Vision Flashcards
Lens
Bends light to focus it on retina.
Iris
Controls how much light enters the pupil thru ciliary muscle
Cornea
Transparent outer layer of the eye whose curvature is fixed. For protection and refraction. Corrects bending of light. Primarily responsible for forming image on retina
Accommodation
The process of focusing by the ciliary muscles and the lens to form a sharp image on the retina.
Extraocular muscle
One of the muscles attached to the eyeball that control its position and movements
Retina
The receptive surface inside the eye that contains photoreceptors and other neurons
Rods
A class of light-sensitive receptor cells in the retina that are most active at low levels of light.
Photopigment= rhodopsin
Part of scotopic system.
Get many rods per ganglion
Cones
A class of photoreceptors cells in the retina that are responsible for color vision Has three classes of photopigments. Small receptive field. Photopic system. One come per ganglion cell.
Bipolar cells
A class of interneurons of the retina that receive info from rods and cones and pass info to retinal ganglion cells. Can only pride graded potentials. Release GLU
Ganglion cells
A class of cells in the retina whose axons form the optic nerve.
Produce action potentials
Have concentric receptive fields
Photoreceptors
Neural cells in the retina that respond to light (rods and cones)
Can only produce graded potentials
Range fractionalization
A hypothesis of stimulus intensity perception stating that a wide range of intensity values can be encoded by a group of cells, each of which is a specialist for a particular range of stimulus intensities. Different receptors handle different intensities, diff thresholds
Photoreceptors adaptation
The tendency of rods and cones to adjust their light sensitivity to match ambient levels or illumination
Lateral inhibition
Info processing that takes place in the eye where some cells cause neighboring cells to be quiet so they can focus.
Done by horizontal and amacrine cells.
Horizontal cells
Specialized retinal cells that contact both the receptor cells and the bipolar cells
Involved in lateral inhibition
Amacrine cells
Specialized retinal cells that contact both bipolar and ganglion cells and are significant in inhibitory interactions within the retina
Visual field
Whole area that you can see without moving head or eyes
Fovea
Central portion of the retina packed with most photoreceptors and therefore center or our gaze. Densely packed with cones
Optic disc
Region of retina devoid of receptor cells bc ganglion cells axons and blood vessels exit the eyeball there. Makes blind spot in vision
Neural pathway of vision
From ganglion cells form optic nerve, to optic chiasm (nasal vs temporal crossing over), to lateral geniculate nucleus (LGN), to optic radiation (thalamus to cortex), to primary visual cortex (V1) in occipital lobe aka striate cortex.
On-center bipolar cells
A retinal bipolar cells that is excited by light in the center of its receptive field because it receives less GLU rich would inhibit it.
Off-center bipolar cell
A retinal bipolar cell that is inhibited by light in the center of its receptive field. Is excited by turning off light in center, receives more GLU which depolarizes it.
On-center ganglion cell
A retinal ganglion cell that is activated (depolarized by GLU from on-center bipolar cells) when light is presented to the center, rather than the periphery, of the cell’s receptive field.
Off-center ganglion cell
A retinal ganglion cell that is activated (depolarized by GLU from off center bipolar cells) when light is presented to the periphery, rather than the center, of the cell’s receptive field.
Concentric receptive fields
Two types:
On-center/off-surround
Off-center/on-surround
LGN
6 layers of cells
Outer 4 layers-parvocellular (small receptive fields, fovea, high acuity)
Inner 2 layers- magnocellular (low acuity, large receptive fields, not detailed)
V1
Has simple and complex cortical cells, feature detectors (grandmother cells theory), hierarchical processing.
Simple cortical cell
Aka bar/edge detector.
Cell in visual cortex that responds best to an edge or a car that had s particular width, as well as a particular orientation and location in the visual field. Simple features, respond to light, small area.
Complex cortical cells
A cell in the visual cortex that responds best to a bar or particular size and orientation anywhere within a particular area of the visual field. More features
Spatial frequency filler model
A model patten of analysis that emphasizes Fournier analysis of visual stimuli
V1 columns
Run parallel to surface of cortex.
4 dif types:
Location, ocular dominance (depth perception, kitten studies), spatial orientation, color.
Ocular dominance column
A region of cortex in which one eye provides greater degree of synaptic input
Orientation column
A column of visual cortex that responds to rod-shaped stimuli of a particular orientation.
Trichromatic theory
Three diff types of cones (red blue green) that respond to diff types of light. Actually 3 types of cones- short, medium, long. Only happens at level of cones
Opponent- process theory
Color pairs: red-green, black-white, yellow-blue. In bipolar/ganglion cells, excited by one color, inhibited by another.
If color blind, missing an opsin
Motion perception
In cortical area V5. If can’t perceive motion, lack columns that perceive motion in medial temporal area in temporal lobe.
Dorsal stream of vision
“Where” pathway.
V1, to medial temporal area, to parietal lobe, to frontal lobe.
Ventral stream of vision
“What” pathway. Object identification.
V1, to inferior temporal area (fusiform gyrus facial rec), to frontal.
Optic ataxia
Difficulty hating vision to reach and manipulate objects. From damage to posterior parietal cortex “where” pathway.
Myopia
Nearsightedness. Eyeball is too long, object image focused in front of retina instead of on it. Spending time indoors w artificial light could be cause
