Brainscape's Knowledge GenomeTM

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


See full index

Brain & Behaviour > Lecture 9 - Vision > Flashcards

Lecture 9 - Vision Flashcards

You may prefer our related Brainscape-certified flashcards:
The Brain flashcards
1
Q

The Visible Spectrum

A

Light is electromagnetic energy.

One nm = one billionth of a meter

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

Properties of light

A
  • hue
  • saturation
  • brightness
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

hue

A

determined by wavelength.

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

saturation

A

relative purity of light.

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

brightness

A

variation in intensity.

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

Distance b/t 2 peaks =

A

wavelength

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

As wavelength increases, frequency _____

A

decreases

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

In order to see things in greatest detail our eyes are moved so that the object being looked at falls on the ____.

A

FOVEA

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

Fovea

A

is a central portion of the retina with the greatest visual acuity.

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

Cones

A

are responsible to BRIGHT light

are responsible for COLOUR vision & our ability to see FINE detail

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

Rods

A

are more NUMEROUS than cones & are more SENSITIVE to DIM light

are mainly used for NIGHT VISION

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

Photoreceptors

A
  • rods and cones contain photopigment that provides input to bipolar and horizontal cells.
  • photoreceptors and bipolar cells do NOT produce action potentials – instead release neurotransmitters to the ganglion cells.
  • ganglion cells connect with the optic nerve. (& travel out the back of the eye)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Blind spot

A

Optic disk – where the optic nerve joins the retina – transmits retinal information to the occipital lobes

(have blind spot in our eye but its masked by parts of our eye)

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

Blind spot

A

close your LEFT eye and move head closer to or further away from the screen until the central red circle disappears - always fixate the CROSS

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

Visual Fields

A

animals that tend to be prey (eyes on side of head) - have WIDE visual field (HAVE LARGE MONOCULAR FIELD)

animals that are hunters (eyes in front of head - concerned with whats in front of them)- have LARGE BInocular field

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

Visual Fields cross over

A

cross over @ optic chiasm

  • info from LEFT visual field ends up making its way to the RIGHT part of the brain
  • info from the RIGHT visual field ends up making its way to the LEFT part of the brain

CONTRALATERAL organization in visual system due to crossing over

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

Visual Field Temporal vs Nasal

A

TEMPORAL portion of LEFT visual field falls on the NASAL portion of the eye

NASAL portion of RIGHT visual field falls on the TEMPORAL portion of the retina

18
Q

Primary geniculostriate visual pathway

A

(main visual pathway for vision)

crossing over of NASAL & TEMPORAL sections

  • which is why in each eye, you can see diff. parts of the visual field are present

BLUE - LEFT visual field

  • falls on temporal portion of R eye & nasal portion of LEFT eye
  • LEFT eyes info crosses over to R side of brain in optic chiasm
  • RIGHT eyes info stays where it is & travels down the geniculate nucleus & through the optic radiations to the primary visual cortex

YELLOW - RIGHT visual field

  • goes to LEFT side of brain
  • info projects to nasal portion of RIGHT eye, but temporal portion of LEFT eye stays on LEFT while nasal portion of RIGHT eye crosses over & goes to lateral geniculate nucleus through optic radiations to primary visual cortex

CONTRALATERAL

19
Q

Primary Geniculastriate Pathway

A

main visual pathway

  1. retina
  2. optic nerve
  3. optic chiasm
  4. optic tract
  5. dorsal lateral geniculate nucleus (LGN)
  6. optic radiations
  7. striate (aka primary) visual cortex
20
Q

Lateral Geniculate Nucleus

A

The LGNd has six layers each of which gets independent input from either the left or the right eye but not both.

There are two major classes of projections, parvocellular (small) and magnocellular (large) projections (known as the P and M pathways).

21
Q

Lateral Geniculate Nucleus

There are two major classes of projections:

A

parvocellular (small) and magnocellular (large) projections (known as the P and M pathways).

22
Q

Magnocellular

A

Large ganglion cells

Centre/Surround

Colour insensitive

Large RFs (tend to be in the perifery)

Fast, transient (if something is coming toward, it picks it up)

High contrast sensitivity

23
Q

Parvocellular

A

Small ganglion cells

Centre/Surround

Colour sensitive

Small RFs

Slow, sustained (reading a book - keeping it still while looking at it)

Low contrast sensitivity

24
Q

Primary Visual Cortex

A

The LGNd projects to primary visual cortex (striate cortex or area V1) in the occipital lobe.

The magno and parvo projections are still somewhat segregated in V1.

