Sensory Six - Vision part two

Question 1

How is colour in light percieved?

Answer 1

using intensity and wavelength

Question 2

How is intensity and wavelength processed?

Answer 2

Firstly they are done separately by the retina, then both are integrated in the brain to give color perception

Question 3

What gives rise to colour of an object?

Answer 3

The object reflects some colours and those are sensed leading to the perception of the object being those colours.

Question 4

What is the colour management system?

Answer 4

A system that is used as convention to ensure monitors, printers all have the same colour schemes

Question 5

What is the first component of colour perception?

Answer 5

Light detection by the photoreceptors

Question 6

What are the three classes of cones called?

Answer 6

Trivariant

Question 7

What are the three cones called?

Answer 7

S cone = short wave length (blue)
M cone = med wave length (green)
L cone = Long wavelength (red)

Question 8

What do rods detect?

Answer 8

They are our night vision
Low threshold to light
Do not detect colour

= Intensity only, contrast

Question 9

What do cones detect?

Answer 9

Day vision
Intensity and Wavelength = Colour vision
Higher threshold to light

Question 10

As we have three classes of cone how else is colour specified?

Answer 10

Can be specified in terms of their: Hue, tone and saturation

Question 11

What is the munsell colour system?

Answer 11

A classification based on
Hue : Dominant wavelenght
Value : Reflectance and luminosity
Chroma : Saturation of the signal

i.e colours of equal hue, value and chroma on opposite sides of the circle are complimentary

when mixed they add

Question 12

Whats the first theory of colour vision?

Answer 12

The trichromatic theory

= Combination of three channels explain the colour discrimination functions of the eye

Question 13

What is unique about each cone?

Answer 13

A range of wavelengths activate each cone to varying degrees (each have a maximum too) this following from the the trichromatic theory could explain how colours mix and form different ones…

Question 14

What is the second theory of colour?

Answer 14

Opponent theory colour:

• Three channels, each with an antagonist
  i. e Red-green, blue-yellow and black-white

Hue cancellation paradigms suggest that there is only every pure colours and never greenish-red. either red or green

Question 15

What is the third theory of vision?

Answer 15

Stage theory (modern theory)

• Incorporates both previous theories but is based on a two stage model

Stage One: Receptor stage, three colour receptors
Stage Two: Neural processing stage, where colour opponency occurs at a post receptoral level, and occurs in the horizontal cells of the retina and continues in the brain.

Question 16

What is meant by colour opponency?

Answer 16

i.e Red and green cancel each other (varying degrees based on intensity etc…) and this is processed by the P cells (retina) before the Parvocellular cells in the LGN

or

I.e Red and green summat, blue is subtracted, then processed by small-bistratified ganglion cells in the retina then Koniocellular neurons in the LGN

Question 17

So according to theory three how is light perceived?

Answer 17

• Activation of L,M,S cone pigments.
• Opponency pathways that allows us to sort colour information for black/white, yellow/blue and red/green
• Brain combines the information received from the retina to give rise to perception of different wavelengths of light.

Question 18

What are people with normal colour vision called?

Answer 18

Trichromats

Question 19

What is colour blindness called?

Answer 19

Dichromacy

X linked, so more common in males

Question 20

People who are less sensitive to red are called?

Answer 20

Protanopia

Question 21

People who are less sensitive to green are called?

Answer 21

Deuteranopia

Question 22

People who see no colour are called?

Answer 22

Monochromats

Question 23

What is the farnsworth panel d15?

Answer 23

A method of detecting colour blindness where subjects are asked to order colours in similarity from a pilot cap colour

Question 24

What are the ventral and dorsal streams also called?

Answer 24

Dorsal = where
Ventral = What

Question 25

What is the ishahara test?

Answer 25

Reading the numbers in the colours

Question 26

How does the colour afterimage occur?

Answer 26

Adaptation, prolonged viewing of a stimulus, cells tire and stop firing.