed to contact only the dendrites of presumptive projection neurons, and these contacts were nearly all in the form of geniculate triads. None of the three interneurons displayed an axon. The receptive fields of these interneurons were similar to those of projection cells, but were larger and had center-response signs that were the opposite of the projection neurons around them (e.g. OFF center for the dorsal part of the parvocellular mass where ON-center projection neurons reside). The squirrel monkey data provides additional evidence that one aspect of the laminar pattern observed in the parvocellular pathway of the primate's dLGN might be related to a segregation of projection neurons of one center-response sign with interneurons of the opposite center-response sign.
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Renehan, W. E., M. F. Jacquin, R. D. Mooney i R. W. Rhoades. "Structure-function relationships in rat medullary and cervical dorsal horns. II. Medullary dorsal horn cells". Journal of Neurophysiology 55, nr 6 (1.06.1986): 1187–201. http://dx.doi.org/10.1152/jn.1986.55.6.1187.
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In Nembutal-anesthetized rats, 31 physiologically identified medullary dorsal horn (MDH) cells were labeled with horseradish peroxidase (HRP). Ten responded only to deflection of one or more vibrissae. Six cells were activated by guard hair movement only, six by deflection of guard hairs or vibrissa(e), and seven by pinch of facial skin with serrated forceps. Different classes of low-threshold cells could not be distinguished on the basis of their somadendritic morphologies or laminar distribution. Neurons activated by multiple vibrissae were unique, however, in that one sent its axon into the medial lemniscus, and three projected into the trigeminal spinal tract. None of the guard hair-only or vibrissae-plus-guard hair neurons had such projections. Cells that responded best to noxious stimulation were located mainly in laminae I, II, and deep V, while neurons activated by vibrissa(e) and/or guard hair deflection were located in layers III, IV, and superficial V. Low-threshold neurons generally had fairly thick dendrites with few spines, whereas high-threshold cells tended to have thinner dendrites with numerous spines. Moreover, the dendritic arbors of low-threshold cells were, for the most part, denser than those of the noxious cells. Neurons with mandibular receptive fields were located in the dorsomedial portion of the MDH; cells with ophthalmic fields were found in the ventrolateral MDH, and maxillary cells were interposed. Cells sensitive to deflection of dorsal mystacial vibrissae and/or guard hairs were located ventral to those activated by more ventral hairs. Neurons with rostral receptive fields were found in the rostral MDH, while cells activated by hairs of the caudal mystacial pad, periauricular, and periorbital regions were located in the caudal MDH. Receptive-field types were encountered that have not been reported for trigeminal primary afferent neurons: multiple vibrissae; vibrissae plus guard hairs; and wide dynamic range. The latter two can be explained by the convergence of different primary afferent types onto individual neurons. Our failure to find a significant relationship between dendritic area (in the transverse plane) and the number of vibrissae suggests that primary afferent convergence may not be responsible for the synthesis of the multiple vibrissae receptive field. Excitatory connections between MDH neurons may, therefore, account for multiple vibrissae receptive fields in the MDH.
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Hyngstrom, Allison, Michael Johnson, Jenna Schuster i C. J. Heckman. "Movement-related receptive fields of spinal motoneurones with active dendrites". Journal of Physiology 586, nr 6 (15.03.2008): 1581–93. http://dx.doi.org/10.1113/jphysiol.2007.149146.
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Dacey, Dennis M., i Sarah Brace. "A coupled network for parasol but not midget ganglion cells in the primate retina". Visual Neuroscience 9, nr 3-4 (październik 1992): 279–90. http://dx.doi.org/10.1017/s0952523800010695.
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AbstractIntracellular 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.
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Chen, Minggang, Seunghoon Lee i Z. Jimmy Zhou. "Local synaptic integration enables ON-OFF asymmetric and layer-specific visual information processing in vGluT3 amacrine cell dendrites". Proceedings of the National Academy of Sciences 114, nr 43 (27.09.2017): 11518–23. http://dx.doi.org/10.1073/pnas.1711622114.
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A basic scheme of neuronal organization in the mammalian retina is the segregation of ON and OFF pathways in the inner plexiform layer (IPL), where glutamate is released from ON and OFF bipolar cell terminals in separate inner (ON) and outer (OFF) sublayers in response to light intensity increments and decrements, respectively. However, recent studies have found that vGluT3-expressing glutamatergic amacrine cells (GACs) generate ON-OFF somatic responses and release glutamate onto both ON and OFF ganglion cell types, raising the possibility of crossover excitation in violation of the canonical ON-OFF segregation scheme. To test this possibility, we recorded light-evoked Ca2+ responses from dendrites of individual GACs infected with GCaMP6s in mouse. Under two-photon imaging, a single GAC generated rectified local dendritic responses, showing ON-dominant responses in ON sublayers and OFF-dominant responses in OFF sublayers. This unexpected ON-OFF segregation within a small-field amacrine cell arose from local synaptic processing, mediated predominantly by synaptic inhibition. Multiple forms of synaptic inhibition compartmentalized the GAC dendritic tree and endowed all dendritic varicosities with a small-center, strong-surround receptive field, which varied in receptive field size and degree of ON-OFF asymmetry with IPL depth. The results reveal a form of short-range dendritic autonomy that enables a small-field, dual-transmitter amacrine cell to process diverse dendritic functions in a stratification level- and postsynaptic target-specific manner, while preserving the fundamental ON-OFF segregation scheme for parallel visual processing and high spatial resolution for small object motion and uniformity detection.
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Stöckl, Anna Lisa, David Charles O’Carroll i Eric James Warrant. "Hawkmoth lamina monopolar cells act as dynamic spatial filters to optimize vision at different light levels". Science Advances 6, nr 16 (kwiecień 2020): eaaz8645. http://dx.doi.org/10.1126/sciadv.aaz8645.
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How neural form and function are connected is a central question of neuroscience. One prominent functional hypothesis, from the beginnings of neuroanatomical study, states that laterally extending dendrites of insect lamina monopolar cells (LMCs) spatially integrate visual information. We provide the first direct functional evidence for this hypothesis using intracellular recordings from type II LMCs in the hawkmoth Macroglossum stellatarum. We show that their spatial receptive fields broaden with decreasing light intensities, thus trading spatial resolution for higher sensitivity. These dynamic changes in LMC spatial properties can be explained by the density and lateral extent of their dendritic arborizations. Our results thus provide the first physiological evidence for a century-old hypothesis, directly correlating physiological response properties with distinctive dendritic morphology.
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Gladfelter, Wilbert E., Ronald J. Millecchia, Lillian M. Pubols, Ramana V. Sonty, Louis A. Ritz, Dorothy Covalt-Dunning, James Culberson i Paul B. Brown. "Crossed receptive field components and crossed dendrites in cat sacrocaudal dorsal horn". Journal of Comparative Neurology 336, nr 1 (1.10.1993): 96–105. http://dx.doi.org/10.1002/cne.903360108.
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Stanford, L. R. "X-cells in the cat retina: relationships between the morphology and physiology of a class of cat retinal ganglion cells". Journal of Neurophysiology 58, nr 5 (1.11.1987): 940–64. http://dx.doi.org/10.1152/jn.1987.58.5.940.
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1. The morphology of 21 physiologically characterized X-cells in the cat retina was studied using intracellular recording and injection with horseradish peroxidase. The data from these experiments were used to test directly the relationships between specific structural and functional characteristics of a sample of individual retinal ganglion cells of the same anatomical and physiological class. Where possible, the response properties of 53 other retinal X-cells that were not successfully injected and recovered are compared with those of the labeled sample. These comparisons, which included conduction velocities (both intraretinal and extraretinal) and receptive-field size, indicate that the labeled X-cells are a representative sample of the population of retinal X-cells at corresponding eccentricities. 2. The somata of this group of injected retinal X-cells increase in size with increasing distance from the area centralis up to 13 degrees eccentricity (the greatest distance from the area centralis at which an X-cell was injected and recovered). The soma sizes of this sample of retinal ganglion cells range from 143.5 to 529.9 micron 2 (diam = 13.5-26.0 micron). Comparison of the soma sizes of the injected and recovered retinal X-cells with those of 300 Nissl-stained neurons at comparable eccentricities in the same retinae indicate that the injected sample had soma sizes that are consistent with their classification as "medium-sized" retinal ganglion cells (5, 69, 74). 3. All of the physiologically characterized retinal X-cells of this study have the compact dendritic arbors described to the morphological class of retinal ganglion cell called beta-cells by Boycott and Wassle (5). The dendrites of some of these neurons have many spinelike appendages, whereas those of other cells are nearly appendage free. We found no obvious correlation between the presence of dendritic appendages and any specific response characteristic ("ON-" or "OFF-center", etc). Like the size of the soma, both the diameter of the dendritic arbors of these cells, and the number of primary dendrites (those dendrites that originate directly from the soma), increase with increasing distance from the area centralis. 4. Since both morphological and physiological data were obtained for these neurons, it is possible to describe the relationship between the size of the receptive-field center and the diameter of the dendritic arbor for individual retinal ganglion cells. These comparisons show that the relationship between the anatomical measure and this response parameter for the entire sample of labeled X-cells is not as strong as had previously been suggested.(ABSTRACT TRUNCATED AT 400 WORDS)
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Jia, Yu, Seunghoon Lee, Yehong Zhuo i Z. Jimmy Zhou. "A retinal circuit for the suppressed-by-contrast receptive field of a polyaxonal amacrine cell". Proceedings of the National Academy of Sciences 117, nr 17 (9.04.2020): 9577–83. http://dx.doi.org/10.1073/pnas.1913417117.
