5&6. Vision and pattern recognition

Question 1

what is perception?

Answer 1

Awareness of the elements of environment
through physical sensation (Merriam-Webster)

Perception is not just receiving information
through sensation; it involves interpretation
and recognition of the information

Question 2

What are the types of perception?

Answer 2

• Visual
• Auditory
• Tactile (haptic)
• Olfactory
• Gustatory
• Object
• Space
• Time
• Speech
• Motion

Question 3

what is required for an object to be visible?

Answer 3

For an object to be visible it must either emit or

reflect light

Question 4

what is light?

Answer 4

One way of understanding light is that it is a wave of electromagnetic radiation
– It is a wave, so one dimension of light is its
wavelength

Question 5

what is the human eye capable of in regards to light?

Answer 5

The human eye is only capable of detecting light
within a narrow range of wavelengths
– Within this range of visible wavelengths, different wavelengths give rise to the perception of different
colors

Question 6

Within the human’s range of visible wavelengths, what do different wave lengths cause?

Answer 6

Within this range of visible wavelengths, different wavelengths give rise to the perception of different colors

Question 7

How does light vary?

Answer 7

Light also varies in intensity, leading to the

percept of brightness

Question 8

what do ciliary muscles do?

Answer 8

The ciliary muscles control
the shape of the lens to
accomodate near or far
targets

Question 9

what happens when the lense is round?

Answer 9

Far Blurred

Near in Focus

Question 10

what happens when the lense is flat?

Answer 10

Far in Focus

Near Blurred

Question 11

what is the retina?

Answer 11

A thin, light sensitive membrane located at the back of the eye

Question 12

what sensory receptors does the retina contain?

Answer 12

Contains two types of visual sensory receptors (cells

that convert physical input—i.e., light—into electrochemical signals): rods and cones

Question 13

what are the rods and cones connected to?

Answer 13

other cells

Question 14

what is the fovea?

Answer 14

a small area in the center of the retina, composed entirely of cones
• Where visual information is most
sharply focused

Question 15

What is the optic disk?

Answer 15

the area of the retina without rods or cones

Question 16

what do rods look like??

Answer 16

– long, thin, and blunt

– primarily for peripheral and night vision

Question 17

what are rods highly sensitive to?

Answer 17

– highly sensitive to light, but not to color

Question 18

what are the rods used primarily for?

Answer 18

– primarily for peripheral and night vision

Question 19

what do cones look like?

Answer 19

short, thick, and pointed

Question 20

what do cones do?

Answer 20

detect color

for color vision and visual acuity

Question 21

what do rods and cones do?

Answer 21

Rods and cones convert light energy into
electrical energy via a photopigments (chemicals
that absorb light)

Question 22

what are photopigments responsive to?

Answer 22

Different kinds of photopigments are responsive
to different wavelengths of light
– That is, different kinds of photopigments “see”
different colors

Question 23

why cant rods provide colour information?

Answer 23

There is just one kind of photopigments in rods
(called rhodopsin)—that’s why signals from rods don’t
provide color information

Question 24

what are the photopigments in cones?

Answer 24

Photopigments in cones (called iodopsin) come in

three variations

Question 25

what do variations in the photopigments in cones sensitive to?

Answer 25

Each variation is sensitive to a different range of wavelengths – Thus, each variation is tuned to a different range of colors

Question 26

how do rods and cones have different levels of acuity?

Answer 26

More rods than cones synapse with each ganglion | cell

Question 27

what are the two major pathways from the retina to the brain?

Answer 27

– retina --> lateral geniculate nucleus (LGN) --> V1 (primary visual cortex in the occipital lobe) – retina --> superior colliculus (SC) (and pulvinar nucleus)

Question 28

what function does the LGN-V1 pathway serve?

Answer 28

conscious aspects of vision (e.g., object recognition)

Question 29

what function does the SC pathway serve?

Answer 29

unconscious visual functions (e.g., object localization)

Question 30

What is blindsight?

Answer 30

some people with damage to the LGN-V1 pathway can still react to visual stimuli (e.g. point tonthem) although they claim that they cannot see them!

Question 31

what do neurons in the V1 respond to?

Answer 31

Neurons in V1 respond to bars of a particular | orientation

Question 32

what does V1 stand for?

Answer 32

the primary visual cortex

Question 33

what areas are involved in visual imformation processing beyond the v1?

Answer 33

There are multiple visual areas in the cortex. Each area performs different types of computation

Question 34

what processing occurs in areas of the cortex that appear later in the information processing stream?

Answer 34

in areas that appear later in the information processing stream, neurons respond to more complex patterns

Question 35

what is our visual perception more closely related to?

Answer 35

Our visual perception is more closely related to neural activity in the higher visual areas

Question 36

what is the receptive field?

Answer 36

Area of the visual field to which a visual neuron responds It is very small in the beginning, but becomes increasingly larger in later stages of visual information processing

Question 37

What is visual information processing?

Answer 37

The visual world is broken down into small elements, | and then it is reconstructed

Question 38

What do ganglion cells do?

Answer 38

Ganglion cells receive input from multiple receptors that are adjacent to each other

Question 39

what do the two ganglion cells in the retina do to frorm a retinotopic map?

