PSY368 Section 2 Practice Questions

Question 1

What percentage of information we get from the world comes through our visual system?

Answer 1

80%

Question 2

Why is vision considered our most important sense?

Answer 2

We intake a majority of environmental information through vision

Question 3

What is the function of the eye in terms of processing visual information?

Answer 3

Focusing electromagnetic energy, transducing it into a neuronal signal, then to start processing the signal

Question 4

How does the placement of eyes differ between prey and predatory animals?

Answer 4

Eyes of prey tend to be on the sides of their head while eyes of predators are usually in the front (binocular vision)

Question 5

Why do primates have eyes positioned centrally on their head?

Answer 5

The binocular vision helps primates to use tools

Question 6

Why is the pigment epithelium in the vascular tunic important?

Answer 6

They are heavily pigmented to absorb scattered light (pigment epithelium)

Question 7

How does the iris affect vision?

Answer 7

determines pupil size

Question 8

What are photoreceptors and how do they contribute to vision?

Answer 8

photoreceptors are pigmented cells that produce electrical signals when struck by light – photoreceptors intake environmental information making them the first source of visual sensation

Question 9

What is the difference between rods and cones in terms of their function?

Answer 9

Rods: peripheral vision, dim lighting, achromatic, poor spatial resolution
Cones: central vision, bright lighting, good spatial resolution, color vision

Question 10

Why does the optic disc create a blind spot in our vision?

Answer 10

There is an absence of photoreceptors at the optic disc

Question 11

How do horizontal cells and amacrine cells affect the processing of visual information in the retina?

Answer 11

Horizontal cells modulate activity between the photoreceptors and the bipolar cells while amacrine cells modulate activity between the bipolar and the ganglion cells

Question 12

Where must light pass through to reach the photoreceptors?

Answer 12

The cornea
The lens
The aqueous and vitreous humors
The ganglion, amacrine, bipolar, and horizontal cells

Question 13

What is the primary function of the eye

Answer 13

To focus light on the retina

Question 14

Which part of the eye accounts for about 80% of the bending needed to focus light on the retina?

Answer 14

The cornea

Question 15

What is the difference between light coming from distant objects and light from near objects in terms of how the eye handles it?

Answer 15

Light coming from near objects requires the lens to bend more while objects far away require less bending

Question 16

Why is the fovea the area of the retina with the best visual acuity?

Answer 16

Few cell bodies are located at the fovea and the fovea contains mainly cones which are specialized for detailed pattern vision

Question 17

How does visual acuity change with increasing distance from the fovea?

Answer 17

As you move away from the optical axis images at the fovea have increasing lens distortions

Question 18

What is the visual angle, and how does it relate to object size and perception?

Answer 18

The visual angle is the angle that a

Question 19

How does the visual angle of an object affect its ability to be resolved at different distances?

Answer 19

A larger visual angle (closer) means a larger image projected on the retina, allowing for better detail perception

Question 20

What is neuronal convergence and how does it affect visual resolution?

Answer 20

Neuronal convergence describes how many cells project to a smaller number of cells
This affects visual acuity because the more photoreceptors converging on a ganglion cell (e.g. 120:1 in rods), the worse spatial resolution is

Question 21

Under what lighting conditions do rods and cones operate?

Answer 21

Rods operate under low light and codes operate under bright light

Question 22

Why is visual acuity better in the fovea compared to the peripheral retina?

Answer 22

Acuity is better in the fovea because the more photoreceptors converging on a ganglion cell, the greater loss of spatial information (the fovea has less cells)

Question 23

What is the difference between photopic vision and scotopic vision?

Answer 23

Photopic vision - mediated by cones (brighter lights)
Scotopic vision - mediated by rods (dimmer lights)

Question 24

What is rhodopsin and how does it function?

Answer 24

Pigment coating rod outer segments. As light hits rhodopsin it changes shape (isomerization) causing receptor sites to open and hyperpolarization. This is where visual sensory transduction happens.

