A model for non-linear processing in cat's retina

The model is based on the concept that non-linear lateral interaction at the inner plexiform layer accounts for most of the specialization and marked non-linearities in cat's retinal ganglion cell responses. The inputs to the lateral interaction processes are a spatio-temporal signal and its retarded, as suggested by the behaviour of simple ganglion cells. Lateral interaction in the model consists of lateral linear inhibition followed by local half wave rectification. The resulting signals are weighted and summated by the ganglion cell thereafter. A transparent and general expression is obtained for the response of the cell model which, albeit its simplicity, leads to most of known types of non-linear responses, including the rarely encountered specialized cells in cat's, retina, except colour coding units. For negligible lateral interaction, the model reduces to spatio-temporal linear models under the two paths hypothesis. A discussion of the possible role of anatomical units in these retinal processes in presented, where a general interpretation for visual processing in cat's retina evolves from.     

低亲和性神经营养素受体p75在人胚胎视网膜中的表达

p75神经营养素受体在视网膜的发育以及再生过程中发挥着重要的作用,而在人类视网膜中的分布状况尚未被研究. 利用免疫组织化学方法,在光镜水平下确定了p75在人胚胎发育5、6和7个月的视网膜中的分布情况. 在视网膜神经节细胞层出现最强的p75免疫阳性反应,在其他各层也有较弱的免疫阳性反应. 在胚胎6、7月的视网膜中,主要由Müller细胞的终足构成的内界膜上出现了比较强的p75表达. p75在人胚胎视网膜中的分布情况与大鼠视网膜中很类似,主要表达在Müller细胞, 在神经节细胞上也可能有表达.     

Electrical coupling of photoreceptors in retinal network models

The spatial width of photoreceptor receptive fields affects the processing of signals in neural networks of the retina. This effect has been examined using the simple recurrent and non-recurrent network models, where lateral interaction strength was adjusted to approximate a prescribed receptive field profile. The results indicate that the optimal performance of the networks is obtained with photoreceptor receptive fields wider than the ganglion cell separation. It is thus concluded that while electrical coupling of photoreceptors in the retina reduces the intrinsic noise in the system, it also improves the sampling efficiency of the laterally coupled neural network of the retina.     

Sensitivity of a sensory process to short time delays: A study in pattern induced flicker colors (PIFCs)

Pattern induced flicker colors (PIFCs) were generated by means of a modified version of Benham's top, the stimulus pattern of which could be varied continuously during stimulation by the human subjects. The sensitivity of the color sensation to small phase shifts between the periodic stimuli on neighboring retinal areas was recorded under several conditions of stimulus parameters. A mathematical model was developed to describe the influence of the stimulus parameters on the recorded sensory effect. Concerning the underlying neurophysiological processes, a hypothesis is advanced according to which the phase sensitive lateral interaction within the retina changes the spatial excitation distribution within color coding receptive fields of the retinal ganglion cells. The resulting ganglion cell excitation is supposed to generate PIFCs.     

Light Exposue Activates Retina Ganglion Cell Lysophosphatidic Acid Acyl Transferase and Phosphatidic Acid Phosphatase by a c-fos-Dependent Mechanism

We previously reported that the biosynthesis of phospholipids in the avian retina is altered by light stimulation, increasing significantly in ganglion cells in light and in photoreceptor cells in dark. In the present work, we have determined that light significantly increases the incorporation of [3H]glycerol into retina ganglion cell glycerophospholipids in vivo by a Fos-dependent mechanism because an oligonucleotide antisense to c-fos mRNA substantially blocked the light-dark differences. We also studied in vitro the enzyme activities of phosphatidate phosphohydrolase (PAPase), lysophosphatidate acyl transferase (AT II), and phosphatidylserine synthase from retinas of chickens exposed to light or dark. Higher PAPase I and AT II activities were found in incubations of retinal ganglion cells from animals exposed to light; no increase was observed in preparations obtained from light-exposed animals treated with the c-fos antisense oligonucleotide. No light-dark differences were found in phosphatidylserine synthase activity. These findings support the idea that a coordinated photic regulation of PAPase I and AT II is taking place in retina ganglion cells. This constitutes a reasonable mechanism to obtain an overall increased synthesis of glycerophospholipids in stimulated cells that is mediated by the expression of Fos-like proteins.     