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Amacrine cells are a diverse population of interneurons in the retina that play a critical role in extracting complex features of the visual world and shaping the receptive fields of retinal output neurons (ganglion cells). While much of the computational power of amacrine cells is believed to arise from the immense mutual interactions among amacrine cells themselves, the intricate circuitry and functions of amacrine–amacrine interactions are poorly understood in general. Here we report a specific interamacrine pathway from a small-field, glutamate–glycine dual-transmitter amacrine cell (vGluT3) to a wide-field polyaxonal amacrine cell (PAS4/5). Distal tips of vGluT3 cell dendrites made selective glycinergic (but not glutamatergic) synapses onto PAS4/5 dendrites to provide a center-inhibitory, surround-disinhibitory drive that helps PAS4/5 cells build a suppressed-by-contrast (sbc) receptive field, which is a unique and fundamental trigger feature previously found only in a small population of ganglion cells. The finding of this trigger feature in a circuit upstream to ganglion cells suggests that the sbc form of visual computation occurs more widely in the retina than previously believed and shapes visual processing in multiple downstream circuits in multiple ways. We also identified two different subpopulations of PAS4/5 cells based on their differential connectivity with vGluT3 cells and their distinct receptive-field and luminance-encoding characteristics. Moreover, our results revealed a form of crosstalk between small-field and large-field amacrine cell circuits, which provides a mechanism for feature-specific local (<150 µm) control of global (>1 mm) retinal activity.
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Nelson, R., i H. Kolb. "A17: a broad-field amacrine cell in the rod system of the cat retina". Journal of Neurophysiology 54, nr 3 (1.09.1985): 592–614. http://dx.doi.org/10.1152/jn.1985.54.3.592.
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A17 amacrine cells of the cat retina have been penetrated with horseradish peroxidase (HRP)-filled microelectrodes and their light responses recorded. These cells depolarize in sustained fashion to steps of light. Viewed in retinal wholemounts, HRP-injected cells have a spokelike radiating splay of very fine dendrites (0.1 micron diam) passing diffusely through all strata of the inner plexiform layer (IPL) to run primarily in strata 4 and 5. There are as many as 1,000 large, regularly spaced beads borne on the 500- to 1,200-micron diameter dendritic field. Cell body sizes range from 9 to 13 micron. In the electron microscope, the dendritic beads in sublamina b of the IPL are seen to synapse reciprocally with rod bipolar axon terminals. Dendritic beads in sublamina a rarely make synapses, but between the beads in this layer, input from at least three distinctive amacrine profiles occurs. Though diffuse at the light microscopic level, A17 thus appears to be structurally bistratified, with amacrine input in sublamina a and bipolar input in sublamina b. It is likely that A17 can be identified with AI. A17 signals are driven almost exclusively by rods. The spectral sensitivity peaks at 507 nm, identical with that of pigment epithelial cells. Light adaptation abolishes all but a small hyperpolarizing component of the signal. The overall intensity-response range is similar to that of AII amacrine cells. When receptive fields of A17 cells are mapped with slit stimuli, a broad, single-component curve is measured approximately covering the dendritic field. The receptive field is well described by a linear electrical model with a mean space constant of 259 +/- 97 micron (SD). On the other hand, responses to centered slit stimuli of varying width yielded space constants of only 38 +/- 29 micron. A17 amacrines are thus broad-field components of the cat's rod system but with very little capacity for spatial integration. Receptive-field measurements are not supportive of the notion of isolated dendritic regions.
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Hirai, T., H. D. Schwark, C. T. Yen, C. N. Honda i E. G. Jones. "Morphology of physiologically characterized medial lemniscal axons terminating in cat ventral posterior thalamic nucleus". Journal of Neurophysiology 60, nr 4 (1.10.1988): 1439–59. http://dx.doi.org/10.1152/jn.1988.60.4.1439.
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1. Medial lemniscal axons were identified by extra- and intracellular recording in the thalamic ventral posterior lateral nucleus (VPL) of cats and injected intracellularly with horseradish peroxidase (HRP). 2. Axons were characterized in terms of their latencies of response to stimulation of the medial lemniscus in the medulla, their receptive fields, and the temporal patterns of their discharge in response to stimulation of the receptive field with natural, hand-held stimuli. One-hundred sixty-six axons were placed in five operational groups: hair transient (Ht) (n = 41); hair sustained (Hs) (n = 45); pressure transient (Pt) (n = 14); pressure sustained (Ps) (n = 27), and deep or joint (Jt) (n = 39). 3. There was a tendency for Jt axons to have their terminations in anterodorsal parts of VPL and for those in the four cutaneous categories to have theirs in more central parts of the nucleus. 4. Nineteen injected axons with receptive fields mainly on the distal forelimb were subjected to detailed morphological analysis in terms of extent of terminal field and number of boutons. All axons ended in localized terminal fields that were more extensive anteroposteriorly than in the other dimensions. All showed an overall similarity and similar ranges of variation. There was a tendency, however, for Jt axons to have the least extensive terminations with fewest boutons. Ps axons had the most extensive terminations and largest number of boutons; Hs axons had small terminations and few boutons but Ht axons had small-to-medium arborizations with many boutons; no Pt axons were sufficiently well stained to enable comparisons of them with the others. There were no marked differences in axon diameter or conduction velocity among the five types. 5. Boutons identified light microscopically tended to be clustered in linear chains along proximal dendrites of relay neurons and electron microscopy revealed that they were terminals making synaptic contacts on relay cell dendrites and on presynaptic dendrites of interneurons. 6. These results reveal more similarities than differences among lemniscal axon terminations in VPL. Further studies of a quantitative nature on stimulus-response coupling and on the geographic distribution of lemniscal synapses on relay neurons will be required to reveal how lemniscal input is translated into relay cell output in VPL.
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Elyada, Yishai M., Juergen Haag i Alexander Borst. "Different receptive fields in axons and dendrites underlie robust coding in motion-sensitive neurons". Nature Neuroscience 12, nr 3 (8.02.2009): 327–32. http://dx.doi.org/10.1038/nn.2269.
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Heikkinen, Hanna, Fariba Sharifian, Ricardo Vigario i Simo Vanni. "Feedback to distal dendrites links fMRI signals to neural receptive fields in a spiking network model of the visual cortex". Journal of Neurophysiology 114, nr 1 (lipiec 2015): 57–69. http://dx.doi.org/10.1152/jn.00169.2015.
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The blood oxygenation level-dependent (BOLD) response has been strongly associated with neuronal activity in the brain. However, some neuronal tuning properties are consistently different from the BOLD response. We studied the spatial extent of neural and hemodynamic responses in the primary visual cortex, where the BOLD responses spread and interact over much longer distances than the small receptive fields of individual neurons would predict. Our model shows that a feedforward-feedback loop between V1 and a higher visual area can account for the observed spread of the BOLD response. In particular, anisotropic landing of inputs to compartmental neurons were necessary to account for the BOLD signal spread, while retaining realistic spiking responses. Our work shows that simple dendrites can separate tuning at the synapses and at the action potential output, thus bridging the BOLD signal to the neural receptive fields with high fidelity.
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Honda, C. N. "Visceral and somatic afferent convergence onto neurons near the central canal in the sacral spinal cord of the cat". Journal of Neurophysiology 53, nr 4 (1.04.1985): 1059–78. http://dx.doi.org/10.1152/jn.1985.53.4.1059.
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One hundred and sixty extracellularly and intracellularly recorded unitary discharges from the sacral or caudal spinal segments of 30 anemically decerebrated cats were studied to examine the effects of somatic and visceral afferent stimulation on neurons near the central canal (CC). The recorded unitary activity was histologically verified (by dye marks or horseradish peroxidase, HRP) as having come from the gray matter surrounding the CC that approximates Rexed's lamina X. In the absence of intentional stimulation or apparent injury by the recording electrode, 62% of the units exhibited ongoing discharges. Each unit was tested for responses to the stimulation of somatic (cutaneous and subcutaneous) and visceral (bladder and colon) structures. Seventy-six (48%) of the units responded exclusively to the stimulation of somatic receptive fields, and 10 (6%) of the units were selectively responsive to stimulation of the pelvic viscera. The activity of the remaining 74 (46%) was influenced by activity in both somatic and visceral afferent fibers. Eighteen of the 160 neurons were intracellularly marked with HRP. Based on perikaryal size and dendritic extent, it was possible to divide these cells into two partially overlapping groups. One group consisted of seven neurons with small to medium-sized perikarya, dendritic arbors largely restricted to the gray matter surrounding the CC, and small, singular somatic receptive fields. The second group comprised 11 cells with medium to large-sized soma and dendrites extending out of lamina X. These larger neurons usually possessed multiple, widely distributed somatic receptive fields. The principal finding of the present study is that in the sacral spinal cord many cells near the CC receive primary afferent inputs converging from a wide range of receptor types in somatic and visceral structures. Such neurons are capable of integrating afferent information from somatic structures on both sides of the body with information originating in pelvic viscera and midline regions such as the genitals.
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Muller, Jay F., Josef Ammermüller, Richard A. Normann i Helga Kolb. "Synaptic inputs to physiologically defined turtle retinal ganglion cells". Visual Neuroscience 7, nr 5 (listopad 1991): 409–29. http://dx.doi.org/10.1017/s0952523800009718.