Question 25

What happens during the isomerization of rhodopsin?

Answer 25

Rhodopsin changes shape due to a photo of light hitting rhodopsin and the retinal and scotopsin binding changes

Question 26

What is the difference between luminance and brightness, and how are they related?

Answer 26

Brightness is the perceptual correlate of luminance - luminance is in the world while brightness is in your head

Question 27

Describe the process of dark adaptation and how the absolute threshold for light intensity changes over time?

Answer 27

Going from a bright room to a dimly lit room will initially leave you nearly blind, but partial vision occurs after remaining in the dark for a few minutes. The longer you spend in the dark, the more sensitive your eyes become to light leading to a lower absolute threshold

Question 28

What are the phases of dark adaptation?

Answer 28

First the cones provide us with a fast boost in sensitivity but quickly max out. Then the rods, which are slower, kick in and enable us to see in extremely dim lights

Question 29

Explain the role of spatial interactions in neurocomputation.

Answer 29

Spatial interactions (convergence, lateral connectivity) explain the relationship between the receptive field location of stimulation and rates of firing. This plays a role in neurocomputation since neurocomputation aims to explain how neuron systems interact to produce behavior.

Question 30

How does the phenomenon of convergence in retinal photoreceptors influence the response of a retinal ganglion cell? What is the effect of convergence on the firing rate of the ganglion cell?

Answer 30

Many rod photoreceptors converge on a single retinal ganglion cell, compared to cones which are in a 1:1 ratio with ganglion cells (no convergence). With convergence (rods) the more receptors stimulate, the greater the response of the ganglion cell. So the firing rate of the ganglion cell increases with the more receptors stimulated.

Question 31

Compare and contrast the convergence patterns in rods vs. cones and explain how this affects the way information is processed in the retina

Answer 31

Rods converge onto ganglion cells with a 1:many ratio while cones are in a 1:1 ratio with ganglion cells. This difference affects how information is processed in the retina because the rods, which have greater convergence, have larger receptive fields since they respond to several photoreceptors. This also explains why we have a large RF for peripheral vision compared to central vision.

Question 32

How does the interaction between excitatory and inhibitory inputs shape the firing rate of the ganglion cell?

Answer 32

The receptive field has an excitatory center with an inhibitory surround, and where the stimulation occurs will influence the firing rate of the ganglion cell. When the cell is stimulated on the excitatory center, firing increases, and when it is stimulated on the inhibitory surround, firing decreases. If stimulation occurs on both at the same time, the result is summed. Essentially, whichever receives more stimulation will be how the cell responds.

Question 33

Using the Hermann Grid as an example, explain how lateral inhibition leads to perceptual phenomena and optical illusions.

Answer 33

When looking at the Hermann Grid, you see grey dots in the intersection that do not appear when looking directly at one of the intersections. This is caused by strong lateral inhibition at the grid intersections. The perception of the dots depends on the size of the RF, since they are large in the visual periphery we can only see the dots out of the corner of our eyes.

Question 34

Using Mach Bands as an example, explain how lateral inhibition leads to perceptual phenomena and optical illusions.

Answer 34

When looking at Mach bands differential lateral inhibition occurs from cells on either side of the band which causes edge enhancement.

Question 35

How can receptive fields be measured experimentally?

Answer 35

An electrode is placed directly into one cell. The participant then interacts with stimuli at different locations. At some locations it responds weakly, and others it responds strongly. The strong locations are marked creating a map of the receptive field.

Question 36

Explain how the center-surround organization of receptive fields contributes to the neural encoding of visual stimuli. How does this organization impact the overall efficiency of the visual system?

Answer 36

The center-surround organization plays a crucial role in the neural encoding of visual stimuli by enabling the differentiation of light and dark regions within the visual fields, as well as enhancing the detection of edges and contrasts. This improves the efficiency by focusing on changes (contrast) in visual stimuli. The inhibition from the surround helps to suppress less relevant stimuli, ensuring that the neural response is focused on significant visual features like edges.