Vision L5

Question 1

does colour depend on illuminance?

Answer 1

no - ideally it should depend on spectral reflectance not how well lit it is

Question 2

Human colour vision extracts _______ in colour
not absolute spectral intensities

Answer 2

Human colour vision extracts differences in colour
not absolute spectral intensities

Question 3

colour triangle picture

Answer 3

Question 4

trichromat colour triangle picture

Answer 4

including unrealised colours.

Question 5

what wavelength stimualtes green cones only?

Answer 5

non - pure green is not a real colour

Question 6

describe the red green colour opponent channel

Answer 6

In the red-green opponent channel, the signal is the difference between the responses of the medium and long wavelength cones

Question 7

describe the blue yelow colour opponent channel

Answer 7

The blue-yellow opponent channel is formed from the difference between the responses of the short wavelength cones, and the sum of the medium and long wavelength cone responses.

Question 8

describe the luminance colour opponent channel

Answer 8

By summing together the responses of the medium and long wavelength cones, a signal representing brightness, or luminance is produced.

Question 9

whats the advantage of these channels?

Answer 9

These opponent channels produce a steep variation of response with wavelength in the regions of pigment curve overlap, giving high sensitivity to changes in wavelength.

Question 10

where are colour opponent channels set up?

Answer 10

the retina

Question 11

label

Answer 11

Question 12

describe broadband magnocellular ganglion cells?

Answer 12

The broad band class of retinal ganglion cell are driven by both red and green cones. They exhibit centre surround antagonism without a chromatic component, thus encoding luminance, and correspond to the M cells, which project via the magnocellular layers of the LGN.

LUMINANCE

Question 13

These single opponent cells provide signals which are ambiguous for colour and brightness. For example, a red-green single opponent cell cannot discriminate between large and small red spots and a small white spot. This problem is resolved by…..

Answer 13

double opponent receptive fields, in which chromatic antagonism takes place not only between centre and surround but also within each region.

Question 14

where are double opponent cells found?

what does the surrounding region do?

Answer 14

Double opponent cells are found in the cytochrome oxidase blobs of the striate cortex, which receive inputs from the parvocellular and koniocellular layers of the lateral geniculate nucleus. The surrounding interblob regions are responsible for analysing spatial form and motion.

Question 15

Answer 15

Question 16

how might double opponent receptive fields be produced from single opponent cells?

Answer 16

Question 17

describe the cells in V4 - how do they respond to spectral colours?

Answer 17

The cells in V4 exhibit a very narrow degree of spectral tuning, each responding only to a narrow band of wavelengths.

Question 18

does V4 represent individual colours and hues?

Answer 18

yes

So V4 no longer represents the opponent channels seen lower down the pathway, but deals instead with individual colours or hues.

Question 19

So V4 no longer represents the opponent channels seen lower down the pathway, but deals instead with individual colours or hues. These properties contribute to the phenomenon of ….

Answer 19

So V4 no longer represents the opponent channels seen lower down the pathway, but deals instead with individual colours or hues. These properties contribute to the phenomenon of colour constancy.

Question 20

which pathways best repsond to

spectral reflectance

detecting colour boundaries

Answer 20

Question 21

Lack of an individual cone pigment in ______ (red), ______ (green), or ______ (blue) results in dichromatic colour vision.

Answer 21

Lack of an individual cone pigment in protanopia (red), deuteranopia (green), or tritanopia (blue) results in dichromatic colour vision.

Question 22

make sure you understand this:

Answer 22

Question 23

contrast cells in V1 and V4

Answer 23

V1: illuminated wihth red light:

will respond to red light reflected within its receptive field, irrespective of the spectral reflectance (or “colour”) of the patch.

area V1 - response depends on wavelength

V4: illuminated wiht red light:

However such a cell in Area V4 will only respond to red light reflected from a red patch, but will not respond to light reflected from a neighbouring patch of another colour.

Question 24

fat

Answer 24

mamba

boy thasta. tough fecking deck