Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Fundamentals of Neuroscience > Lecture 13/14 Visual Systems > Flashcards

Lecture 13/14 Visual Systems Flashcards

1
Q

which 2 key properties of sensory systems foes the motion after-effect/waterfall illusion illustrate?

A

feature detection and adaptation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

overall, what does the visual system aim to do?

A

to build a predictive model of the external world based on incidental light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is transduction in the context of vision?

A

light (electromagnetic radiation) being converted into neural pulses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

which wavelengths make up those the eye is sensitive to?

A

380-760nm (visible light)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Overall, what does the eye do?

A

begins the process of filtering out information and putting it into useful form by controlling light entering eye and ensuring it is sharp on the retina and transducing signals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

describe the iris

A

a donut shaped band of contractile tissue that regulates the amount of light that reaches the retina by adjusting the size of the pupil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

why does the pupil appear black?

A

it absorbs almost all wavelengths of visible light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

describe what happens to the iris in the dark?

A

its muscle relaxes, more light enters eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

is sensitivity greater or worse in the dark?

A

greater

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

is acuity greater or worse in the dark?

A

worse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

why is acuity worse in the dark?

A

pupil increasing so greater area of light projection, with more overlap- so blurry image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what happens when bright light is shined in the eye?

A

the iris contracts and the pupil constricts. Less light enters the eye (but sharper image on retina- improved acuity).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

how does pupil size change with age?

A

reduces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

if pupil size reduces with age, how does this affect adaptation to low light?

A

it worsens it- reduced light sensitivity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe the cornea?

A

transparent covering of the front of the eye, which, along with the lens, helps focus incoming light on to the retina (contributes to most of the eye’s focusing power)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

describe the lens

A

found behind the pupil, works with the cornea to focus light on retina
held in place by suspensory ligaments called zonules
the lens can change shape to change focal distance- accommodation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

define accommodation

A

whereby the lens changes shape to maintain clear image focus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what happens when the lens is rounder/thicker and what distance does it accommodate?

A

it bends light more, reducing focal distance for near image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what happens when the lens is flatter/thinner and what distance does it accommodate?

A

it bends light less, increasing foal distance, far objects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

describe the retina

A

light sensitive tissue lining the back of the eye, containing layer of photoreceptive cells which transduce light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

name the 2 photoreceptive cells

A

rods and cones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

describe the optic disk

A

where axons and blood vessels from retina leave eye- no photoreceptors hence is a blind spot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

describe the macula

A

centre of retina with high concentration of photoreceptor cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

describe fovea

A

centre of the macula (which is itself centre of retina) with the highest concentration of photoreceptors- sharpest vision

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what does age-related macular degeneration cause?

A

loss of central vision

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

why is the object you are staring directly at seen in highest acuity?

A

the image is positioned on the fovea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what is the population of rods and cones on fovea

A

all cones, no rods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what proportion of nerve fibres in optic nerve are suppled by the fovea?

A

around 50%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

why does dim light, such as stars, disappear when you look directly at it?

A

no rods in fovea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

despite having a blind-spot behind the disc, why do we not perceive a blind-spot?

A

the brain uses completion using the information provided by surrounding receptors to fill in the gap

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what is the sclera?

A

the white of eye- tough protective connective tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what is the choroid

A

layer between retina and sclera- containing blood vessels which provide O2 and glucose to retinal cells and removing waste products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

why does taking flash photos of humans sometimes result in red pupils in the image?

A

reflection off light of the blood in choroid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

why does taking flash photos of nocturnal animals sometimes result in white reflective flash in pupils?

A

many nocturnal animals have reflective tissue layer called tapetum lucidum which bounces light back, giving it a second chance to hit photoreceptors (useful in dark environments)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what is the main theory as to why the layers of cells of retina are ‘back to front’?

A

to allow eyes to stay small- if other way round the eyes would need to be bigger to focus light on receptors

36
Q

what are the 3 main layers of retinal cells from back to front

A

back- photoreceptors
bipolar cells
front- retinal ganglion cells

37
Q

do rods and cones have similar or different structure?

A

similar

38
Q

describe the activity of rods cells in dark vs light

A

in dark, rhodopsin is inactive –> cyclic GMP is present keeping Na+ channels open –> cell depolarises –> releasing continual glutamate
in light, rhodopsin is activated–> leads to break down of cyclic GMP and Na+ channels close –> hyperpolarised –> reduced Glutamate release

39
Q

what level of light do rods best work in?

A

Scotopic (dim)

40
Q

do rod cells have a high or low convergence to bipolar cells?

A

high- many rods connected to one bipolar cell

41
Q

how does high convergence of rod cones to bipolar cells affect acuity and sensitivity

A

poor acuity, high sensitivity

42
Q

is rod vision coloured or monochromatic?

A

monochromatic

43
Q

is rod function involved more in central or peripheral vision

A

peripheral (as they are further on the sides of macula)

44
Q

what kind of light do cones function best in?

A

photopic (well-lit- think best light to take photos)

45
Q

do cones have high or low convergence with bipolar cells?

A

low- 1 to 1 relationship

46
Q

what does a low cone to bipolar convergence mean for acuity and sensitivity?

A

high acuity, low sensitivity

47
Q

what are the 3 types of cones?

A

red, green and blue

48
Q

are cones more responsible for central or peripheral vision?

A

central- in fovea

49
Q

how does having 2 or more photoreceptors allow colour vision?

