Week Six

Question 1

Function of eye lenses

Answer 1

Lenses in our eyes invert the image and project is back onto the photoreceptors.

Question 2

Retinal Ganglions

Answer 2

• 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.

Question 3

What is the Fovea

Answer 3

• 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.

Question 4

Photoreceptors

Answer 4

Split into two categories

• cones
• rods

Question 5

cones

Answer 5

• Cones are for coloured vision
  ○ They can see very fine detail as they are densely packed with fovea.
  Work primarily in bright light.

Question 6

rods

Answer 6

- Rods are black and white vision 
	○ Mostly widely spaced throughout the retina
	○ More in the peripheral visual field 
	○ Low acuity 
Work well at night

Question 7

Process of Seeing

Answer 7

• 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

Question 8

Primary Visual Cortex Cell Division

Answer 8

• 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’)

Question 9

agnosia

Answer 9

• Inability to recognise objects

* Prosopagnosia – specific inability to recognise faces

Question 10

temporal lobe and vision

Answer 10

• Temporal lobe – detectors for combinations of lines/eges (squares or cone shapes)

Question 11

parietal lobe and vision

Answer 11

damage to parietal lobe causes problems of spatial awarenesss

Question 12

visual maps

Answer 12

• 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)

Question 13

stabalisation of visions

Answer 13

• 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

Question 14

blindsight

Answer 14

• Unconscious, but not conscious, awareness of a visual stimulus
May be observed in some cases of visual neglect