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Results for “Retinal Horizontal Cells”

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PubMed1990

Macaque vision after magnocellular lateral geniculate lesions.

Ibotenic-acid lesions of the magnocellular portion of the macaque lateral geniculate nucleus were used to examine the role of the M-cell pathway in spatio-temporal contrast sensitivity. A lesion was placed in layer 1 of the lateral geniculate of each of two monkeys. Physiological mapping in one animal demonstrated that the visual-field locus of the lesion was on the horizontal meridian, approximately 6 deg in the temporal field. Visual thresholds were tested monocularly in the contralateral eye, and fixation locus was monitored with a scleral search coil to control the retinal location of the test target. Three threshold measures were clearly disrupted by the magnocellular lesions. Contrast sensitivity for a 1 cycle/deg grating that drifted at 10 Hz was reduced from about twofold greater than, to about the same as, that for 10-Hz counterphase modulated gratings. Sensitivity for a very low spatial frequency (Gaussian blob), 10-Hz flickering stimulus was reduced so severely that no threshold could be measured. In addition, flicker resolution was greatly reduced at lower modulation depths (0.22), but not at higher depths (1.0). Two of the measured thresholds were unaffected by the lesions. Contrast sensitivity for 2 cycle/deg stationary gratings remained intact, and little or no effect on sensitivity was found for 1 cycle/deg, 10-Hz counterphase modulated gratings. Together, these results suggest that the magnocellular pathway makes little contribution to visual sensitivity at low to moderate temporal frequencies. On the other hand, some contribution to detection sensitivity is evident at lower spatial and high temporal frequencies, especially for drifting stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Activation of the cGMP/nitric oxide signal transduction system by nicotine in the retina.

Acetylcholine is one of the primary excitatory neurotransmitters/neuromodulators in the retina, but little is known about the downstream signaling pathways it can activate. The present study immunocytochemically examines the potential sources of acetylcholine and the location of the nicotinic cholinergic receptors in the turtle retina. It also examines how activation of these receptors can influence the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signal-transduction pathways. Photoreceptors, amacrine cells, and potentially ganglion cells contain choline acetyltransferase-like immunoreactivity (LI). Nicotinic acetylcholine receptors are immunocytochemically localized on photoreceptors, horizontal, bipolar, and ganglion cells. Nitric oxide imaging indicates that stimulation with nicotine increases NO production primarily in photoreceptors, horizontal, Muller, bipolar, and ganglion cells. In turn, very select populations of amacrine cells respond to this NO with increased levels of cGMP-LI. Selective inhibitors reveal that nitric oxide synthase is involved in most, but not all, of these increases in cGMP-LI. These results show that acetylcholine can activate the NO/cGMP signal-transduction pathways in both the inner and outer retina. This indicates that both of the major excitatory retinal transmitters, glutamate and acetylcholine, can stimulate NO production that increases levels of cGMP-LI in overlapping populations of retinal cells.

Animals↗

PubMedDate not supplied

The cone/horizontal cell network: a possible site for color constancy.

Color vision is spectrally opponent, suggesting that spectrally opponent neurons, such as the horizontal cells in fish and turtle retinae, play a prominent role in color discrimination. In the accompanying paper (Kraaij et al., 1998), it was shown that the output signal of the horizontal cell system to the cones is not at all spectrally opponent. Therefore, a role for the spectrally opponent horizontal cells in color discrimination seems unlikely. In this paper, we propose that the horizontal cells play a prominent role in color constancy and simultaneous color contrast instead of in color discrimination. We have formulated a model of the cone/horizontal cell network based on measurements of the action spectra of the cones and of the feedback signal of the horizontal cell system to the various cone types. The key feature of the model is (1) that feedback is spectrally and spatially very broad and (2) that the gain of the cone synapse strongly depends on the feedback strength. This makes the synaptic gain of the cones strongly dependent on the spectral composition of the surround. Our model, which incorporates many physiological details of the outer retina, displays a behavior that can be interpreted as color constancy and simultaneous color contrast. We propose that the horizontal cell network modulates the cone synaptic gains such that the ratios of the cone outputs become almost invariant with the spectral composition of the global illumination. Therefore, color constancy appears to be coded in the retina.

