Vision.csv

a small central pit located in the macula region of the retina; composed of closely packed cones

the retinal area responsible for fixed central vision during good light

sensory part of the eye; transforms light into electrical impulses; found at the the inner surface of the eye

transmits visual information from the retina to the brain

location in which retinal ganglion fibers exit the eye to form the optic nerve; no photoreceptors exist at this point; causes the blind spot

found in the center of the fovea; contains only cones and no rods

specialized neurons that are capable of phototransduction; includes rods and cones

layer of cells found just outside the retina; responsible for maintaining retinal environment

photoreceptors; first-order neurons; detect low levels of light (scotopic); low temporal resolution; exist in greater number than cones

photoreceptors; first-order neurons; functional in high levels of light (photopic); high temporal resolution

short cone-shaped outer segment; inner segment; synaptic terminal

long cylindrical outer segment; inner segment; synaptic terminal

rod systems are highly convergent - many rods synapse on a single bipolar cell; cone systems are not convergent - one cone sypapses on one bipolar cell

visual pigment that absorbs light for rods; composed of opsin and 11 -cis retinal molecules; captured light causes a conformational change to metarhodopsin

light activates rhodopsin to metarhodopsin; metarhodopsin activates transducin (a G-protein); transducin activates cGMP phosphodiesterase; cGMP levels are reduced; the photoreceptor cell is hyperpolarized

cGMP is high in the dark; cells are depolarized and produce current in the dark; light closes potassium channels and prevents potassium from leaving the cell; light hyperpolarizes cells

light opens calcium channels; influx of calcium reduces cGMP; reduction in cGMP helps to shut down channels in bright light

have center and antagonistic surround receptive fields

cell is activated when the cell is stimulated in the center and deactivated when the cell is stimulated in the surround; good at recognizing increases in light

cell is deactivated when the cell is stimulated in the center and activated when the cell is stimulated in the surround; good at recognizing decreases in light

hyperpolarized by glutamate; are depolarized following illumination; have metabotropic receptors

depolarized by glutamate; are hyperpolarized following illumination; have ionotropic receptors

right visual field is projected onto the left hemiretinas and vice versa; nasal hemiretinas cross at the optic chiasm while temporal hemiretinas follow an ipsilateral path

90% project -> LGN of thalamus -> occipital lobe; others project to hypothalamus and tectum (among other areas)

pretectal neurons proceed to bilateral Edinger-Westphal nuclei -> production of bilateral pupil constriction

bright light shined in one eye will provoke the pupil of that eye to constrict

bright light shined in one eye will provoke the pupil of the contralateral eye to constrict

found with the thalamus; important relay center; 6-layered structure; project via optic radiations to the occipital lobe

have on- and off-center receptive fields; are magnocellular (layers 1 & 2) or parvocellular (layers 3-6)

LGN and cortex are retinotopically organized; retina is topographically represented

results from damage to one optic nerve; complete loss of vision in one eye

results from splitting of the optic chiasm; bilateral loss of temporal vision

results from damage to one optic chiasm; bilateral loss of vision in one half of the visual field

results from damage to the optic projections; bilateral loss of vision in one-quarter of the visual field

foveal vision often is not lost when cortical visual damage occurs; may be spared due to extensive cortical representation

projections from the LGN enter in layer 4C of the cortex; ocular dominace columns are formed; L/R eye separation is maintained

cells in the primary visual cortex are maximally receptive to specifically oriented bars of light

there is a columnar organization of orientation selective cells in the visual cortex

found in layers 2 and 3 of the primary visual cortex; respond selectively to color

cells with preferences for specific orientations of light are arranged in columns that show preference for input from one eye

hypercolumns are groups of columns that possess a complete representation of visual input -- all orientations & blobs & both ocular dominance columns are represented

damage between the occipital and temporal lobe may lead to an inability to recognize color

damage in the middle temporal region may lead to an inability to assess motion

damage to the inferior temporal area may lead to an inability to recognize faces

spatial vision pathway and object recognition pathway

also called the dorsal pathway; involves projections from V1 -> V2 -> middle temporal region -> parietal lobe; involved in motion detection

also called the ventral pathway; involves projections from V1 -> V2 -> V4 -> temporal lobe; involved in identification of fine detail and color

M RGCs ->layers 1 & 2 of LGN -> layer 4-alpha of cortex; involved in analysis of gross features and movement

P RGCs -> layers 3-6 of LGN -> layer 4-beta of cortex; involved in analysis of color and fine detail

K RGCs -> areas in between LGN layers; analyze color information; primarily involved in ventral pathway

M RGCs and LGN cells = large; extensively branched; large receptive fields; respond optimally to large objects; high tempora resolution

P RGCs and LGN cells = small; small receptive fields; high spatial resolution

familiar size; occlusion; linear perspective; size perspective; illumination; motion parallax

differences in visual input between eyes helps brain to construct 3-D image (depth perception)

shows the reflectance/absorbance of different objects for light of different wavelengths

S (blue) cones - most sensitive to short wavelengths; M (green) cones - most sensitive to middle wavelengths; L (red) cones - most sensitive to long wavelengths

loss of L cone function

loss of M cone function

loss of S cone function

colorblindness involving abnormal cone types

replacement of L cone pigment with L/M hybrid

replacement of M cone pigment with L/M hybrid