Vision

Question 1

What is light?

Answer 1

Discrete particles of energy, photons, or waves of electromagnetic energy

Question 2

What do we perceive as wavelength?

Answer 2

Perception of colour

Question 3

What do we perceive as amplitude?

Answer 3

Perception of brightness or intensity

Question 4

What are the 3 achromatic colours?

Answer 4

Black = produced by lack of light

White = produced by an intense mixture of wavelengths in equal proportions

Grey = produced by a mixture of wavelengths in equal proportions at lower intensities

Question 5

What are hues/colours?

Answer 5

Depend on wavelengths of light that a stimulus or object reflects into the eye
Most objects absorb different wavelengths and reflect the rest

Question 6

What is the monocular visual field?

Answer 6

Visible to one eye

Contains one blind spot

Question 7

How are monocular visual fields measured?

Answer 7

Using perimetry

Question 8

What is the binocular visual field?

Answer 8

Area of overlap between monocular fields

What is seen by both eyes

Question 9

What is the cornea?

Answer 9

Where light first enters the eye
Works with the lens to bend light onto the retina
Cannot change shape

Question 10

What is the lens?

Answer 10

Focuses light onto the retina

Can move

Question 11

How do we focus on a nearby object?

Answer 11

Less tension on ligaments holding lens in place
Holds lens in natural shape
Brings close objects into sharp focus
Loss common cause of presbyopia or hyperopia

Question 12

How do we focus on a distant object?

Answer 12

Increase tension on ligaments holding the lens in place
Flattens the lens
Loss with myopia lens

Question 13

Where is the site of transduction of light rays?

Answer 13

The retina

Question 14

What are the 5 layers of cells in the retina?

Answer 14

Photoreceptors
Horizontal cells 
Bipolar cells 
Amacrine cells 
Retinal ganglion cells

Question 15

What are the photoreceptors?

Answer 15

Cones and rods

Question 16

What do horizontal cells and amacrine cells do?

Answer 16

Lateral communication

Question 17

What do retinal ganglion cells do?

Answer 17

Axons project on surface of retina

Make up optic nerve

Question 18

What are 2 disadvantages to the retina inside-out design?

Answer 18

Light is distorted

Optic disk has no receptors

Question 19

How do we fill in the blind spot?

Answer 19

Use info from receptors around the blind spot

Surface interpolation

Question 20

What is the fovea?

Answer 20

Tiny indentation in the center of the retina
High acuity vision in the center
Densely packed cones and rod free

Question 21

What type of vision requires good lighting?

Answer 21

The cone vision

Question 22

What is the photopic system?

Answer 22

Provides high acuity coloured perception

Question 23

What are S-cones?

Answer 23

Short wavelength
Least abundant 
Blue 
High sensitivity 
Less concentrated in fovea

Question 24

What are M-cones?

Answer 24

Medium wavelength

Green

Question 25

What are L-cones?

Answer 25

Long-wavelength | Red

Question 26

What is the trichromatic theory of colour vision?

Answer 26

3 different colour receptors Any colour in visible spectrum can be matched by mixing together 3 different wavelengths of light in different proportions Needs to have at least 3 wavelengths to match every colour

Question 27

What vision is used in dimly lit conditions?

Answer 27

Rod vision

Question 28

What is the scotopic visual system?

Answer 28

Lacks detail and colours

Question 29

What is the convergence of the scotopic visual system?

Answer 29

Several hundred rods converge on one bipolar cell | Poor acuity

Question 30

What happens if you lack rods?

Answer 30

Night blindness

Question 31

What is the achromatic vision?

Answer 31

Shades of grey from black to white Not colour sensitive Do not detect red light

Question 32

What is ON firing?

Answer 32

Detect light objects in the dark

Question 33

What if OFF firing?

Answer 33

Detect dark objects in light environments

Question 34

What are OFF firing bipolar cells

Answer 34

Depolarize when light is off

Question 35

What are ON firing bipolar cells?

Answer 35

Depolarize when light is on

Question 36

What cells are inhibited by glutamate?

Answer 36

ON firing cells | IPSP

Question 37

What cells are excited by glutamate?

Answer 37

OFF firing cells | EPSP

Question 38

Firing in ON center cells?

Answer 38

Light in center of receptive field increase firing | Light in periphery of receptive field = off firing inhibition

Question 39

Firing in OFF center cells or ON surround?

Answer 39

Increase firing when light is on in the surrounding area of receptive field Light in the center of the receptive field by decrease firing

Question 40

What are horizontal cells responsible for?

Answer 40

Axoaxonic contact of photoreceptors Acts as an interneuron Enhances brightness contrast

Question 41

What do ON center and OFF center cells respond best to?

Answer 41

Contrast | Most effective way to influence firing is to illuminate entire center and keep entire surround unilluminated

Question 42

What is the geniculate striate pathway?

Answer 42

Retina to optic nerve to LGN to striate visual cortex

Question 43

What is the SCN?

Answer 43

Control diurnal rhythms, RGC sensitive to blue light

Question 44

What is the superior colliculus?

Answer 44

Reflexive eye and head movements

Question 45

What is the pretectum?

Answer 45

Pupillary eye reflex

Question 46

What is the LGN?

Answer 46

Receives input from the contralateral visual field | Disproportionately large foveal representation in striate cortex

Question 47

What are the parvocellular layers?

Answer 47

Projections from small p RGC, more p cells than m cells Project to top 4 layers of LGN Responsive to colour, slow moving or stationary details, and fine pattern detail, small receptive field Input primarily from cones Project to bottom of striate layer 4 neurons

Question 48

What are the magnocellular layers?

Answer 48

projections from big m RGC Project to the bottom 2 layers of LGN Responsive to movement, large receptive field Input primarily from rods Project to top part of striate layer 4 neurons

Question 49

What is the striate cortex involved in?

Answer 49

The initial cortical processing of all visual information necessary for visual perception

Question 50

What does damage to the striate cortex result in?

Answer 50

loss of vision in the contralesional hemifield

Question 51

What is scotoma?

Answer 51

Damage in one hemisphere in V1 | Area of blindness in the contralateral visual field of both eyes

Question 52

What is an opponent-process theory?

Answer 52

``` 2 different classes of cells encode colour and a third that encodes brightness Each class encodes 2 complementary perceptions ```

Question 53

What is the secondary visual cortex?

Answer 53

Input mostly from V1 | 24 subsections

Question 54

What is the association cortex?

Answer 54

Prestriate cortex and inferotemporal cortex

Question 55

What is the dorsal stream?

Answer 55

Directs behavioural interaction with visual stimuli but not recognition of objects Perception of where objects are

Question 56

What is akinetopsia?

Answer 56

Inability to perceive fluid motion Unilateral or bilateral MT damage in the dorsal stream See the world in snapshots Cannot appropriately control behaviour

Question 57

What is the ventral stream?

Answer 57

Mediates conscious perception of objects

Question 58

What is prosopagnosia?

Answer 58

Failure of face recognition | Can recognize other objects