Spatial Vision Flashcards
Define spatial vision
The details in an image in terms of lines and elements that make up that 2D image
The details in an image in terms of lines and elements that make up that 2D image
This is known as…?
Spatial vision
How do we resolve the detail in an image?
Using spatial vision
Describe a receptive field
The area on the retina which, when stimulated by light, elicits a change in the firing rate of the cell
A cell’s _____ is the area on the retina which, when stimulated by light, elicits a change in the firing rate of the cell
This is known as…?
Receptive field
A cell’s receptive field is the area on the retina which, when stimulated by light, elicits a change in the firing rate of the cell
The effect of the stimulus can be either ___ or ___ on firing rate of that cell
Excitatory or Inhibitory
How do we measure a cell’s firing rate?
Single cell recording
What happens in single cell recording?
A stimulus is shown
An electrode, inserted into a neuron (e.g. V1) measures electrical activity
We then measure the activity of that single neuron overtime
What are the cells located in the V1?
List 3
- Simple cells
- Complex cells
- Hypercomplex cells
What are the 6 cells with receptive fields?
- Photoreceptors
- Ganglion cells
- LGN cells
- Simple cells
- Complex cells
- Hypercomplex cells
What stimulus do V1 simple cells respond to?
Oriented bars and edges
Which bars of light do V1 simples cells respond to the most?
a. Vertical line
b. Tilted vertical line
c. Horizontal lines
a. Vertical line
What did Hubel and Wiesel discover about V1 cells in cats?
Found oriented bar detectors in V1 of cats using single cell recording
Describe the study on the tilt after-effect
List 3 points
- Adapt = Ps stared at lines tilted clockwise
- Test = They were tested with lines that were physically vertical
- Perceived = Ps perceived lines that were tilted slightly in the other direction to the adapting pattern (tilted anti-clockwise)
What is the tilt-after effect?
Perceiving lines tilted in the other direction after being tested with vertical lines following staring at lines tilted a certain direction
Perceiving lines tilted in the other direction after being tested with vertical lines following staring at lines tilted a certain direction
This is known as…?
The tilt after-effect
What are the 3 components of the tilt after effect?
- Orientation tuned neurons respond best to preferred orientation but also respond to other similar orientations
- Perceived orientation determined by distribution of responses across cells
- Adaptation – cell’s response decreases following prolonged
activity
If a cell is responding really strongly to a particular stimulus and you keep looking at that stimulus, and the cell keeps responding to it, eventually, that cell’s response is going to decrease
This is known as…?
Adaptation
Rearrange these components of the tilt after-effect in order
Perceived orientation determined by distribution of responses across cells
Adaptation – cell’s response decreases following prolonged activity
Orientation tuned neurons respond best to preferred
orientation but also respond to other similar orientations
- Orientation tuned neurons respond best to preferred orientation but also respond to other similar orientations
- Perceived orientation determined by distribution of responses across cells
- Adaptation – cell’s response decreases following prolonged activity
Before adaptation vertical line looks
a. vertical
b. horizontal
c. tilted
a. vertical
At the start of adaptation tilted line looks …?
a. vertical
b. horizontal
c. tilted
c. tilted
During adaptation tilted line looks …?
a. vertical
b. horizontal
c. tilted
c. tilted
After adaptation vertical line looks …?
a. vertical
b. horizontal
c. tilted
c. tilted
After adaptation vertical line looks tilted
Why?
Because of asymmetrical response distribution
During adaptation tilted line continues to look
tilted, but cells’ responses …?
Decrease
What does the size of tilt after-effect depend on?
Difference between adapt and test
Size of tilt after-effect depends on difference between adapt and test
What is the effect size if the difference between adapt and test is large?
Small after effect, peak shifted slightly
Size of tilt after-effect depends on difference between adapt and test
What is the effect size if the difference between adapt and test is small?
Large after effect, peak shifted significantly
Size of tilt after-effect depends on difference between adapt and test
What is the effect size if the difference between adapt and test is zero?
