Brainscape's Knowledge GenomeTM

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


See full index

neuro 80 > lecture 14 relaying visual info from eye to brain > Flashcards

lecture 14 relaying visual info from eye to brain Flashcards

1
Q

what do photoreceptors do in response to light

A

hyperpolarize and release less glutamate

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

what do on bipolar cells do in response to light

A

depolarize and release more glutamate

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

what do off bipolar cells do in response to light

A

hyperpolarize and release less glutamate

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

what do photoreceptors do in response to dark (and what do the on and off bipolar cells do)

A

depolarize and release more glutamate (on cells inverse the signal so they release less, and off cells do the same as photoreceptors so they release more too)

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

what neurotransmitter is released by photoreceptors and how is the the response different between bipolar cells despite the same neurotransmitter

A

glutamate

on cells have mglur6
(inhibitory, metabotropic)

off cells have ampa kainate (excitatory, ionotropic)

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

what cells do bipolar cells synapse onto

A

retinal ganglion cells (rgc)

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

retinal ganglion cells

A

output neurons in retina

only cells in retina that fire true action potentials (have to send electric signal from eye to brain)

have two types; on and off

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

what is the optic nerve made of

A

axons of retinal ganglion cells

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

action potentials

A

large enough membrane potential change that can be recorded without sticking electrode in

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

how did stephen kuffler learn about recording responses of retinal ganglion cells

A

experimental animal is anesthetized and positioned facing a screen

electrode positioned near a retinal ganglion cell to record action potentials (lots of spontaneous activity)

shine spots or other shapes on screen and record frequency of action potentials

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

what is this

A

spontaneous background activity of retinal ganglion cells, basically baseline

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

region or characteristics of the
sensory space that elicits the greatest activity (action
potentials or largest graded potentials in the retina) from either a sensory cell or neuron within the CNS. For neurons in the retina, receptive filled properties include
the area of the visual field (location in space) where light (or dark) would hit the neuron

A

receptive field

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

neurons that are locating near to each other

A

have receptive fields that are near each other (retinotopic map)

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

receptive field of a specific neuron

A

sometimes includes other aspects of the stimulus like color, movement, etc

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

receptive fields tend to

A

enlarge and increase in complexity as information passes through the brain

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

neurons in the eye respond to-

A

a relatively basic stimulus: light on and off

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

receptive field of retinal ganglion cells

A

dim light: background (spontaneous) activity

bright spot: response

another bright spot nearby: response

distant bright spot: no response, not part of receptive field

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

what happens if we enlarge stimulus

A

bright spot of light: response

bigger bright spot: more response

huge bright spot: firing rate back to spontaneous baseline

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

spot near receptive field (right outside, right above, right below)

A

small inhibition

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

bright annulus (donut)

A

big inhibition, neuron stops firing for some time

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

what does this experiment with the lights tell us

A

receptive field not just a single location of light

consists of center and surround parts of receptive field

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

on and off response of visual neurons

A

both bipolar cells and rgcs have center surround type receptive fields

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

if you cover entire receptive field with uniform light or dark

A

go back to baseline- they’re balanced

rgc’s will remain near resting firing rate

bipolar cells will not change membrane potential (graded response)

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

lateral pathway

A

responsible for surround

horizontal cells at synapse between photoreceptors and bipolar cells

amacrine cells at synapse between bipolar cells and rgcs

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

direct pathway (the center)

A

photoreceptors to bipolar cells to retinal ganglion cells to optic nerve

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

horizontal and amacrine cells

A

both inhibitory

release gaba

linked via gap junctions forming a network

can also help adjust entire retinal circuit response to changing levels of illumination

—a page of paper will look white inside or illuminated by a flashlight and white when out in bright sun even though number of photons is different

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

visual systems cares about…

A

relative light intensity, not absolute

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

lateral inhibition

A

neurons are inhibited when neighbors are active

helps with contrast

each photoreceptor and interneuron can be part of a center for one rgc and a surround for another rgc

