Vision

Question 1

Cornea

Answer 1

Consists of transparent cells that slightly refract the light passing through
Not adjustable

Question 2

Pupil

Answer 2

Opening in the center of the iris that allows light to enter the eye (aperture formed by the iris)

Question 3

Iris

Answer 3

Coloured portion of the eye

Question 4

Lens

Answer 4

Oval shape can be narrowed or widened by the ciliary muscle that surrounds the lens
Adjustable
Function is to focus the light optimally on the retina

Question 5

Vitreous Humour

Answer 5

Clear fluid which fills the chamber of the eye and gives the eye its firmness

Question 6

Retina

Answer 6

Rear surface of the eye, linked to visual receptors (photoreceptors)
Light from left side of world strikes right half of retina
Light from above strikes bottom half of retina
Like a computer: information that light is on upper left, but doesn’t have to be stored in upper left of computer

Question 7

Optic Disc

Answer 7

Blind spot
Blood vessels and axons from retinal cells exit the eye
No photoreceptors on this disc

Question 8

Reasons For Increase In Myopia

Answer 8

Genetics (maybe)
Book/screen time (maybe)
Bright light influences biochemical processes involved in the development of the eye
If children are not exposed to enough light, their eyes become misshapen, leading to myopia

Question 9

Fovea

Answer 9

Tiny area specialized for acute, detailed vision
Central portion of retina
Blood vessels and ganglion cell axons are almost absent near fovea, so it has nearly unimpeded vision
Tight packing of receptors aids perception of detail
Better acuity (sensitivity to detail)
Good colour vision
Each receptor connects to single bipolar cell which connects to single ganglion cell with axon to brain

Question 10

Midget Ganglion Cell

Answer 10

Ganglion cells in fovea
Small and responds to just a single cone
Provide 70% of input to brain
Vision is dominated by what is seen in and near the fovea

Question 11

Rods

Answer 11

Respond to faint light
Not useful in daylight because bright light bleaches them
Abundant in periphery of retina
Situated in pigment epithelium

Question 12

Cones

Answer 12

Essential for colour vision
More useful in bright light
Abundant in and near the fovea
Situated in pigment epithelium

Question 13

Photopigments

Answer 13

Chemicals that release energy when struck by light

Question 14

Opponent Process Theory

Answer 14

Perceive colour in terms of opposites
Explains kickbacks of visual perception
Brain has a mechanism that perceives colour on a continuum (pairs) from red to green, another from yellow to blue, and another from white to black
If you stare at one colour in one location for long enough, you fatigue that response and switch to the opposite (e.g. stare at green for too long, look to white you see red)

Question 15

Colour Contrast

Answer 15

Regions emitting the same wavelength of light are perceived as having different colours

Question 16

Colour Constancy

Answer 16

Regions emitting different wavelengths of light are perceived as having the same colour

Question 17

Retinex Theory

Answer 17

Explains colour constancy
Perceive the brightness of an object by comparing it to other objects
Brain compares the colour of one object with the colour of another to subtract the result
Cortext compares information from various parts of the retina to determine the brightness and colour for each area
White and gold vs black and blue dress
Take away surrounding information and they become the same colour in either picture

Question 18

Colour Vision Deficiency

Answer 18

Colour blindness
Results because people with certain genes fail to develop one type of cone or develop an abnormal type of cone
Red-green colour deficiency (most common, more in men)

Question 19

Lateral Inhibition

Answer 19

Reduction of activity in one neuron by activity in neighbouring neurons
Retina’s way of sharpening contrasts to emphasize the borders of objects

Question 20

Receptive Field

Answer 20

Area in visual space that excites or inhibits it (area of space a cell responds to)

Question 21

Feature Detectors

Answer 21

Neurons whose responses indicate the presence of a particular feature

Question 22

Retinal Disparity

Answer 22

Discrepancy between what the left and right eyes see
Required for stereoscopic depth perception
Experience fine tunes binocular vision and abnormal experience disrupts it

Question 23

Strabismus

Answer 23

Condition when eyes don’t point in same direction (attend to one eye and not the other)
Treatment generally is to put patch over good eye to work on bad eye
Works best when begun early but most refuse to wear it for as long as needed
Second treatment to use 3D video games that require attending to both eyes
Neither procedure has effect on stereoscopic depth perception

Question 24

Astigmatism

Answer 24

Blurring vision for lines in one direction
Caused by asymmetric curvature of the eyes

Question 25

Ventral Vision Stream

Answer 25

The ‘what’ pathway
Important for identifying and recognizing objects
Through temporal cortex
Responsible for processing object form, colour, and object identification
Part of brain is responsible for perception of colour
Parahippocampal place area and fusiform face area

Question 26

Parahippocampal Place Area

Answer 26

Spatial awareness and spatial memory
Ventral Stream

Question 27

Fusiform Face Area

Answer 27

Recognizing things we have expertise in

Question 28

Dorsal Stream

Answer 28

The How pathway
Important for visually guided movements
Action pathway
Through parietal cortex
Responsible for processing object movement and location, as well as visually guided action

Question 29

Patient DF

Answer 29

Use vision to guide actions but cannot identify the objects
Carbon monoxide exposure damaged ventral stream
Can walk around room but can’t say where objects are

Question 30

Damage To Dorsal Stream

Answer 30

Problem using vision to control certain arm/leg movements
Cannot reach out to grasp object
Describe where walking but bump into things

Question 31

Visual Agnosia

Answer 31

Inability to recognize objects despite otherwise satisfactory vision
Common result from temporal lobe damage

Question 32

Prosopagnosia

Answer 32

Impaired ability to recognize faces
Damage to fusiform gyrus

Question 33

Optic Ataxia

Answer 33

Issues with dorsal stream
Problems with visually guided reaching
Especially for objects in periphery

Question 34

Akinetopsia

Answer 34

Motion blindness
Better at reaching for moving object than describing its motioon
Can’t pour liquids

Question 35

Trichromatic Theory

Answer 35

Compare responses from three cone types to figure out colour
Short (blue), medium (green), long (red)

Question 36

How is a rod photoreceptor affected in light vs. dark

Answer 36

Light: rod releases less glutamate at synapse with bipolar cells (hyper polarized)
Dark: rod releases more glutamate at synapse with bipolar cells (depolarized)
Reverse is true for cone, because it works well in light

Question 37

ON Bipolar Cell

Answer 37

Connected to cone
Depolarized in light
Hyperpolarized in dark
Light activates the cell

Question 38

OFF Bipolar Cell

Answer 38

Connected to rod
Depolarized in the dark
Hyperpolarized in the light
Dark activates the cell