occipital & temporal lobe - visual perception & memory Flashcards

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1
Q

what is the role of the occipital lobe?

A
  • visual processing area of the brain
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2
Q

what is the role of the inferior temporal lobe?

A
  • important role in visual recognition of objects
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3
Q

what is the order visual processing in the brain?

A

visual processing in the brain = hierarchal

  • visual complexity increases from retina to visual association cortices
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4
Q

what is there at different stages of information processing?

A
  • functional differentiation with different neurone types

AKA:
- different brain regions processing different properties of visual stimuli

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5
Q

give step by step of different brain regions processing different properties of visual stimuli

A
  • simple features
    (e.g.: cones dealing with wavelength)
  • at different hierarchical stages, information from different neuronal types = combined via processing in parallel channels
  • results in more complex visual representation for perception and memory

in later stages of occipital temporal lobe:
(e.g. integrated information for surface - colour, texture etc.)

when moved into the medial temporal lobe:
(e.g.: integration with other sensory modalities - smell, touch, sound etc.)

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6
Q

identify the primary visual pathway sequence

A
  • retina
  • optic nerve
  • lateral geniculate nucleus (LGN) of the thalamus - - visual cortex of occipital lobe
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7
Q

how is visual information further processed following the primary visual cortex?

A
  • first major stage occurs within occipital lobe
  • occurs in the extrastriate/prestriate cortex
  • primary visual cortex sends input to extrastriate cortex
  • information from the “colour”, “shape/form”, “location” and “motion” detected in primary visual cortex (V1)
  • neurones are sent to different areas of the extrastriate cortex
  • neurones in extrastriate cortex signal ‘global’ properties of visual scene rather than ‘component’ properties
  • global properties = features of scene environment, describes an image’s spatial layout, affordances, or surface properties
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8
Q

what is the general principle of visual processing in the extrastriate cortex (compared to primary visual pathway)?

A
  • specialises in colour perception
  • neurones within the region of the extrastriate cortex signal global properties of visual scene rather than component

compared to primary visual pathway:
- at photoreceptor level, neurones signal absence/presence of light of distinct wavelength

  • not real colour vision
  • neurones only represent contrast and boundaries
  • complex cells represent movement of small parts of visual field
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9
Q

what is real colour vision?

A
  • where the colour of one part of a scene is represented depending on the bits of the surrounding colour
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10
Q

where is colour vision mediated?

A
  • area V4 of extrastriate cortex
  • this is where you have global colour vision
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11
Q

what is perceived colour of an object dependent on?

A
  • wavelength reflected by object
  • wavelength reflected by surroundings of an object
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12
Q

what is the functional significance of being able to perceive wavelengths reflected by objects and surrounding objects?

A
  • colour constancy
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13
Q

what is colour constancy?

A
  • being able to perceive colour of objects independently of different light levels
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14
Q

identify a difference between the neurones in the primary visual pathway and the extrastriate cortex

A
  • neurones in area V4 (extrastriate cortex) are colour sensitive (where global colour sensitivity comes from)
  • neurones in primary visual pathway are only wavelength sensitive
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15
Q

how is the perception of global/pattern motion formed?

A
  • in area V5
  • combination of neurones is combined to result in perception of global/pattern motion
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16
Q

what are the two visual information processing streams?

A
  • dorsal stream
  • ventral stream

these are both anatomically and functionally different

17
Q

describe the dorsal stream

A
  • goes up to parietal cortex
  • processes visual information for the purpose of executing movements
  • main responsibility = visual processing that allows us to determine WHERE objects are
  • help us with visuo-motor processing (HOW you direct your movement to something)
18
Q

describe the ventral stream

A
  • goes down to inferior temporal lobe
  • processes visual information for the purpose of visual perception (“vision for perception”)
  • main responsibility = visual object analysis
  • helps recognise what object is
19
Q

describe evidence for ventral stream

A
  • lesions in inferior temporal lobe (ventral stream) in monkeys
  • found this impaired object-discrimination/recognition
  • could not identify WHAT object was
  • however could still locate WHERE object was
20
Q

describe evidence for dorsal stream

A
  • posterior parietal lesions (dorsal stream) impairs ability to locate WHERE object is
  • but could still determine WHAT object was
21
Q

what did Milner and Goodale propose about the ventral and dorsal stream?

