Primary visual pathway

Question 1

information processing stages

Answer 1

retina > lateral geniculate area > visual cortex
experimental strategy to reveal mechanisms of visual perception
- neural responses

Question 2

contributions

Answer 2

Hubel and Wiesel
information processing in vision

Question 3

photoreceptors

Answer 3

rods
- more abundant
- no colour discrimination
- sensitive to low light levels
- higher density in periphery
- track high rate changes
cones
- less abundant
- 3 discriminative waves
- less sensitive to low light
- high concentration in fovea
- cannot follow rapid changes

vary voltage as they are stimulated detection of light translated to excitation or inhibition of retinal ganglion cells

Question 4

receptive field of visual neurons

Answer 4

• portion of retina in visual stimulation evoke change in firing rate
  substructure - how visual stimulation need to be presented to evoke firing rate change

Question 5

retinal ganglion neurons

Answer 5

receive input from photoreceptors
on-off surrounds receptive fields
1. light presented in on regions excites cell, and light off inhibits
2. on and off organised centre surround fashion
3. response rate based on sum of stimulation in on region minus stimulation in off regions
sum of stimulation in ON regions minus stimulation in OFF regions

Question 6

functional significance of centre surround fields

Answer 6

• responding to only changes and boundaries in efficient
• luminance is relative to surround preserve appearance regardless of light level > illusions

Question 7

colour sensitivity of retinal ganglion and LGN neurons

Answer 7

• receive input for cones are sensitive to colour
• receptive fields that show colour opponency
• firing rate adaption explains negative afterimages

Question 8

orientation selective cells in V1

Answer 8

respond to elongated stimuli with specific orientation
simple
- excitatory and inhibitory regions
- combining on and off cell input
complex
- no discrete on and off
- combine simple cell output

Question 9

maps and modules

Answer 9

1. retino topic maps - orderly
2. modules - combine neurons sensitive presented in visual field

Question 10

further processing

Answer 10

• need to combine to result in perception and memory
• visual association cortices

Question 11

blindsight

Answer 11

• lesions and blindness show responses to unconscious visual stimuli
• additional visual pathways - direct LGN projections to extrastriate cortex crirical
• brain performs visual info processing that guides behaviour without conscious awareness

Question 12

colour constancy

Answer 12

appearance same in all lighting, disrupted by damage to V4