Vision L5 Flashcards
does colour depend on illuminance?
no - ideally it should depend on spectral reflectance not how well lit it is
Human colour vision extracts _______ in colour
not absolute spectral intensities
Human colour vision extracts differences in colour
not absolute spectral intensities
colour triangle picture
trichromat colour triangle picture
including unrealised colours.
what wavelength stimualtes green cones only?
non - pure green is not a real colour
describe the red green colour opponent channel
In the red-green opponent channel, the signal is the difference between the responses of the medium and long wavelength cones
describe the blue yelow colour opponent channel
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.
describe the luminance colour opponent channel
By summing together the responses of the medium and long wavelength cones, a signal representing brightness, or luminance is produced.
whats the advantage of these channels?
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.
where are colour opponent channels set up?
the retina
label
describe broadband magnocellular ganglion cells?
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
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…..
double opponent receptive fields, in which chromatic antagonism takes place not only between centre and surround but also within each region.
where are double opponent cells found?
what does the surrounding region do?
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.
how might double opponent receptive fields be produced from single opponent cells?
describe the cells in V4 - how do they respond to spectral colours?
The cells in V4 exhibit a very narrow degree of spectral tuning, each responding only to a narrow band of wavelengths.
does V4 represent individual colours and hues?
yes
So V4 no longer represents the opponent channels seen lower down the pathway, but deals instead with individual colours or hues.
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 ….
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.
which pathways best repsond to
spectral reflectance
detecting colour boundaries
Lack of an individual cone pigment in ______ (red), ______ (green), or ______ (blue) results in dichromatic colour vision.
Lack of an individual cone pigment in protanopia (red), deuteranopia (green), or tritanopia (blue) results in dichromatic colour vision.
make sure you understand this:
contrast cells in V1 and V4
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.
fat
mamba
boy thasta. tough fecking deck
