Horizontal Cell

Information about Horizontal Cell

Horizontal cells are the laterally interconnecting neurons in the outer plexiform layer of the retina.

Organization

There are three basic types of horizontal cells, designated HI, HII and HIII. The selectivity of these three horizontal cells, towards one of the three cone types, is a matter of debate. According to studies conducted by Boycott and Wassle neither HI cells nor HII cells were selective towards S,M, or L cones. By contrast, Anhelt and Kolb claim that in their observations HI cells connected to all three cone types indiscremenantly, however, HII cells tended to contact S cones the most. They also identified a third type of horizontal cell, HIII, which was identical to HI but did not make contact with S cones.

The HII cells also make connections with rods, but do so far enough away from the horizontal cell's soma such that they do not interfere with the activities of the cones.

They span across cones and summate inputs from them all to control the amount of GABA released back onto the photoreceptor cells, which hyperpolarises them. Their arrangement together with the on-centre and off-centre bipolar cells that receive input from the photoreceptors constitutes a form of lateral inhibition, increasing spatial resolution at the expense of some information on absolute intensity. The eye is thus more sensitive to contrast and differences in intensity.

Functional Properties

When light is shown onto a photoreceptor, the photoreceptor hyperpolarizes and reduces the release of glutamate, when this happens, horizontal cells reduce the release of GABA, which has an inhibitory affect on the photoreceptors. This reduction of inhibition leads to a depolarization of the photoreceptors. We therefore have the following negative feedback

Illumination $\text{[math]}$ photoreceptor hyperpolarization $\text{[math]}$ horizontal cell hyperpolarization $\text{[math]}$ photoreceptor depolarization

One proposed theory for facilitation by the horizontal cells proceeds as follows. Assume we have 11 photoreceptors, one hyperpolarizing (H) bipolar cell, and one horizontal cell. All ten photoreceptors connect to the horizontal cell, and the middle photoreceptor ( $\text{[math]}$ ) connects to the bipolar cell. The surrounding cells, which represent the outer receptive field, will be designated $\text{[math]}$ then we can explain an off-centre arrangement as follows. If light is shown onto the $\text{[math]}$ then

$\text{[math]}$ is activated by light and therefore hyperpolarizes
$\text{[math]}$ reduces release of glutamate
Reduction of glutamate hyperpolarizes the H bipolar cell
Reduction of glutamate hyperpolarizes the horizontal cell and it reduces release of GABA
Since $\text{[math]}$ is still releasing glutamate, reduction in GABA is marginal

If the light is shown onto the surrounding area then

$\text{[math]}$ is activated and therefore hyperpolarizes
$\text{[math]}$ reduce release of glutamate
Reduction of glutamate hyperpolarizes the horizontal cell
Horizontal cell reduces release of GABA
Reduction of GABA depolarizes photoreceptors
$\text{[math]}$ not affected since they are strongly being hyperpolarized by activation
$\text{[math]}$ is affected and therefore depolarizes
$\text{[math]}$ releases glutamate
H Bipolar cell is depolarized

To explain diffuse light, then we consider both cases together, and as it turns out, the two effects cancel each other out, and we get little or no net effect.

External links

Webvision horizontal cell entry.

References

Nicholls, John G.; A. Robert Martin, Bruce G. Wallace, Paul A. Fuchs (2001). From Neuron to Brain. Boston, Massachusetts: Sinauer Associates, Inc. ISBN 0-87893-439-1.
Masland RH (2001). "The fundamental plan of the retina". Nat. Neurosci. 4 (9): 877-86. DOI:10.1038/nn0901-877. PMID 11528418.
Dacey, Dennis M (1999). "Primate Retina: Cell Types, Circuits and Color Opponency". Progress in Retinal and Eye Research 18: 737-763.

• • [ e] Sensory system - Visual system - Eye - Retina
cells	Photoreceptor cells (Cone cell, Rod cell) → (Horizontal cell) → Bipolar cell → (Amacrine cell) → Ganglion cell Giant retinal ganglion cells - Photosensitive ganglion cell - Muller glia
layers	Inner limiting membrane - Nerve fiber layer - Ganglion cell layer - Inner plexiform layer - Inner nuclear layer - Outer plexiform layer - Outer nuclear layer - External limiting membrane - Layer of rods and cones - Retinal pigment epithelium

For the moth genus, see Retina (moth).