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AbstractTwo physiologically distinct, HRP-marked turtle retinal ganglion cells were examined for their morphology, GABAergic, glycinergic, and bipolar cell synaptic inputs, using electron-microscopic autoradiography and postembedding immunocytochemistry. One cell was a color-opponent, transient ON/OFF ganglion cell. Its center response to red was a sustained hyperpolarization, and its center response to green was a depolarization with increased spiking at onset. The HRP-injected cell most resembled G6, from previous Golgi-impregnation studies (Kolb, 1982; Kolb et al., 1988). It was a narrow-field bistratified cell, whose two broad dendritic strata peaked at approximately levels L20–25 (sublamina a) and L60 (sublamina b) of the inner plexiform layer. Bipolar cell synapses onto G6 were found evenly distributed between its distal and proximal dendritic strata, spanning L20–75. These inputs probably originated from several different bipolar cells, reflecting the complexity of the center response. GABAergic inputs were found onto both the distal and proximal strata, from near L20–L85. Only a few glycinergic inputs, confined to dendrites at L50–70, were observed.A second ganglion cell type that we physiologically characterized and HRP-injected had sustained ON-center, sustained OFF-surround responses. Two examples were studied; both were bistratified in sublamina b, near L60–70 and L85–100, with branches up to near L40. They resembled G10, from previous Golgi-impregnation studies (Kolb, 1982; Kolb et al., 1988). One cell was partially reconstructed to look at the distributions of GABAergic and glycinergic amacrine cell, and bipolar cell inputs. Although synapses from bipolar cells were equally divided between the two major dendritic strata of G10, the inputs to the distal stratum were close to the soma, and the inputs to the more proximal stratum were on the peripheral dendrites. This arrangement may reflect input from two distinct types of ON-bipolar cell. GABAergic and glycinergic inputs to G10 costratified to both strata and to the distal branches; but where glycinergic inputs were found distributed throughout the arbor, GABAergic inputs appeared to be confined to peripheral dendrites. We hypothesize on the neural elements involved and the circuitry that may underlie the physiologically recorded receptive fields of these two very different ganglion cell types in the turtle retina.
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KASAMATSU, TAKUJI, KEIKO MIZOBE i ERICH E. SUTTER. "Muscimol and baclofen differentially suppress retinotopic and nonretinotopic responses in visual cortex". Visual Neuroscience 22, nr 6 (listopad 2005): 839–58. http://dx.doi.org/10.1017/s0952523805226135.
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This study relates to local field potentials and single-unit responses in cat visual cortex elicited by contrast reversal of bar gratings that were presented in single, double, or multiple discrete patch (es) of the visual field. Concurrent stimulation of many patches by means of the pseudorandom, binary m-sequence technique revealed interactions between their respective responses. An analysis identified two distinct components of local field potentials: a fast local component (FLC) and a slow distributed component (SDC). The FLC is thought to be a primarily postsynaptic response, as judged by its relatively short latency. It is directly generated by thalamocortical volleys following retinotopic stimulation of receptive fields of a small cluster of single cells, combined with responses to recurrent excitation and inhibition derived from the cells under study and immediately neighboring cells. In contrast, the SDC is thought to be an aggregate of dendritic potentials related to the long-range lateral connections (i.e. long-range coupling). We compared the suppressive effects of a GABAA-receptor agonist, muscimol, on the FLC and SDC with those of a GABAB-receptor agonist, baclofen, and found that muscimol more strongly suppressed the FLC than the SDC, and that the reverse was the case for baclofen. The differential suppression of the FLC and SDC found in the present study is consistent with the notion that intracortical electrical signals related to the FLC terminate on the somata and proximal/basal dendrites, while those related to the SDC terminate on distal dendrites.
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Paul, Dorothy H., i Jan Bruner. "Receptor Potentials and Electrical Properties of Nonspiking Stretch-Receptive Neurons in the Sand Crab Emerita analoga (Anomura, Hippidae)". Journal of Neurophysiology 81, nr 5 (1.05.1999): 2493–500. http://dx.doi.org/10.1152/jn.1999.81.5.2493.
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Receptor potentials and electrical properties of nonspiking stretch-receptive neurons in the sand crab Emerita analoga (Anomura, Hippidae). Four nonspiking, monopolar neurons with central somata and large peripheral dendrites constitute the sole innervation of the telson-uropod elastic strand stretch receptor in Emerita analoga. We characterized their responses to stretch and current injection, using two-electrode current clamp, in intact cells and in two types of isolated peripheral dendritic segments, one that included and one that excluded the dendritic termini (mechanosensory membrane). The membrane potentials of intact cells at rest (mean ± SD: −57 ± 4.4 mV, n = 30), recorded in peripheral or neuropil processes, are similar to the membrane potentials of isolated dendritic segments and always less negative than membrane potentials of motoneurons and interneurons recorded in the same preparations. Ion substitution experiments indicate that the membrane potential is influenced strongly by Na+ conductance, probably localized in the mechanotransducing terminals within the elastic strand. The form of the receptor potential in response to ramp-hold-release stretch remains the same as stretch amplitude is varied and is not dependent on initial membrane potential (−70 to −30 mV) or recording site: initial depolarization (slope follows ramp of applied stretch), terminated by rapid, partial repolarization to a plateau (delayed depolarization) that is intermediate between the peak depolarization and the initial potential and sustained for the duration of the stretch. Responses to depolarizing current pulses are similar to stretch-evoked receptor potentials, except for small amplitude stimuli: an initial peak occurs only in response to stretch and probably reflects elastic recoil of the extracellular matrix surrounding the dendritic terminals. The rapid, partial repolarization depends on holding potential and is abolished by 4-aminopyridine (4-AP; 10 mM), implicating a fast-activating, fast-inactivating K+ conductance; TEA (60 mM) abolishes the remaining slow repolarization to the plateau. In intact cells, but not dendritic segments, regenerative depolarizations can arise in response to stretch or depolarizing current pulses; they are reduced by CdCl2 (10 μM) in the saline containing TEA and 4-AP and probably reflect current spread from Ca2+ influx at presynaptic terminals in the ganglion. We found no evidence for other voltage-activated conductances. Unlike morphologically similar “nonspiking” thoracic receptors of other species, E. analoga’s nonspiking neurons are electrically compact and do not boost the analogue afferent signal by voltage-activated inward currents. The most prominent (only?) voltage-activated extra-ganglionic conductances are for potassium; by reducing the slope of the stretch-plateau depolarization curve, they extend each neuron’s functional range to the full range of sensitivity of the receptor.
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Montgomery, J. C., i D. Bodznick. "HINDBRAIN CIRCUITRY MEDIATING COMMON MODE SUPPRESSION OF VENTILATORY REAFFERENCE IN THE ELECTROSENSORY SYSTEM OF THE LITTLE SKATE RAJA ERINACEA". Journal of Experimental Biology 183, nr 1 (1.10.1993): 203–16. http://dx.doi.org/10.1242/jeb.183.1.203.
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Elasmobranch fish have an electrosensory system which they use for prey detection and for orientation. Sensory inputs to this system are corrupted by a form of reafference generated by the animal's own ventilation, but this noise is reduced by sensory processing within the medullary nucleus of the electrosensory system. This noise cancellation is achieved, at least in part, by a common mode rejection mechanism. In this study we have examined characteristics of neurones within the medullary nucleus in an attempt to understand the neural circuitry responsible for common mode suppression. Our results are in accord with previous indications that ascending efferent neurones of the medullary nucleus are monosynaptically activated from the ipsilateral electrosensory nerves and project to the midbrain. We demonstrate that in Raja erinacea, as has been previously shown in one other species (Cephaloscyllium isabella), ascending efferent neurones typically have a discrete focal excitatory receptive field and an inhibitory receptive field which may be discrete or diffuse and which often includes a contralateral component. We identify a group of interneurones within the medullary nucleus which are driven monosynaptically from the electrosensory nerves, have simple discrete excitatory receptive fields and respond vigorously to imposed common mode signals. The simplest model of the circuitry underlying common mode rejection that is consistent with the evidence is that direct afferent input impinges onto the basal dendrites of the ascending efferent neurones and onto interneurones within the nucleus, and the interneurones in turn inhibit the ascending efferents. The pattern of this projection, including commissural inputs, determines the nature and extent of ascending efferents' inhibitory surrounds and mediates the suppression of common mode signals.
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Zhu, J. Julius, i Barry W. Connors. "Intrinsic Firing Patterns and Whisker-Evoked Synaptic Responses of Neurons in the Rat Barrel Cortex". Journal of Neurophysiology 81, nr 3 (1.03.1999): 1171–83. http://dx.doi.org/10.1152/jn.1999.81.3.1171.
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Intrinsic firing patterns and whisker-evoked synaptic responses of neurons in the rat barrel cortex. We have used whole cell recording in the anesthetized rat to study whisker-evoked synaptic and spiking responses of single neurons in the barrel cortex. On the basis of their intrinsic firing patterns, neurons could be classified as either regular-spiking (RS) cells, intrinsically burst-spiking (IB) cells, or fast-spiking (FS) cells. Some recordings responded to current injection with a complex spike pattern characteristic of apical dendrites. All cell types had high rates of spontaneous postsynaptic potentials, both excitatory (EPSPs) and inhibitory (IPSPs). Some spontaneous EPSPs reached threshold, and these typically elicited only single action potentials in RS cells, bursts of action potentials in FS cells and IB cells, and a small, fast spike or a complex spike in dendrites. Deflection of single whiskers evoked a fast initial EPSP, a prolonged IPSP, and delayed EPSPs in all cell types. The intrinsic firing pattern of cells predicted their short-latency whisker-evoked spiking patterns. All cell types responded best to one or, occasionally, two primary whiskers, but typically 6–15 surrounding whiskers also generated significant synaptic responses. The initial EPSP had a relatively fixed amplitude and latency, and its amplitude in response to first-order surrounding whiskers was ∼55% of that induced by the primary whisker. Second- and third-order surrounding whiskers evoked responses of ∼27 and 12%, respectively. The latency of the initial EPSP was shortest for the primary whiskers, longer for surrounding whiskers, and varied with the neurons’ depth below the pia. EPSP latency was shortest in the granular layer, longer in supragranular layers, and longest in infragranular layers. The receptive field size, defined as the total number of fast EPSP-inducing whiskers, was independent of each cell’s intrinsic firing type, its subpial depth, or the whisker stimulus parameters. On average, receptive fields included >10 whiskers. Our results show that single neurons integrate rapid synaptic responses from a large proportion of the mystacial vibrissae, and suggest that the whisker-evoked responses of barrel neurons are a function of both synaptic inputs and intrinsic membrane properties.
