Vision Study Guide Flashcards
What are the qualities of light?
-a form of electromagnetic radiation
(energy produced by vibrations of electrical light)
-measured according to wavelength
-can be reflected (visible), absorbed, or refracted (bent)
What do opsins absorb?
Photons
-tiny particles that each consist of one quantum of energy
What are the parts of the eye?
-Cornea
-Aqueous humor
-Iris and pupil
-Lens
-Vitrous humor
-Retina
Cornea
§ External structure of the eye
§No blood vessels or blood but lots of sensory nerve endings
Function: Thin transparent protective layer of your eye
Aqueous Humor
§ Under the cornea
§ Fluid filled chamber derived from blood (no red blood cells but a fluid filtered from blood)
Transparent
Function: supplies oxygen and nutrients while removing waste from the cornea and lens
Pupil
= the hole (black portion) in the muscular iris
Function: can expand and constrict
Iris
§ Colored portion of the eye
Function: Regulates the size of the pupil
(modifying the amount of light that enters the eye)
Lens
Function: refracts and focuses light
-accommodation
Vitrous humor
§ Fluid-filled chamber, gel-like, and viscous and is generally transparent in posterior eye
§ Experience Floaters
Function: accommodate light to hit the back of the retina
Retina
Function: transduce light energy into a neural signal by photoreceptors
Components of a photoreceptor
Function: detect visual information
-Rods
-Cones
Inner & Outer segment
Function of Inner segment of photoreceptors
produces:
visual pigments
neurotransmitters
proteins
and other cellular machinery
Function of outer segment of Photoreceptors
-stores visual pigments (opsin and chromophore)
Rods
= amount of light
-shapes and contrast of objects
-specialized for low light situations
-respond to scotopic conditions
-heavily relief on by nocturnal animals
Cones
= detect color; color vision
-respond to photopic conditions
-3 types of opsin +other colors appear via activation of multiple cones at once
What are the 3 types of Opsin in Cones?
S-cones
M-cones
L-cones
Opsin
=protein that determines what wavelength the photopigment transduces
What are the names of the different Opsins?
○ Rhodopsin
○ Photopsins
S-cones: color, size of wavelength, and distribution
-Blue
-Short
-highest density in Peripheral Retina
M-cones: color, size of wavelength, and distribution
-Green
-Medium
-highest density in Fovea
L-cones: color, size of wavelength, and distribution
-Red
-Long
-highest density in Fovea
Rhodopsin
= rod opsin
-low-light vision
Photopsins
= cone opsin
-transduce red, blue, and green light
-3 cone opsins
What are the 3 cone opsins for photopsins and the color for each?
OPN1LW- Red
OPN1MW- Green
OPN1SW- Blue
Melanopsin
= circadian rhythms
Pathway of Optic information to and in the brain
Optic Nerve (start: optic disc)
Optic Chiasm
Optic Tract projects to multiple areas:
-Superior Colliculus
-Lateral Geniculate Nucleus (LGN) of Thalamus
Primary Visual Cortex (V1, A17)
Extrastriate Cortex
Inferotemporal Cortex
Temporal Cortex
Optic Nerve
-begins at optic disc
Optic Chiasm
-1/2 of the neurons cross to contralateral side
Superior Colliculus
-process movement
-blindsight
Lateral Geniculate Nucleus (LGN) of Thalamus
-relays information bound for cortex
§ Part of the thalamus
§ Axons from retinal ganglion cells synapse in the left and right lateral geniculate nuclei
§ Information from the right visual field maps to the left lateral geniculate nucleus and vice versa (topographical mapping)
§ 6 layers
Primary Visual Cortex (V1, A17)
-Other name: Striate (“Striped”) Cortex
-In Occipital Lobe
○ Neurons within V1 (or the first cortical processing area) respond to basic features of the stimulus (lines/edges, angles, movement, faces)
○ Respond to the pattern of something in order to assist in putting the
○ Neurons in V1 don’t care about border ownership, considering all of the circumstances to be the same
What are the two types of layers in the LGN?
Magnocellular layers
Parvocellular layers
Magnocellular layers
® bottom two layers
® =big cells
Receive M ganglion cell
Parvocellular layers
® Top 4 layers
® =small cells
Receive input from P ganglion cells
Extrastriate Cortex (V2, V3, V4, etc.)
○ A set of visual area that lie just outside the visual (or striate cortex)
○ Extra areas
○ Neurons in V2 (extrastriatal area) responds differently to each situation
○ Sees how things fit together; Border ownership
Inferotemporal Cortex
= Neurons within inferotemporal cortex respond to objects, even faces (any)
§ Fusiform Face area
○ Has connections with the temporal lobe (includes hippocampus)
Fusiform Face Area
= a brain region within the inferotemporal cortex that preferentially responds to faces holistically
Temporal Cortex
○ Neurons can respond to specific concepts
○ Grandmother cells
Grandmother cells
= neurons that respond to object-related concepts
§ only fire to a specific concept (ex: recognizing a close relative or celebrity)
§ Brain doesn’t recognize someone forever
§ Can recognize someone after a long period of time because of a strong memory situation (paired with an emotional aspect)
Parahippocampal Place Area
= a brain region near the hippocampus that specifically is activated by images of places rather than any other stimuli
Optic disc
-no photoreceptors at all
-Optic nerve bundles together and leaves the eye location where ganglion cell axons exit the eye to form the optic nerve.
>There are no light sensitive rods or cones to respond to a light stimulus at this point.
>This causes a break in the visual field called “the blind spot”
-But we don’t notice the blind-spot because our mind “fills in the gaps”
Flickering Technique
=Two images alternate very rapidly
-Brief blank screen is presented between them
-Image appears to flicker
-Mimics saccades because the image “jumps” around (i.e., not smooth )
-Using the flicker technique, the eyes must search (AKA attend to) each object in the scene in order to detect the change
-Changes to objects that are more important to the picture will be noticed more quickly than changes to objects less important to the scene (you’re more likely to scan the important objects first)
Know how we typically detect change and why the flicker technique results in change blindness.
-Typically a change is detected by local motion signals
-Flicker disrupts the smoothness of motion
-Can’t rely on continuous motion (processing of the superior colliculus disrupted)
>The brain is forced to search the scene item by item until the change is detected
What are the monocular cues in depth perception?
-Texture
-Linear perspective
-Relative size
-Occlusion (AKA interposition)
Describe Monocular cue
-Increases field of view
-Limits depth perception
-horses, birds, lizards
-largely prey animals
Monocular cue: Texture
-closer an item is, the clearer and sharper the image is
Monocular cue: Linear Perspective
-parallel lines converge as they move away from the perceiver and toward the horizon line
Relative size
-if we know two objects are similar in size, the one with the smaller retinal image will appear farther; i.e., closer objects will appear larger
Occlusion (Interposition)
-overlapping objects block the views of other objects
Describe Binocular cue
-Increases depth perception
-Limits field view
-2 eyes
-humans, eagles, cats
-largely predator animals
What are the binocular cues involved in depth perception?
-Convergence
-Retinal Disparity
Binocular cue: Convergence
-Difference between the eyes caused by differences in angle and retinal image
-Cued by muscles which adjusts for angle
Binocular cue: Retinal Disparity
-Each eye receives slightly different visual information
-Brain combines similarities and uses differences to create sense of depth
