Week Six Flashcards
1
Q
Function of eye lenses
A
Lenses in our eyes invert the image and project is back onto the photoreceptors.
2
Q
Retinal Ganglions
A
- In order to see objects/ lines/ shapes etc. we have a system for enhancing edges.
- Ganglion cells in the retina have a receptive field. Some of these cells can be excited by light inside the receptive field or inhibited by light outside the receptive field.
- Retinal ganglions cells can act as edge detectors. They an integrate patterns of light over an area and indicate whether that pattern is different to that in an adjacent area.
3
Q
What is the Fovea
A
- The exact centre of the visual field.
- Represents the location they eye is pointing when you look at something.
- The fovea has the greatest concentration of photoreceptors.
4
Q
Photoreceptors
A
Split into two categories
- cones
- rods
5
Q
cones
A
- Cones are for coloured vision
○ They can see very fine detail as they are densely packed with fovea.
Work primarily in bright light.
6
Q
rods
A
- Rods are black and white vision ○ Mostly widely spaced throughout the retina ○ More in the peripheral visual field ○ Low acuity Work well at night
7
Q
Process of Seeing
A
- Left side of the visual field of each eye projects to the right side of the brain and vice versa.
- Nerve cells cross over at the optic chiasm
- Travel to lateral geniculate nucleus of thalamus (LGN) then back to occipital cortex at the back of the brain
8
Q
Primary Visual Cortex Cell Division
A
- Simple cells
* Respond to an edge at a particular orientation in a specific part of the visual field- Complex cells
- Respond to an edge at a particular orientation but falling anywhere within a wider field. May also repond to direction of motion
- Hypercomplex cells
- Respond to a line which ends within the receptive field (‘end-stopping’)
- Complex cells
9
Q
agnosia
A
- Inability to recognise objects
* Prosopagnosia – specific inability to recognise faces
10
Q
temporal lobe and vision
A
• Temporal lobe – detectors for combinations of lines/eges (squares or cone shapes)
11
Q
parietal lobe and vision
A
damage to parietal lobe causes problems of spatial awarenesss
12
Q
visual maps
A
- At all levels of the visual system, information is distributed in multiple parallel visual maps
- Retinotopic – mimics the layout of the visual field
- Often center-weighted (central 5 degrees represented most strongly)
13
Q
stabalisation of visions
A
- Other connections exist with higher cortical levels, including frontal association cortex
- Tell you where your eyes are pointing to make an internal map of where things are located
14
Q
blindsight
A
• Unconscious, but not conscious, awareness of a visual stimulus
May be observed in some cases of visual neglect