Animals↗

PubMed2001

Hemichannel-mediated inhibition in the outer retina.

An essential feature of the first synapse in the retina is a negative feedback pathway from horizontal cells to cones. Here we show that at this synapse, connexin26 forms hemichannels on horizontal cell dendrites near the glutamate release site of the cones. Blocking these hemichannels hyperpolarizes horizontal cells, modulates the Ca2+ channels of the cones, and abolishes all feedback-mediated responses. We propose a feedback mechanism in which the activity of the Ca2+ channels and the subsequent glutamate release of the cones are modulated by a current through these hemichannels. Because the current through the hemichannels depends on the polarization of the horizontal cells, their activity modulates the output of the cones.

Animals↗

PubMed1988

The accessory optic system of rabbit. I. Basic visual response properties.

1. The response properties of accessory optic system (AOS) neurons were assessed using single-unit extracellular recording from each of the three AOS terminal nuclei [medial, lateral, and dorsal terminal nuclei (MTN, LTN, and DTN)] in the anesthetized rabbit. 2. AOS neurons had large, monocular (contralateral) receptive fields (tens of degrees on a side) and exhibited a pronounced selectivity to the speed and direction of movement of large, textured patterns. The greatest responses occurred at slow speeds on the order of 0.5 degrees/s. 3. MTN and LTN neurons responded best to movement in near vertical directions. However, the stimulus directions corresponding to the greatest excitation and the greatest inhibition both had a posterior component and, thus, the preferred excitatory and inhibitory directions were not opposite each other. DTN neurons responded most strongly to horizontal movement and were excited by temporal to nasal movement. 4. AOS neurons were unresponsive to natural vestibular stimulation presented as sinusoidal oscillations of the rabbit about the yaw, pitch, and roll axes. 5. The response properties of AOS neurons are remarkably similar to those of the ON, direction-selective ganglion cells of the rabbit retina, and therefore this class of ganglion cell is most likely the predominant, if not the only, direct retinal input to the AOS. The local direction-selective properties of AOS neurons can be accounted for by combining the tuning curves of ON, direction-selective ganglion cells in a simple manner. 6. The low speed preference of AOS neurons, along with their large receptive fields suggests that they are suited to complement the vestibular system in detecting self-motion.

Animals↗

PubMed1997

Lateral interactions in peripherally viewed texture arrays.

A horizontal array of vertically oriented Gabor elements was used to examine lateral masking in the near periphery (1.9 degrees-5.7 degrees eccentricity). Thresholds were assessed for detecting changes in the contrast, the spatial frequency, and the orientation of the central element within the array. The presence of surround elements induced marked threshold elevations that increased in strength as interelement spacing decreased and as retinal eccentricity increased. A model incorporating spatial summation by complex cells and reciprocal inhibition between simple and complex cells is shown to provide a quantitative fit to the data. This model suggests that complex cells analyze highly redundant textures, whereas simple cells function predominantly in the presence of isolated contours.

Contrast Sensitivity↗

PubMedDate not supplied

[Analysis of the expression pattern of regulatory genes Pax6, Prox1, and Six3 during regeneration of eye structures in the newt].

We studied tissue-specific expression of homeobox genes Pax6, Prox1, and Six3 during regeneration of the retina and lens. In the native retina, mRNA of Pax6, Prox1, and Six3 was predominantly localized in ganglion cells and in the inner nuclear layer of the retina. Active Pax6, Prox1, and Six3 expression was detected at early stages of regeneration in all proliferating neuroblasts forming the retinal primordium. Low levels of Pax6, Prox1, and Six3 mRNA were revealed in depigmented cells of the pigment epithelium as compared to the proliferating neuroblasts. At the intermediate stage of retinal regeneration, the distribution of Pax6, Prox1, and Six3 mRNA was diffuse and even all over the primordium. During differentiation of the cellular layers in the course of retinal regeneration, Pax6, Prox1, and Six3 mRNA was predominantly localized in ganglion cells and in the inner part of the inner nuclear layer, which was similar to the native retina. An increased expression was revealed in the peripheral regenerated retina where multipotent cells were localized. The dual role of regulatory genes Pax6, Prox1, and Six3 during regeneration of eye structures has been revealed; these genes controlled cell proliferation and subsequent differentiation of ganglion, amacrine, and horizontal cells. High hybridization signal of all studied genes was revealed in actively proliferating epithelial cells of the native and regenerating lens, while the corneal epithelium demonstrated a lower signal. Pax6 and Prox1 expression was also revealed in single choroid cells of the regenerating eye.