A dialogue between glia and neurons in the retina: modulation of neuronal excitability

Bidirectional signaling between neurons and glial cells has been demonstrated in brain slices and is believed to mediate glial modulation of synaptic transmission in the CNS. Our laboratory has characterized similar neuron-glia signaling in the mammalian retina. We find that light-evoked neuronal activity elicits Ca(2+) increases in Müller cells, which are specialized retinal glial cells. Neuron to glia signaling is likely mediated by the release of ATP from neurons and is potentiated by adenosine. Glia to neuron signaling has also been observed and is mediated by several mechanisms. Stimulation of glial cells can result in either facilitation or depression of synaptic transmission. Release of D-serine from Müller cells might also potentiate NMDA receptor transmission. Müller cells directly inhibit ganglion cells by releasing ATP, which, following hydrolysis to adenosine, activates neuronal A(1) receptors. The existence of bidirectional signaling mechanisms indicates that glial cells participate in information processing in the retina.     

A unified neural network model of spatiotemporal processing in X and Y retinal ganglion cells

This article makes use of a push-pull shunting network, which was introduced in the companion article, to model certain properties of X and Y retinal ganglion cells. Input to the push-pull network is preprocessed by a nonlinear mechanism for temporal adaptation, which is ascribed here to photoreceptor dynamics. The complete circuit is used to show that a simple change in receptive field morphology within a single model equation can change the network's response characteristics to closely resemble those of either X or Y cells. Specifically, an increase in width of the receptive field center mechanism is sufficient to account for generation of on-off (Y-like) instead of null (X-like) responses to modulated gratings. In agreement with experimental data, the Y cell on-off response is independent of spatial phase. Also, the model accurately predicts that on-off responses can be observed in X cells for particular stimulus configurations. Taken together, the results show how the retina combines individually inadequate modules to efficiently handle the tasks required for accurate spatial and temporal visual information processing. The model is also able to clarify a number of controversial experimental findings on the nature of spatiotemporal visual processing in the retina.     

Nitric oxide synthase immunoreactivity in the developing and adult human retina

Nitric oxide synthase (NOS) catalyzes the formation of nitric oxide (NO) from L-arginine. In this study, the cellular localization of neuronal NOS (nNOS) activity in the human retina since fetal development was examined by immunohistochemistry. No detectable staining in the fetal retina was present at 14 weeks of gestation (wg), the earliest age group examined. A centro-peripheral gradient of development of nNOS immunoreactivity was evident at 16–17 wg, with the midperipheral retina showing nNOS immunoreactivity in most of the cell types and the inner plexiform layer while the peripheral part demonstrated moderate immunoreactivity only in the ganglion cell layer and photoreceptor precursors. A transient increase in nNOS immunoreactivity in the ganglion cells and Müller cell endfeet between 18–19 and 24–25 wg was observed at the time when programmed cell death in the ganglion cell layer, loss of optic nerve fibres as well as increase in glutamate immunoreactivity and parvalbumin (a calcium binding protein) immunoreactivity in the ganglion cells was reported. These observations indicate that programmed cell death of ganglion cells in the retina may be linked to glutamate toxicity and NO activity, as also suggested by others in the retina and cerebral cortex. The presence of nNOS immunoreactivity in the photoreceptors from 16–17 weeks of fetal life to adulthood indicates other functions, besides their involvement in photoreceptor function of transduction and information processing.     

Interactions leading to colour opponency in ganglion cells of the turtle retina

In the turtle retina, colour-dependent photoresponses could be recorded intracellularly from ganglion cells receiving only bipolar cell input. Thus, the mechanism for colour discrimination by these ganglion cells (type A) is contained in the outer plexiform layer of the retina and depends on interaction between horizontal and cone cells. Ganglion cells receiving an additional amacrine input (type B) are not influenced by colour, and have about 0.7 logarithmic unit lower absolute sensitivity to peak wavelength than have type A ganglion cells.     

Directional Summation in Non-direction Selective Retinal Ganglion Cells

Retinal ganglion cells receive inputs from multiple bipolar cells which must be integrated before a decision to fire is made. Theoretical studies have provided clues about how this integration is accomplished but have not directly determined the rules regulating summation of closely timed inputs along single or multiple dendrites. Here we have examined dendritic summation of multiple inputs along On ganglion cell dendrites in whole mount rat retina. We activated inputs at targeted locations by uncaging glutamate sequentially to generate apparent motion along On ganglion cell dendrites in whole mount retina. Summation was directional and dependent13 on input sequence. Input moving away from the soma (centrifugal) resulted in supralinear summation, while activation sequences moving toward the soma (centripetal) were linear. Enhanced summation for centrifugal activation was robust as it was also observed in cultured retinal ganglion cells. This directional summation was dependent on hyperpolarization activated cyclic nucleotide-gated (HCN) channels as blockade with ZD7288 eliminated directionality. A computational model confirms that activation of HCN channels can override a preference for centripetal summation expected from cell anatomy. This type of direction selectivity could play a role in coding movement similar to the axial selectivity seen in locust ganglion cells which detect looming stimuli. More generally, these results suggest that non-directional retinal ganglion cells can discriminate between input sequences independent of the retina network.     