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

what does center surround organization do

A

enhances sensitivity to edges and contrast (which is why we can interpret one line drawings, visual field is used to finding edges)

30
Q

parallel output pathways from the retina

A

retina doesnt send point by point intensity and color information to brain

high processed- breaks up visual world in many different features

around 30 different types of rgcs
-color center/surround (red center, green surround for example)
-prefer moving stimuli
-large or small receptive fields, etc

31
Q

m type retinal ganglion cells (magnocellular)

A

larger

color insensitive receptive fields

respond to stimulation with a burst of action potentials

often fire rebound action potentials
(cell fires after being inhibited for a while)

32
Q

p type retinal ganglion cells (parvocellular)

A

smaller and smaller receptive fields

large majority of rgcs

often color specific receptive fields

respond to prolonged stimulation with sustained action potential rate

33
Q

retina

A

the innermost layer of the eye and is Itself a layered structure that contains the visual
sensory neurons, circuitry for the initial processing of visual information, as well as neurons that
transmit that information to the brain. But the neurons of the retina do not simply detect light and pass
that message on, a great deal of processing and filtering occurs in the retina, before the visual
information reaches the brain

34
Q

Photoreceptor

A

visual sensory cell that
converts light into electrical signals. Located at the innermost layer of the retina. Photoreceptors are depolarized in the dark and hyperpolarize when activated by light

35
Q

Bipolar cell

A

excitatory neuron in the retina
that transmits information from the
photoreceptors to the retinal ganglion cells and amacrine cells. Bipolar cells do not fire action potentials, but have a graded release of neurotransmitter

36
Q

Horizontal cell

A

inhibitory neuron in the retina whose actions influence the signals that are transmitted from the photoreceptors to the bipolar cells. They make inhibitory, GABAergic
synapses on the synaptic terminals of photoreceptors

37
Q

Amacrine cell

A

inhibitory/modulatory neuron whose actions influence the signals that are transmitted from the bipolar cells to the retinal ganglion cells

38
Q

Retinal ganglion cell (RGC)

A

Output cell of the retinal that transmits information from the eye to the brain. Only type of neuron in the retina that fires action potentials. There are both “on” and “off” that can be further divided into many different subtypes of RGCs based on specific receptive field
properties (color, size of receptive field, etc

39
Q

Center/surround

A

In the retina, both bipolar cells and
RGCs have center surround receptive fields. For an “ON cell”, that means that the cell is excited by center stimulation (i.e. light/“on”), inhibited by light in the surround, and would be more optimally stimulated by dark in the surround. These receptive fields are
very useful because they enable cells to detect more than the brightness of a spot of light, but rather detect contrast (edges or boundaries between light and dark)

In the visual system, center/surround receptive fields are first found in the bipolar cells of the retina. The center of the
receptive field is formed by the direct synapses between
photoreceptors and the bipolar cell while the surround is caused
by the inhibitory actions of horizontal cells being activated by
the surrounding photoreceptors

40
Q

OFF bipolar cell

A

bipolar cell that is inactivated by light (activated by dark). Their dendrites contain excitatory
ionotropic (AMPA type) glutamate receptors. Since photoreceptors release more glutamate in the dark, “OFF” cells also release more neurotransmitter in the dark and less neurotransmitter in the light

41
Q

ON bipolar cell -

A

bipolar cell that is active by light. Their dendrites contains inhibitory mGluR6 type glutamate
receptors, thus they invert the signal the photoreceptors send.
Since photoreceptors release less glutamate in the light, “ON”
cells invert that signal and release more NT in the light

42
Q

ON RGC

A

retinal ganglion cell that fires more action potentials when light is in the center. Receives excitatory
synaptic input from ON-bipolar cells via AMPA type glutamate
receptors

43
Q

OFF RGC

A

retinal ganglion cell that fires fewer action potentials when light is in the center. Receives excitatory
synaptic input from OFF-bipolar cells via AMPA type
glutamate receptors

44
Q

Illustrate how the major cell types of the retina are connected to each other and the function of
each

A
45
Q

Explain how shining light on either the center or the surround of an on-center (or off-center)
ganglion cell’s receptive field differentially affects the cell’s activity and how that response may
differ from an on or off-center bipolar cell.

