S2W3 - Vision Flashcards
(29 cards)
Characteristics of rods
Perceive dim light; scotopic; no colour perception; many grouped onto a retinal ganglion cell
Characteristics of cones
Perceive bright light; photopic; colour perception; single cone connected (indirectly) to retinal ganglion cell
Which area has only cones and no rods?
The fovea
Where is the blind spot, and why can’t we see it?
Where the optic nerve is; No retinal receptors in that area; Our brains “fill in” that gap in our vision with previous knowledge
3 main types of cells in the retina
Receptor (rod and cone); Bipolar: Retinal Ganglion
Characteristics of amacrine cells
Receive information from bipolar cells and interact with bipolar and retinal ganglion cells
Characteristics of horizontal cells
Receive information from receptors and adjust signals sent to bipolar cells, also regulate activity in the receptors
Pathway from the eye to V1
Optic nerve; optic chiasm; optic tract; thalamus, lateral geniculate nucleus; optic radiations; V1
Achromatopsia
damage to V4; inability to (consciously) perceive colour with no damage to the cones in the eye
Akinetopsia
damage to V5; inability to perceive (consciously) perceive motion; motion appears as a series of static images
What degree do you find the most rods?
20˚ on the nasal and temporal side
What degree range is the blind spot?
~12-18˚ on the nasal side
Purkinji effect
Scotopic vision peaks at 560nm ∫, photopic peaks at 500nm ∫, therefore, green/blue light appears brighter in dim light and red/yellow light appears brighter in sunlight
Trichromatic colour theory
We perceive only 3 colours, and interpret others from there
S, blue, 420nm ∫
M, green, 540nm ∫
L, red, 570nm ∫
Opponent process theory
Excititory and inhibitory cells interact to produce colours that are either one colour or its negative
Red/green vs blue/yellow
Rhodopsin (active)
Is a pigment molecule
Activates with scotopic vision; sodium channels close; rod becomes hyperpolarised; limits release of glutamate (which is inhibitory)
Dorsal stream (V)
Moves towards parietal lobe
“Where”
Control of behaviour
Ventral stream (V)
Moves towards temporal lobe
“What”
Conscious perception
Stereotopic Vision
Your left and right eye see two different images, but your brain combines into a single percept
Uncrossed disparity is
the point further from your focus
you must uncross your eyes to put it in focus
Crossed disparity is
the point nearer to you from your focus
you must cross your eyes to put it in focus
Pulfrich illusion
SETUP: Eyes follow a left to right oscillating object with a filter over one eye.
ILLUSION: You perceive the object as moving along a oliptical path (rather than straight path)
REASON: your filtered eye is delayed in following the object, and this misalignment results in a disparity that your brain will try to rectify with stereotopic vision
Motion parallax
As the amount you see increases by the distance squared, objects in motion that are further away appear to move slower than that which is closer
i.e. a moving object 5m from the face appears to be moving 4x faster than an object at 10m and 9x faster than an object at 15m (2^2 and 3^2, respectively)
Monocular Depth
being able to interpret depth with cues beside stereovision
