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U1 Psychology of Perception 212 > M2 Lecture 8: Feb7 > Flashcards

M2 Lecture 8: Feb7 Flashcards

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1
Q

By combining information from several retinal ganglion cells, it is possible to detect what

A

the orientation of lines.

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2
Q

Simple cells preferentially respond to what

A

lines that have a certain orientation.

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3
Q

what is a Hypercolumn

A

A 1-mm block of striate cortex containing “all the machinery necessary to look after everything the visual cortex is responsible for, in a certain small part of the visual world” (Hubel, 1982).

Each hypercolumn contains cells responding to every possible orientation (0–180 degrees), with one set preferring input from the left eye and one set preferring input from the right eye.

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4
Q

what is Retinotopy

A

visual information coming from adjacent locations in the retina will project to adjacent locations in the primary visual cortex (V1).

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5
Q

is it possible to reconstruct the retinal image based on brain activity

A

theoretically– through Retinotopy

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6
Q

how did the experiment for mind reading/retinotopy go

A
  1. `Show hundreds of random images and shapes to a participant (10 x 10 patches).
  2. Use patterns of activity across thousands of voxels in V1 to predict the luminosity of smaller rectangles within the 10 x 10 patch.
  3. Use the predictive patterns to predict which shape the participant is seeing based solely on brain activity.
  4. Record activity in Higher Visual Cortex (HVC; lateral occipital complex (LOC), fusiform face are (FFA), and parahippocampal place area (PPA), and Lower Visual Cortex (LVC; V1 to V3) while participants are sleeping.
    2) Wake them up in sleep stages 1 or 2, and ask them what they were dreaming about.
    3) Use the patterns of activity in the ~20 sec before awekening to predict what a participant is dreaming of.
    4) Use the predictive patterns to predict dream content solely based on brain activity.
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7
Q

is Decoding accuracy is better in higher visual cortex or lower

A

higher

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8
Q

what is Extrastriate cortex

A

Brain regions bordering primary visual cortex that contains other areas involved in visual processing

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9
Q

what is included in Extrastriate cortex

A

V2, V3, V4, etc

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10
Q

After extrastriate cortex, visual processing is split into what pathways

A

a dorsal “where” pathway and a ventral “what” pathway

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11
Q

“Where” pathway is concerned with what

A

the locations and shapes of objects but not their names or functions.

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12
Q

“What” pathway is concerned with what

A

the names and functions of objects regardless of location.

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13
Q

what is included in V1 Organisation

A

Parvocellular (ventral/“what”) and magnocellular (dorsal/“where”) pathways

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14
Q

what is Parvocellular

A

ventral/“what”

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15
Q

what is magnocellular

A

dorsal/“where”

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16
Q

Early areas (V1, V2, V3, V4 and MT) maintain what

A

retinotopic organization

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17
Q

Receptive field sizes increase from V1 to where

A

higher level areas.

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18
Q

what increases from V1 to higher level areas.

A

Receptive field sizes

Receptive field complexity

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19
Q

explain how Receptive field complexity increases from V1 to higher level areas

A

For instance, “boundary ownership.” Neurons in V1 would respond equally to the identical edge, but V2 neurons would respond more in “a” because the black edge is owned by the square.

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20
Q

Neurons in V4 respond to what

A

concave, convex, or straigth edges.

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21
Q

Neurons in V4 respond to concave, convex, or straigth edges

what are the conditions for ths

A

The contour has to have a precise relationship with the rest of the figure (e.g. convex countour pointing up from the figure).

22
Q

Preffered location covers a large portion of what

A

the retinal image

aka certain neurons will be more responsive to certain edges

23
Q

what is the INFEROTEMPORAL (IT) CORTEX

A

Part of the cerebral cortex in the lower portion of the temporal lobe, important for object recognition.

24
Q

what is Visual agnosias

A

Failure to recognize objects in spite of the ability to see them.

25
Q

what are the types of Visual agnosias

A

Apperceptive agnosia
Associative agnosia
Prosopagnosia

26
Q

what is Apperceptive agnosia

A

inability to form a percept despite normal vision. The basic elements of the object are seen (lines, etc.) but cannot be integrated into a stable percept.

	- lesion closer to V1
	- cannot copy
27
Q

what is Associative agnosia

A

There is a perceptual representation of the object, but the patient doesn’t know what the object is.

	- lesion further away from V1
	- can copy, but cannot identify
	- can recognize object if presented in another modality
28
Q

what is Prosopagnosia

A

An inability to recognize the identity of faces.

29
Q

what are the characteristics of Receptive field properties of IT neurons

A

Very large—some cover half the visual field
Don’t respond well to spots or lines
Do respond well to stimuli such as hands, faces, or objects

30
Q

is Object recognition fast or slow in IT cortex

A

can be fast (~150 ms)

Not a lot of time for feedback from higher brain area

31
Q

what is the Feed-forward process in the IT cortex

A

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

32
Q

where are grandmother cells found

A

IT cortex

33
Q

(IT cortex) The temporal lobe also comprises the hippocampus, a structure that is important for what

A

storing and retrieving memories.

34
Q

Grandmother cells might therefore be important for what

A

our recognition of certain learned objects

35
Q

Grandmother cells might therefore be important for our recognition of certain learned objects.
However, our experience of an object can’t only just depend on these types of cells, explain

A

For instance, when we look at an object (say a toaster), we know exactly where it is, and whether or not we are looking at an actual toaster or just the word “toaster

A truly invariant neuron wouldn’t give us information about these important details, which are essential in guiding action

36
Q

what is The problem of object recognition

A

The pictures are just a bunch of pixels on a screen, but in each case you perceive a house.

How do you recognize the first and third images as depicting the same house, but from different viewpoints?

How does your visual system move from points of light, like pixels, to whole entities in the world, like houses?

37
Q

what is Structuralism

A

Dots make lines -> lines make corners -> corners make shapes -> shapes are connected one to another and make objects.

38
Q

How can we know for instance that house continues behind the snowman? How do we know the car is in front (not under) the house?

A

gestalt principles

39
Q

Our perceptual system needs to make inferences based on what

A

rules

40
Q

what is Gestalt

A

In German, “form” or “whole.”

41
Q

what is Gestalt psychology:

A

“The whole is different than the sum of its parts.”

42
Q

what is Gestalt grouping rules:

A

A set of rules that describe when elements in an image will appear to group together

43
Q

what is Good continuation

A

two elements will tend to group together if they lie on the same contour.

44
Q

what is Occlusion:

A

The perception that a form (here a circle) is occluding another form can be understood using the principles of good continuation and closure.

45
Q

what is Similarity:

A

Similar looking items tend to group (color, size, orientation, etc…)

But items have to be similar on only one dimension,
Not a complex conjunction of dimensions.

46
Q

what is Proximity

A

Items that are near each other tend to group.

47
Q

proximity can be overruled by what

A

grouping or connecting the dots.

48
Q

what is Common region

A

Items will group if they appear to be part of the same larger region.

49
Q

what is Connectedness:

A

Items will tend to group if they are connected.

50
Q

what is Texture segmentation

A

Carving an image into regions of common texture properties.

51
Q

what does Texture grouping depend on

A

depends on the statistics of textures in one region versus another, i.e. the gray “chunks” in the middle don’t have, in average, the same size as in the surround.

U1 Psychology of Perception 212 (18 decks)

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