Task 5 - Mechanisms of low-high-level vision

Question 1

Visual information moves out along two main pathways

Answer 1

1. The where pathway: This pathway heads up into the parietal lobe – (visual areas in this pathway seem to be important for processing information relating to the location of objects in space and the actions required to interact with them) – this pathway plays an important role in the deployment of attention
2. The what pathway: This pathway heads down into the temporal lobe and appear to the locus for the explicit acts of object recognition

Question 2

Agnosia

Answer 2

a failure to recognize objects in spite of the ability to see them. Agnosia is typically due to brain damage

Question 3

Inferotemporal (IT) cortex

Answer 3

Part of the cerebral cortex in the lower portion of the temporal lobe, important in object recognition (the what pathway)

Question 4

Grandmother cell

Answer 4

any cell that seems to be selectively responsive to one specific object

Question 5

Homologous regions

Answer 5

brain regions that appear to have the same function in different species

Question 6

Feed-forward process

Answer 6

a process that carries out a computation (e.g. object recognition) one neural step after another, without need for feedback from a later stage to an earlier stage

Question 7

Middle (or midlevel) vision

Answer 7

a loosely defined stage of visual processing that comes after basic featured have been extracted from the image (low-level, or early, vision) and before object recognition and scene understanding (high-level vision)

Question 8

Illusory contours

Answer 8

a contour that is perceived even though nothing changes from one side of it to the other in an image – they are perceived because they are the best guess about what is happening in the world at that location

Question 9

Structuralists

Answer 9

a school of thought believing that complex objects or perceptions could be understood by analysis of the components

Question 10

Gestalt

Answer 10

a school of thought stressing that the perceptual whole could be greater than the apparent sum of the parts

Question 11

Gestalt theory

Answer 11

the perceptual whole is more that the sum of its sensory parts

Question 12

Gestalt grouping rules

Answer 12

a set of rules describing which elements in an image will appear to group together. The original list was assembled by members of the Gestalt school of thought

Question 13

Good continuation

Answer 13

a Gestalt grouping rule stating that two elements will tend to group together if they seem to lie on the same contour

Question 14

Closure

Answer 14

in reference to perception, closure is the name of a Gestalt principle that holds that a closed contour is preferred to an open contour

Question 15

Texture segmentation

Answer 15

carving an image into regions of common texture properties

Question 16

Similarity

Answer 16

image chunks that are similar to each other will be more likely to group together – a Gestalt grouping rule stating that the tendency of two features to group together will increase as the similarity between them increases

Question 17

Proximity

Answer 17

items near each other are more likely to group together than are items more widely separated – a Gestalt grouping rule stating that the tendency of two features to group together will increase as the distance between them decreases

Question 18

Parallelism

Answer 18

a rule for figure-ground assignment stating that parallel contours are likely to belong to the same figure

Question 19

Symmetry

Answer 19

a rule for figure-ground assignment stating that symmetrical regions are more likely to be seen as figure

Question 20

Ambiguous figure

Answer 20

a figure that generates two or more plausible interpretations - a visual stimulus that gives rise to two more interpretations of its identity or structure

Question 21

Necker cube

Answer 21

an outline that is perceptually bi-stable. Unlike the situation with most stimuli, two interpretations continually battle for perceptual dominance

Question 22

Accidental viewpoint

Answer 22

a viewing position that produces some regularity in the visual image that is not present in the world (e.g., the slides of two independent objects lining up perfectly)

Question 23

Figure-ground assignment

Answer 23

the process of determining that some regions of an image belong to a foreground object (figure) and other regions are part of the background (ground)

Question 24

Surroundedness

Answer 24

a rule figure-ground assignment stating that if one region is entirely surrounded by another, it is likely that the surrounded region is the figure

Question 25

Relatability

Answer 25

the degree to which two line segments appear to be part of the same contour

Question 26

Heuristic

Answer 26

a mental shortcut

Question 27

Nonaccidental features

Answer 27

a feature of an object that is not dependent on the exact (or accidental) viewing position of the observer

Question 28

Global superiority effect

Answer 28

the finding in various experiments that the properties of the whole object take precedence over the properties of parts of the object

Question 29

Bayesian approach

Answer 29

a way of formalizing the idea that our perception is a combination of the current stimulus and our knowledge about the conditions of the world - what is and is not likely to occur

Question 30

Subtraction method

Answer 30

in functional magnetic imaging, brain activity is measured in two conditions: one with and one without the involvement of the mental process of interest. Subtracting the two conditions shows regions of brain specifically activated by that process

Question 31

Parahippocampal place area (PPA)

Answer 31

a region of extrastriate visual cortex in humans that is specifically and reliably activated more by images of places than by other stimuli

Question 32

Fusiform face area (FFA)

Answer 32

a region of extrastriate visual cortex in humans that is specifically and reliably activated by human faces

Question 33

Extrastriate body area (EBA)

Answer 33

a region of extrastriate visual cortex in humans that is specifically and reliably activated by images of the body other than the face

Question 34

Naïve template theory

Answer 34

the proposal that the visual system recognizes objects by matching the neural representation of the image with a stored representation of the same “shape” in the brain -- difficulty with this model is that too many templates are required

Question 35

Structural description

Answer 35

a description of an object in terms of the nature of its constituent parts and the relationships between those parts

Question 36

Geon

Answer 36

in Biederman’s recognition-by-components model, any of the geometric ions” out of which perceptual objects are built

Question 37

Recognition-by-components model

Answer 37

Biederman’s model of object recognition, which holds that objects are recognized by the identities and relationships of their component parts

Question 38

Viewpoint invariant

Answer 38

1. A property of an object that does not change when observer viewpoint changes. 2. A class of theories of object recognition that proposes representations of objects that do not change when viewpoint changes

Question 39

Entry-level category

Answer 39

for an object, the label that comes to mind most quickly when we identify it (e.g., “bird”). At the subordinate level, the object might be more specifically names (e.g., “eagle”); at the superordinate level, it might be more generally names (e.g., “animal”)

Question 40

Double dissociation

Answer 40

the phenomenon in which one of two functions, such as hearing and sight, can be damaged without harm to the other, and vice versa

Question 41

Congenital prosopagnosia

Answer 41

a form of “face blindness” apparently present from birth, as opposed to “acquired prosopagnosia,” which would typically be the result of an injury to the nervous system