Test 4 Flashcards
What is the part of the eye that an image is projected onto?
Retina
What is the hole in the front of the eye?
Pupil
What is the color part of the eye, located around the pupil?
Iris
What is the hard, clear part of the eye, that turns the image upside-down?
Lens
What is the clear part of the eye, located in front of the iris and pupil?
Cornia
What is the sclera?
The white of the eye
What nerve takes the image from the retina, out of the eye?
Optic Nerve
Light interacts with the environment in 3 ways. What are they?
Reflection, absorption, refraction
Predators generally have eyes positioned where?
Front of the head
Why do predators have eyes on the front of their heads?
Facilitates depth perception
Binocular disparity is greater, when?
when objects are close
What is binocular disparity?
The difference of how an image falls on each eye
Prey have eyes where?
On the sides of their head
Why do prey have eyes on the side of their head?
Gives them a panoramic view
We continually scan the world with small and quick eye movements called ______
saccades
What do saccades do?
Integrate bits of images to create the image processed by the brain
What happens if you stabilize your eye?
Everything fades to black
The visual system responds to ______
change
The left visual field moves through which optic tract?
Right
What is the optic chiasm?
Where the optic tracts cross
Where do the optic tracts lead to?
Lateral Geniculate Nucleus (LGN)
What does the LGN do?
Releases optic radiations to V1
What is the pathway between the retina, optic nerves, and LGN called?
Retino-geniculate-striate pathway
Where is V1 located?
Occipital lobe
The superior visual cortex is responsible for what?
“Where/how”
The Inferior visual cortex is responsible for what?
“What”
The left ______ of each eye connects to the left LGN
Hemiretina
The retina-geniculate-striate system is composed of _____% of axons of retinal ganglion cells
90%
10% of retinal axons go to the _____
superior colliculus
What is visual transduction?
Light is turned into neural signals
What is duplexity theory?
Cones and rods mediate different kinds of vision
What are cones used for?
Photopic (daytime) vision…high-acuity color information in good lighting
What are rods used for?
Scotopic (nighttime) vision…high-sensitivity, low-acuity vision in dim light
Why don’t rods work well in light?
Light bleaches rhodopsin molecules and close sodium channels, which hyperpolarizes the rods
What is phosphenes?
Seeing light without light entering the eye
What is scotoma?
area of blindness due to v1 damage. May appear dark or “filled in”
The neurons in v2 interpret what?
lines
When a person has a migraine in v2, what do they see?
zig-zagging lines that start central, and move peripherally
Migraines have a ____ component, which is different than other headaches
neural
Where is the primary visual cortex, aka striate cortex, located?
Posterior occipital lobe
What is located above the striate cortex?
Prestriate cortex
What is the prestriate cortex involved in?
slightly more complex visual processing
Where is the posterior parietal cortex located?
above the prestriate cortex
V1 processes what?
lines
V2 processes what?
combination of lines
If you remove the Inferotemporal cortex (temporal lobe), what happens?
You cannot tell the difference between two objects
If you remove the parietal lobe, what happens?
You will no longer have the knowledge of spacial relationships
The dorsal stream specializes in what, according to the “Where vs what theory”?
visual spatial perception
The ventral stream specializes in what, according to the “Where vs what theory”?
visual pattern recognition
According to the “control of behavior vs conscious perception theory,” what does the dorsal stream specialize in?
visually guided behavior
According to the “control of behavior vs conscious perception theory,” What does the ventral stream specialize in?
conscious visual perception
What does the ebbinghaus illusion do?
tricks the inferior temporal gyrus into thinking that the dots in the middle of the two pictures are different sizes, when, in reality, they are the same size
What is visual neglect?
Neglect half of space. Knowledge of that half of space breaks down.
What is optic ataxia?
Difficulty with spacial relations. If only one lobe is affected, can affect certain visual field areas
What is motion blindness?
All you see is one status image, then another. No fluid progression of images
What is the term for facial blindness?
prosopagnosia
What is the term for not knowing about a particular object or class of objects?
object agnosia
V4 processes what information?
Color, basic 2D and 3D shape, curvature
What does the VTC process?
Complex features and objects
Damage to what causes prosopagnosia?
The fusiform face area
What is the area that recognizes body parts and images?
Extra-striate body area (EBA)
Why don’t autistic individuals discriminate faces very well?
The FFA doesn’t build up when they are very young, because they don’t look at faces much
Where is the EBA located?
outside of the striate cortex
What area responds to places?
Parahippocampal Place Area
Where is the Parahippocampal Place Area located?
Around the hippocampus
What is binocular rivalry?
Competition between your eyes. One image is seen by one eye, while the other is shown a different image.
What happens during binocular rivalry?
Brain will alternate between one image or the other, not see both.
What cortex receives visual, auditory, and somatosensory information?
