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Biological Psychology > Lecture 12 - How Do We See? > Flashcards

Lecture 12 - How Do We See? Flashcards

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1
Q

What is light?

A

Light is electromagnetic radiation.

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2
Q

What is the retina?

A

The retina is a layer of photoreceptors and glial cells that lines the back of the eye and is where light signals are transmitted into electrical and chemical signals that are sent to the brain for interpretation.

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3
Q

What is the fovea?

A

The fovea is an area of the retina that has the highest density of photoreceptors. As you move away from the fovea the density of photoreceptors decreases?

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4
Q

What are cone cells and rod cells?

A

Cone and rod cells are specialized neurons that are able to absorb light and transmit it as an electrical signal to the brain.

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5
Q

There are ganglion, horizontal, amacrine, and bipolar cells that light must pass through before reaching the photoreceptors. Why is this the case and what happens to the light when it passes through these cells?

A

The cone and rod cells need to be on a steady base, as too much movement would affect the accuracy through which these cells can represnt light from different areas of the visual field. They are therefore located on the more stable back of the retina and the horizontal and amacrine cells and bipolar cells and ganglion cells are all in front of the photoreceptors. They do not absorb light and this is how the light can reach the photoreceptors unimpeded.

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6
Q

What are bipolar, horizontal and amacrine cells?

A

Bipolar, amacrine and horizontal cells are neurons in the eye that allow for modulation and transmission of signals between photoreceptors and retinal ganglion cells.

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7
Q

What do retinal ganglion cells do? What information do they receive and what information to they output?

A

Retinal ganglion cells receive signals from bipolar and amacrine cells and they receive them as graded potenitals. If they receive enough signals their output is an action potential.

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8
Q

What is the cornea?

A

The cornea is the protective layer that protects the lens and the opening to the retina.

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9
Q

What is the difference between cone and rod photoreceptors and how does this difference influence the spectrum of colours we can see when there are higher levels of light compared to lower levels of light?

Hint: 1 and 3

A
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10
Q

Are photoreceptors, bipolar, horizontal, amacrine, and retinal ganglion cells neurons?
What is the difference between them?

A

Yes.

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11
Q

Prior to the retinal ganglion cells there are no action potentials generated, just changes (hyperpolarisation and depolarisation) of the cell membranes of photoreceptors and bipolar cells.
True or false?

A

True.

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12
Q

What are the five types of neurons found in the retina?

A

Photoreceptors, horizontal cells, bipolar cells, amacrine cells, and retinal ganglion cells.

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13
Q

What “three” colours do the different cone photoreceptors receive information from?

A

Blue, Green, Red.

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14
Q

What is the name of a test that examines colour-blindness?

A

Ishihara colour plates.

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15
Q

Colour-blindness is a sex-linked trait. True or false?

A

True.

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16
Q

The fact that colour-blindness is a sex-linked trait, with the genes being on the x-chromosome, means that male or XY karyotypes are more likely to be affected by it, hence we see a higher proportion of the population with colour-blindness being male.
True or false?

A

True.

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17
Q

Why is there a higher proportion of males with colour-blindness than females?

A
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18
Q

What is deuteranopia?

A

Deuteranopia is the absence of green cone photoreceptors.

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19
Q

What is protanopia?

A

Protanopia is the absence of red cone colour receptors.

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20
Q

What is the difference between communication between photoreceptors and ganglion cells in the FOVEA and PERIPHERY?

A

Photoreceptors in the fovea have more of an impact on retinal ganglion cells, because they make our “central vision”. The information in our central vision is of more importance than the periphery.
Photoreceptors in our peripheral vision therefore have less of an impact on retinal ganglion cells than those in the fovea.
This translates as photoreceptors in the fovea having a more 1-to-1 influence/connection with retinal ganglion cells via bipolar cells, whereas photoreceptors in the peripheral vision connect (via bipolar cells) to retinal ganglion cells that are receiving information from multiple/many different photoreceptors.

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21
Q

What does retinotopic mean?

A
22
Q

What is a receptive field in the visual system at the level of the retina?

