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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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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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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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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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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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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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. Circuitry for cone signals. Cone photoreceptors are the sensors of bright light and different wavelengths of light in the retina. They are sensitive in photopic (bright light) conditions and come in several types according to the structure of the visual pigments or opsins in their outer segment regions. In dichromatic …
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Helga Kolb 1. Bipolar, amacrine and ganglion cells interact in the inner plexiform layer. The axonal endings of bipolar cells bring information from the outer plexiform layer (OPL) to the neuropil of the inner plexiform layer (IPL). Here bipolar cells talk to different varieties of functionally specialized amacrine cells and to dendrites of …
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Helga Kolb Two or three types of cone photoreceptor and a single type of rod photoreceptor are present in the normal mammalian retina. Some non-mammalian retinas have even more cone types (see later). 1. Light microscopy and ultrastructure of rods and cones. In vertical sections of retina prepared for light microscopy with …
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Helga Kolb 1. General characteristics. Todays research on the retina focuses a great deal of attention on neurotransmission between the neurons of the retina. Varous techniques using autoradiography, immunocytochemistry and molecular biology are being used to mark neurons for neurochemicals, their synthesizing enzymes, calcium binding proteins and receptors and transporters of these neurochemicals. …
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