Mahnoosh Farsaii and Victoria P. Connaughton 1. Introduction. The AII amacrine cell is characterized by a multifaceted connectivity and physiology. It is unique among amacrine cells in that it participates predominantly in the vertical flow of information though the inner retina, contributing to center mechanisms, rather than in lateral inhibitory pathways. As its multilayer …
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Helga Kolb 1. General characteristics. Amacrine cells of the vertebrate retina are interneurons that interact at the second synaptic level of the vertically direct pathways consisting of the photoreceptor-bipolar-ganglion cell chain. They are synaptically active in the inner plexiform layer (IPL) and serve to integrate, modulate and interpose a temporal domain to the …
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1Dustin M. Graham and 2,3Kwoon Y. Wong 1Nature Publishing Group, New York, NY. 2Department of Ophthalmology & Visual Sciences, Department of Molecular, Cellular & Developmental Biology, University of Michigan, Ann Arbor, MI 48105. 3Correspondence: kwoon@umich.edu 1. Introduction. For the greater part of 150 years it was assumed that the mammalian retina contained only …
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Helga Kolb 1. General morphology. Ganglion cells are the final output neurons of the vertebrate retina. The ganglion cell collects the electrical messages concerning the visual signal from the two layers of nerve cells preceding it in the retinal wiring scheme. A great deal of preprocessing has been accomplished by the neurons of …
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Ido Perlman, Helga Kolb and Ralph Nelson 1. Introduction Horizontal cells are the interneurons of distal vertebrate retina. They provide the pathways for both local and long range interactions between photoreceptors. These interactions are called feedback signals. Feedback signals adjust the gain of photoreceptor synaptic output, both as seen in the horizontal cells themselves …
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1. Size of the retina. 32 mm from ora to ora along the horizontal meridian (Van Buren, 1963; Kolb, unpublished measurements). Area of the human retina is 1094 square mm (Bernstein, personal communication) calculated from the expectations that the average dimension of the human eye is 22 mm from anterior to posterior poles, and …
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The Role of Dopamine in Retinal Function Abstract Dopamine (DA) is the major catecholamine in all vertebrate retinas including man. All vertebrates have dopaminergic neurons identified as amacrine cells (ACs) and interplexiform cells (IPCs), with great variations among different species. DA neurons are comparatively rare with density about 10-100 per mm2, which means that they …
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What is glaucoma? David Križaj Abstract Glaucoma, a leading cause of blindness in the world, can be challenging to diagnose because symptoms often appear at late stage of the disease, and challenging to treat because of the irreversible loss of retinal neurons. The term encompasses a heterogenous group of diseases that are characterized by altered …
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Ethan D. Cohen, Ph.D., Abstract Retina prostheses try to reactivate the residual circuitry in a blind patient’s retina to produce a synthetic form of usable vision. Using an array of stimulus electrodes or light-sensitive proteins, the neurons in the degenerate retinal network are activated to elicit a series of light percepts termed “phosphenes”. If …
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Ido Perlman 1. Historical view. As early as 1865 Holmgren found that a light stimulus could cause a change in the electrical potential of the amphibian eye. Shortly afterwards, similar findings were reported by Dewar from Scotland. He showed that light illumination through the pupil, which had previously been covered, caused a …
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Peter Gouras 1. Introduction. Color vision is an illusion created by the interactions of billions of neurons in our brain. There is no color in the external world; it is created by neural programs and projected onto the outer world we see. It is intimately linked to the perception of form where color …
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Helga Kolb 1. General characteristics. Over the last few years, psychophysicists, electrophysiologists, geneticists and anatomists have concluded that there is something unique about the short wavelength system compared with the two longer wavelength systems in the visual system. Fig. 1. Cone mosaic in the fovea where the S-wave or blue …
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Helga Kolb 1. Rods. Rod photoreceptors and rod-connected nerve cells through the retina are responsible for pathways concerned with night vision and increased sensitivity of our visual system under what is called scotopic conditions (conditions of very little ambient light). Most vertebrates have a preponderance of rod photoreceptors in their retinas and such …
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Ralph Nelson 1. Overview. Ganglion cells are the final output neurons of the vertebrate retina. Ganglion cells collect information about the visual world from bipolar cells and amacrine cells (retinal interneurons). This information is in the form of chemical messages sensed by receptors on the ganglion cell membrane. Transmembrane receptors, in turn, transform …
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Helga Kolb A certain degree of integration of the visual message goes on at the first synapse in the retina, in the outer plexiform layer. Here cone pedicles and rod spherules are synaptic upon various bipolar cell and horizontal cell types. In addition, as mentioned in the previous section, cone pedicles pass electrical messages …
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