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Ezeh, P. I., D. P. Wellis i J. W. Scott. "Organization of inhibition in the rat olfactory bulb external plexiform layer". Journal of Neurophysiology 70, nr 1 (1.07.1993): 263–74. http://dx.doi.org/10.1152/jn.1993.70.1.263.
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1. Intracellular recordings were made from the output neurons (mitral and tufted cells) of the rat olfactory bulb during electrical orthodromic stimulation of the olfactory nerve layer (ONL) and antidromic stimulation of the lateral olfactory tract and posterior piriform cortex (pPC) to test for physiological differences among the neuron types. Many of these neurons were identified by intracellular injections of biocytin, and others were identified by their pattern of antidromic activation. 2. Both marked and unmarked mitral cells showed large inhibitory postsynaptic potentials (IPSPs) in response to antidromic stimulation of the pPC, whereas tufted cells exhibited small IPSPs in response to pPC stimulation. Tufted cells, however, showed large IPSPs in response to ONL stimulation. In many cases, these tufted cell responses to ONL stimulation were larger than the mitral cell responses. The marked superficial tufted cells, those with basal dendrites in the superficial sublayer of the external plexiform layer (EPL), had the smallest IPSPs in response to pPC stimulation. These data support anatomic observations suggesting that the granule cell populations responsible for the IPSPs may be different for mitral and for superficial tufted cells. 3. The different types of output cells also showed differences in their responses to orthodromic stimulation. Type I mitral cells, which have basal dendrites confined to the deep sublayer of the EPL, were significantly less excitable by ONL stimulation than were the type II mitral cells, which have basal dendrites distributed within the intermediate sublayer of the EPL. Half of the type I mitral cells could not be excited at all by ONL stimulation. Superficial tufted cells showed even greater orthodromic excitability than type II mitral cells, usually responding to ONL stimulation with two or more spikes. 4. The ionic basis of the IPSPs in the superficial tufted cells appeared similar to those described for mitral cells. These IPSPs could be reversed by chloride injection and were associated with increased membrane conductance. 5. For both mitral and tufted cells, the number of ONL electrodes evoking IPSPs was greater than the number evoking spikes. These data suggest a kind of center-surround organization of inputs to these cells from the ONL, although this does not yet imply that the sensory receptive field of these output cells has a center-surround organization. 6. In conclusion, the properties of rat olfactory bulb output cells correlate with the sublayers of the EPL in which their basal dendrites lie.(ABSTRACT TRUNCATED AT 400 WORDS)
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FAMIGLIETTI, E. V. "“Small-tufted” ganglion cells and two visual systems for the detection of object motion in rabbit retina". Visual Neuroscience 22, nr 4 (lipiec 2005): 509–34. http://dx.doi.org/10.1017/s0952523805224124.
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Small-tufted (ST) ganglion cells of rabbit retina are divided into eight types based upon morphology, branching pattern, level of dendritic stratification, and quantitative dimensional analysis. Only one of these types has been previously characterized in Golgi preparations, and four may be discerned in the work of others. Given their small dendritic-field size, and assuming uniform mosaics of each across the retina, ST cells comprise about 45% of all rabbit ganglion cells, and are therefore of major functional significance. Four ST cells occur as two paramorphic (a/b) pairs, and thus belong to class III, as previously defined. Four branch in sublaminaeaandbof the inner plexiform layer (IPL) and therefore belong to class IV. ST cells have small cell bodies 10–15 μm in diameter, small axons 0.7–1.3 μm in diameter, and small dendritic-field diameters, 40–110 μm in mid-visual streak. The dendrites of ST cells are highly branched, and bear spines and appendages of varying length, but vary from type to type. Class III.2 cells and class III.3 cells are partly bistratified. Class IV small-tufted cells differ characteristically in multiple features of dendritic branching and stratification. Class III small-tufted cells apparently have concentric (ON-center and OFF-center) receptive fields and may have “sluggish-transient” (class III.2) and “sluggish-sustained” (class III.3) physiology. Class IV cells include the “local-edge-detector” (LED) (class IVst1), and are all expected to give ON–OFF responses to small, centered, slowly moving visual stimuli. Based upon systematic variation in dendritic-field size across the retina, ST cells may be divided into two groups. In this “universal prey” species, they may belong to two systems of motion detection, typified by ON–OFF directionally selective and LED ganglion cells, respectively, specialized for detection of rapid motion at the horizon for land-based predators, and slow motion for airborne predators.
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HERTEL, HORST, i ULRIKE MARONDE. "The Physiology and Morphology of Centrally Projecting Visual Interneurones in the Honeybee Brain". Journal of Experimental Biology 133, nr 1 (1.11.1987): 301–15. http://dx.doi.org/10.1242/jeb.133.1.301.
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Visual interneurones with projections into the median protocerebrum of the honeybee brain were characterized by electrophysiological and neuroanatomical methods. Extrinsic medulla neurones with wide ramifications in the medulla and terminations in the median posterior protocerebrum show spatial opponency in their tonic responses to stationary light. Wide-field lobula neurones projecting into the dorsal lobe code the direction of movement of visual stimuli by changing the sign of their tonic response. Lobula neurones, with two branches ipsi- and contralateral to the oesophagus, are binocularly sensitive. A moving stimulus in either direction causes excitation or inhibition of these neurones, the sign of the response being dependent on the side of stimulation. The presumed dendrites of an extrinsic lobula neurone, showing combined spectral and spatial opponency, differ markedly in shape from those of lobula movement-detecting neurones. Neurones that connect the optic tubercle with the contralateral dorsal lobe are characterized. They show a non-directionally selective movement sensitivity within a binocular receptive field. Note: Present address: B A M, FG 5.1; Unter den Eichen 87, D-1000 Berlin 45, FRG.
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Schnell, B., M. Joesch, F. Forstner, S. V. Raghu, H. Otsuna, K. Ito, A. Borst i D. F. Reiff. "Processing of Horizontal Optic Flow in Three Visual Interneurons of the Drosophila Brain". Journal of Neurophysiology 103, nr 3 (marzec 2010): 1646–57. http://dx.doi.org/10.1152/jn.00950.2009.
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Motion vision is essential for navigating through the environment. Due to its genetic amenability, the fruit fly Drosophila has been serving for a lengthy period as a model organism for studying optomotor behavior as elicited by large-field horizontal motion. However, the neurons underlying the control of this behavior have not been studied in Drosophila so far. Here we report the first whole cell recordings from three cells of the horizontal system (HSN, HSE, and HSS) in the lobula plate of Drosophila. All three HS cells are tuned to large-field horizontal motion in a direction-selective way; they become excited by front-to-back motion and inhibited by back-to-front motion in the ipsilateral field of view. The response properties of HS cells such as contrast and velocity dependence are in accordance with the correlation-type model of motion detection. Neurobiotin injection suggests extensive coupling among ipsilateral HS cells and additional coupling to tangential cells that have their dendrites in the contralateral hemisphere of the brain. This connectivity scheme accounts for the complex layout of their receptive fields and explains their sensitivity both to ipsilateral and to contralateral motion. Thus the main response properties of Drosophila HS cells are strikingly similar to the responses of their counterparts in the blowfly Calliphora, although we found substantial differences with respect to their dendritic structure and connectivity. This long-awaited functional characterization of HS cells in Drosophila provides the basis for the future dissection of optomotor behavior and the underlying neural circuitry by combining genetics, physiology, and behavior.
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Stasheff, Steven F., i Richard H. Masland. "Functional Inhibition in Direction-Selective Retinal Ganglion Cells: Spatiotemporal Extent and Intralaminar Interactions". Journal of Neurophysiology 88, nr 2 (1.08.2002): 1026–39. http://dx.doi.org/10.1152/jn.2002.88.2.1026.
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We recorded from on-off direction-selective ganglion cells (DS cells) in the rabbit retina to investigate in detail the inhibition that contributes to direction selectivity in these cells. Using paired stimuli moving sequentially across the cells' receptive fields in the preferred direction, we directly confirmed the prediction of Wyatt and Daw (1975) that a wave of inhibition accompanies any moving excitatory stimulus on its null side, at a fixed spatial offset. Varying the interstimulus distance, stimulus size, luminance, and speed yielded a spatiotemporal map of the strength of inhibition within this region. This “null” inhibition was maximal at an intermediate distance behind a moving stimulus: ½ to 1½ times the width of the receptive field. The strength of inhibition depended more on the distance behind the stimulus than on stimulus speed, and the inhibition often lasted 1–2 s. These spatial and temporal parameters appear to account for the known spatial frequency and velocity tuning of on-off DS cells to drifting contrast gratings. Stimuli that elicit distinct onand off responses to leading and trailing edges revealed that an excitatory response of either polarity could inhibit a subsequent response of either polarity. For example, an offresponse inhibited either an on or off response of a subsequent stimulus. This inhibition apparently is conferred by a neural element or network spanning the on andoff sublayers of the inner plexiform layer, such as a multistratified amacrine cell. Trials using a stationary flashing spot as a probe demonstrated that the total amount of inhibition conferred on the DS cell was equivalent for stimuli moving in either the null or preferred direction. Apparently the cell does not act as a classic “integrate and fire” neuron, summing all inputs at the soma. Rather, computation of stimulus direction likely involves interactions between excitatory and inhibitory inputs in local regions of the dendrites.
