occipital & temporal lobe - visual perception & memory

Question 1

what is the role of the occipital lobe?

Answer 1

• visual processing area of the brain

Question 2

what is the role of the inferior temporal lobe?

Answer 2

• important role in visual recognition of objects

Question 3

what is the order visual processing in the brain?

Answer 3

visual processing in the brain = hierarchal

• visual complexity increases from retina to visual association cortices

Question 4

what is there at different stages of information processing?

Answer 4

• functional differentiation with different neurone types

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

Question 5

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

Answer 5

• 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.)

Question 6

identify the primary visual pathway sequence

Answer 6

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

Question 7

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

Answer 7

• 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

Question 8

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

Answer 8

• 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

Question 9

what is real colour vision?

Answer 9

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

Question 10

where is colour vision mediated?

Answer 10

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

Question 11

what is perceived colour of an object dependent on?

Answer 11

• wavelength reflected by object
• wavelength reflected by surroundings of an object

Question 12

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

Answer 12

• colour constancy

Question 13

what is colour constancy?

Answer 13

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

Question 14

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

Answer 14

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

Question 15

how is the perception of global/pattern motion formed?

Answer 15

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

Question 16

what are the two visual information processing streams?

Answer 16

• dorsal stream
• ventral stream

these are both anatomically and functionally different

Question 17

describe the dorsal stream

Answer 17

• 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)

Question 18

describe the ventral stream

Answer 18

• 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

Question 19

describe evidence for ventral stream

Answer 19

• 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

Question 20

describe evidence for dorsal stream

Answer 20

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

Question 21

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

Answer 21

• 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)

Question 22

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

Answer 22

• 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

Question 23

what is the role of the inferior temporal cortex?

Answer 23

• 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

Question 24

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

Answer 24

• 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

Question 25

what do some neurones in the inferior temporal lobe show?

Answer 25

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

Question 26

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

Answer 26

• 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

Question 27

what are face cells?

Answer 27

• neurones that specifically respond to faces
• not all faces, specific faces

Question 28

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

Answer 28

areas showing selective responses to faces

Question 29

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

Answer 29

• the medial temporal lobe

Question 30

what does the medial temporal lobe do?

Answer 30

• 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

Question 31

where is the final stage of purely visual processing hierarchy?

Answer 31

within the inferior temporal lobe

Question 32

what is also included in the medial temporal lobe?

Answer 32

• hippocampus
• amygdala

Question 33

where is the medial temporal lobe located?

Answer 33

• sits close to temples

Question 34

give examples of complex representations mediated by the medial temporal lobe

Answer 34

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

Question 35

outline the case of Patient H.M.

Answer 35

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

Question 36

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

Answer 36

• 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

Question 37

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

Answer 37

• 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

Question 38

what are place cells?

Answer 38

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