Week 4A: Spatial vision

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42 Terms

1
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Contrast formula

Abs (luminance difference/total luminance) ((lmax-lmin)/(lmax+lmin))

2
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ON-cells: Stimulation in centre

Excitatory

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ON-cells: Stimulation in surround

Inhibitory

4
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Receptive field definition

The stimulus space that causes a neuron to fire

5
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Difference beween spatial and spectral opponency

Location vs. colour content

6
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<p>Lateral inhibition of cones: Difference spatial opponency and spectral opponency</p>

Lateral inhibition of cones: Difference spatial opponency and spectral opponency

Neighbouring cones vs. different cone types inhibit each other

7
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<p>Which one spikes the most on-cells?</p>

Which one spikes the most on-cells?

The one in the middel because it is light in the center and no light in the surround and thus has the biggest contrast between the inner and outer ring of the receptive field

8
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<p>Why does this visual image fire little neurons in the receptive field</p>

Why does this visual image fire little neurons in the receptive field

Because there are light and dark object both on the on and off area and there is no clear contrast between the center and the outer ring of the receptive field

9
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<p>1 and 2</p>

1 and 2

On, Off

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Why do we have OFF detection cells next to the ON detection cells

To detect a decrease in stimulus. (the ON cells will fire as long as there is a stimulus, but the OFF cells will start firing the moment something decreases and so a decrease can be detected)

11
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<p>Read through: the left circle on the graph corresponds to the most left receptive field in the image on the left (answer is ‘read through’)</p>

Read through: the left circle on the graph corresponds to the most left receptive field in the image on the left (answer is ‘read through’)

Read through

12
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Mach Band Illusion

It exaggerates the contrast between edges of the slightly differing shades of gray, as soon as they contact one another, by triggering edge-detection in the human visual system (edges of darker objects next to lighter objects will apear darker and vice versa, creating a false shadow)

13
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<p>Name</p>

Name

Midget cell

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<p>Name</p>

Name

Parasol cell

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<p>1 and 2</p>

1 and 2

Midget cell, parasol cell

16
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At low light levels: Lateral inhibition (…), reception field center size (…)

Decreases, increases

17
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Hermann grid

In the fovea the receptive fields fit in the white area, in the extra-foveal the receptive fields do not fit in the white area, which causes the sensation of seeing gray dots

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Lightness constancy

Assumptions play a role in how we perceive images, snow always looks white and the sky should have 1 colour

19
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Kofka Ring

You see a difference between the grey circle parts when a white line is added in the middle

20
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Perceived lightness depends on luminance and contrast, primary cause is (…) but (…)

receptive fields of retinal ganglion cells but contast effects over very large distance

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Problem of lightness perception

White paper in the shadow reflects less light than black paper in the sun

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Albedo

How much light is reflected by a surface

23
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Colour opponency in midget cells

Red green

24
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Midget cells: sustained or transient response

Sustained

25
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Parasol cells: sustained or transient response

Transient

26
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Bistratified ganglion cells: colour opponency

Blue yellow

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Scotopic

Low light levels

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LGN abbreviation

Lateral Geniculate Nucleus

29
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Receptive fields are smaller for (…) than for (…)

Cones, rods

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<p>Function of parve, mango and konio pathway</p>

Function of parve, mango and konio pathway

Colour and detail, contrast and movement, movement

31
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Vernier acuity is typically (…) of the distance between adjacent photoreceptors

1/6th

32
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Gratings have four cruciul parameters to find the contrast threshold

Spatial frequency, contrast, orientation, phase

33
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Contrast threshold

Minimum contrast required to detect a grating

34
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Spatial frequency = cycles per degree

Inverse of visual angle size of an object

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<p>1,2,3,4</p>

1,2,3,4

Scotopic, photopic, scotopic, photopic

36
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Sensitivity is highest for (…) Hz in photopic conditions

8

37
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At low temporal frequencies, sensitivity is highest at (…) spatial frequenices

Medium

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At high temporal frequencies, sensitivity is highest at (…) spatial frequencies

Low

39
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At low termoral frequencies contrast sensitivity reflects activity of the (…) pathway

Parvocellular

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At high temporal frequencies contrast sensitivity reflects activity of the (…) pathway

Magnocellular

41
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Spatial filters are important for tasks like

Edge localization, texture analysis and stereo and motion analysis

42
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At low temporal frequencies, sensitivity is highest at (…) spatial frequencies

At high temporal frequencies, sensitivity is highest at (…) spatial frequencies

Medium, low