| what are the 2 visual receptor cells in the retina? | cones
rods |
| what is the function of the cone receptor? | colour and detail perception
mostly located in the fovea |
| what is the function of the rod receptor? | vision in dim light
located in the periphery |
| what is the function of the ganglion cells? | ganglion cells receive input from a few cones or hundred rod signals from the optic nerve to the LGN (Lateral geniculate nucleus ) |
| what is the Parvocellular (P) pathway? | sensitive to colour and fine detail - most input from cones |
| what is the Magnocellular (M) pathway? | most sensitive to motion - most input from rods |
| what is V1 and V2? | V1: primary visual cortex
V2: secondary visual cortex |
| what is the receptive field? | the area sensitive to the visual field |
| there are 5 Vs theorised for visual processing, what are they? | V1 and V2 = involved in basic visual processing
V3 = deals with forms of perception
V4 = deals with colour perception
V5 = processes motion perception |
| feature detectors in V1: | only certain neurons would fire at specific features on visual screen
measured cat's cortex
found some neurons reacted specifically to dots, lines, movement etc
suggests each element of visual field is broken down within the visual cortex stage |
| where does Form (shape) processing happen? | V1, V2, V3, V4 process object shape and form |
| Where does colour processing happen? | in the V4
research found more activation in V4 area when looking at colour clips |
| Where does motion processing happen? | V5 - ppts had TMS (magnetic stimulation) to disrupt V5 - ppts had an impaired ability to discriminate between different speeds |
| What is Feature integration theory? | selective attention plays a role
suggestion 1: binding-by-synchrony - features from single object fire in synchrony
suggestion 2: patterns of neural activity over time help coordinate binding |
| What is the dorsal pathway? | where something is
visual-for-action
processes spatial info to guide movement
egocentric (represents object in space relative to self)
short-lived representations
usually unconscious |
| what is the ventral pathway? | what something is named
vision-for-perception
identifies objects
allocentric (labelling of objects without reference to self)
sustained representation
usually conscious
input from the fovea (details from the cones) |
| What happens when there is dorsal stream damage? | Optic Ataxia: poor guided movement |
| What happens when there is ventral stream damage? | visual form agnosia (trouble naming visual forms) |
| perceptions of visual illusions | researchers found when pointing (using vision-for-action system) the illusion size 5.5%
when verbalising a response (using vision-for-perception system) the illusion size was 22% |
| Colour vision: what is the trichromatic theory? | the theory that there are 3 types of cones identified |
| opponent-process theory: | when some colours such as red and green, oppose one another in processing similarly with blue and yellow, and light and dark |
| what is dual process theory? | combination of the trichromatic and opponent process theory |
| what is colour constancy? | The tendency for an object/surface to appear to have the same colour despite change in wavelengths
i.e. blue mug is blue even if reflections on the mug show a different colour |
| what is depth perception and how do we do this? | being able to judge depth of an object
we do this by using:
linear perspective
texture
interposition - something is infront of other objects
shading
familiar size
image blur
motion parallax - when we move sideways and diff. objects move at diff speeds |
| what is Binocular disparity? | slight different in 2 retinal images |
| what is Size constancy? | Tendency for objects to appear the same size whether their size in the image is large or small |