A

Retinal ganglion cells receive input, in the form of stimulation or inhibition, from multiple photoreceptors representing light from an area of our visual field. The receptive field is the area of the visual field that light is coming from that the retinal ganglion cells then pass back to the brain.
The receptive field of ganglion cell is represented by inhibitory or excitatory signals from the photoreceptors. The receptive field is a circular shape with the centre being excitatory and periphery being inhibitory or vice versa. Whether a photoreceptor will excite or inhibit a ganglion cell is determined by whether the bipolar cells between the two will translate the signal from the photoreceptor to an excitatory or inhibitory signal for the retinal ganglion cell.

23
Q

What determines whether the signal from the photoreceptor to the retinal ganglion cell will be excitatory or inhibitory?

A

Bipolar cells.

24
Q

On what side of the brain is information from the right visual field processed?

A

Signals from the right visual field are processed on the left side of the brain.

Note: both eyes are receiving light/signals from both the right and left visual field.

25
Q

What is the Lateral Geniculate Nucleus (LGN)?

A

The Lateral Geniculate Nucleus relays signals from the retinal ganglion cells to the primary visual cortex located in the occipital lobe.
There are fibres going FROM the visual cortex to the LGN than from the LGN to visual cortex, which implies that there is something more than just relaying light information from the visual field happening in the LGN.

26
Q

How is the LGN structured?

A

The LGN consists of layers of different neurons that receptive to signals from different
The different neurons in the LGN layers are receptive to different qualities of light.

27
Q

Are there receptive fields in the LGN?

A

Yes, the neurons in the LGN are organised as centre-surround receptive fields and represent areas of the visual field. The neurons in the LGN are organised in a retinotopic manner is another way to say this.

28
Q

The position and pattern of the light, not just the presence of light itself, at both the level of the retina and LGN determine whether signals will be sent back to the primary visual cortex. This is how we are able to produce such a complex perception of the visual world.
True or false?

A

True.

29
Q

What percentage of fibres and signals go back to the LGN and onto the primary visual cortex? In other words, what percentage of the information received by the eyes contributes to our conscious visual perception of the world?

A

80%

30
Q

What percentage of fibres and signals go back to the LGN and onto the primary visual cortex? In other words, what percentage of the information received by the eyes contributes to our conscious visual perception of the world?

A

80%

31
Q

If 80% of the fibres from the retina to the brain go through the LGN and onto the primary visual cortex, where do the other fibres and signals go and what do they contribute to?

A

The other 20% of the fibres go to the suprachiasmic nucleus in the hypothalamus. The suprachiasmic nucleus is the “body clock”.
Retinal ganglion cells that contain melanopsin send signals to the suprachiasmic nucleus in the hypothalamus conveying information based on brightness/darkness to entrain/instruct other cells on what hormones or physiological processes to produce/engage in based on how alert we need to be or if we are resting/sleeping, i.e they are key players in directing and influencing our circadian rhythm.

32
Q

There are cone and rod photoreceptors. These photoreceptors contribute to our conscious perception of the visual world.
What is a third class of photoreceptors and how do they influence the brain and body?

A

A third class of retinal photoreceptors are melanopsin-containing retinal ganglion cells. The process light information based on dimness/brightness and send this information back to the suprachiasmic nucleus, which is the body clock and instructs brain and body in accordance with our circadian rhythm.

33
Q

How does the bionic eye work?

Hint: camera, a receiver to process the data, microelectrode array, retinotopic organisation.

A
34
Q

What are cells that are selective to orientation called?

A

Simple cells. Simple cells are found in the primary visual cortex (V1).

35
Q

What is the fovea?

A

The FOVEA is an area of the retina that is the most densely packed with photoreceptors.

36
Q

What cone types are present in the retina?

A

Cone cells are types of photoreceptors that are sensitive to different wavelengths of light. The signal they send is the same as each other, however, they will only send a signal if they absorb a certain wavelength of light. We have RED, GREEN, and BLUE cone receptors. They themselves are not these colours however the light they absorb corresponds to the wavelengths of these colours.

37
Q

What are rod cells?

A

Rod cells are photoreceptors that are sensitive to low levels of light and light of around 496nm (A blueish tone colour). They are not very sensitive to wavelengths of light oustide of this, hence, as light levels dip we become less able to distinguish colours.

