Vision (L7-8) Flashcards
1
Q
Axons in the optic nerve connect the retina to…
A
- 90% to the lateral geniculate nucleus in the thalamus then to the primary visual cortex
- 10% to the pulvinar nucleus and the superior colliculus
2
Q
Visual perception
A
- Anterior-posterior organisation
- The further down in the visual processing stream cells are, they respond to stimuli of increasing complexity and larger receptive fields
- 2 visual pathways: dorsal and ventral
3
Q
Area V1
A
- Primary visual cortex
- Contains many neurons tuned to bars in different positions of the visual field
- Important in the ability to detect edges
- Show outlines with no colour
4
Q
What is a receptive field?
A
- The region of the sensory surface that, when stimulated, causes a change in the firing rate of that neuron
- Complex cells have a medium sized RF
- Hypercomplex cells have a large RF
5
Q
Damage to V1
A
- Causes blindsight
- Patient W: injury to left visual area causes right hemianopia
- Patient DB: removal of right primary visual cortex causes left visual hemifield blind
- Patient TN: removal of V1 causes blindness but patient is still able to navigate around objects in their environment
6
Q
Area V2/3
A
- V1 connects to V2 which connects to V3
- Many complex and hypercomplex neurons
- Visual info is then passed onto V4 and V5
7
Q
Zeki
A
- Conducted PET experiments
- Colour-greyscale contrast is controlled by area V4
- Motion-static contrast is controlled by area V5
8
Q
Area V4
A
- Colour processing
- Damage causes cerebral achromatopsia
- Left sided stroke causes patient to lost ability to perceive colours in right visual field
9
Q
Area V5
A
- ‘Human middle temple’
- Detects motion
- Damage causes cerebral akinetopsia (world appears static)
- Stevens showed that TMS to V5 impaired ability to identify the global direction of movement
10
Q
Ungerleider + Mishkin
A
- Proposed there are 2 streams of visual processing…
1. Dorsal: where, spatial vision
2. Ventral: what, visual characteristics of objects
11
Q
Milner + Goodale
A
- Proposed the 2 streams were…
1. Dorsal: how, visually guided action
2. Ventral: what
12
Q
Ventral stream
A
- Important for visual perception and identification of objects
- fMRI study by Kelly showed words activate the left fusiform gyrus, pictures produce bilateral activity and faces activate the right fusiform gyrus
- fMRI study by Grill-Spector showed faces activate the fusiform face area, scenes activate the para-hippocampal place area and both activate the lateral occipital cortex
13
Q
Damage to the lateral occipital cortex
A
- Causes visual form agnosia
- Apperceptive agnosia: patient is unable to form a percept to copy the image
- Associative agnosia: patient is able to form a percept to copy the image but can’t associate semantic knowledge
- Integrative agnosia: patient is able to form a partial representation but have problems integrating the parts
14
Q
Damage to the fusiform gyrus
A
- Causes prosopagnosia
15
Q
Are faces special?
A
- Patient WJ: patient with prosopagnosia but no difficulty recognising his sheep
Y - special brain region (fusiform face area)
N - in car experts, the FFA is activated by both faces and cars, suggesting it’s activated by expertise (Isobel Gauthier)
N - Subordinate judgment of faces caused greater activation of FFA than basic judgement (Turk et al.)
16
Q
Capgras syndrome
A
- A condition in which sufferers believe someone they know has been replaced by an imposter
- Damage to link between ventral stream and emotion
17
Q
Haxy’s model for face processing
A
- Ventral stream is involved in structure and visual percept
- Dorsal stream is involved in processing changeable aspects
- Information is passed forward to determine emotional responses, person knowledge and motor stimulation
18
Q
Dorsal stream
A
- Important for visually guided action