Vision Flashcards
Retina
where photoreceptors transform light into a neural signal (transduction)
Ganglion Cells
gather information from photoreceptors
*responsible for the opponent process, which occurs AFTER the trichromatic color scale
Photoreceptors
rods and cones
Cones
-located in the center of the retina
-low sensitivity to dim light, high color sensitivity, high detail sensitivity
Rods
-located in the periphery
-high sensitivity to dim light, low color sensitivity, low detail sensitivity
Fovea
the center of the retina
Do we have more rods or cones in the eye?
Rods
Why can’t nearsighted people see far away?
light reflected from an object is focused in front of the retina
Why can’t far sighted people see up close?
their point of focus fall beyond the surface of the retina
Trichromatic Color Theory
there are 3 different cones each sensitive to wavelengths of light (short, medium, and long wavelengths)
*phototransuction, level of cones
*short: blue
*medium: green
*long: red
How are color blindness and cones related?
Those who are color blind have a deficiency on one or more of the cones
Opponent process theory
we perceive color in terms of opposing pairs: red/green, yellow/blue, black/white
How do photoreceptors travel through the brain?
the signal travels down the optic nerve to the brain and passes through the thalamus and is sent to the primary visual cortex
What happens after neurons are sent to the visual cortex?
information is routed to other cortical areas for processing (these are the dorsal and ventral pathways)
Dorsal Pathway
“where pathway”- visually guided movements
*e.g. putting an envelope in the mail
Ventral Pathway
“what pathway” - object identification, identifying who a person is
Visual agnosia
inability to recognize objects
Prosopagnosia
inability to recognize faces
Monocular depth cues
help us perceive depth using one eye
Monocular depth cues examples
relative height, relative size, linear perspective, light & shadow, interposition (things in front cover up what’s behind)
Binocular depth cues
help us perceive depth using both eyes
Retinal disparity
different retinal images each eye receives based on its different perspectives
Convergence
when a person views a nearby object, the eye muscles turn the eyes inward
How do we keep our perception of an object constant despite different input?
-size constancy
-brightness constancy
Size constancy
we understand that objects appear smaller when further away
Brightness constancy
we understand that shadow/darkness affects color
Feature detectors
cells that respond selectively to specific features
*respond to lines, angles, and corners in particular orientations on the retina
*this is bottom-up processing
*first discovered by Hubel and Weisel in cat study
