Vision

Question 1

sensation

Answer 1

registration of physical stimuli from the environment by the sensory organs

Question 2

perception

Answer 2

the interpretations of sensations by the brain

Question 3

law of specific nerve energies

Answer 3

activity by a particular nerve always conveys the same type of info to the brain.

Question 4

what is light?

Answer 4

Range of electromagnetic energy that is visible to humans:
-about 400 nanometers (violet) to 700 nanometers (red)
-nanometer (nm): one-billionth of a meter

Question 5

blind spot:

Answer 5

region of retina without photoreceptors (optic nerve, blood vessels)

Question 6

fovea

Answer 6

specialized centre of retina specialized for high acuity

Question 7

myopia

Answer 7

Inability to bring distant objects into clear focus
Focal point of light falls short of the retina

Question 8

hyperopia

Answer 8

Inability to focus on near objects
Focal point of light falls beyond the retina

Question 9

presbyopia

Answer 9

Common form of hyperopia seen in older adults.

Question 10

rods

Answer 10

Sensitve to low levels of light (dim light)
Used mainly for night vision
One type of pigment only

Question 11

cones

Answer 11

Highly responsive to bright light
Specialized for color and high visual acuity
Located in the fovea only
Three types of pigment (RED, GREEN, BLUE)

Question 12

phototopic

Answer 12

“Bright lights vision”
High acuity
Low sensitivity with few receptors
Low convergence
Fovea
Cones (RGB)

Question 13

scotopic

Answer 13

dark/dim vision
Low acuity
High sensitivity with many receptors
High convergence
Periphery
Rods (only one pigment)

Question 14

colourblindness

Answer 14

Genetic: sex-linked (X-chromosome)
5-8% of males are colourblind
0.5% of females are colourblind
Red-green colour blindness is more common than blue-yellow colourblindness
Result of some kind of anomaly in cones (e.g., low number or a complete lack of a particular cone)

Question 15

trichromacy

Answer 15

Explanation of colour vision based on the coding of three primary colours: red, green, blue
Color we see is determined by the relative responses of the different cone types.
Pro: can explain different types of colorblind
Con: cannot explain afterimages

Question 16

opponent-process theory

Answer 16

Emphasizes the importance of opposite colours
Red-green continuum
Blue-yellow continuum
Opponent processing in retinal ganglion cells
on-off/center-surround receptive fields
Approx. 60% of retinal ganglion cells

Question 17

colour/brightness constancy

Answer 17

the ability to recognize colour/brightness despite changes in lighting is not easily explained by these theories

Question 18

retinex theory

Answer 18

suggests the cortex compares info from various parts of the retina to determine the brightness and color for each area

Question 19

magnocellular cell (M cell)

Answer 19

magno= large body
Receives input primarily from rods (evenly distributed throughout the retina)
Sensitive to light and moving stimuli

Question 20

parvocellular cell (P-cell)

Answer 20

parvo= small body
Receives input primarily from cones (mostly foveal)
Sensitive to colour

Question 21

geniculostriate system

Answer 21

Projections from the retina to the lateral geniculate nucleus to the visual cortex (striate cortex, primary visual cortex, V1)

Question 22

tectopulvinar system

Answer 22

Projections from the retina to the superior colliculus to the pulvinar (thalamus) to the parietal and temporal visual areas.

Question 23

dorsal visual stream “how”

Answer 23

Originates in the occipital cortex and projects to the parietal cortex
Action pathway- grasping, reaching, etc

Question 24

ventral visual stream “what”

Answer 24

Originates in the occipital cortex and projects to the temporal cortex
Object recognition

Question 25

optic ataxia

Answer 25

Difficulties making reaching movements, but otherwise normal vision

Question 26

visual agnosia

Answer 26

Difficulties with recognizing objects, but otherwise normal vision.

Question 27

medial pulvinar

Answer 27

projects to the parietal lobe

Question 28

lateral pulvinar

Answer 28

projects to the temporal lobe

Question 29

striate cortex

Answer 29

Cellular oganization that represents a functional unit
6 cortical layers deep and aprox. 0.5mm2
Information from each LGN is sent to adjacent cortical columns, thus maintaining the separation of into from each retina.

Question 30

occipital (visual) cortex

Answer 30

At least 6 different visual reasons

Question 31

primary visual cortex (V1)

Answer 31

Striate (striped) cortex
Receives input from the LGN (thalamus)

Question 32

extrastriate cortex

Answer 32

Visual cortex areas outside the striate cortex

Question 33

receptive fields

Answer 33

Region in the visual world that stimulates a receptor cell or neuron
Ganglion cells have RF on the retina
Coding location: light shone in one place on the retina will activate one ganglion cell, and light shone in another place will activate a different ganglion cell.

Question 34

topographic map

Answer 34

Neural representation of the external world
Cells in the LGN and in the cortex also have RFs
More cortical tissue is devoted to cells in the fovea than in the periphery.

Question 35

retinal ganglion cells

Answer 35

respond simply to the presence or absence of light in their receptive field; there is no coding of shape
Center-surround mechanism
On-center cells
Off-center cells
Retinal cells code edges, what about V1?
Primary Visual Cortex (V1)
Cells in V1 detect orientations
Excited by bars of light oriented in particular directions

Question 36

simple cells

Answer 36

RF has a rectangular on-off arrangement
- The more light that shines in the excitatry zone, the more the cell responds.
The more light that shines in the inhibitory zone, the less the cell responds.

Question 37

complex cells

Answer 37

Maximally excited by bars of light moving in a particular direction through the RF

Question 38

hypercomplex cells

Answer 38

Maximally responsive to moving bars but theu also have a strong inhibitory area at one end of its RF.

Question 39

temporal cortex

Answer 39

Maximally excited by complex visual stimuli (e,g, faces, scenes, houses)
Neurons in the temporal lobe alter their preference with experience (expertise)
Temporal cortex: respnods to objects (e.g. faces) when they are consciously recognized.