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Psychology > Vision > Flashcards

Flashcards in Vision Deck (50):
1

Light

the stimulus
detected they eye, where the initial stages of processing are taken care of, then the result is sent to the brain for further processing

2

Variations in light waves

Amplitude
Wavelength
Purity

3

Amplitude

height of each wave
-variations affect brightness
-the bigger it is, the more light is being reflected or emitted

4

Wavelength

distance between peaks of successive waves
-variations affect perceptions of colour
-measured in nanometers
-larger = lower frequency; smaller = higher frequency

5

Visible Spectrum

the tiny position of the total range of wavelengths of the electromagnetic radiation that humans are sensitive to (360nm-750nm)
-some animals see other spectrums

6

Purity

affects perception of saturation
-light that is made up of a single wavelength is pure. We typically see a mixture of wavelengths and they are less intense than pure colour

7

Cornea

begins focusing process when light passes through
-transparent window out front of eye

8

Sclera

tougher membrane that covers rest of eye

9

Pupil

processes light after cornea
-round window (black dot)

10

Iris

controls size of pupil
-coloured part of the eye
-consists of a band of muscles controlled by the brain
-dilate pupil to allow more light
-constrict pupil to restrict light

11

Lens

processes light after pupil
-final focusing
-curvature causes images to land on the retina upside down and reversed left to right (the brain corrects this)
-flexible piece of tissue whose shape can be altered by surrounding muscles

12

Lens Accomodation

the lens can change shape to focus on object that vary in distance
-fatter/rounder for close objects
-flatter/elongated for far away objects

13

Vitreous Humor

light passes through after lens
-clear, jelly-like substance that comprises the main chamber inside the eyeball

14

Retina

light finally lands here
-natural tissue that lines back of eye
-made up of complex network that neural cells arranged in 3 layers

15

3 Layers of Retina

Ordered in an inside out fashion based on nutrition requirements of different cells
Photoreceptors
Bipolar Cells
Ganglion Cells

16

Photoreceptors

translate the physical stimulus of light into a neural signal that the brain can understand
-light must pass through other layers first

17

Retinal Pigment Epithelium (RPE)

provide nutrients for photoreceptors and located at back of eye (which is why the layers are arranged backwards)

18

Rods

125 Million
lower light intensities
night vision
no colour, poor visual acuity, concentrated surrounding fovea/periphery

19

Cones

6 Million
day vision
colour, good visual acuity, concentrated in fovea

20

Ganglion Cells

collect info from larger segment of retina
-axons of these cells converge at optic disk
-leave optic nerve which travels to brain

21

Blind Spot

area of the eye where the optic nerve leaves - there are no photoreceptors

22

Bipolar Cells

receive info from photoreceptors and send it to ganglion cells

23

Horizontal and Amacrine Cells

cells in the retina that allow areas in the retinal layer to communicate with each other
-allow info from adjacent photoreceptors to combine their info - cones and rods converge to travel along only one million

24

Receptive Field

collection of rods and cones in the retina that, when stimulated, affects the firing of a particular ganglion cell
-photoreceptors get divided into groups that get assimilated into one signal that affects a ganglion cell down the line

25

Visual Fields

right and left halves of our visual fields are processed by contralateral sides of the brain
-sends info to both eyes which are then received by both hemispheres
-right visual field = left hemisphere
-left visual field = right hemisphere

26

Optic Chiasm

the point at which the optic nerves form the inside half of each eye cross over to the opposite hemisphere

27

Main Pathway

when each visual field arrives in respective hemisphere after optic chiasm, optic nerves split and travel along 2 pathways
-most retinal/ganglion cells travel along main pathway and synapse in LGN

28

Lateral Geniculate Nucleus (LGN)

part of thalamus that receives visual information

29

Primary Visual Cortex

made up of areas in occipital lobe and processes visual info after LGN
-cells here are made up of receptive fields of LGN cells (made up of receptive fields of ganglion cells)
-area V1 on occipital lobe
-striate cortex

30

Extrastriate Cortex

occipital lobes V2-V5
-visual processing areas in occipital lobe outside of striate cortex

31

Topographical Organization in Visual Cortex

retinal coordinates are topographically mapped in visual cortex
-neighbouring locations in retina project to neighbouring location in visual cortex

32

Processing Streams of Extrastriate Cortex

processed visual info is sent out and separated into either the Dorsal or Ventral stream
-info is compressed as it travels along pathways

33

Dorsal Stream

"where" pathway
-depth and motion
-to parietal lobe

34

Ventral Stream

"what" pathway
-color and gorm
-to temporal lobe

35

Evolution of the Eye

new adaptations being layered upon old adaptations
-may have started out as a light sensitive patch
-may have mutated which caused a slight depression (allows light to be sensed)

36

Crude Lens

an early adaptation of the eye
-allows visual input at different distances
-allow better focusing and accommodation

37

Cumulative selection

evolutionary process whereby new adaptations are layered upon old adaptations

38

Cost Effectiveness of the Eye

benefits must outweigh the costs
-eyes are metabolically expensive
-has many evolutionary advantages

39

Evolutionary Advantages of the Eye

in most environments, vision makes it easier to find food, water, shelter, a mate, avoid predators/dangers

40

Factors that influence Variance among Species

do they live in an area with light or nah?
does the food come from above or below?
movement, shape and colour of prey

41

Compound Eyes

anthropods
-arrangement of individual tubular units called ommatidia that each point in a slightly different direction
-to gather light that lies directly in front
-form a single image by putting together many separate signals from each ommatidium
-good at detecting movement at close distances

42

Simple Eyes

vertebrates and molluscs
-eyeball, lens, retina
-vary according to environment (shape and orientation of pupil, size of eye, location of eye on head)

43

2 Functions of the Eye

Resolution (acuity)
Sensitivity (ability to get enough light)

44

Larger Eyes

better at both functions of the eye
-this benefit varies as some species need better resolution in the day and some need better sensitivity at night

45

Laterally Directed Eyes

on side of head = large total view, two separate fields of view
-poor depth perception (for avoiding predators)

46

Eyes Facing Front

narrow total view, single field of view = good depth perception (good for hunting)

47

Development in Visual Architecture

least developed at birth
formed at second prenatal month
reacts to light random firing of retinal cells at 6th prenatal month

48

At Newborn

weak lens muscles, single field of view, inconsistent pupil reactions, low cell density in retina (especially in fovea)
-dismal visual acuity

49

3 Months

adult-like focusing

50

11 years

Visual brain area development complete