A

allows differentiation between light intensity and wavelength

50
Q

what is happening in the eyes of someone with colour blindness

A

one of there cone-types is deficient, for example in red-green colour blindness the green cones have shifted towards red wavelength detection

51
Q

why do we move our eyes so much?

A

we have a small foveal area so we’re continuously scanning visual field to allow objects of interest to project onto our fovea

52
Q

what do bipolar cells do?

A

process input from photoreceptors and output to retinal ganglion cells
allow some low-level signalling processing to occur in retina with input of interneurons (such as horizonal and amacrine cells)

53
Q

what do retinal ganglion cells do?

A

they have input from bipolar cells (which have been inputted by photoreceptors)
they detect spots of contrasting illumination

54
Q

how was lateral inhibition first identified?

A

studies into horseshoe crab which contain visual receptors called ommatidia. They found that the axons in ommatidia were connected by a lateral inhibitory neural network
when light hits ommotidia, they fire at a rate proportional to intensity of light
the more they fire, the more they inhibit their neighbours- lateral inhibition

55
Q

what causes contrast enhancement in Mach bands

A

lateral inhibition

56
Q

describe the Hermann grid and how it exhibits lateral inhibiton

A

bright white grid with black background
grey blobs appear at intersections
disappear when close/foveated
the grey blobs are due to lateral inhibition of the cells inhibiting the central cell where white lines intersect
they disappear when you foveate because the fovea has a small receptive field so surround inhibition doesn’t produce grey blobs

57
Q

how does lateral inhibition affect relative difference?

A

it amplifies it

58
Q

what are the 3 important classes of projection from the eye?

A

Pretectal, superior colliculi and lateral geniculate

59
Q

at the optic chiasm, where does information from the right visual field go?

A

left

60
Q

describe projections to the pretectal area and the pupillary reflex

A

projections to the brainstem pretectal nuclei are responsible for reflex including pupillary control
light shined on one eye causes pupillary constriction in both eyes as it sends AP to left and right pretectal areas which go on to stimulate both sides on Edinger-Westphal nucleus, generating APs through both left and right oculomotor neurons- both pupils constrict

61
Q

if one pupil constricts and the other doesn’t when light is shined, what could this mean?

A

brain damage in this pretectal pathway

62
Q

describe projections to the superior colliculus

A

an evolutionarily ancient pathway- preserved in reptiles etc. which causes an animal to turn head towards/away from change in visual world
signals down retinotectal pathway
involved in survival and behaviour
superior colliculus has a basic retinotopic spatial topographic map

63
Q

briefly describe the retino-geniculate striate (lateral geniculate pathway)

A

from retina to layer IV of the primary visual cortex (V1) via lateral geniculate nuclei of thalamus

64
Q

describe the spatially organised retinopic projection

A

through the retina and thalamus, they are organised according to a spatial map of the retina so 2 stimuli presented in adjacent regions of retina (visual field) excite adjacent neurons at all levels

65
Q

is the visual field proportional to the space used in the V1?

A

no- around 25% of V1 analyses input from the fovea

66
Q

which parts of the eyes does the right primary cortex receive information from?

A

temporal right eye and nasal left eye (which are looking at left visual field)

67
Q

what cells make up the lateral geniculate nucleus?

A

magnocellular (m) and parvocellular (p)

68
Q

describe parvocellular layers

A

small cell bodies
responsive to colour (input from cones), stationary/slow objects
OBJECT IDENTFICATION

69
Q

describe magnocellular layers

A

large cell bodies, responsive to luminance, change/movement, majority input from rods

70
Q

what brain region does the magnocellular layer have some function redundancy with?

A

superior colliculus (movement/light)

71
Q

what is a receptive field

A

the area of the visual field that a visual neuron is influenced by (decrease or increase in firing rate)

72
Q

what did Hubel and Weisel find studying the V1 of cats regarding receptive fields?

A

there is little change in receptive fields along pathway
but 4 commonalities:
- receptive fields of neurons representing foveal area were smaller than periphery
- they were circular
- they were monocular
- they had receptive fields that comprised and excitatory and inhibitory area

73
Q

do V1 neurons respond to small visual spots like retinal/thalamic neurons?

A

no

74
Q

what do V1 neurons respond to?

A

contrast of light/dark at specific orientation

75
Q

what 2 categories do most V1 neurons fall into?

A

simple an complex

76
Q

describe simple cells

A

antagonistic on/off regions with straight borders- best respond to bars of light at specific orientations and locations in visual field

77
Q

describe complex cells

A

more common (75% V1) respond to straight edge stimulus at a particular orientation- regardless of position

78
Q

what are the 2 columns in cortical organisation?

A

orientation columns
occuluar dominance columnsd

79
Q

describe orientation columns

A

responsive to a progressive range of line orientations

80
Q

describe ocular dominance columns

A

for each eye to allow 3D processing

81
Q

what’s V2?

A

similar to V1 but more complex shape characteristics

82
Q

what’s V3 do?

A

involved in form/motion/depth

83
Q

what’s V4 do?

A

involved in colour/form/attention

84
Q

what’s V5 do?

A

involved in motion

85
Q

describe the ventral stream

A

travels in temporal lobe
scene analysis and object identification
what streamdes

86
Q

describe the dorsal stream

A

travels in parietal lobe and processes spatial locations (where stream)

Fundamentals of Neuroscience (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions