Ch 6: What is visual perception Flashcards
lower-order visual information
perception of color
higher-order visual information
recognising objects
Cones
Color perception
short wavelength –> blue
medium –> green
long –> red
Rods
perception in the dark
more sensitive to light information
Magnocellular cells (M cells)
pass on motion related information
Parvocellular cells (P cells)
small receptive fields and mainly pass on information relating to color perception
What- route
occipital-temporal (ventral)
info from parvocellular system
recognition of objects and processing of color, shape and texture
Where-route
occipital-parietal (dorsal)
input from the magnocellular system
visuospatial processing, location of objects in space, guiding of visually controlled movements to these objects
apperceptive agnosia
the percept cannot be formed
associative agnosia
the formed percept cannot be associated with semantic knowledge
Visual acuity
measure of the smallest details a person can distinguish
Achromatopsia
only seeing pale or grey tones
Prosopagnosia
problems with face recognition and identification
akinetopsia
movement blindness
visual form agnosia
patient cannot recognise, match, copy or discriminate simple visual stimuli
ventral stimulation agnosia (integrative agnosia)
patient cannot merge the independent detached parts into one percept
color agnosia
not being able to categorise, name or recognise colours
brightness agnosia
the inability to recognise brightness
someone cannot see if light are on or off
object agnosia
patients cannot name objects and are even unable to organise objects from the same category on the basis of semantic knowledge
Blindsight
some people with loss of the visual field can still perceive visual stimuli in the blind field (unconscious)
demonstrated with the forced-choice paradigms
Visual illusion
distortion of the actual external stimulus
visual hallucination
no external stimulus present but you see something
Charles Bonnet Syndrome (CBS)
caused by an impaired transmission of visual information to the visual cortex –> patient sees thing that aren’t there.
Anton’s syndrome (anosognosia)
some patients that are cortically blind due to bilateral infarctions in the V1 deny their blindness and confabulate a very detailed visual world