Posterior Parietal Association Cortex
What does the Posterior Parietal Association Cortex do?
Integrates information about body part location and external object location
What creates a mosaic of small areas that guides a particular movement of eyes, head, arm, or hand?
Posterior Parietal Association Cortex
What is apraxia?
Negation of voluntary movement
When is apraxia evident?
When instructed to perform an action
What is contralateral neglect?
Unable to respond to stimuli contralateral to the side of the lesion
What is the trichromacy theory?
Color is percepted by three cones
The way light ________ gives rise to the different colors we see
reflects off the colors
What animals are quadchromats?
some birds, fish, and reptiles
What animals are trichromats?
Primates
What animals are dichromats?
almost all nonprimate animals
What animals are monochromats?
Some nocturnal animals
What does the opponent process theory say?
Color is processed in pairs
What is stage 1 of color perception?
Trichromacy theory
Trichromacy theory takes place where?
In the retina
What is stage 2 of color perception?
Opponent Processing theory?
Opponent Processing Theory takes place where?
LGN & v1
What is stage 3 of color perception?
Cortex (v4)
What is cerebral achromatopsia?
color blindness due to cerebral damage
What is the cortex contributing to color perception?
Unclear. Perhaps color constancy
What is color constancy?
Color perception is not altered by varying reflected wavelengths (something blue is blue nomatter if in daylight or fluorescent)
What is retinex theory?
Color is determined by the proportion of light of different wavelengths that a surface reflects.
Color is NOT determined by whaT?
the direct wavelengths hitting your face
What is the duplexity theory of vision?
Retina contains two different types of photoreceptors
What is scotopic vision?
Vision of the eye under low light conditions
Where do you find the greatest amount of cones in the retina?
Fovea centralis
Where do you find the greatest amount of rods in the retina?
In the peripheral area
What are the five types of cells in the retina?
Photoreceptors, bipolar cells, ganglion cells, horizontal cells, and amacrine cells
What is the basic idea of optigenics?
Combination of genetics and optics to control well-defined events within specific cells of living tissues
What are the characteristics of the magnocellular layers of the LGN?
Large size, detect the “where” properties of visual information
What are the characteristics of the parvocellular layer of the LGN?
small cells, more modern than magnocellular, receive input from midget cells, sensitive to color, more capable of discriminating fine details
Which cells have center-surround receptive fields?
ganglion cells
What are the differences between simple and complex cells in V1?
Simple cells: 1) have distinct exitatory and inhibitory regions 2) linearity of spatial summation 3) Antagonism between excitatory and inhibitory regions
Complex Cells: 1) No clear excitatroy and inhibitory regions 2) Maximal response regardless of where stimulus is placed in RF 3) A stimulus with uniform intensity covering the entire RF will evoke no response
What is a hypercolumn?
A group of neurons in the cortex that have nearly identical receptive fields.
What is an ocular dominance column?
Stripes of neurons in visual cortex of certain mammals that respond preferentially to input from one eye or the other
What is an orientation column?
Organized regions of neurons that are excited by visual line stimuli of varying angles
What is a Blob (in V1)?
sections of visual cortex where groups of neurons that are sensitive to color assemble in cylindrical shapes
What is an interblob?
areas between blobs which receive the same input, but are sensitive to orientation instead of color
What is cortical magnification in the striate cortex?
Describes how many neurons in the striate cortex are responsible for processing a stimulus
What is retinotopic organization?
Mapping of visual input from the retina to neurons
In which lobe does the dorsal visual pathway terminate?
Parietal lobe
In which lobe does the ventral visual pathway terminate?
Temporal Lobe
What is bottom-up processing?
data-driven processing. perception begins with stimulus itself. Carried out from the retina to the visual cortex, each stage perceiving more and more.
What is top-down processing?
The use of contextual information in pattern recognition. Taking things that are formed together to process smaller parts
What is accomodation?
reflex action when you are focusing on a near object, then look at a distant object, which changes vergence, lens shape, and pupil size
What is the optic disk?
The head of the optic nerve, where axons leave the eye
What is photopigment?
Unstable pigments that undergo a chemical change when they absorb light
What is the blind spot?
Where the optic nerve exits the eye. No photoreceptors
What is blindsight?
the ability to respond to visual stimuli without consciously perceiving them.
What is transduction?
Light is channeled to the back of the eye and flipped upside-down
What is lateral inhibition?
Neighboring neurons respond less than the active neuron if they are activated at the same time
What are mach bands?
Optical illusion which exaggerates the contrast between edges of slightly differing shades of gray by triggering edge-detection in the visual system. Makes darker areas falsely appear darker
What is akinetopsia?
Visual motion blindness
What is dark current?
Inward sodium current that depolarizes the cell to around -40 mV. This is more depolarized than other neurons.
Under what contitions is binocular (retinal) disparity greatest?
When objects are close