A
  • suggested dorsal steam = processes visual information for visuo-spatially guided action (HOW we direct movement to object)
  • suggested ventral stream = processes visual information for object perception (WHAT an object is)
22
Q

outline key evidence from Milner and Goodale regarding the two visual streams

A
  • patients with occipito-temporal brain damage show severe forms of visual agnosia
  • visual agnosia = where person can see visual information but not recognise/interpret visual information

EXAMPLE:
- patient DF with extensive ventral-stream (identifying object) lesions has profound visual agnosia BUT shows visually guided reaching

  • DF can act of visual stimulus
  • DF unable to make perceptual judgements
23
Q

what is the role of the inferior temporal cortex?

A
  • inferior temporal cortex receives input from extrastriate cortex
  • forms the final stage in visual processing hierarchy of ventral stream
  • neurones in this cortex respond very selectively to specific shapes and objects
24
Q

what do the responses of the neurones in the inferior temporal cortex show?

A
  • neurones can show invariance to changes in size, orientation of object
  • neurone recognises object regardless of viewpoint
  • sustained activity of neurones that represent certain visual objects even when visual object = removed
  • thought to reflect short-term object memory
25
Q

what do some neurones in the inferior temporal lobe show?

A
  • some show highly selective responses to individual faces
  • these are called face cells
26
Q

what have the highly selective properties of neurones in the inferior temporal lobe been compared to?

A
  • gnostic units
  • grandmother neurones

i.e.:
hypothetical neurones at end of processing hierarchy that recognise individual entities (such as your Grandmother)

you have individual neurones (gnostic units) that are responsible for recognising certain concepts/entities

27
Q

what are face cells?

A
  • neurones that specifically respond to faces
  • not all faces, specific faces
28
Q

what has been shown in human inferior temporal lobe using functional imaging?

A

areas showing selective responses to faces

29
Q

what is at the end of the visual-processing hierarchy?

A
  • the medial temporal lobe
30
Q

what does the medial temporal lobe do?

A
  • combines inputs from ventral and dorsal stream
  • receives additional inputs from other sensory modalities
  • this helps elaborate visual representations further and to generate multi-modal representations
31
Q

where is the final stage of purely visual processing hierarchy?

A

within the inferior temporal lobe

32
Q

what is also included in the medial temporal lobe?

A
  • hippocampus
  • amygdala
33
Q

where is the medial temporal lobe located?

A
  • sits close to temples
34
Q

give examples of complex representations mediated by the medial temporal lobe

A

complex spatial representations
- that requires encoding of relations between many visual stimuli

multimodal representations
- of experiences (episodic memories)
- of facts (semantic memory)
- both of these together = declarative memory

35
Q

outline the case of Patient H.M.

A
  • following surgery, HM showed severe deficit in remembering new/recent experiences, facts, places
  • despite deficit, other cognitive functions including procedural learning = largely intact
36
Q

what does study looking into rats with hippocampus lesions show about spatial learning?

A
  • rats with no lesions were able to escape using spatial cues
  • rats with lesions failed to
  • provided evidence for marked impairment of spatial learning following damage to hippocampus
37
Q

explain what John O’Keefe and colleagues did with rats and electrodes in the hippocampus

A
  • implanted electrodes into the hippocampus
  • had rats move around in square arena chasing Cheerios
  • found that specific neurones in hippocampus only fire if animal = in particular location
  • because of very clear firing correlates with these neurones, they were called place cells
38
Q

what are place cells?

A
  • neurones that only fire in a particular place/location
  • found in humans and animals