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Sensation and Perception > Extrastriate cortex > Flashcards

Extrastriate cortex Flashcards

1
Q

orientation selectivity at cortex:

A

Attributed to synapse
pattern of circular
concentric receptive
fields of the LGN to
simple cells of the
primary visual cortex

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2
Q

Multiple simple cells
with slightly different
orientation selectivity
will synapse with a
neuron in V4

A

This neuron will be
selective to contours

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3
Q

Visual Areas in the brain can be compared on four
characteristics

A
  • differ according to the types and distributions of neurons within them
    -differ according to the other areas in the brain from which they receive signals or to which they send signals
    -differ according to properties to which their constituent neurons are tuned (motion, color, orientation)
    -each visual area contains a retinotopic map of the visual field
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4
Q

Segregation of information occurs early in visual system due to:

A

RGCs

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5
Q

dorsal stream:

A

where pathway
v1 -> v2 -> MT -> Parietal lobe

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6
Q

The dorsal stream is responsible for:

A

-Representing properties that relate to an objects motion or location
-Guided action

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7
Q

Ventral stream is responsible for:

A

representing properties that relate to an objects identity (shape, color)
“What” pathway

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8
Q

ventral stream passes from:

A

v1 -> v2 -> v4 -> It

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9
Q

Impaired performance in landmark task (where)

A

perietal lesion

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10
Q

impaired performance in objet task (what):

A

IT lesion

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11
Q

lesion to lateral occipital area is associated with impaired:

A

ventral stream

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12
Q

visual form agnosia:

A

Inability to recognize
objects by their shape in
spite of the ability to see
them

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13
Q

manual estimation:

A

Use distance between index and thumb to estimate the size of an
object

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14
Q

Grasp Calibration

A

Adjust distance between fingers to match the object size as you
reach to grasp it

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15
Q

LO Lesion
(Visual Form Agnosia) shows impaired

A

object recognition

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16
Q

optic axtaxia has lesion to

A

parietal lobe

17
Q

Parietal Lobe Lesion
(Optic Ataxia) shows impaired performance to

A

visually guided action

18
Q

While the ventral and dorsal streams provide a simplified framework, they do not operate independently or exclusively in their respective domains. Research highlights several key points that challenge a strict dichotomy:

A

many interactions
feedforward and feedback processes
pathways connecting both streams

19
Q

Individuals that are cortically
blind (damage to striate cortex)
can

A

still respond to visual stimuli
at a higher than chance level

20
Q

V4 -

A

Colour / Edges /
Curvatures

21
Q

LOC and IT

A

Objects / Faces /
Places

22
Q

MT -

A

motion

23
Q

Fusiform Face Area (FFA)

A

Subregion of the Inferotemporal
cortex where cells preferable
respond to faces

24
Q

Cells in the FFA
respond to:

A

Faces and other stimuli
that contain similar features to
faces

  • fine detail discrimination
25
Q

The three modules in IT include:

A

-Fusiform face area (FFA) responds best to faces as well as when
context implies a face.
* Parahippocampal place area (PPA) responds best to spatial layout
(e.g. Rooms).
* Extrastriate body area (EBA) responds best to pictures of full bodies
and body parts.

26
Q

Parahippocampal place area (PPA) responds best to:

A

spatial layout

27
Q

Extrastriate body area (EBA) responds best to:

A

pictures of full bodies
and body parts.

28
Q

How do we develop modules that are selective to very specific
features?

A

Natural Selection
‣ Genetically based characteristics that enhance the survival and reproduction
of an animal will be passed on to future generations
‣ An individual who had the ability to encode faces (emotions) may be more
likely to survive and reproduce

29
Q

The presence of selectivity in the neurons of the visual
system is:

A

not a fixed trait, and can change based on the visual
experience obtained in the first few months of life

30
Q

Feed-forward process:

A

A process that carries out a computation
one neural step after another, without need for feedback from a
later stage to an earlier stage

31
Q

Object recognition occurs so quickly that:

A

Feed-forward processes
must be occurring.

32
Q

Studies indicate that object recognition:

A

happens in as little as 150
ms

33
Q

Sensory code:

A

Representation of perceived objects through neural firing

34
Q

Specificity coding -

A

specific neurons responding to specific stimuli.

35
Q

Problems with specificity coding

A
  • Too many different stimuli to assign specific neurons.
  • Most neurons respond to a number of different stimuli.
36
Q

Distributed (Sparse) coding -

A

pattern of firing across many neurons
codes specific objects

Sensation and Perception (20 decks)

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