INTRODUCTION TO VISUAL PROSTHETICS by Eduardo Fernandez and Richard Normann “The best and most beautiful things in the world cannot be seen or even touched – they must be felt with the heart ” Hellen Keller. 1. Introduction. Loss of vision affects millions of people worldwide and poses extraordinary challenges to individuals in …
Continue reading “Introduction To Visual Prostheses by Eduardo Fernandez and Richard Normann”
1. Introduction The ability to detect moving objects in the visual scene is fundamental to our daily survival. It originates within the sensory organ, the retina, where a significant proportion of retinal ganglion cell (RGC) responses is dedicated to detecting motion in different directions (Fig.1). The first evidence for such retinal computation …
Continue reading “The Anatomy and Physiology of Direction-Selective Retinal Ganglion Cells by Jinyue Liu”
Geoffrey. B. Arden and David J. Ramsey 1. Introduction There is a pandemic of diabetes. More than 350 million people are affected world-wide. In the UK more than 4.2 million people (6.3% of the population) are estimated to be living with diabetes, many without even knowing it (1). In the USA 29.1 million (9.3% …
Continue reading “Diabetic Retinopathy and A Novel Treatment Based On The Biophysics Of Rod Photoreceptors And Dark Adaptation by Geoffrey. B. Arden and David J. Ramsey”
Frederic Gaillard and Yves Sauve 1. Introduction Injury to the brain areas concerned with vision can cause a variety of disorders ranging from visual field defects to much more complex deficits like visual agnosia. It all depends on the location and the extent of the damage. Injury to the occipital striate cortex results in corresponding …
Continue reading “Fetal tissue allografts in the central visual system of rodents by Frederic Gaillard and Yves Sauve”
Ralph Nelson and Victoria Connaughton 1. Introduction. Retinal ganglion cells are typically only two synapses distant from retinal photoreceptors, yet ganglion cell responses are far more diverse than those of photoreceptors. The most direct pathway from photoreceptors to ganglion cells is through retinal bipolar cells. Thus, it is of great interest to understand how bipolar …
Continue reading “Bipolar Cell Pathways in the Vertebrate Retina by Ralph Nelson and Victoria Connaughton”
Yingbin Fu 1. Introduction. Vertebrates rely on retinal rods and cones for the conventional, image-forming vision while non-image-forming vision is mediated by intrinsically photosensitive retinal ganglion cells (ipRGCs) (see Part II Chapter 7). Rods are specialized for low-light vision. They are extremely sensitive and can signal the absorption of single photons. Cones mediate …
Continue reading “Phototransduction in Rods and Cones by Yingbin Fu”
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 …
Continue reading “AII Amacrine Cells by Mahnoosh Farsaii and Victoria P. Connaughton”
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 …
Continue reading “Roles of Amacrine Cells by Helga Kolb”
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 …
Continue reading “Circuitry for Rod Signals Through The Retina by Helga Kolb”
Helga Kolb Three basic types of glial cell are found in the human retina, Muller cells, astroglia and microglia. All were described for the retina by Cajal more than one hundred years ago (1892). 1. Muller cells. Muller cells are the principal glial cell of the retina. They form architectural support structures stretching …
Continue reading “Glial cells of the Retina by Helga Kolb”
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 …
Continue reading “Melanopsin-expressing, Intrinsically Photosensitive Retinal Ganglion Cells (ipRGCs) by Dustin M. Graham and Kwoon Y. Wong”
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 …
Continue reading “Morphology and Circuitry of Ganglion Cells by Helga Kolb”
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 …
Continue reading “S-Potentials and Horizontal Cells by Ido Perlman, Helga Kolb and Ralph Nelson”
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 …
Continue reading “The Role of Dopamine in Retinal Function By Elka Popova”
By Helga Kolb, Ralph Nelson, Peter Ahnelt, Isabel Ortuño-Lizarán and Nicolas Cuenca Abstract We summarize the development, structure, different neural types and neural circuitry in the human fovea. The foveal pit is devoid of rod photoreceptors and of secondary and tertiary neurons, allowing light to directly stimulate cones and give us maximal visual acuity. The …
Continue reading “The Architecture of the Human Fovea By Helga Kolb, Ralph Nelson, Peter Ahnelt, Isabel Ortuño-Lizarán and Nicolas Cuenca”