Chicken retinal ganglion cells response characteristics: multi-channel electrode recording study

A fundamental question in neuroscience is how the information relevant to behavior is presented in the activity of neurons[1]. The visual system, especially the retina, offers some advantage to explore the neural code owing to its explicitly layered structure and relatively simple neuron types[2]. However, most of what we know about retinal signaling is derived from single neuron recordings[2,3]. The assumptions underlying this approach are that individual neuron acts as a unique element dedi…     

Chicken retinal ganglion cells response characteristics: multi-channel electrode recording study

The first stage of visual processing occurs in the retina, the function of which is to process the raw information obtained from the outside world. In the present study, the electrical activities of a group of retinal ganglion cells were recorded from a small functioning piece of retina, using multi-electrode array (MEA), and the action potentials were detected by applying nonlinear algorithm. By analyzing the ensemble retinal ganglion output characteristics, it is revealed that both firing rates and correlated activity between adjacent neurons in the retina contribute to visual information encoding.     

A dynamic model of the vertebrate retina

In this paper a mathematical model of the retina was proposed to clarify the spatio-temporal information processing mechanism in the retina of vertebrates. In order to explain spatio-temporal characteristics of an on-center receptive field of a ganglion cell, excitatory and inhibitory cell layers were introduced of which time lags increased with the lateral distance from a point of stimulation. The characteristics of this model were found to agree well with the physiological data: e.g., this model shows on-response to the input stimulus given on the center, off-response to the input on the surround, and on-off response to the input on the border between on- and off-response regions of the on-center field.     

Differential enhancement of neural and photoreceptor cell differentiation of cultured pineal cells by FGF-1, IGF-1, and EGF

There are several common features between the pineal organ and the lateral eye in their developmental and evolutionary aspects. The avian pineal is a photoendocrine organ that originates from the diencephalon roof and represents a transitional type between the photosensory organ of lower vertebrates and the endocrine gland of mammals. Previous cell culture studies have shown that embryonic avian pineal cells retain a wide spectrum of differentiative capacities, although little is known about the mechanisms involved in their fate determination. In the present study, we investigated the effects of various cell growth factors on the differentiation of photoreceptor and neural cell types using pineal cell cultures from quail embryos. The results show that IGF-1 promotes differentiation of rhodopsin-immunoreactive cells, but had no effect on neural cell differentiation. Simultaneous administration of EGF and IGF-1 further enhanced differentiation of rhodopsin-immunoreactive cells, although the mechanism of the synergistic effect is unknown. FGF-1 did not stimulate proliferation of neural progenitor cells, but intensively promoted and maintained expression of a neural cell phenotype. FGF-1 appeared to lead to the conversion from an epithelial (endocrinal) to a neuronal type. It also enhanced phenotypic expression of retinal ganglion cell markers but rather suppressed expression of an amacrine cell marker. These results indicate that growth factors are important regulatory cues for pineal cell differentiation and suggest that they play roles in determining the fate of the pineal organ and the eye. It can be speculated that the differences in environmental cues between the retina and pineal may result in the transition of the pineal primordium from a potentially ocular (retinal) organ to a photoendocrine organ.     

A simple model of human foveal ganglion cell responses to hyperacuity stimuli

We developed a physiologically plausible model of the first steps of spatial visual information processing in the fovea of the human retina. With the predictions of this model we could support the hypothesis that, for moderate contrasts ( 40%), hyperacuity is mediated by the magnocellular (MC-) pathway. Despite the lower sampling density in the MC pathway, as compared to the parvocellular (PC-) pathway, the information that is transferred by the MC ganglion cells is sufficient to achieve thresholds comparable to those of human subjects in psychophysical tasks. This is a result of the much higher signal-to-noise ratio of the MC pathway cell signals. The PC pathway cells do not transfer enough information for hyperacuity thresholds.     