Animals↗

PubMed1994

Immunohistochemical localization of calbindin-D28K and calretinin in the lamprey retina.

Calbindin-D28K and calretinin are homologous cytosolic calcium binding proteins localized in many retinal neurons from different species. In this report, location of cells immunoreactive to both proteins was investigated in the retina of the lamprey, Lampetra fluviatilis. This organism constitutes one of the older representative vertebrates and possesses a peculiar organization, probably unique: two-thirds of the ganglion cells are in the classical amacrine cell layer and the nerve fiber layer is located in the scleral part of the inner plexiform layer. Calbindin-like immunoreactivity was demonstrated in large bipolar cells and in cell bodies located in the inner retina. Although the distinction between labelled ganglion cells and labelled amacrine cells was rendered difficult, we hypothesized that the majority of calbindin-immunoreactive cells observed in the inner retina are ganglion cells, because of the high number of labelled fibers in the nerve fiber layer. Calretinin-like immunoreactivity was detected in both large and small bipolar cells, and also in cells located in the inner retina. Since few calretinin-immunoreactive fibers were observed in the nerve fiber layer, we assume that the latter category of cells are amacrine cells. Horizontal cells were both negative for calbindin and calretin-like immunoreactivities. Calbindin and calretinin, which are present in cones from many species, could not be detected in the photoreceptor layer favouring the rod-dominated lamprey retina. Although their distribution differs from those observed in most vertebrates, the present results indicate the good conservation of both calcium binding proteins in the retina during the vertebrate evolution.

Animals↗

PubMedDate not supplied

D2-like dopamine receptors promote interactions between calcium and chloride channels that diminish rod synaptic transfer in the salamander retina.

Activation of D2-like dopamine receptors in rods with quinpirole stimulates L-type calcium currents (ICa). This result appears inconsistent with studies showing that D2-like dopamine receptor activation diminishes rod signals in second-order retinal neurons. Since small reductions in [Cl-] can inhibit photoreceptor ICa, we tested the hypothesis that enhancement of ICa with the D2/D4 receptor agonist, quinpirole, increases calcium-activated chloride currents (ICl(Ca)) causing an efflux of Cl- from rods that would provide a negative feedback inhibition of ICa. In agreement with studies from Xenopus, quinpirole reduced rod input to second-order neurons of tiger salamander retina without significantly altering rod voltage responses. Quinpirole also diminished the amplitude of depolarization-evoked increases in [Ca2+]i measured with Fura-2 in rods, a finding consistent with inhibition of synaptic transmission from rods. Electrophysiological and Cl(-)-imaging experiments indicated ECl in rods is approximately -20 mV. Quinpirole enhanced ICl(Ca) and elicited an efflux of Cl- at the resting potential. A similar Cl- efflux was produced by extracellular replacement of 24 mM Cl- with CH3SO4- and this low Cl- solution inhibited Ca2+ responses to a similar degree as quinpirole did. When ICl(Ca) was inhibited with niflumic acid, quinpirole enhanced both ICa and depolarization-evoked increases in [Ca2+]i. Furthermore, with niflumic acid, quinpirole no longer inhibited rod inputs into horizontal and bipolar cells. These results suggest an initial enhancement of ICa by quinpirole is followed by a stimulation of Cl- currents, including ICl(Ca). The net result is a Cl- efflux that inhibits depolarization-evoked increases in [Ca2+]i and synaptic transmission from rods.

Ambystoma↗

PubMed2006

An analog silicon retina with multichip configuration.

