Visual Perception Flashcards
What did we study in relation to the structure of the eye?
The lens
The retina
Ganglion cells
What was studied in relation to depth perception?
Monocular cues
Binocular depth perception
What was studied in relation to vision in the brain?
Lateral geniculate nuclei
The primary visual cortex
Development of binocular stereopsis
Where are rods and cones located?
In the retina
What muscle controls the lens?
The cilary muscle
What is the soft outer coating of the eyeball called?
The cornea
What is the point of central focus called?
The fovea
What is the path of light through the different parts of our eye?
Cornea > pupil > lens > retina
What does the iris do?
Expand and contract the pupil to regulate the amount of light that can enter
When the target is near in focus the lens is __________ and _______ and the iris ________.
Shorter and thicker
Expands
When the target is further away in focus the lens is __________ and _______ and the iris ________.
Taller and thinner
Contracts
What is near sightedness called?
Myopia
What is far sightedness called?
Hyperopia
What is myopia?
When the light doesn’t reach the retina (focused too early)
What is hyperopia?
When the light goes beyond the retina (focuses too late)
What can you use to correct myopia?
Concave lenses
What can you use to correct hyperopia?
Convex lenses
What is the retina?
The light sensitive membrane at the back of the eye that contains photoreceptors
What is the blind spot?
Where the optic nerve exits the eye (on the retina)
How many photoreceptors does the retina contain?
100 million
What are the two types of photoreceptors?
Rods and cones
What are cones responsible for?
Daylight vision
Colour
Visual acuity
Where are cones located?
At the centre of the foveal
Less near the periphery
Each cone cell synapses onto its own ?
ganglion cell
What are rods responsible for?
Night vision
Periphery vision
More than one rod converges onto the same ganglion cell. How does this affect our vision?
Less precision
More sensitively to light (when there isn’t much) so we can see in the dark
What is a ganglion cell?
A retinal cell that receives visual information from photoreceptors and transmits to the brain
What was studied in relation to visual perception?
The structure of the eye
Depth perception
Vision in the brain
How many ganglion cells are there?
100x fewer than photoreceptors
How often do ganglion cells fire?
Spontaneously at a regular resting rate
When does the firing rate change of a ganglion cell?
When light hits it’s receptive field
What are the receptive fields of a ganglion cell called?
Centre-surrounded and either:
On-centre
Off-centre
What’s the difference between on- centre and off-centre ganglion cells?
On-centre: when light hits the middle firing rate is FACILITATED
Off-centre: when light hits the middle firing rate is INHIBITED
What is the grid (visual illusion) called where you can see black dots in the intersections between a grid of black boxes?
Germans grid
What two processes give us 3D vision?
Monocular depth cues
Binocular depth perception
What are 6 monocular depth cues?
Occlusion Relative size and position Height cues Aerial perspective (haziness) Linear perspective Accommodation
What is occlusion?
Assuming things are further away when they are behind
What is accommodation?
When something is blurry it can be assumed it’s super close or super far away
What is binocular disparity?
Not receiving the same information from both eyes because each has slightly different visual fields
What is it called when can perceive depth because of binocular vision?
Stereopsis
What is the size of the angle both eyes can see at the same time?
110-120 degrees
The circle which can be drawn between the focal point and the sides of our eye when focusing is called the?
Horopter (or the Vieth Mueller Circle)
What is said about any point that falls on the Horopter?
It will cast the same image on one retina as it does on the other
When the object is closer than the Horopter it is called ?
Crossed disparity
When the object is further away than the Horopter it is called ?
Uncrossed disparity
What is used in binocular stereopsis to determine the depth?
Disparity magnitude (crossed = less disparity, or uncrossed = more disparity)
What is the effective that happens with your eyes when disparity is either crossed or uncrossed.
Crossed disparity = cross eyed = 3D
Uncrossed disparity = parallel viewing = 3D
What is it called when you see 3D images from either parallel viewing or viewing two similar, adjacent images cross eyed?
Free fuse
When each eye revives two different kinds of information, which stimuli is more likely to be dominant?
More interesting stimuli: More salient (brighter, more contrast, moving) More meaningful
What does LGN stand for?
lateral geniculate nuclei
What does the LGN do?
All 4 LGNs act as relay stations from the eye to the cortex (each responsible for one half of each eye)
What does each side of the visual cortex process?
Left visual cortex = processes right visual field
Right visual cortex = processes left visual field
So both LGN axons cross sides?
No, the axons closest to the nose cross but the axons closest to the ears don’t cross
What is cortical magnification?
Where the information coming from near the fovea is given more space in the brain than the periphery is given for processing
When does binocular vision develop?
3-5 months
