Ch6-Vision Flashcards
information is stored in terms of responses by neurons based on….
- which neurons respond
- their amount of response
- timing of their responses
whatever excites a particular nerve establishes a special kind of energy unique to that nerve
law of specific nerve energies (influences what we perceive)
Every stimulation of the optic nerve is perceived as light. This statement is an example of….
law of specific nerve energies
center of the iris, where light enters
pupil
rear surface of the eye, lined with receptors
retina
located closer to center of the eye, receive messages from receptors at back of the eye (retina)
bipolar cells
located still closer to center of eye, receive messages from bipolar cells
ganglion cells
additional cells that get info from bipolar cells & send it to other bipolar cells, other amacrine cells, and ganglion cells
amacrine cells
consists of ganglion cell axons, exits through the back of the eye and travels to brain
optic nerve
has no receptors, where optic nerve leaves the back of the eye
blind spot
why do we not notice our blind spot?
compensation between eyes
in the retina, messages go from the back of the eye to _____
bipolar cells, then to ganglion cells, then exits through the optic nerve
tiny area specialized for acute, detailed vision [packed tight with receptors]
fovea
each receptor in ____ connects to a single bipolar cell, which in turn connects to a single ganglion cell, which has an axon to the brain
fovea
ganglion cells in fovea of humans and primates
midget ganglion cells
less detailed vision, allows for greater perception of much fainter light
peripheral vision
abundant in periphery of retina, respond to faint light, not useful in bright light
rods (useful for night vision)
abundant in & near fovea, less active in dim light, more useful in bright light, & essential for color vision
cones (useful for color vision)
ratio of rods to cones in humans
cones are 1/20 as abundant as rods
cones provide 90% of brains input
number of axons in optic nerve
average is 1 million
some have 2 to 3 times more; ex) tennis players show faster brain response to stimuli
chemicals in both rods & cones that release energy when struck by light
photo-pigments
we perceive color through relative rates of response by 3 kinds of cones, each kind maximally sensitive to a different set of wavelengths [short, medium, and long wavelengths]
Trichromatic (Young-Helmholtz) Theory
perceive color in terms of opposites-the brain has a mechanism that perceives color on a continuum
Red to Green
Yellow to Blue
White to Black
Opponent-Process Theory
afterimages occur due to ____
rebound effect from wavelengths being saturation while some are inhibited
cortex compares info from various parts of the retina to determine the brightness & color for each area [includes color constancy]
Retinex Theory
ability to recognize colors despite changes in lighting
color constancy