module 4 part 2 - textbook stuff Flashcards
primary visual cortex
the first part of the visual cortex - v1
- contains neurons that respond to simple patterns consisting of oriented edges of particular sizes
damage leads to conscious vision loss
visual hierarchy
as we travel ‘higher up’ in the visual system, away from the original sensory input, the properties that neurons respond to become more complex and specific
visual agnosias
cases in which a person has difficulty recognizing or perceiving one kind of visual stimulus while maintaining the ability to process other kinds of stimuli - the existence of various types of visual agnosias suggests that different areas of the brain may be important for different visual abilities- functional localization???
prosopagnosia
marked difficulty in recognizing individual faces - damage to fusiform face area
semantic agnosia
difficulty in recognizing everyday objects
fusiform face area
area of the temporal cortex that shows greater activity when people engage in a facial recognition task - or…ability to discriminate between visually similar stimuli (greebles study)
lateral occipital cortex
part of the brain that is selectively activated when people do an object recognition task
dorsal stream of visual input
projects upward from the visual cortex and ends in the parietal lobe - action - ‘where’
ventral stream of visual input
projects downward from the visual cortex and ends in the temporal lobe - perception - ‘what’
image segmentation
how the brain divides up the retinal image into different objects and regions - depends on a combination of bottom up and top down processes
depth perception
the ability of the brain to determine where objects are in three dimensions (in space)
- does so based on cues - objects that occlude (block) other objects , motion parallax, and binocular disparity
all depth cues are bottom up
motion parallax
objects farther away from you will change their position more slowly on your retina as you move
binocular disparity
because our two eyes are on slightly different positions on our head, they see slightly different images
the amount of disparity of the images changes as a function of how far away in depth an object is from the point you are fixating on - more disparity = further away in depth
stereopsis
ability of the brain to use differences in binocular disparity to determine the depth of an object
object recognition
ability of the brain the recognize what objects are - potentially the final step of perception
depends on matching some incoming stimulus to a stored representation in memory
gestalt laws
similarity: tendency to group together features of an image that have similar properties
proximity: tendency to group features of an image that are close together
good continuation: tendency to group together features that form a smooth, continuous path rather than those with a sharp discontinuity
template model of recognition
matching an object to an image stored in memory point by point - keeping an exact photographic representation of the object in memory
identification
ability to identify the same object or person across variations - challenge to the template model of recognition
classification
recognizing something as a member of a specific category even if we have never encountered that specific example before
feature based recognition
using features of objects that remain common across different views and examples in order to overcome variability in order to recognize objects
structural model to recognition
model that suggests that our brain extracts three dimensional features from the objects it encounters and it uses these features to determine what an object will look like under different conditions so that it can match a given example to the stored representation
geon theory
example of a structural model - suggests that we recognize geons (volumentric 3d primitives that can be recovered from 2d images) and compose them into objects
view based models
we use two dimensional images of objects in order to identify them- in order to overcome variability we store multiple views of the object that we encounter over time - an object has to be close enough to one of the learned examples in order to recognize it
viewpoint dependency
prediction that we should be best at recognizing objects from the specific viewpoint from which you have seen it versus other viewpoints
scene schema
people learn which objects tend to appear in particular contests
phonemic restoration effect
the brain fills in details of missing sounds from a speech signal based on expectation
blindsight
patients have no conscious awareness of visual objects in their damaged visual field but can implicitly respond to questions about objects presented in the damaged visual field - suggests that we can ‘see’ unconsciously - processing division between conscious and non conscious perception
visual imagery and blindsight
blindsight patients have less brain activity when perceiving images compared to control participants but similar activity when it comes to imagining images
akinetopsia
inability to perceive motion
optic ataxia
inability to reach for objects - but can name them
damage to dorsal pathway
suggests that there might be action specificity in this pathway because selective damage leads to problems with certain types of movement
against functional specialization for faces
greebles - fusiform face area active when study participants learn to discriminate between greebles (computer generated creatures) - suggests that ffa might be more for distinguishing between visually similar objects
in support of functional specialization for faces
sheep farmer with prosopagnosia who could still recognize and distinguish his sheep
apperceptive agnosia
problems perceiving objects - faces for prosopagnosia would look contorted
cannot group visual features to form perceptions that can be interpreted as meaningful - single visual feature perception is intact
- can draw from memory but not copy
associative agnosia
problems assigning meaning or labelling objects - can’t recognize familiar famous faces for prosopagnosia
can’t access information from memory - can’t draw from memory. can’t name objects, can’t determine if a visual object is possible or impossible, can’t indicate functions
principle of experience
experience and knowledge drives perception - we are more likely to notice things that are familiar to us
direct models
perception involves using information directly from our environment, without transforming it in our minds
there are enough cues in the real world to guide our perception and action that we don’t need prior knowledge/top down processes
examples of environmental cues in direct models
texture gradients : density of a texture provides information about distance - near objects tend to be farther apart and far objects are closer together
topological breakages: discontinuity created by the intersection of two textures tells us about the edges of objects and aids in object identification
types of object recognition models
pattern recognition: identifying a pattern in visual input and matching the pattern to existing patterns stored in memory
feature detection: visual input is broken down into individual parts and processed separately - then brought back together for pattern recognition
examples of pattern recognition models
template matching theory: every object has a template in long term memory - can’t explain identification or classification
prototype theory:
every object has an average representation in memory - recognition is based on resemblance - more flexible
examples of feature detection
recognition by components: all objects are reducible to basic geometric shapes (geons) - recognition = mentally separating a visual object into geons and matching the arrangement to memory representations
geons can be perceived from any angle which accounts for how we can recognize objects with shifts in perspective
recognition in context
scene consistency effect - we are better at recognizing things when they appear in the contexts we expect them to be in
