Visual perception

Question 1

What is the cornea?

Answer 1

Focuses light, fixed, transparent

Question 2

What is the pupil?

Answer 2

Aperture in the iris, changes size according to light levels

Question 3

What is the lens?

Answer 3

Focuses light

Question 4

What is the retina?

Answer 4

Rods and Cones are cells in the retina that convert light into an electrochemical signal

Question 5

What are rod and cone cells?

Answer 5

Light sensitive receptors that convert light into electrical activity
More rod than cone cells
When light falls on the cells, it sends a signal like an action potential

Question 6

What is the optic nerve?

Answer 6

Nerve fibres pool signals from multiple rod or cone receptors

Question 7

What is the purpose of rod cells?

Answer 7

Night vision
One type
More outside the fovea
Specialised for low-light conditions
Does not distinguish between colour

Question 8

What is the purpose of cone cells?

Answer 8

Daytime
3 types
Red cone- long wavelength
Green cone- middle wavelength
Blue cone- short wavelength
Mostly in the fovea

Question 9

What is circade?

Answer 9

where our eyes are constantly moving

Question 10

What is foveation?

Answer 10

moving our eyes to control what info falls on the fovea

Question 11

What is high acuity?

Answer 11

fine details visible at fovea

Question 12

What happens in the parvocellular pathway?

Answer 12

Cone cells L + M
They are sensitive to colour and fine detail

Question 13

What happens in the magnocellular pathway?

Answer 13

Cones + Rod
Sensitive to luminance and motion in periphery

Question 14

What happens in the koniocellular pathway?

Answer 14

Cones S, M + L
Mediated mostly colour vision

Question 15

What is V4?

Answer 15

colour

Question 16

What is V1 + V2?

Answer 16

detects simple information

Question 17

What is V5?

Answer 17

motion

Question 18

What is LO?

Answer 18

shape

Question 19

What is akinetopsia?

Answer 19

Difficulty seeing motion
- Can be caused by damage to V5

Question 20

What happens with damage o the MST?

Answer 20

Vaina (1998)
- Impairs optic flow used for walking
- first order motion = luminance defined
- second order= contrast defined

Question 21

What is the binding problem?

Answer 21

If we had different groups of neurons responding to different features and these neurons are in different neuroanatomical regions – how do we group the features which belong to a particular object?

Question 22

What is the ventral stream responsible for?

Answer 22

‘What’
identifying objects

Question 23

What is the dorsal stream responsible for?

Answer 23

‘Where’
Controls actions

Question 24

What is double dissociation?

Answer 24

Milner & Goodale (1995)
- Damage to ventral stream should impair object recognition but not action planning, while damage to dorsal streams should impair action planning but not object recognition

Question 25

What is optic ataxia?

Answer 25

Damage to the posterior parietal lobe - difficulties with action planning - can label objects well

Question 26

What is visual form agnosia?

Answer 26

Cannot name drawings of objects No problem with action planning

Question 27

What are the four characteristics of ventral and dorsal streams

Answer 27

Ventral stream- vision for perception Dorsal- vision for action Ventral- coding is allocentric Dorsal- coding is egocentric Ventral- representations sustained over time Dorsal- representations are short-lasting Ventral- processing leads to conscious awareness Dorsal- does not

Question 28

How can our brains tell that things are the same colour when the lighting conditions vary dramatically?

Answer 28

We can slowly adjust to stable properties of light At dusk: Surface 1 makes red cones fire 1 time per second, Surface 2 makes them fire 3 times per second In the day: Surface 1 makes the red cones fire 10 times per second, Surface 2 makes them fire 30 times per second ratio is still 1:3 at night and day