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75 Cards in this Set

  • Front
  • Back
How much of the brain is associated with vision?
30%
Sensation
-actual effects of stimulus on sensory organs
-"real input"
Perception
-internal experience of the external world
-post-processing affected by knowledge, expectations, etc.
Direct route (important now)
--> Action/Attention
Indirect (cortical) route (put the pieces back together)
--> what ---> frontal
--> where/how ---> frontal
retina
surface of the eye that contains photoreceptors (satellite dish)
rods
receptors for low light (night time)
cones
receptors for high light intensity and different wavelengths (color)
Geniculostriate Pathway (cortical route)
-Lateral geniculate nucleus
-Striate (striped) cortex
Lateral geniculate nucleus
-visual relay in the thalamus
-parvocellular
-magnocellular
parvocelluar
small details and color
magnocellular
motion and rough outlines
Striate (striped) cortex
early visual cortex
Primary vision cortex
-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
How is the primary vision cortex arranged?
-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
retinotopy
angular
blindsight
-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
Convergent Findings
-fMRI
-Patient Model
fMRI
track activation when presenting information in different parts of the visual field
Patient Model
-Explore how damage to region of V1 relates to scotoma
-Show through experiment how now all visual information is lost (dissociation)
Visual processing beyond V1
elaboration of visual information
What provides the building blocks?
-V1
*Primary visual cortex:
-detecting edges and orientations
-light intensity
*"Upstream" regions process more complex
features of visual input
What are the two visual streams that process different types of information?
-Ventral pathway
-Dorsal pathway
Ventral (what) pathway
-do the visual features correspond to a shape, object, fact, ect.?
Dorsal (where) pathway
-where in spaces are these features located?
Two independent streams but...
-belong to the same visual experience
*move together
V4
-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
Color constancy
We perceive an object having the same color even under different lighting conditions
V1
responds to local wavelengths of light
V4
-responds to relative wavelength
*Take into consideration surrounding regions
V5 (MT)
-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)
MT
sits on the gyrus in the temporal lobe
V5 and firing of neurons
-fire strongly for downward motion
-fire weakly for down-left motion
-don't fire at all for upward motion
Bottom up processing
comes from sense organs (sensation)
Top down processing
-perception
-frontal cortex, temporal lobe
Complex visual perception
integrate bottom up and top down processing to recognize the world
Object recognition
-Combine visual features (bottom up) and knowledge (top down) to form representation of complex objects
Gestalt Grouping Principles
-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
proximity
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)
similarity
visual elements that similar (e.g. same color) are likely to be grouped together
continuation
edges are grouped together to avoid interruptions
closure
missing parts of an object are "filled in"
common fate
elements that move in the same direction are grouped together
object constancy
perceive as the same object even if shown in different views, (what pathway)
inferior temporal gyrus
involved in representation of objects, independent of view, lightening, etc...
Category Specificity
hypothesis that different types of categories are represented differently in the brain
face processing
faces are complex stimuli and very important to social functioning
Faces are special (and get their own system)
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
Imagining
-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
Attended information
the incoming sensory input that get priority for conscious processing
Unattended information
does not reach awareness, but might still affect the brain (and behavior)
Why do we need attention?
-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
spatial attention
-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
spotlight metaphor for spatial attention
-inattentional blindness, change blindness
(unless it's in the spotlight, you don't consciously process it)
exogenous orienting
(controlling the spotlight)
-attention is guided [captured] by external information (e.g., movement, change, appearance)
Inhibition of Return
(Controlling the spotlight)
slower to direct attention to a region that you just focused on
WHAT to attend to
endogenous orienting
endogenous orienting
-attention is guided by internal goals and motivation
-set attention on specific feature or object
-car
Feature integration
binding lower level features together requires focused attention (i.e., the spotlight)
illusory binding
Binding features into Coherent whole
Parietal Lobe and directing attention
-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
Parietal lobe lesions
hemineglect
inhibition of return
a slowing of reaction time associated with going back to a previously attended location
facial processing fusiform
inferior temporal lobe
visual search
a task of detecting the presence or absence of a specified target object in an array of other distracting objects
pop out
the ability to detect an object amongst distractor objects in situations in which the number of distractors presented is unimportant
temporal lobe
auditory and visual
occipital lobe
auditory input sent
parietal lobe
sensory, (space and attention?)
neglect
a failure to attend to stimuli on the opposite side of space to the lesion
Parietal lobe lesions symptoms
-neglect
-extinction
-denial
-spatial orientation deficit
Parietal lobe lesions
hemineglect
Parietal lobe and patient models
Not a problem with low level visual information
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
Controlling the spotlight
exogenous orienting
inhibition of return