Small retinal cells {amacrine cell, vision} inhibit inner-plexiform-layer ganglion cells, using antitransmitter to block pathways. There are 27 amacrine cell types.
Photoreceptor cells excite retinal neurons {bipolar cell, vision}. There are ten bipolar-cell types. Parasol ganglion cells can receive from large-dendrite-tree bipolar cells {diffuse bipolar cell}.
input
Central-retina small bipolar cells {midget bipolar cell} receive from one cone. Peripheral-retina bipolar cells receive from more than one cone. Horizontal cells inhibit bipolar cells.
output
Bipolar cells send to inner plexiform layer to excite or inhibit ganglion cells, which can be up to five neurons away.
ON-center cells
ON-center midget bipolar cells increase output when light intensity increases in receptive-field center and/or decreases in receptive-field periphery. OFF-center midget bipolar cells increase output when light intensity decreases in receptive-field center and/or increases in receptive-field periphery.
Retinal neurons {ganglion cell, retina} can receive from bipolar cells and send to thalamus lateral geniculate nucleus (LGN), which sends to visual-cortex hypercolumns.
midget ganglion cell
Small central-retina ganglion cells {midget ganglion cell} receive from one midget bipolar cell. Midget cells respond mostly to contrast. Most ganglion cells are midget ganglion cells.
parasol cell
Ganglion cells {parasol cell} {parasol ganglion cell} can receive from diffuse bipolar cells. Parasol cells respond mostly to change. Parasol cells are 10% of ganglion cells.
X cell
Ganglion X cells can make tonic and sustained signals, with slow conduction, to detect details and spatial orientation. X cells send to thalamus simple cells. X cells have large dendritic fields. X cells are more numerous in fovea.
Y cell
Ganglion Y cells can make phasic and transient signals, with fast conduction, to detect stimulus size and temporal motion. Y cells send to thalamus complex cells. Y cells have small dendritic fields. Y cells are more numerous in retinal periphery.
W cell
Ganglion W cells are small, are direction sensitive, and have slow conduction speed.
ON-center neuron
ON-center ganglion cells respond when light intensity above background level falls on their receptive field. Light falling on field surround inhibits cell. Bipolar cells excite ON-center neurons.
Four types of ON-center neuron depend on balance between cell excitation and inhibition. One has high firing rate at onset and zero rate at offset. One has high rate at onset, then zero, then high, and then zero. One has high rate at onset, goes to zero, and then rises to constant level. One has high rate at onset and then goes to zero.
OFF-center neuron
OFF-center ganglion cells increase output when light intensity decreases in receptive-field center. Light falling on field surround excites cell. Bipolar cells excite OFF-center neurons.
ON-OFF-center neuron
ON-OFF-center ganglion cells for motion use ON-center-neuron time derivatives to find movement position and direction. Amacrine cells excite transient ON-OFF-center neurons.
similar neurons
Ganglion cells are like auditory nerve cells, Purkinje cells, olfactory bulb cells, olfactory cortex cells, and hippocampal cells.
spontaneous activity
Ganglion-cell spontaneous activity can be high or low [Dowling, 1987] [Enroth-Cugell and Robson, 1984] [Wandell, 1995].
Retinal cells {horizontal cell} can receive from receptor cells and inhibit bipolar cells.
Retina has pigment cells {photoreceptor cell}, with three layers: cell nucleus, then inner segment, and then outer segment with photopigment. Visual-receptor cells find illumination logarithm.
types
Human vision uses four receptor types: rods, long-wavelength cones, middle-wavelength cones, and short-wavelength cones.
hyperpolarization
Visual receptor cells hyperpolarize up to 30 mV from resting level [Dowling, 1987] [Enroth-Cugell and Robson, 1984] [Wandell, 1995]. Photoreceptors have maximum response at one frequency and lesser responses farther from that frequency.
Rod-shaped retinal cells {rod cell} are night-vision photoreceptors, detect large features, and do not signal color.
frequency
Rods have maximum sensitivity at 498 nm, blue-green.
Just above cone threshold intensity {mesopic vision, rod}, rods are more sensitive to short wavelengths, so blue colors are brighter but colorless.
number
Retinas have 90 million rod cells.
layers
Rods have cell nucleus layer, inner layer that makes pigment, and outer layer that stores pigment. Outer layer is next to pigment epithelium at eyeball back.
size
Rods are larger than cones.
pigment
Rod light-absorbing pigment is rhodopsin. Cones have iodopsin.
rod cell and long-wavelength cone
Brain can distinguish colors using light that only affects rod cells and long-wavelength cone cells.
fovea
Fovea has no rod cells. Rod cells are denser around fovea.
Cone-shaped retinal cells {cone, cell} have daylight-vision photoreceptors and detect color and visual details.
types
Humans have three cone types. Cone maximum wavelength sensitivities are at indigo 437 nm {short-wavelength cone}, green 534 nm {middle-wavelength cone}, and yellow-green 564 nm {long-wavelength cone}. Shrimp can have eleven cone types.
evolution
Long-wavelength cones evolved first, then short-wavelength cones, and then middle-wavelength cones. Long-wavelength and short-wavelength cones differentiated 30,000,000 years ago. Three cone types and trichromatic vision began in Old World monkeys.
fovea
Fovea has patches of only medium-wavelength or only long-wavelength cones. To improve acuity, fovea has few short-wavelength cones, because different colors focus at different distances. Fovea center has no short-wavelength cones [Curcio et al., 1991] [Roorda and Williams, 1999] [Williams et al., 1981] [Williams et al., 1991].
number
There are five million cones, mostly in fovea. Short-wavelength cones are mostly outside fovea.
size
Cones are smaller than rods.
pigment
Cone light-absorbing pigment is iodopsin. Rods have rhodopsin.
frequency
When rods saturate, cones have approximately same sensitivity to blue and red.
Just above cone threshold {mesopic vision, cone}, rods are more sensitive to short wavelengths, so blue colors are brighter but colorless. Retinal receptors do not detect pure or unmixed colors. Red light does not optimally excite one cone type but makes maximum excitation ratio between two cone types. Blue light excites short-wavelength cones and does not excite other cone types. Green light excites all cone types.
output
Cones send to one ON-center and one OFF-center midget ganglion cell.
Most mammals, including cats and dogs, have two photopigments and two cone types {dichromat}. For dogs, one photopigment has maximum sensitivity at 429 nm, and one photopigment has maximum sensitivity at 555 nm. Early mammals and most mammals are at 424 nm and 560 nm.
Animals can have only one photopigment and one cone type {monochromat} {cone monochromat}. They have limited color range. Animals can have only rods and no cones {rod monochromat} and cannot see color.
Reptiles and birds have four different photopigments {quadchromat}, with maximum sensitivities at near-ultraviolet 370 nm, 445 nm, 500 nm, and 565 nm. Reptiles and birds have yellow, red, and colorless oil droplets, which make wavelength range less, except for ultraviolet sensor.
Women can have two different long-wavelength cones {L-cone} {L photopigment}, one short-wavelength cone {S-cone} {S photopigment}, and one middle-wavelength cone {M-cone} {M photopigment}, and so have four different pigments {tetrachromacy}. Half of men have one or the other long-wavelength cone [Asenjo et al., 1994] [Jameson et al., 2001] [Jordan and Mollon, 1993] [Nathans, 1999].
People with normal color vision have three different photopigments and cones {trichromat}.
1-Consciousness-Sense-Vision-Anatomy-Cells
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Date Modified: 2022.0225