The retina is a thin layer of neural cells that lines the back of the eyeball of vertebrates and some cephalopods. It is comparable to the film in a camera.
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Gaba may refer to:

GABA, the gamma-aminobutyric acid neurotransmitter
GABA receptor, in biology, receptors with GABA as their endogenous ligand
Gabâ or gabaa (Philippines), the concept of negative karma of the Cebuano people

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photoreceptor, or photoreceptor cell, is a specialized type of neuron found in the eye's retina that is capable of phototransduction. More specifically, the photoreceptor absorbs photons from the visual field and signals this information to other neurons through a change in
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Off-Centre is a release by Meat Beat Manifesto which follows the album At The Center. Drums and percussion from tracks 1-4 are credited to David King. Steinway Grand Piano, Fender Rhodes and Hammond B3 instrumentation from tracks 1-4 are credited to Craig Taborn.
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A bipolar cell is a type of neuron which has two extensions. Bipolar cells are specialized sensory neurons for the transmission of special senses. As such, they are part of the sensory pathways for smell, sight, taste, hearing and vestibular functions.
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insufficient context for those unfamiliar with the subject matter.
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Photoreceptor can refer to:

In anatomy/cell biology:

Photoreceptor cell: a photosensitive cell, most commonly referring to a specialized type of neuron found in the retina of vertebrate eyes that is capable of phototransduction;

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Location Retina (Inner Nuclear Layer)
Function Convey gradients between photoreceptor cells to retinal ganglion cells

Morphology bipolar
Presynaptic connections Rods , cones and Horizontal Cells
Postsynaptic connections
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Location INL of the retina
Function inhibitory or neuromodulatory interneurons
Neurotransmitter GABA, glycine, DA, or 5-HT
Morphology Varies
Presynaptic connections Bipolar cells
Postsynaptic connections
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Location Varies by type
Function Varies but often excitatory projection

Morphology Varies

A ganglion cell (more correctly, a retinal ganglion cell) is a type of neuron typically located near the inner surface of the retina of the eye that
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digital object identifier (or DOI) is a permanent identifier given to a document, which is not related to its current location. A typical use of a DOI is to give a scientific paper or article a unique identifying number that can be used by anyone to locate details of the paper, and
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sensory system: in this case, vision, for the visual system. ]]

A sensory system is a part of the nervous system responsible for processing sensory information.
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The visual system is the part of the nervous system which allows organisms to see. It interprets the information from visible light to build a representation of the world surrounding the body.
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Eyes are organs of vision that detect light. Different kinds of light-sensitive organs are found in a variety of organisms. The simplest eyes do nothing but detect whether the surroundings are light or dark, while more complex eyes can distinguish shapes and colors.
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For the moth genus, see Retina (moth).

Cone cells, or cones, are photoreceptor cells in the retina of the eye which function best in relatively bright light. The cone cells gradually become more sparse towards the periphery of the retina.
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Location Retina
Function Low light photoreceptor

Morphology rod shaped
Presynaptic connections None
Postsynaptic connections Bipolar Cells and Horizontal cells

Rod cells, or rods
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Giant retinal ganglion cells are ganglion cells with large dendritic trees discovered in the human and macaque retina by Dacey et al (2005).

Giant retinal ganglion cells contain a visual pigment, melanopsin, allowing them to respond directly to light.
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Photosensitive ganglion cells, or melanopsin-containing ganglion cells, are a recently discovered type of nerve cell in the retina of the eye which, unlike other retinal ganglion cells, are intrinsically photosensitive.
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Müller glia, or Müller cells, are glia found in the vertebrate retina, which normally serve the functions of any normal glial cells. However, following injury to the retina, it has been seen that Müller glia actually de-differentiate into a neural progenitor.
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The introduction to this article provides insufficient context for those unfamiliar with the subject matter.
Please help [ improve the introduction] to meet Wikipedia's layout standards.

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The nerve fiber layer (or layer of nerve fibers or stratum opticum) is formed by the expansion of the fibers of the optic nerve; it is thickest near the porus opticus, gradually diminishing toward the ora serrata.
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The ganglion cell layer (ganglionic layer) consists of a single layer of large ganglion cells, except in the macula lutea, where there are several strata.

The cells are somewhat flask-shaped; the rounded internal surface of each resting on the stratum opticum, and
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The inner plexiform layer is made up of a dense reticulum of minute fibrils formed by the interlacement of the dendrites of the ganglion cells with those of the cells of the inner nuclear layer; within this reticulum a few branched spongioblasts are sometimes imbedded.
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The inner nuclear layer or layer of inner granules is made up of a number of closely packed cells, of which there are three varieties, viz.: bipolar cells, horizontal cells, and amacrine cells.
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The outer plexiform layer (external plexiform layer) is a layer of neuronal synapses in the retina of the eye. It consists of a dense network of synapses between dendrites of horizontal cells from the inner nuclear layer, and photoreceptor cell inner segments from the outer
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Horizontal Cell

Information about Horizontal Cell

Organization

Functional Properties

See Also

External links

References