The neuromorphic silicon retina is a novel analog very large scale integrated circuit that emulates the structure and the function of the retinal neuronal circuit. We fabricated a neuromorphic silicon retina, in which sample/hold circuits were embedded to generate fluctuation-suppressed outputs in the previous study [1]. The applications of this silicon retina, however, are limited because of a low spatial resolution and computational variability. In this paper, we have fabricated a multichip silicon retina in which the functional network circuits are divided into two chips: the photoreceptor network chip (P chip) and the horizontal cell network chip (H chip). The output images of the P chip are transferred to the H chip with analog voltages through the line-parallel transfer bus. The sample/hold circuits embedded in the P and H chips compensate for the pattern noise generated on the circuits, including the analog communication pathway. Using the multichip silicon retina together with an off-chip differential amplifier, spatial filtering of the image with an odd- and an even-symmetric orientation selective receptive fields was carried out in real time. The analog data transfer method in the present multichip silicon retina is useful to design analog neuromorphic multichip systems that mimic the hierarchical structure of neuronal networks in the visual system.

Algorithms↗

PubMed1984

Basic optokinetic-ocular reflex pathways in the frog.

Frogs (Rana temporaria) have two midbrain nuclei that receive contralateral retinal afferents, and whose neurons respond to optokinetic stimulation. The basal optic nucleus is composed of direction-selective neurons with different response types. One type is activated exclusively by upward moving optokinetic targets; another type is activated only by downward moving targets. Two other types of basal optic neurons show this vertical preference, but each is also activated by patterns moved horizontally from the nasal to temporal visual field. No activation of these cells was found with patterns moved horizontally from the temporal to nasal visual fields. Rather, cells in a discrete pretectal region have this type of sensitivity: they increase their resting rate with temporal to nasal stimulation and decrease it with nasotemporal stimulation. Oculomotor neurons (antidromically identified) have similar optokinetic sensitivities. As with basal optic neurons, these cells have exclusively upward or downward sensitivity, and some also have nasotemporal sensitivity. An additional type of oculomotor neuron and abducens motoneurons are activated by temporonasal pattern movement. In general, the extraocular motoneurons have similar velocity and pattern size preferences, as have the sensory nuclei. Investigations of the connectivity between the sensory and motor nuclei were primarily restricted to the relation between the pretectum and the abducens. A monosynaptic connection between the pretectum and the abducens is suggested by four points: (1) excitatory postsynaptic potential onset latency in antidromically identified abducens motoneurons, following optic nerve stimulation, is consistent with the interpretation of a disynaptic pathway to the abducens from the retina; (2) pretectal cells, sensitive to optokinetic stimulation, can be activated antidromically from stimulation of the abducens nucleus; (3) horseradish peroxidase injections into the pretectum result in labeling of axons, which terminate in the abducens nucleus; (4) horseradish peroxidase injections into the abducens result in labeling of cells in the pretectal region, where optokinetically sensitive cells are found. In the frog, there seem to be three-neuronal retino-ocular reflexes mediating optokinetic slow phase behavior as there are three-neuronal vestibulo-ocular reflexes that also mediate compensatory spatial behavior. It is suggested that these direct connections act to initiate ocular movements and accelerate the eye, whereas more indirect pathways may act to maintain eye position.

Afferent Pathways↗

PubMed1996

Ultrastructure and organisation of the retina and pigment epithelium in the cutlips minnow, Exoglossum maxillingua (Cyprinidae, Teleostei).