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Chacron, Maurice J. "Nonlinear Information Processing in a Model Sensory System". Journal of Neurophysiology 95, nr 5 (maj 2006): 2933–46. http://dx.doi.org/10.1152/jn.01296.2005.
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Understanding the mechanisms by which sensory neurons encode and decode information remains an important goal in neuroscience. We quantified the performance of optimal linear and nonlinear encoding models in a well-characterized sensory system: the electric sense of weakly electric fish. We show that linear encoding models generally perform better under spatially localized stimulation than under spatially diffuse stimulation. Through pharmacological blockade of feedback input and spatial saturation of the receptive field center, we show that there is significantly less synaptic noise under spatially diffuse stimuli as compared with spatially localized stimuli. Modeling results suggest that pyramidal cells nonlinearly encode sensory information through shunting in their dendrites and clarify the influence of synaptic noise on the performance of linear encoding models. Finally, we used information theory to quantify the performance of linear decoders. While the optimal linear decoder for spatially localized stimuli could capture 60% of the information in pyramidal cell spike trains, the optimal linear decoder for spatially diffuse stimuli could only capture 40% of the information. These results show that nonlinear decoders are necessary to fully access information in pyramidal cell spike trains, and we discuss potential mechanisms by which higher-order neurons could decode this information.
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Millecchia, R. J., L. M. Pubols, R. V. Sonty, J. L. Culberson, W. E. Gladfelter i P. B. Brown. "Influence of map scale on primary afferent terminal field geometry in cat dorsal horn". Journal of Neurophysiology 66, nr 3 (1.09.1991): 696–704. http://dx.doi.org/10.1152/jn.1991.66.3.696.
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1. Thirty-one physiologically identified primary afferent fibers were labeled intracellularly with horseradish peroxidase (HRP). 2. A computer analysis was used to determine whether the distribution of cutaneous mechanoreceptive afferent terminals varies as a function of location within the dorsal horn somatotopic map. 3. An analysis of the geometry of the projections of these afferents has shown that 1) terminal arbors have a greater mediolateral width within the region of the foot representation than lateral to it, 2) terminal arbors have larger length-to-width ratios outside the foot representation than within it, and 3) the orientation of terminal arbors near the boundary of the foot representation reflects the angle of the boundary. Previous attribution of mediolateral width variations to primary afferent type are probably in error, although there appear to be genuine variations of longitudinal extent as a function of primary afferent type. 4. Nonuniform terminal distributions represent the first of a three-component process underlying assembly of the monosynaptic portions of cell receptive fields (RFs) and the somatotopic map. The other two components consist of the elaboration of cell dendritic trees and the establishment of selective connections. 5. The variation of primary afferent terminal distributions with map location is not an absolute requirement for development of the map; for example, the RFs of postsynaptic cells could be assembled with the use of a uniform terminal distribution for all afferents, everywhere in the map, as long as cell dendrites penetrate the appropriate portions of the presynaptic neuropil and receive connections only from afferent axons contributing to their RFs.(ABSTRACT TRUNCATED AT 250 WORDS)
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Buzás, Péter, Sára Jeges i Robert Gábriel. "The number and distribution of bipolar to ganglion cell synapses in the inner plexiform layer of the anuran retina". Visual Neuroscience 13, nr 6 (listopad 1996): 1099–107. http://dx.doi.org/10.1017/s0952523800007744.
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AbstractThe main route of information flow through the vertebrate retina is from the photoreceptors towards the ganglion cells whose axons form the optic nerve. Bipolar cells of the frog have been so far reported to contact mostly amacrine cells and the majority of input to ganglion cells comes from the amacrines. In this study, ganglion cells of frogs from two species (Bufo marinus, Xenopus laevis) were filled retrogradely with horseradish peroxidase. After visualization of the tracer, light-microscopic cross sections showed massive labeling of the somata in the ganglion cell layer as well as their dendrites in the inner plexiform layer. In cross sections, bipolar output and ganglion cell input synapses were counted in the electron microscope. Each synapse was assigned to one of the five equal sublayers (SLs) of the inner plexiform layer. In both species, bipolar cells were most often seen to form their characteristic synaptic dyads with two amacrine cells. In some cases, however, the dyads were directed to one amacrine and one ganglion cell dendrite. This type of synapse was unevenly distributed within the inner plexiform layer with the highest occurrence in SL2 both in Bufo and Xenopus. In addition, SL4 contained also a high number of this type of synapse in Xenopus. In both species, we found no or few bipolar to ganglion cell synapses in the marginal sublayers (SLs 1 and 5). In Xenopus, 22% of the bipolar cell output synapses went onto ganglion cells, whereas in Bufo this was only 10%. We conclude that direct bipolar to ganglion cell information transfer exists also in frogs although its occurrence is not as obvious and regular as in mammals. The characteristic distribution of these synapses, however, suggests that specific type of the bipolar and ganglion cells participate in this process. These contacts may play a role in the formation of simple ganglion cell receptive fields.
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Umino, Osamu, Michiyo Maehara, Soh Hidaka, Shigeo Kita i Yoko Hashimoto. "The network properties of bipolar–bipolar cell coupling in the retina of teleost fishes". Visual Neuroscience 11, nr 3 (maj 1994): 533–48. http://dx.doi.org/10.1017/s0952523800002443.
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AbstractRetinal bipolar cells exhibit a center-surround antagonistic receptive field to a light stimulus (Werblin & Dowling, 1969; Kaneko, 1970), and thus constitute an early stage of spatial information processing. We injected Lucifer Yellow and a small biotinylated tracer, biocytin, into bipolar cells of the teleost retina to examine electrical coupling in these cells. Lucifer-Yellow coupling was observed in one of 55 stained bipolar cells; the coupling pattern was one injected bipolar cell and three surrounding cells. Biocytin coupling was observed in 16 of 55 stained bipolar cells, six of which were ON center and ten OFF center. Although biocytin usually coupled to three to six bipolar cells, some OFF-center bipolar cells showed strong coupling to more than 20 cells. The biocytin-coupled bipolar cells were morphologically homologous. Membrane appositions resembling gap junctions were found between dendrites and between axon terminals of neighboring bipolar cells.In the strongest biocytin-coupled bipolar cells, the contacts between bipolar cells and cone photoreceptor cells were examined after reconstruction of the dendritic trees of five well-stained, serially sectioned OFF-center bipolar cells. Each of these bipolar cells was in contact with different numbers of cones: 11 to 20 for twin cones and two to four for single cones. This implies that, although these bipolar cells belong to the same category, the signal inputs differ among bipolar cells. Numerical simulation conducted on a hexagonal array network model demonstrated that the electrical coupling of bipolar cells can decrease the difference in input (≈80%) without causing significant loss of spatial resolution. Our results suggest that electrical coupling of bipolar cells has the advantage of decreasing the dispersion of input signals from cones, and permits bipolar cells of the same class to respond to light with similar properties.
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Iwata, K., Y. Tsuboi, J. Yagi, K. Kitajima i R. Sumino. "Morphology of primary somatosensory cortical neurons receiving input from the tooth pulp". Journal of Neurophysiology 72, nr 2 (1.08.1994): 831–46. http://dx.doi.org/10.1152/jn.1994.72.2.831.
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1. To elucidate the morphological and electrophysiological characteristics of tooth pulp-driven neurons (TPNs) in the primary somatosensory cortex (SI), we injected neurobiotin into TPNs whose electrophysiological characteristics had been identified. 2. TPNs, responsive to electrical stimulation of the tooth pulp, were recorded intracellularly and injected from areas 3a and 3b of SI. A total of 58 TPNs in SI were successfully injected and reconstructed. Nineteen of these TPNs were located in area 3a and 39 in area 3b. Three area 3a TPNs were identified in lamina II, eight in lamina III, seven in lamina V, and one in lamina VI. Five 3b TPNs were identified in lamina II, 19 in lamina III, 7 in lamina IV, 7 in lamina V, and 1 in lamina VI. 3. Thalamic and tooth pulp latencies of lamina III and IV TPNs were shorter than those of lamina II and V TPNs. On the other hand, lingual and masseteric nerve latencies of TPNs were not consistent with thalamic and tooth pulp latencies. 4. Three of 19 area 3a TPNs and 7 of 39 area 3b TPNs were classified as pulp-specific TPNs, which received only tooth pulp input. Thirteen of 19 area 3a TPNs and 24 of 32 area 3b TPNs were classified as low-threshold mechanoreceptive TPNs, which responded to nonnoxious mechanical stimulation of the receptive field, and only 2 area 3b TPNs were classified as wide-dynamic range TPNs. Six of the area 3a TPNs and 14 of the area 3b TPNs responded to electrical stimulation of the lingual and/or masseteric nerves. Nociceptive-specific TPNs were not recorded in this study. 5. Lamina II TPNs in areas 3a and 3b had small somata, and those in area 3a had dendrites spreading into laminae I–II. Two TPNs in area 3a had axon collaterals extending into area 4. In contrast, area 3b TPNs in lamina II have dendrites spreading into laminae I–III. Their axons did not extend deeply into the subcortical regions, and the axon collaterals reached into area 3a. 6. Lamina III TPNs were classified according to their morphological characteristics as pyramidal or nonpyramidal stellate TPNs. Pyramidal lamina III TPNs had typical pyramidal somata, like those of lamina V pyramidal cells. Furthermore, those in areas 3a and 3b had dendrites with numerous spines spreading into laminae I–III, and some of the area 3a TPNs have axons with collaterals projecting into area 4. Lamina III area 3b TPNs had morphological properties similar to those in area 3a.(ABSTRACT TRUNCATED AT 400 WORDS)
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LEBEDEV, D. S., i D. W. MARSHAK. "Amacrine cell contributions to red-green color opponency in central primate retina: A model study". Visual Neuroscience 24, nr 4 (lipiec 2007): 535–47. http://dx.doi.org/10.1017/s0952523807070502.