A
46
Q

Define receptive field and explain why a center-surround receptive field enhances sensitivity to
contrast and edges

A
47
Q

the science u

A

phenomenon
reduction
synthesis

48
Q

two important lessons from the retina

A

hierarchical processing

parallel processing

49
Q

hierarchical processing

A

the receptive field properties get more complicated as the signal moves from photoreceptors to retinal ganglion cells

50
Q

parallel processing

A

streams of information related to properties of the visual scene are dealt with simultaneously by different circuits

51
Q

properties of visual world that visual system encodes

A

shape
color
position
movement

52
Q

what doesnt the visual system encode

A

we sense relative not absolute intensities- how bright is it compared to its surrounding, even if theyre the same one will look darker/brighter

movements faster than 30fps per second

movements slower than minute hand on a watch

wavelength that are infrared or lower wavelengths (microwave)

wavelengths that are uv or shorter

lights brighter than some saturating photon flux

light that is dimmer than some very low photon flux

vertical depth disparity

53
Q

retinofugal projection

A

pathway of optic nerve to brain called retinofugal

has 5 parts before reaching visual cortex

54
Q

r and l optic nerves cross at

A

optic chiasm

55
Q

two sides of retina

A

temporal (close to temple)
nasal (closer to nose)

56
Q

visual field

A

right visual field comprised of right nasal and left temporal

left visual field comprised of left nasal and right temporal

57
Q

temporal part

A

does not leave the side of visual field it’s on

58
Q

optic chiasm

A

site of a decussation (crossing) so that the L visual field from both eyes projects to the R cortical hemisphere and R field to left hemisphere. the nasal part of retina crosses to the contralateral side, the temporal part remains on ipsilateral side

59
Q

after the chiasm, the right and left optic nerves are called

A

optic tracts, and contain ipsilateral temporal and contralateral nasal rgc axons

60
Q

lateral geniculate nucleus (lgn)

A

nucleus of thalamus dealing with vision

thalamus takes in sensory info, but lgn is focused solely on vision

is in dorso lateral part of thalamus

left lgn is right visual field

right lgn is left visual field

has 6 layers, each layer filled with cells

retinal axons that stay ipsilateral (from temporal side of retina) project to 3 layers of lgn (2,3,5)

contralateral (nasal lateral) projects to other layers, (1,4,6)

61
Q

optic radiations

A

r and l optic radiations exit thalamus to primary visual cortex (area 17, v1, or striate cortex) of r and l occipital lobes of cerebral cortex

62
Q

nissl stain

A

stains material with nucleic acid in it

63
Q

ventralmost layers 1 and 2

A

contain larger neurons (magnocellular) for motion

64
Q

dorsalmost small cells

A

smaller cells, parvocellular, for shape

65
Q

ventral to each layer of lgn

A

numerous tiny neurons, koniocellular, for color

66
Q

three functional streams in lgn

A

magnocellular
parvocellular
koniocellular

67
Q

magnocellular

A

layers 1 and 2 of lgn
larger neurons
motion
m type rgc

68
Q

parvocellular

A

layers 3, 4, 5, 6
smaller neurons
shape
p type rgc

69
Q

konoiocellular

A

ventral to each layer of lgn
numerous tiny neurons
color
non m non p rgc

70
Q

m type, p type, nonm-nonp

A

retinal ganglion cells thought to innervate 3 lgn cell types respectively

71
Q

parallel processing

A

rather than doing each separately, retina is doing all three at once

72
Q

cortiofugal pathway

A

retina is not main source of synaptic input to lgn

80% of excitatory synapses in lgn are from primary visual cortex

neuro 80 (25 decks)

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