The structure of the light- and dark-adapted retina, pigment epithelium and choriocapillaris of the cutlips minnow, Exoglossum maxillingua (Cyprinidae, Teleostei) is examined by light and electron microscopy. A pronounced vitreal vascularisation overlies the inner retina where the blood vessel walls, the inner limiting membrane and the Müller cell endfeet are all closely apposed. The thick Müller cell processes divide the inner plexiform layer and nerve fibre layer into discrete compartments. The ganglion cells do not form fascicles and lie within both the ganglion cell and inner plexiform layers. The inner nuclear layer consists of amacrine, bipolar, Müller cell somata and two rows of horizontal cells. The photoreceptor terminals comprise either multiple (3-5 in cone pedicles) or single (rod spherules) synaptic ribbons. These photoreceptor terminals form either a triad (rods and cones) or a quadrad (cones) arrangement of contact with the invaginating processes of the inner nuclear layer cells. The horizontal cell processes of the cone photoreceptor terminals reveal spinule formation in the light-adapted condition. Five photoreceptor types are classified using morphological criteria; triple cones, unequal double cones, large single cones, small single cones and rods. The ratio of rods to cones is approximately 7:1. All photoreceptor types show retinomotor responses. Only the cones possess accessory outer segments but both rods (8-11) and cones (15-19) possess calycal processes. The retinal pigment epithelium displays retinomotor responses where pigment granules within fine apical processes move vitread to mask the rods in the light. The cells of the retinal pigment epithelium are joined by various types of junctions and contain numerous phagosomes, mitochondria and polysomes. Bruch's membrane or the complexus basalis is trilaminate with two types of collagen fibrils comprising the central layer. The endothelia of the blood vessels of the choriocapillaris, facing Bruch's membrane, are fenestrated. Two to three layers of melanocytes interspersed between large thin-walled capillaries and several layers of collagen fibrils comprise the choriocapillaris.

Adaptation, Ocular↗

PubMed2003

Expression of glutamate transporters in human and rat retina and rat optic nerve.

l-Glutamate is the major excitatory transmitter in the vertebrate retina and plays a central role in the transmission of the various retinal neurons. Glutamate is removed from the extracellular space by at least five different glutamate transporters. The cellular distribution of these has been studied so far mainly using immunocytochemistry. In the present study non-radioactive in situ hybridisation using complementary RNA probes was applied in order to identify the cell types of rat retina and optic nerve expressing generic GLT1, GLT1 variant (GLT1v or GLT1B), GLAST and EAAC1. The results were compared with immunocytochemical data achieved using affinity-purified antibodies against transporter peptides. In the immunohistochemical studies the human retina was included. The study showed that in the rat retina GLT1v and EAAC1 were coexpressed in various cell types, i.e. photoreceptor, bipolar, horizontal, amacrine, ganglion and Müller cells, whereas GLAST was only detected in Müller cells and astrocytes. In the rat optic nerve GLT1v and EAAC1 were preferentially expressed in oligodendrocytes, whereas GLAST was revealed to be present mainly in astrocytes. Generic GLT1 could not be detected in the retina or optic nerve. The cellular distribution of glutamate transporters (only immunocytochemistry) in the human retina was very similar to that of the rat retina. Remarkable results of our studies were that generic GLT1 was not detectable in the rat (and human) retina and that GLT1v and EAAC1 were demonstrable in most cell types of the retina (including photoreceptor cells and their terminals).

Amacrine Cells↗

PubMed1987

Rhodopsin topography and rod-mediated function in cats with the retinal degeneration of taurine deficiency.

Cats on a taurine-deficient diet were studied with imaging fundus reflectometry and full-field electroretinography. The pattern of rhodopsin loss and the natural history of the disease were determined from maps of the rhodopsin distribution in the central and nasal retina of cats with different degrees of severity of the retinopathy. Rhodopsin loss is first detectable in a focal region of the central retina. Subsequently, there are decreases in rhodopsin in the paracentral and nasal midperipheral retina. The horizontal streak of high rhodopsin levels is preferentially reduced in this retinopathy. The b-wave amplitude of the rod-dominated ERG is markedly reduced in cats with only mildly decreased levels of rhodopsin in the peripheral retina. In an affected cat with moderate rhodopsin loss in the central retina but minimal loss nasally, a light-microscopic study of the retina showed that there was disorganization and shortening of rod outer segments and loss of rod photoreceptor cells in the areas of reduced rhodopsin levels.

Animals↗

PubMed2003

A physiological theory of depth perception from vertical disparity.

It has been known since the time of Helmholtz that vertical differences between the two retinal images can generate depth perception. Although many ecologically and geometrically inspired theories have been proposed, the neural mechanisms underlying the phenomenon remain elusive. Here we propose a new theory for depth perception from vertical disparity based on the oriented binocular receptive fields of visual cortical cells and on the radial bias of the preferred-orientation distribution in the cortex. The theory suggests that oriented cells may treat a vertical disparity as a weaker, equivalent horizontal disparity. It explains the induced effect, and the quadrant and size dependence of vertical disparity. It predicts that horizontal and vertical disparities should locally enhance or cancel each other according to their depth signs, and that the effect of vertical disparity should be orientation dependent. These predictions were confirmed through psychophysical experiments.

Depth Perception↗

PubMed2003

Local differences in GABA release induced by excitatory amino acids during retina development: selective activation of NMDA receptors by aspartate in the inner retina.

Glutamate and GABA are the major excitatory and inhibitory neurotransmitters in the CNS. In the retina, it has been shown that glutamate and aspartate and their agonists kainate and NMDA promote the release of GABA. In the chick retina, at embryonic day 14 (E14), glutamate and kainate were able to induce the release of GABA from amacrine and horizontal cells as detected by GABA-immunoreactivity. NMDA also induced GABA release restricted to amacrine cell population and its projections to the inner plexiform layer (E14 and E18). Although aspartate reduced GABA immunoreactivity, specifically in amacrine cells of E18 retinas, it was not efficient to promote GABA release from retinas at E14. As observed in differentiated retinas, dopamine inhibited the GABA release promoted by NMDA and aspartate but not by kainate. Our data show that different retinal sites respond to distinct EAAs via different receptor systems.

Animals↗

PubMed1988

Analysis of vertebrate eye movements following intravitreal drug injections. II. Spontaneous nystagmus induced by picrotoxin is mediated subcortically.

1. Eye movements were observed following an injection of picrotoxin, a GABA antagonist, into the vitreous of one eye. A spontaneous nystagmus was observed in cats, rabbits, and turtles, even in total darkness, with slow-phase eye movements in the temporal-to-nasal direction for the injected eye. 2. During visual stimulation by a horizontal drifting pattern, injected eyes moved in the temporal-to-nasal direction, irrespective of stimulus direction. In cats, however, the nystagmus was usually slower when the injected eye viewed nasal-to-temporal motion (opposite to the direction of the spontaneous nystagmus). The spontaneous nystagmus could be halted or even reversed by allowing cats to view motion opposite to the direction of the nystagmus with the uninjected eye alone. The nystagmus could not be overridden in this fashion in rabbits or turtles. 3. The nystagmus induced by picrotoxin could also be modified by vestibular stimulation. When cats were placed on their sides, the spontaneous horizontal nystagmus often decreased and spontaneous vertical nystagmus with upward slow phase movements occurred. During sinusoidal horizontal vestibular stimulation, the horizontal nystagmus due to picrotoxin added to the vestibuloocular reflex as a velocity offset in the temporal-to-nasal direction. 4. Following bilateral ablation of the cat visual cortex, picrotoxin's effect became even more pronounced than before the ablation. Therefore, at least some picrotoxin-sensitive cells can use subcortical pathways, perhaps to the accessory optic nuclei. The visual cortex, which also processes directional information, may be able to compensate for changes in retinal processing induced by picrotoxin in intact animals. 5. This study demonstrates the importance of retinal GABA in the control of eye stability. As GABA is known to be responsible for null direction inhibition of directionally sensitive retinal ganglion cells, these results suggest that the output of these cells may be critical for the normal functioning of central optokinetic pathways, even in the absence of visual cortex.

Animals↗

PubMed2001

Temporal contrast adaptation in salamander bipolar cells.

This work investigates how the light responses of salamander bipolar cells adapt to changes in temporal contrast: changes in the depth of the temporal fluctuations in light intensity about the mean. Contrast affected the sensitivity of bipolar cells but not of photoreceptors or horizontal cells, suggesting that adaptation occurred in signal transfer from photoreceptors to bipolars. This suggestion was confirmed by recording from photoreceptor-bipolar pairs and observing a direct dependence of the gain of signal transfer on the contrast of the light input. After an increase in contrast, the onset of adaptation in the bipolar cell had a time constant of 1-2 sec, similar to a fast component of contrast adaptation in the light responses of retinal ganglion cells (Kim and Rieke, 2001). Contrast adaptation was mediated by processes in the dendrites of both on and off bipolars. The functional properties of adaptation differed for the two bipolar types, however, with contrast having a much more pronounced effect on the kinetics of the responses of off cells than on cells.

Adaptation, Ocular↗