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To investigate the contributions of amacrine cells to red-green opponency, a linear computational model of the central macaque retina was developed based on a published cone mosaic. In the model, amacrine cells of ON and OFF types received input from all neighboring midget bipolar cells of the same polarity, but OFF amacrine cells had a bias toward bipolar cells whose center responses were mediated by middle wavelength sensitive cones. This bias might arise due to activity dependent plasticity because there are midget bipolar cells driven by short wavelength sensitive cones in the OFF pathway. The model midget ganglion cells received inputs from neighboring amacrine cells of both types. As in physiological experiments, the model ganglion cells showed spatially opponent responses to achromatic stimuli, but they responded to cone isolating stimuli as though center and surround were each driven by a single cone type. Without amacrine cell input, long and middle wavelength sensitive cones contributed to both the centers and surrounds of model ganglion cell receptive fields. According to the model, the summed amacrine cell input was red-green opponent even though inputs to individual amacrine cells were unselective. A key prediction is that GABA and glycine depolarize two of the four types of central midget ganglion cells; this may reflect lower levels of the potassium chloride co-transporter in their dendrites.
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Scherer, Warren J., i Susan B. Udin. "Differential intertectal delay between Rana pipiens and Xenopus laevis: Implications for species-specific visual plasticity". Visual Neuroscience 12, nr 5 (wrzesień 1995): 1007–11. http://dx.doi.org/10.1017/s0952523800009548.
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AbstractIn the frog Xenopus laevis, the isthmotectal projection, which relays input from the ipsilateral eye, exhibits anatomical reorganization following surgical eye rotation performed during tadpole stages while the isthmotectal projection in the frog Rana pipiens fails to show reorganization. This plasticity has been shown to be dependent upon activation of the N-methyl-D-aspartate (NMDA) receptor located on tectal cell dendrites. The reorganization process in Xenopus is hypothesized to employ a Hebbian mechanism requiring correlated firing of ipsilateral and contralateral inputs to a given tectal cell; when an ipsilateral axon synapses onto a tectal cell that receives input from a contralateral axon with a matching receptive-field location, the correlation in activity triggers stabilization of the ipsilateral synapse. However, in neither Xenopus nor Rana do ipsilateral and contralateral inputs begin to fire simultaneously in response to a given visual stimulus; the ipsilateral input is delayed because it reaches the tectum indirectly, through a polysynaptic relay via the opposite tectum and nucleus isthmi. The objective of this experiment was to test whether there is a significant difference in this intertectal delay between Xenopus laevis and Rana pipiens in order to determine whether intertectal delay could be a contributing factor in this species-specific ability to exhibit visual plasticity. We have found that intertectal delay is 26.16 ms longer in Rana pipiens (36.53 ms) than in Xenopus laevis (10.37 ms).
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Nagayama, Shin, Yuji K. Takahashi, Yoshihiro Yoshihara i Kensaku Mori. "Mitral and Tufted Cells Differ in the Decoding Manner of Odor Maps in the Rat Olfactory Bulb". Journal of Neurophysiology 91, nr 6 (czerwiec 2004): 2532–40. http://dx.doi.org/10.1152/jn.01266.2003.
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Mitral and tufted cells in the mammalian olfactory bulb are principal neurons, each type having distinct projection pattern of their dendrites and axons. The morphological difference suggests that mitral and tufted cells are functionally distinct and may process different aspects of olfactory information. To examine this possibility, we recorded odorant-evoked spike responses from mitral and middle tufted cells in the aliphatic acid- and aldehyde-responsive cluster at the dorsomedial part of the rat olfactory bulb. Homologous series of aliphatic acids and aldehydes were used for odorant stimulation. In response to adequate odorants, mitral cells showed spike responses with relatively low firing rates, whereas middle tufted cells responded with higher firing rates. Examination of the molecular receptive range (MRR) indicated that most mitral cells exhibited a robust inhibitory MRR, whereas a majority of middle tufted cells showed no or only a weak inhibitory MRR. In addition, structurally different odorants that activated neighboring clusters inhibited the spike activity of mitral cells, whereas they caused no or only a weak inhibition in the middle tufted cells. Furthermore, responses of mitral cells to an adequate excitatory odorant were greatly inhibited by mixing the odorant with other odorants that activated neighboring glomeruli. In contrast, odorants that activated neighboring glomeruli did not significantly inhibit the responses of middle tufted cells to the adequate excitatory odorant. These results indicate a clear difference between mitral and middle tufted cells in the manner of decoding the glomerular odor maps.
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Uhlrich, D. J., J. B. Cucchiaro, A. L. Humphrey i S. M. Sherman. "Morphology and axonal projection patterns of individual neurons in the cat perigeniculate nucleus". Journal of Neurophysiology 65, nr 6 (1.06.1991): 1528–41. http://dx.doi.org/10.1152/jn.1991.65.6.1528.
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1. The lateral geniculate nucleus is the primary thalamic relay through which retinal signals pass en route to cortex. This relay is gated and can be suppressed by activity among local inhibitory neurons that use gamma-aminobutyric acid (GABA) as a neurotransmitter. In the cat, a major source of this GABAergic inhibition seems to arise from cells of the perigeniculate nucleus, which lies just dorsal to the A-laminae of the lateral geniculate nucleus. However, the morphological characteristics of perigeniculate cells, and particularly the projection patterns of their axons, have never been fully characterized. We thus examined the morphology of these cells: individually by intracellular injection of horseradish peroxidase (HRP) and en masse with the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHAL). 2. We recorded from 12 perigeniculate cells that we impaled and successfully labeled with HRP. These cells exhibited response properties generally consistent with those described previously. They had long response latencies to stimulation of the optic chiasm and relatively large, often diffuse, receptive fields. The visually evoked responses of most of the cells were dominated by one eye. Compared with cells of the lateral geniculate nucleus, perigeniculate cells had large somata (517 +/- 136 microns 2 in cross-sectional area, mean +/- SD), which were fusiform or multipolar in shape, and dendritic arbors that extended a considerable distance (1,095 +/- 167 microns) parallel to the border between the perigeniculate and lateral geniculate nuclei. Terminal arbors of some dendrites were quite complex and beaded. 3. The axons of six perigeniculate cells were labeled sufficiently well to trace and reconstruct over a considerable distance. Each of these axons formed branches that descended to innervate the lateral geniculate nucleus, and this geniculate innervation was exclusively limited to the A-laminae. Terminal boutons within the A-laminae were nearly all en passant, which gave the axons a beaded appearance. Furthermore, branches of five of these six axons provided local innervation of the perigeniculate nucleus, generally within each labeled cell's own dendritic arbor. Three of the cells also exhibited an axon branch that extended medially and caudally away from the soma, but we were unable to trace these axon branches to their targets. 4. Within the lateral geniculate nucleus, each arbor of perigeniculate axons derived from two main components. One was a narrow, sparse medial component that innervated laminae A and A1.(ABSTRACT TRUNCATED AT 400 WORDS)
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Schmidt, John T. "The modulatory cholinergic system in goldfish tectum may be necessary for retinotopic sharpening". Visual Neuroscience 12, nr 6 (listopad 1995): 1093–103. http://dx.doi.org/10.1017/s095252380000674x.
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AbstractThe cholinergic circuit within the tectum and the cholinergic input from the nucleus isthmi mediate a presynaptic augmentation of retinotectal transmitter release via nicotinic receptors. In this study, the cholinergic systems were either eliminated using the cholinergic neurotoxin AF64A or blocked using nicotinic antagonists to test for effects on the activity-driven sharpening of the regenerating retinotectal projection. The effectiveness of the AF64A was verified by recording field potentials elicited by optic tract stimulation and by immunohistochemical staining for choline acetyltransferase (ChAT). At 1 week after intracranial (IC) injection of AF64A (12 to 144 nmoles) into the fluid above the tectum, field potentials showed a selective dose-dependent decrement of the cholinergic polysynaptic component with no effect on the amplitude of the glutamatergic monosynaptic component. The decrement was only partially recovered in recordings at 2 and 6 weeks. In normal fish, the ChAT antibody stains a population of periventricular neurons, their apical dendrites, and a dense plexus within the optic terminal lamina that consists of their local axons and fine dendrites and of input fibers from the nucleus isthmi. One week after IC AF64A injection (48–72 nmoles), most immunostaining in superficial tectum was lost but most neuronal somas in the deep tectum could still be seen, and staining in the tegmentum below the tectum was completely intact. At 2 weeks and later, the staining of neuronal somata largely recovered, but staining of the superficial plexus did not. AF64A treatment at 18 days after nerve crush, when regenerating retinal fibers are beginning to form synapses, prevented retinotopic sharpening of the projection. Recordings showed a rough retinotopic map on the tectum but the multiunit receptive fields (MURFs) at each tectal point averaged 34 deg vs. 11 deg in vehicle-injected control regenerates. AF64A treatment before nerve crush also blocked sharpening, ruling out a direct effect on retinal growth cones or retinal fibers, as AF64A rapidly decomposes, whereas its effect on the cholinergic fibers is long-lasting. IC injection or minipump infusion of the nicotinic antagonists α-bungarotoxin (αBTX), neuronal bungarotoxin (nBTX), and pancuronium during regeneration also prevented sharpening (MURFs averaging 29.4 deg, 33.0 deg, and 31.4 deg, respectively). Control Ringer≈s solution infusions or injections over the same period (19–37 days postcrush) had no effect on regenerated MURF size (11.7 deg). The results show that the cholinergic innervation, which modulates transmitter release, is required for activity-driven retinotopic sharpening, thought to be triggered by NMDA receptor activation.