25
Q

Retinotopic map in striate visual cortex

A

means ways your field maps out & falls onto your retina is represented as separate areas in cortex

fixation point - stuff falling on fovea/central vision (central vision)

small circle gets quite a bit of real estate devoted to it
- b/c that small circle of info is falling onto the fovea that’s packed full of high acuity receptors –> tons of info coming from that area so it needs a lot of processing power in the brain so it gets more area of the brain devoted to it

large part of lower visual field gets projected on a relatively smaller section of cortex
- b/c there’s bigger receptive fields in the periphery, fewer cells can cover a much larger area, so it takes less processing power, less real estate space then the v. small section of the visual field that’s covered by the fovea that has a ton of cells recording info from the space

BOTTOM PART OF VISUAL WORLD GETS MAPPED UP ON UPPER PART OF VISUAL FIELD & VV

26
Q

Retinotopic organization…

A

basically, the way are visual map is layed out in our retinal world, maps on to how its layed out across the brain

27
Q

Visual receptive fields

A
  • receptive fields of retinal ganglion cells correspond to specific regions in space – hence a retinotopic map of the world in the occipital cortex.
  • receptive fields in visual cortex also respond selectively to other stimulus properties (e.g., orientation, brightness).

piece of visual cortex
- if you were to stick an electrode down the orientation columns along the side, all of the cells in that column will all respond maximaley to a cell that’s oriented almost perfectly horizontantly, if you go next to it, all of the cells in that column will respond maximately to a cell that’s angled up more

therefore, cells are organized by the amount of excitation that they have to a partic. stimulus orientation

28
Q

Centre – surround organization

A
  • TUNING – different types of cells are “tuned” to respond to different aspects of visual information
    e. g., brightness, location, direction of motion, colour etc…
29
Q

Coding information at the retina - brightness

A
  • centre / surround ORGANIZATION
  • ON, OFF and OFF/ON cells
  • ON/OFF cells project primarily to the superior colliculus (midbrain)
  • the SC is important for directing reflexive saccades
30
Q

Coding information at the retina - colour

A

the 3 types of cones are called “blue,” “green,” & “red.”

these names loosely refer to the frequencies of light to which each cone is maximally sensitive (the peak sensitivities are 419, 531, & 559 nm respectively)

  • trichomatic sensitivity AND colour opponency
  • red – green
  • blue – yellow
  • on/off surround organization

impossibility of seeing a redish green colour!

31
Q

Adaptation – negative afterimages

A
  • after staring at the green Canadian flag you see a red one because the “green” component of red/green cells has adapted to the stimulus.
  • some red/green cells are inhibited for a long period.
  • when looking at neutral light (white light) these cells “rebound” due to the absence of inhibition creating the afterimage.
  • Big Spanish Castle
  • can get afterimages for motion – waterfall illusion .
32
Q

Striate cortex

A
  • 6 layers (bands or striations).
  • input from magno and parvocellular information processed at layer IV.
  • disproportionate representation of the fovea (brain would weigh over 30,000 pounds (≈13,600 kg) if the whole visual field had as many neurons dedicated to it as are dedicated to the fovea!!!).
33
Q

Orientation and movement

A
  • cells in striate cortex sensitive to specific orientations.
  • simple cells – opponent system.
  • complex cells – no inhibitory surround – direction specific movement detectors (also in MT).
  • cells organized in columns.
34
Q

Simple cells

A

opponent system.

35
Q

Complex cells

A

no inhibitory surround – direction specific movement detectors (also in MT).

36
Q

Spatial frequency

A

many of the cells in striate cortex are actually tuned to different spatial frequencies.

everything you see in the world can be described in terms of spatial frequency.

37
Q

Information not lost at low spatial frequencies

A

Gender and can still be extracted from the low frequency image (right) but identity requires the high frequency image (left).

38
Q

Modularity in vision

A

Different “modules” sensitive to different visual processes

V4 – colour
MT – motion
FFA – face perception
PPA – place recognition
IT – object recognition
39
Q

A unique feature of the fovea is that it

A) contains mostly rods.
B) contains mostly cone photoreceptors.
C) is devoid of photoreceptors.
D) mediates vision in dim light.
E) has very poor acuity.
A

B) contains mostly cone photoreceptors.

40
Q

The reason for a “blind spot” in the visual field is that

A) rods are less sensitive to light than are cones.
B) blood vessels collect together and enter the eye at the blind spot.
C) the lens cannot focus all of the visual field onto the retina.
D) retinal cells die with age and overuse, resulting in blind spots.
E) there are no photoreceptors in the retina where the axons exit the eye.

A

E) there are no photoreceptors in the retina where the axons exit the eye.

41
Q

Action potentials in the visual system are first observed in the

A) bipolar cells.
B) horizontal cells.
C) ganglion cells.
D) photoreceptors.
E) axons leaving the internal surface of the retina.
A

C) ganglion cells.

42
Q

Select the correct sequence for processing of information in the primary visual pathway.

A) Retina - > dorsal lateral geniculate (DLG) -> striate cortex
B) Retina -> striate cortex -> extrastriate cortex -> inferior temporal cortex
C) DLG -> retina -> striate cortex -> primary visual cortex
D) Retina -> DLG -> inferior temporal cortex -> amygdala
E) DLG-> frontal cortex -> amygdala -> extrastriate cortex

A

A) Retina - > dorsal lateral geniculate (DLG) -> striate cortex

Brain & Behaviour (17 decks)

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