Non-image-forming ocular photoreception in vertebrates

It has been accepted for a hundred years or more that rods and cones are the only photoreceptive cells in the retina. The light signals generated in rods and cones, after processing by downstream retinal neurons (bipolar, horizontal, amacrine and ganglion cells), are transmitted to the brain via the axons of the ganglion cells for further analysis. In the past few years, however, convincing evidence has rapidly emerged indicating that a small subset of retinal ganglion cells in mammals is also intrinsically photosensitive. Melanopsin is the signaling photopigment in these cells. The main function of the inner-retina photoreceptors is to generate and transmit non-image-forming visual information, although some role in conventional vision (image detection) is also possible.     

The developing avian retina expresses agrin isoforms during synaptogenesis

The localization, isoform pattern, and mRNA distribution of the synapse-organizing molecule agrin was investigated in the developing avian retina. Injection of anti-agrin Fab fragments into the vitreous humor of chick eyes of embryonic days 3 to 20, a procedure that labels only extracellular agrin, reveals staining in the inner and outer plexiform layers before, during, and after the period of synapse formation. The labeling in these layers changes from a diffuse to a punctate pattern at the time when synapses form. At all stages investigated, the inner limiting membrane (a basal lamina that separates vitreous from neural retina) is intensely labeled, as are the axonal processes of retinal ganglion cells in the optic fiber layer and in the optic nerve, although the staining intensity declines after embryonic day 10 in both retina and optic nerve. In culture, axons of retinal ganglion cells also express agrin-like immunoreactivity on their surfaces. Polymerase chain reaction analysis reveals that several different agrin isoforms are expressed in the developing neural retina. In situ hybridization studies show that agrin isoforms are expressed in the ganglion cell and inner nuclear layers, correlating well with the staining for agrin protein in the optic fiber and plexiform layers. The expression of mRNA coding for several agrin isoforms and the presence of extracellular agrin in the synapse-containing layers during the period of synapse formation is consistent with the idea that agrin isoforms might play a role during synapse formation in the central nervous system. © 1996 John Wiley & Sons, Inc.     

Diversity of Retinal Ganglion Cells Identified by Transient GFP Transfection in Organotypic Tissue Culture of Adult Marmoset Monkey Retina

The mammalian retina has more diversity of neurons than scientists had once believed in order to establish complicated vision processing. In the monkey retina, morphological diversity of retinal ganglion cells (RGCs) besides dominant midget and parasol cells has been suggested. However, characteristic subtypes of RGCs in other species such as bistratified direction-selective ganglion cells (DSGC) have not yet been identified. Increasing interest has been shown in the common marmoset (Callithrix jacchus) monkey as a “super-model” of neuroscientific research. Here, we established organotypic tissue culture of the adult marmoset monkey retina with particle-mediated gene transfer of GFP to survey the morphological diversity of RGCs. We successfully incubated adult marmoset monkey retinas for 2 to 4 days ex vivo for transient expression of GFP. We morphologically examined 121 RGCs out of more than 3240 GFP-transfected cells in 5 retinas. Among them, we identified monostratified or broadly stratified ganglion cells (midget, parasol, sparse, recursive, thorny, and broad thorny ganglion cells), and bistratified ganglion cells (recursive, large, and small bistratified ganglion cells [blue-ON/yellow-OFF-like]). By this survey, we also found a candidate for bistratified DSGC whose dendrites were well cofasciculated with ChAT-positive starburst dendrites, costratified with ON and OFF ChAT bands, and had honeycomb-shaped dendritic arbors morphologically similar to those in rabbits. Our genetic engineering method provides a new approach to future investigation for morphological and functional diversity of RGCs in the monkey retina.     

The receptor tyrosine phosphatase CRYPalpha affects growth cone morphology

During development of the nervous system receptor tyrosine kinases and receptor protein tyrosine phosphatases act in a coordinate way during axon growth and guidance. In the developing avian retinotectal system, many different receptor protein tyrosine phosphatases are expressed. Most of them have unknown functions. Retinal ganglion cells express at least three different members of this receptor family on their axons and growth cones: CRYPalpha, CRYP-2 and PTPmu. CRYPalpha interacts heterophilically with at least two different ligands found in the basal membranes of the retina and the optic tectum. To analyze the role of the CRYPalpha-ligand interaction, retinal ganglion cell axons were grown on retinal basal membranes (inner limiting membrane) and the receptor-ligand interaction was blocked from both the receptor side (by receptor specific antibodies) and from the ligand side by using a receptor-alkaline phosphatase fusion protein. Both of these treatments reduced average retinal axon length and induced a dramatic change in morphology of retinal ganglion cell growth cones on basal membranes, but not on other substrates like laminin, N-cadherin, matrigel- and detergent-treated basal membranes. These results suggest that CRYPalpha and its ligand act as growth-promoting molecules during intraretinal axon growth.