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DOUGLASS, JOHN K., i NICHOLAS J. STRAUSFELD. "Sign-conserving amacrine neurons in the fly's external plexiform layer". Visual Neuroscience 22, nr 3 (maj 2005): 345–58. http://dx.doi.org/10.1017/s095252380522309x.
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Amacrine cells in the external plexiform layer of the fly's lamina have been intracellulary recorded and dye-filled for the first time. The recordings demonstrate that like the lamina's short photoreceptors R1–R6, type 1 lamina amacrine neurons exhibit nonspiking, “sign-conserving” sustained depolarizations in response to illumination. This contrasts with the sign-inverting responses that typify first-order retinotopic relay neurons: monopolar cells L1–L5 and the T1 efferent neuron. The contrast frequency tuning of amacrine neurons is similar to that of photoreceptors and large lamina monopolar cells. Initial observations indicate that lamina amacrine receptive fields are also photoreceptor-like, suggesting either that their inputs originate from a small number of neighboring visual sampling units (VSUs), or that locally generated potentials decay rapidly with displacement. Lamina amacrines also respond to motion, and in one recording these responses were selective for the orientation of moving edges. This functional organization corresponds to the anatomy of amacrine cells, in which postsynaptic inputs from several neighboring photoreceptor endings are linked by a network of very thin distal processes. In this way, each VSU can receive convergent inputs from a surround of amacrine processes. This arrangement is well suited for relaying responses to local intensity fluctuations from neighboring VSUs to a central VSU where amacrines are known to be presynaptic to the dendrites of the T1 efferent. The T1 terminal converges at a deeper level with that of the L2 monopolar cell relaying from the same optic cartridge. Thus, the localized spatial responses and receptor-like temporal response properties of amacrines are consistent with possible roles in lateral inhibition, motion processing, or orientation processing.
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XIA, YINGQIU, i SCOTT NAWY. "The gap junction blockers carbenoxolone and 18β-glycyrrhetinic acid antagonize cone-driven light responses in the mouse retina". Visual Neuroscience 20, nr 4 (lipiec 2003): 429–35. http://dx.doi.org/10.1017/s0952523803204089.
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Gap junctions are widely expressed throughout the retina, and play an important role in the processing of visual information. It has been proposed that horizontal cells express unpaired gap junctions, or hemichannels, in their dendrites, and that current flowing through hemichannels reduces transmembrane voltage at cone terminals, promoting the opening of Ca2+ channels near sites of transmitter release. This model predicts that pharmacological block of gap junctions should reduce the Ca2+ current at the equivalent cone voltage, thereby decreasing the postsynaptic light response. To test this prediction, and estimate the relative magnitude of this effect on third-order cells, we recorded light responses in mouse ganglion cells under photopic conditions and applied two gap junction antagonists, carbenoxolone and the structurally related 18β-glycyrrhetinic acid (GA). Both carbenoxolone and GA decreased the size of the light response to about 30% of control. Cells that were physiologically identified as ON, OFF, or ON/OFF were equally affected by carbenoxolone/GA. These gap junction blockers did not interfere with gamma-aminobutyric acid (GABA) or glutamate receptors, as they did not affect responses to direct activation of these receptors. Under control conditions, spots larger than 200 μm in diameter activated ganglion cell receptive-field surrounds. Comparing responses to small and large spots before and during carbenoxolone treatment, we found that carbenoxolone did not preferentially inhibit surround antagonism at the ganglion cell level, but instead scaled the responses to all spot sizes. Our results extend the findings of studies in lower vertebrates which showed that light responses in horizontal cells are decreased by carbenoxolone treatment, and support the idea that hemichannels in the outer retina, most likely on horizontal cells, constitute important gates that are critical for allowing light responses to move forward into the retinal circuit. Furthermore, it suggests that ganglion cell surrounds are generated in the inner retina.
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Dacheux, R. F., i E. Raviola. "Light responses from one type of ON-OFF amacrine cells in the rabbit retina". Journal of Neurophysiology 74, nr 6 (1.12.1995): 2460–68. http://dx.doi.org/10.1152/jn.1995.74.6.2460.
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1. The light responses from one type of ON-OFF amacrine cell were recorded intracellularly in the superfused rabbit retina under various conditions of light adaptation. These recordings were obtained from cells located in a central area. 5-7 mm inferior and directly below the optic nerve head. 2. ON-OFF amacrine cells responded to the initiation and termination of light stimuli with transient depolarizations. Their receptive fields were approximately 0.8-1 mm diam and did not exhibit antagonistic center-and-surround organization. 3. The cells received rod input because they responded to very dim scotopic stimuli. With prolonged dark adaptation, the cells became more sensitive to the initiation than termination of the stimulus, because the ON component of the light response had a lower threshold than the OFF component. 4. The cells continued to respond to test flashes when the retina was adapted to a background illumination of rod-saturating intensity. Thus ON-OFF amacrine cells also receive cone input. Under these photopic conditions, a secondary afterpotential was observed following the OFF component. Its characteristics were different from those of the rod aftereffect reported in other retinal cells of the rabbit because its latency and amplitude changed with increasing stimulus intensity. 5. Intracellular injections of horseradish peroxidase showed that the recordings were obtained from a class of ON-OFF amacrine cells whose wide-field, unistratified dendrites were rigorously confined to the middle of the inner plexiform layer or stratum 3. 6. The conspicuous rod and cone inputs into a class of amacrine cells that are connected neither to rod bipolars nor to All amacrine cells strongly support the idea that in the rabbit the rod pathway uses cone bipolars as interneurons to distribute scotopic signals to ganglion and cone-driven amacrine cells.
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Brown, Craig E., Jamie D. Boyd i Timothy H. Murphy. "Longitudinal in vivo Imaging Reveals Balanced and Branch-Specific Remodeling of Mature Cortical Pyramidal Dendritic Arbors after Stroke". Journal of Cerebral Blood Flow & Metabolism 30, nr 4 (18.11.2009): 783–91. http://dx.doi.org/10.1038/jcbfm.2009.241.
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The manner in which fully mature peri-infarct cortical dendritic arbors remodel after stroke, and thus may possibly contribute to stroke-induced changes in cortical receptive fields, is unknown. In this study, we used longitudinal in vivo two-photon imaging to investigate the extent to which brain ischemia can trigger dendritic remodeling of pyramidal neurons in the adult mouse somatosensory cortex, and to determine the nature by which remodeling proceeds over time and space. Before the induction of stroke, dendritic arbors were relatively stable over several weeks. However, after stroke, apical dendritic arbor remodeling increased significantly (dendritic tip growth and retraction), particularly within the first 2 weeks after stroke. Despite a threefold increase in structural remodeling, the net length of arbors did not change significantly over time because dendrite extensions away from the stroke were balanced by the shortening of tips near the infarct. Therefore, fully mature cortical pyramidal neurons retain the capacity for extensive structural plasticity and remodel in a balanced and branch-specific manner.
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Bastian, J. "Plasticity in an electrosensory system. I. General features of a dynamic sensory filter". Journal of Neurophysiology 76, nr 4 (1.10.1996): 2483–96. http://dx.doi.org/10.1152/jn.1996.76.4.2483.
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1. In this study we describe changes in neuronal responses within the primary electrosensory processing nucleus of a weakly electric fish that occur when the fish are exposed to repetitive patterns of electrosensory stimuli. Extracellular single-unit recordings show that pyramidal cells within the electrosensory lateral line lobe develop, over a time course of several minutes, an insensitivity to repetitive stimuli applied to a cell's receptive field (local stimulus). The pyramidal cell response cancellation only develops if the local stimulus is applied simultaneously with a diffuse pattern of electrosensory stimulation that affects the entire fish, or with proprioceptive stimuli. 2. The mechanism by which responses to repetitive afferent inputs are canceled relies on the central generation of "negative image inputs" that provide increased inhibitory input to a cell's apical dendrites at times when excitatory afferent input is increased. The negative image input becomes excitatory when afferent excitation is reduced or when input from inhibitory interneurons is predominant. The integration of a specific pattern of receptor afferent input with the complementary negative image input results in strong attenuation of pyramidal cell responses. The negative image inputs are plastic, so that a single pyramidal cell can learn to reject a variety of afferent input patterns. 3. These electric fish commonly experience repetitive electrosensory signals as a result of changes in posture. Because the electric organ is located in the trunk and tail, cyclical movements associated with exploratory behaviors result in amplitude modulations (AMs) of the electric field, and these AMs alter electroreceptor afferent firing frequency but not the firing frequency of second-order pyramidal cells. The adaptive cancellation mechanism described in this study can account for the insensitivity of pyramidal cells to reafferent electrosensory stimulation caused by tail movements and other postural changes. 4. The tail movements generate proprioceptive as well as electrosensory inputs, and either of these signals alone provides sufficient information for the generation of negative image inputs. The size of the negative image is larger, however, if both inputs are active. 5. The synaptic plasticity underlying the development of negative image inputs has a long-term component; under appropriate conditions changes in synaptic efficacy persist for > 30 min. 6. Normally functioning glutamatergic synapses are necessary for the expression of the synaptic plasticity associated with this cancellation mechanism. The development of negative image responses is blocked by micropressure ejection of the glutamate antagonist 6,7-dinitroquinoxaline-2,3-dione into the neighborhood of the pyramidal cell apical dendrites. 7. The adaptive cancellation of repetitive inputs is based on anti-Hebbian mechanisms; that is, correlated pre- and postsynaptic activity lead to a reduction in the excitatory input provided by the plastic synapses. As has been shown for several other systems, the cancellation mechanism reduces the cells responses to reafferent patterns of sensory input. In addition, the results of this study indicate that the mechanism may be more general, enabling the system to also cancel patterns of input resulting from exogenous stimuli.
