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75 Cards in this Set
- Front
- Back
How much of the brain is associated with vision?
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30%
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Sensation
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-actual effects of stimulus on sensory organs
-"real input" |
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Perception
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-internal experience of the external world
-post-processing affected by knowledge, expectations, etc. |
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Direct route (important now)
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--> Action/Attention
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Indirect (cortical) route (put the pieces back together)
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--> what ---> frontal
--> where/how ---> frontal |
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retina
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surface of the eye that contains photoreceptors (satellite dish)
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rods
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receptors for low light (night time)
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cones
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receptors for high light intensity and different wavelengths (color)
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Geniculostriate Pathway (cortical route)
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-Lateral geniculate nucleus
-Striate (striped) cortex |
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Lateral geniculate nucleus
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-visual relay in the thalamus
-parvocellular -magnocellular |
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parvocelluar
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small details and color
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magnocellular
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motion and rough outlines
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Striate (striped) cortex
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early visual cortex
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Primary vision cortex
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-First stage of visual "processing"
*retains spatial relationships among the inputs *begins to combine simple features -How light/dark, what color, is there an edge, movement -Single cell recording *Identified simple cells: detect points of light in a specific orientation *Complex cells: detect long stretch of light in a specific orientation |
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How is the primary vision cortex arranged?
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-Retinotopic organization
-V1 maintains the spatial layout from the retina -Close in space on the retina=close in V1 -Scotoma (gap in visual field) and anopia *cortical blindness |
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retinotopy
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angular
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blindsight
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-impaired vision and loss of awareness
* "loss of conscious perception" -Cannot report what is shown -But can still make decisions about that information: *Is it straight or curvy? -Suggests role of other, non-cortical visual routes |
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Convergent Findings
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-fMRI
-Patient Model |
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fMRI
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track activation when presenting information in different parts of the visual field
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Patient Model
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-Explore how damage to region of V1 relates to scotoma
-Show through experiment how now all visual information is lost (dissociation) |
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Visual processing beyond V1
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elaboration of visual information
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What provides the building blocks?
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-V1
*Primary visual cortex: -detecting edges and orientations -light intensity *"Upstream" regions process more complex features of visual input |
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What are the two visual streams that process different types of information?
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-Ventral pathway
-Dorsal pathway |
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Ventral (what) pathway
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-do the visual features correspond to a shape, object, fact, ect.?
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Dorsal (where) pathway
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-where in spaces are these features located?
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Two independent streams but...
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-belong to the same visual experience
*move together |
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V4
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-the main color center in the brain
*Where we process the wavelength of the light *Colors might look different amongst different different people but we still know the difference between "red" and "blue" *Lesions to this region results in loss of color vision |
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Color constancy
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We perceive an object having the same color even under different lighting conditions
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V1
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responds to local wavelengths of light
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V4
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-responds to relative wavelength
*Take into consideration surrounding regions |
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V5 (MT)
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-motion center in the brain
-Single-cell recordings in monkeys *90% of cells respond to motion and prefer a specific direction -still can perceive biological motion (motion of something alive) with damage to V5 *suggests role of other route (e.g., direct pathway) |
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MT
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sits on the gyrus in the temporal lobe
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V5 and firing of neurons
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-fire strongly for downward motion
-fire weakly for down-left motion -don't fire at all for upward motion |
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Bottom up processing
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comes from sense organs (sensation)
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Top down processing
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-perception
-frontal cortex, temporal lobe |
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Complex visual perception
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integrate bottom up and top down processing to recognize the world
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Object recognition
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-Combine visual features (bottom up) and knowledge (top down) to form representation of complex objects
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Gestalt Grouping Principles
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-The whole is greater than the sum of it's parts
-Visual system groups features together in principled ways *proximity *similarity *continuation *closure *common fate |
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proximity
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visual elements that are close together are likely to be part of the same object (closer together objects are much more likely to belong to the same thing)
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similarity
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visual elements that similar (e.g. same color) are likely to be grouped together
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continuation
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edges are grouped together to avoid interruptions
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closure
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missing parts of an object are "filled in"
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common fate
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elements that move in the same direction are grouped together
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object constancy
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perceive as the same object even if shown in different views, (what pathway)
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inferior temporal gyrus
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involved in representation of objects, independent of view, lightening, etc...
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Category Specificity
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hypothesis that different types of categories are represented differently in the brain
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face processing
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faces are complex stimuli and very important to social functioning
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Faces are special (and get their own system)
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1) Requires holistic processing
-combination of features is what constitute a face 2) Difficult to discriminate because of similar features 3) Expertise at recognizing faces -years of practice -but trouble discriminating faces in different race |
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Imagining
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-imagining an object (or face) activates many of the same systems as perceiving the object
*top down activation of the representation of the object -Consequence: according to the brain, remembering/imaging an object is functionally equivalent to experiencing that object *when you remember something, your brain is essentially re-experiencing that event |
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Attended information
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the incoming sensory input that get priority for conscious processing
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Unattended information
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does not reach awareness, but might still affect the brain (and behavior)
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Why do we need attention?
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-Limited processing resources in the brain
-Can't process everything all the time -Makes downstream processing more efficient -ignore/suppress irreverent information -boost/enhance important information |
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spatial attention
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-ability to direct our attention toward space
-dorsal (where) pathway -Feature/object: are there certain features in the environment that I need to focus on? -ventral (what) pathway |
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spotlight metaphor for spatial attention
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-inattentional blindness, change blindness
(unless it's in the spotlight, you don't consciously process it) |
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exogenous orienting
(controlling the spotlight) |
-attention is guided [captured] by external information (e.g., movement, change, appearance)
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Inhibition of Return
(Controlling the spotlight) |
slower to direct attention to a region that you just focused on
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WHAT to attend to
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endogenous orienting
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endogenous orienting
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-attention is guided by internal goals and motivation
-set attention on specific feature or object -car |
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Feature integration
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binding lower level features together requires focused attention (i.e., the spotlight)
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illusory binding
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Binding features into Coherent whole
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Parietal Lobe and directing attention
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-single cell recordings in monkeys
-cells in parietal lobe reflect both 1) Spatial location of visual information (retinotopic) 2) Bodily information like posture, eye position |
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Parietal lobe lesions
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hemineglect
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inhibition of return
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a slowing of reaction time associated with going back to a previously attended location
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facial processing fusiform
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inferior temporal lobe
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visual search
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a task of detecting the presence or absence of a specified target object in an array of other distracting objects
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pop out
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the ability to detect an object amongst distractor objects in situations in which the number of distractors presented is unimportant
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temporal lobe
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auditory and visual
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occipital lobe
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auditory input sent
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parietal lobe
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sensory, (space and attention?)
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neglect
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a failure to attend to stimuli on the opposite side of space to the lesion
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Parietal lobe lesions symptoms
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-neglect
-extinction -denial -spatial orientation deficit |
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Parietal lobe lesions
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hemineglect
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Parietal lobe and patient models
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Not a problem with low level visual information
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Neglect vs. Blindsight
(Loss of low level visual information vs. purposeful processing of complex information) |
Neglect:
1) Other senses 2) Might have object information 3) Directing attention to region can overcome neglect 4) Egocentric Blindsight: 1) Visual only 2) Only have low-level info 3) Directing attention doesn't help 4) Retinocentric: Retina is the center of the world |
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Controlling the spotlight
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exogenous orienting
inhibition of return |