Answer 39

Two ganglion cells that are next to each other in the retina will have receptive fields that are also next to each other – Forming a retinotopic map

Question 40

What are the properties of neurons in the LGN?

Answer 40

Neurons in the LGN have similar properties – Center-surround antagonism – Retinotopic map (i.e., adjacent LGN neurons have receptive fields on the retina)

Question 41

How do cells and neurons respond in the LGN ?

Answer 41

ganglion cells and visual neurons in the LGN respond simply to the presence of a spot of light on the retina

Question 42

What are the characteristics and positioning of neurons in the V1?

Answer 42

– Receptive fields of two adjacent V1 neurons are still adjacent to each other on the retina – These neurons receive input from multiple LGN neurons • This enables V1 neurons to function as bar detectors

Question 43

What happens to visual neurons in higher order areas and what does this enable?

Answer 43

In higher order areas, neurons have larger receptive fields by combining input from multiple lowerlevel neurons This enables those higherlevel neurons to respond to more complex visual patterns

Question 44

What is agnosia?

Answer 44

Impairment of object recognition ability

Question 45

What processes are intact in agnosia patients and what does this cause?

Answer 45

In agnosia, processes such as color, shape, and motion perception are intact. This recognizing a whole object is more than just recognizing its parts

Question 46

What are the two cortical pathways for vision?

Answer 46

Ventral pathway | Dorsal pathway

Question 47

What is the ventral pathway, what information does it process and what is it important for?

Answer 47

– Occipital à temporal – Processes information about object appearance and identity – Important for object perception

Question 48

What is the dorsal pathway, what information does it process and what is it important for?

Answer 48

– Occipital à parietal – Processes spatial information about objects – Important for guiding action

Question 49

Who was patient DF?

Answer 49

– Severe agnosia | – Her visual acuity and nonvisual object recognition are intact

Question 50

What is optic ataxia and what is it associated with?

Answer 50

– Intact object recognition – Inability to use visual information to guide action – Associated with lesions in the dorsal pathway (typically in the parietal cortex)

Question 51

What does face perception require?

Answer 51

Face perception requires holistic processing

Question 52

What was the study on Larry with regard to face perception?

Answer 52

study phase – Larry had round eyes, a pointed nose, and a narrow mouth. – Larry lived in a house with a three-paneled door, shuttered living room window, and rounded bedroom windows. Test phase * picture of nose (part condition) and whole face (whole condition)* * picture of larry's door (part condition) and whole house (whole condition)* Results: Face condition - 65% correctly identified faces in isolated condition - 75% correct in whole condition House condition - 82% in islated condition - 80% in whole condition

Question 53

What is involved in the gestalt principles?

Answer 53

* Similarity * Closure * Good continuation * Proximity

Question 54

Wat do we tend to do in relation to template-matching and feature analusis?

Answer 54

We tend to recognize different stimuli as the same object (e.g., letter “A”) irrespective of superficial variation Gestalt principles don’t really help explain why Another theory of pattern recognition, template matching, doesn’t explain this either

Question 55

In the template-matching model what is good matching?

Answer 55

Good matching (successful perception) Slight difference between input and template (unsuccessful perception)

Question 56

How are visual patterns perceived and what model helps to explain this?

Answer 56

``` A visual pattern is perceived as a combination of elemental features – Selfridge’s pandemonium model ```

Question 57

What would happen when this pattern is presented on the retina without eye movements? (HB on top of eachother)

Answer 57

``` Whole features (e.g., an entire vertical bar) tend to disappear simultaneously ```

Question 58

What does the recognition by component theory suggest?

Answer 58

Similar mechanisms have been proposed for 3-D object recognition • An object is first segmented into a set of basic sub-objects (called geons), and then recognized as a pattern composed of geons

Question 59

what is the grandmother cell hypothesis?

Answer 59

If we keep going down the visual information processing pathway, can we eventually find a cell that responds to a very, very, very specific stimulus?

Question 60

what are the weaknesses of the grandmother cell hypothesis?

Answer 60

– The final percept of an object is coded by a single neuron • However, each neuron’s firing is not so reliable • If that neuron is lost, our perception of the corresponding object would be lost – Perception of novel objects cannot be explained well – Flexibility of object recognition cannot be explained well

Question 61

what is ensemble coding in the grandmother cell hypothesis?

Answer 61

Object recognition results from the firing of an ensemble of cells (ensemble coding)

Question 62

what has more recent evidence suggested about ensemble coding?

Answer 62

– More recent evidence suggests that grandmothercell- like neurons might exist (Quiroga et al., 2005) – But not necessarily in the visual object recognition system per se

Question 63

What is bottom up processing?

Answer 63

A? or H? | When the word CAT is presented by the top of the A is cut off to look like a H

Question 64

What is top-down processing?

Answer 64

recognising the entire word as CAT even though it is presented with the top of the A is cut off to look like a H

Question 65

what is the word-superiority effect?

Answer 65

Superior recognition of letters in a word context than alone – Indicates top-down influence on pattern recognition

Question 66

what is the phoneme-restoration effect?

Answer 66

Participants were presented with the sentence: “The state governors met with their respective legi…latures convening in the capital city.” Where the ... is 120 ms tone prelaced 's' • Only 1 in 20 participants reported hearing this tone – And this one participant was unable to locate the tone correctly