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Werblin, Frank, Greg Maguire, Peter Lukasiewicz, Scott Eliasof i Samuel M. Wu. "Neural interactions mediating the detection of motion in the retina of the tiger salamander". Visual Neuroscience 1, nr 3 (maj 1988): 317–29. http://dx.doi.org/10.1017/s0952523800001978.
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AbstractThe neural circuitry underlying movement detection was inferred from studies of amacrine cells under whole-cell patch clamp in retinal slices. Cells were identified by Lucifer yellow staining. Synaptic inputs were driven by “puffing“ transmitter substances at the dendrites of presynaptic cells. Spatial sensitivity profiles for amacrine cells were measured by puffing transmitter substances along the lateral spread of their processes. Synaptic pathways were separated and identified with appropriate pre- and postsynaptic pharmacological blocking agents.Two distinct amacrine cell types were found: one with narrow spread of processes that sustained excitatory synaptic current, the other with very wide spread of processes that transient excitatory synaptic currents. The transient currents found only in the wide-field amacrine cell were formed presynaptically at GABAB receptors. They could be blocked with baclofen, a GABAB agonist, and their time course was extended by AVA, a GABAB antagonist. Baclofen and AVA had no direct affect upon the wide-field amacrine cell, but picrotoxin blocked a separate, direct GABA input to this cell.The narrow-field amacrine cell was shown to be GABAergic by counterstaining with anti-GABA antiserum after it was filled with Lucifer yellow. Its narrow, spatial profile and sustained synaptic input are properties that closely match those of the GABAergic antagonistic signal that forms transient activity (described above), suggesting that the narrow-field amacrine cell itself is the source of the GABAergic interaction mediating transient activity in the inner plexiform layer (IPL). Other work has shown a GABAB sensitivity at some bipolar terminals, suggesting a population of bipolars as the probable site of interaction mediating transient action.The results suggest that two local populations of amacrine cell types (sustained and transient) interact with the two populations of bipolar cell types (transient forming and nontransient forming). These interactions underlie the formation of the change-detecting subunits. We suggest that local populations of these subunits converge to form the receptive fields of movement-detecting ganglion cells.
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BLOOMFIELD, STEWART A., i BÉLA VÖLGYI. "Response properties of a unique subtype of wide-field amacrine cell in the rabbit retina". Visual Neuroscience 24, nr 4 (29.05.2007): 459–69. http://dx.doi.org/10.1017/s0952523807070071.
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We studied the morphology and physiology of a unique wide-field amacrine cell in the rabbit retina. These cells displayed a stereotypic dendritic morphology consisting of a large, circular and monostratified arbor that often extended over 2 mm. Their responses contained both somatic and dendritic sodium spikes suggesting active propagation of synaptic signals within the dendritic arbor. This idea is supported by the enormous size of their ON-OFF receptive fields. Interestingly, these cells exhibited separate ON and OFF receptive fields that, while concentric, were vastly different in size. Whereas the ON receptive field of these cells extended nearly 2 mm, the OFF receptive field was typically 75% smaller. Blockade of voltage-gated sodium channels with QX-314 dramatically reduced the large ON receptive field, but had little effect on the smaller OFF receptive field. These results indicate a spatial disparity in the location of on- and off-center bipolar cell inputs to the dendritic arbor of wide-field amacrine cells. In addition, the active propagation of signals suggests that synaptic inputs are integrated both locally and globally within the dendritic arbor.
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Simmons, Aaron B., Samuel J. Bloomsburg, Joshua M. Sukeena, Calvin J. Miller, Yohaniz Ortega-Burgos, Bart G. Borghuis i Peter G. Fuerst. "DSCAM-mediated control of dendritic and axonal arbor outgrowth enforces tiling and inhibits synaptic plasticity". Proceedings of the National Academy of Sciences 114, nr 47 (7.11.2017): E10224—E10233. http://dx.doi.org/10.1073/pnas.1713548114.
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Mature mammalian neurons have a limited ability to extend neurites and make new synaptic connections, but the mechanisms that inhibit such plasticity remain poorly understood. Here, we report that OFF-type retinal bipolar cells in mice are an exception to this rule, as they form new anatomical connections within their tiled dendritic fields well after retinal maturity. The Down syndrome cell-adhesion molecule (Dscam) confines these anatomical rearrangements within the normal tiled fields, as conditional deletion of the gene permits extension of dendrite and axon arbors beyond these borders. Dscam deletion in the mature retina results in expanded dendritic fields and increased cone photoreceptor contacts, demonstrating that DSCAM actively inhibits circuit-level plasticity. Electrophysiological recordings from Dscam−/− OFF bipolar cells showed enlarged visual receptive fields, demonstrating that expanded dendritic territories comprise functional synapses. Our results identify cell-adhesion molecule-mediated inhibition as a regulator of circuit-level neuronal plasticity in the adult retina.
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Komai, Shoji. "Dendritic excitability maturates somatosensory receptive field". Neuroscience Research 58 (styczeń 2007): S13. http://dx.doi.org/10.1016/j.neures.2007.06.071.
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Amthor, Franklin R., Norberto M. Grzywacz i David K. Merwine. "Extra-receptive-field motion facilitation in on-off directionally selective ganglion cells of the rabbit retina". Visual Neuroscience 13, nr 2 (marzec 1996): 303–9. http://dx.doi.org/10.1017/s0952523800007549.
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AbstractThe excitatory receptive-field centers of On-Off directionally selective (DS) ganglioncells of the rabbit retina correspond closely to the lateral extent of their dendritic arborizations. Some investigators have hypothesized from this that theories for directionalselectivity that entail a lateral spread of excitation from outside the ganglion cell dendritic tree, such as from starburst amacrine cells, are therefore untenable. We show herethat significant motion facilitation is conducted from well outside the classical excitatory receptive-field center (and, therefore, dendritic arborization) of On-Off DS ganglioncells for preferred-direction, but not null-direction moving stimuli. These results are consistent with a role in directional selectivity for cells with processes lying beyond the On-Off ganglion cell's excitatory receptive-field center. These results also highlight the fundamental distinction in retinal ganglion cell receptive-field organization between classical excitatory mechanisms and those that facilitate other excitation without producing directly observable excitation by themselves.
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Bloomfield, S. A. "Relationship between receptive and dendritic field size of amacrine cells in the rabbit retina". Journal of Neurophysiology 68, nr 3 (1.09.1992): 711–25. http://dx.doi.org/10.1152/jn.1992.68.3.711.
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1. Intracellular recordings were obtained from 40 amacrine cells in the isolated, superfused retina eyecup of the rabbit. Cells were subsequently labeled with horseradish peroxidase for morphological identification. Many of these cells displayed dendritic morphology consistent with that of amacrine cells described in prior anatomic studies, including starburst, A17, AII, and DAPI-3 cells. 2. The center receptive field of amacrine cells was measured with a 50- or 95-microns-wide, 6.0-mm-long rectangular slit of light that was displaced along its minor axis (parallel to the visual streak) in increments as small as 3 microns. The extent of the receptive field was calculated as the total distance over which the displaced slit could evoke a center response. Area summation of amacrine cells was measured with concentric spots of light with increasing diameters centered over the cell. 3. For a single amacrine cell, the receptive field size was comparable to the extent of its dendritic arbor. For the total population of amacrine cells, there was a strong, linear relationship between receptive field and dendritic field size. The receptive fields were, on average, 27% larger than the corresponding dendritic arbors, but this discrepancy can be accounted for entirely by tissue shrinkage associated with histological processing and a small imprecision of the light stimuli. Area summation measurements were consistent with those of receptive fields and were also related linearly to the dendritic field size of cells. 4. These findings indicate that even when the slit of light was placed at the distal edges of the dendritic arbor, synaptic inputs activated there were propagated effectively to the soma and recorded by microelectrodes placed there. In addition, amacrine cells were capable of summating synaptic inputs distributed throughout the entire arbor. 5. These results are inconsistent with the findings of prior computational modeling studies of passive, dendritic current flow in A17 and starburst amacrine cells that synaptic inputs on distal dendritic branches are isolated electrically from the soma and that these branches form autonomous, functional subunits. 6. The majority of amacrine cells encountered displayed light-evoked and/or spontaneous action potentials. These action potentials often took the form of high-amplitude somatic and low-amplitude dendritic spikes. On average, spiking amacrine cells showed considerably larger dendritic fields than nonspiking amacrine cells. In fact, all amacrine cells with arbors greater than 436 microns, which formed 45% of the total population, displayed spike activity.(ABSTRACT TRUNCATED AT 400 WORDS)