38
Q

What are amacrine, horizontal and bipolar cells?

A

Horizontal, Bipolar, and Amacrine cells are neurons that monitor and modulate the signals sent from the photoreceptors to the retinal ganglion cells. Unlike other neurons,Horizontal, Bipolar and Amacrine cells do NOT communicate through action potentials, instead they communicate through graded potentials.
Horizontal cells allow for communication between photoreceptors.
Bipolar cells allow for communication between photoreceptors and retinal ganglion cells.
Amacrine cells allow for communication between retinal ganglion cells and the signals being received by the bipolar cells.

39
Q

Are photoreceptors in the eye neurons?

A

Yes.

40
Q

What are 5 neuron types in the eye?

A

Photoreceptors (cones and rods)
Horizontal cells
Bipolar cells
Amacrine cells
Retinal Ganglion cells

41
Q

What happens to the membrane potential of photoreceptors when they absorb the wavelength of light they are sensitive to? And how does this translate to activating a retinal ganglion cell?

A

The membrane potential hyperpolarizes.
This hyperpolarization results in a depolarization of the bipolar cells which, if the signal is strong enough, will lead to the depolarisation of the ganglion cells such that they send an action potential.

42
Q

Why is colour blindness more common in males than in females?

A

The genes responsible for colour blindness are located on the X chromosome. As females or people with an XX karyotype have two X chromosome they are less likely to exhibit the symptoms of colour blindness.

43
Q

What is one way to test for colour blindness discussed in the lecture?

A

Ishihara colour plates.

44
Q

What is the relationship between the photoreceptors and ganglion cells in the FOVEA and how is it different to the relationship between the photoreceptors and ganglion cells in the PERIPHERY?

A

The photoreceptors on the FOVEA directly influence the the ganglion cells in a one-to-one relationship.
The photoreceptors in the PERIPHERY are in a many-to-one relationship with the ganglion cells. Many photoreceptors influence the activity of one ganglion cell. This is why our visual acuity is less in our peripheral vision and more focused in our central vision.

45
Q

When photoreceptors absorb light they send a signal to the bipolar cells/they activate bipolar cells. However, ganglion cells can be influenced by photoreceptors in an activating or inhibiting manner. How is this so and why is this important?

A

Bipolar cells are what determine whether a photoreceptor will activate or inhibit a retinal ganglion cells. This allows for ganglion cells to have specific centre-surround receptive fields that allow us to perceive shapes, edges, movement etc.

46
Q

What type of organisation does the visual system have?

A

It has a retinotopic organisation.

47
Q

What is the LATERAL GENICULATE NUCELEUS?

A

The LGN is a structure in the THALAMUS that receives information from the optic nerve coming from the eyes.
Information from the right visual field from both eyes are processed in the left hemisphere of the brain and information from the left visual field is processed in the right hemisphere of the brain.

48
Q

Around what percentage of signals from the retina are sent to the LGN and through to the primary visual cortex? And what is this pathway called?

A

Around 80%.
The Retinogeniculate Pathway.

49
Q

How many layers of neurons are there in the LGN?

A

There are 2 magnocellular layers, then four parvocellular layers, and in between these layers are koniocellular layers. The neurons in the magnocellular layers are particularly receptive to signals related to movement and neurons in the parvocellular layers are particularly receptive to signals regarding colour.

50
Q

There are more fibres FROM the visual cortex to the LGN than there are from LGN to the visual cortex.
What does this suggest?

A

This suggest that the LGN is doing more than just relaying signals from the retina to the visual cortex.

51
Q

Do all the signals generated in the retina contribute to our conscious visual experience?

A

No.
About 20% of the signals generated in the retina are sent to the hypothalamus, specifically the suprachiasmic nucleus, which is our biological clock and regulates our circadian rhythm.
The ganglion cells that send these signals are melanopsin-containing retinal ganglion cells.

52
Q

When will a retinal bionic eye not be a suitable device?

A

If the retinal ganglion cells or any other part of the visual pathway (Except photoreceptors) is damaged.
Bionic eyes are only suitable for people who have damaged retinal cells.

Biological Psychology (24 decks)

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