There is no after effect
What wave represents the relationship between the difference in orientation between the adapting pattern of the test and the size pattern of the effects
Sine wave
As the difference in adapt and test gets bigger, the size of the after effects …?
a. Increases
b. Reduces
b. Reduces
As the difference in adapt and test gets bigger, the size of the after effects reduces until adapting pattern after-effects go down to …?
0
What evidence does tilt after-effects provide?
Evidence for orientation
tuned cells in human
visual system
Provides evidence for orientation tuned cells in human visual system
This is known as…?
Tilt after-effect
Cats and monkeys have cells with ____ receptive fields at each orientation
Different sized
Cats and monkeys have cells with different sized
receptive fields at …?
Each orientation
True or False?
Some cells might give their best response to vertical lines that are very fat or very skinny
Some cells might give their best response to horizontal lines that are very fat or very skinny
True
List the 3 components of size after-effects
- Adapt
- Test
- Perceived
Before adaptation the size of the stimulus is perceived …?
a. Vertically
b. Horizontally
c. Fatter
a. Vertically
During adaptation cells’ response …?
a. Stays the same
b. Increases
c. Decreases
c. Decreases
After adaptation lines look …?
a. Fatter
b. Thinner
c. Shorter
d. Longer
b. Thinner
After adaptation, why do the lines look thinner?
Due to asymmetrical response distribution
Provides evidence for orientation-tuned cells in human visual system
This is known as…?
Tilt after-effect
Provides evidence for size-tuned cells in human visual system
This is known as…?
Size after-effect
Size after-effect is evidence for …?
Size-tuned cells in human visual system
What are the fundamental features of parts of the visual scene?
List 2
- Size
- Orientation
The brain has cells
tuned to these features
These are known as…?
- Size
- Orientation
Define size in terms of visual perception
Spatial frequency
Define spatial frequency
Number of bars per unit
distance (usually cycles per degree)
simply = Number of bars you can fit in a given distance
Number of bars per unit
distance (usually cycles per degree)
simply = Number of bars you can fit in a given distance
This is known as…?
Spatial frequency
Do fat bars have:
a. Low spatial frequency
b. High spatial frequency
a. Low spatial frequency
Do skinny bars have:
a. Low spatial frequency
b. High spatial frequency
b. High spatial frequency
High spatial frequency
a. Fat bars
b. Thin bars
b. Thin bars
Low spatial frequency
a. Fat bars
b. Thin bars
a. Fat bars
Natural images
contain information
at many …?
Spatial frequencies
Fine details:
a. Low spatial frequency
b. High spatial frequency
b. High spatial frequency
Course information:
a. Low spatial frequency
b. High spatial frequency
a. Low spatial frequency
Low spatial frequency
a. Fine details
b. Course information
b. Course information
High spatial frequency
a. Fine details
b. Course information
a. Fine details
Define contrast
The difference in the luminance between lighter area and darker area on either side of the boundary
The difference in the luminance between lighter area and darker area on either side of the boundary
This is known as…?
Contrast
Going from black to white
a. High contrast
b. Low contrast
a. High contrast
Going from dark grey to light grey
a. High contrast
b. Low contrast
b. Low contrast
We have greater sensitivity to ___ spatial frequencies
a. intermediate
b. high
c. low
a. intermediate
We have greater sensitivity to intermediate spatial frequencies
What does this mean?
We are very sensitive to the middle spatial frequency
We can still see those lines at low contrast
We have ___ sensitivity to high and low spatial frequencies
a. Higher
b. Lower
b. Lower
We have lower sensitivity to high and low spatial frequencies
How can we perceive these frequencies?
The frequencies need
higher contrast to be perceived
Spatial frequency tells us about the …?
a. Size on the retina
b. Real size in the wolrd
a. Size on the retina
Why does spatial frequency tell us about size on the retina but not indicate real size in the world?
Because the projected size depends on distance
simply = Because size of the retina is dependent on how big the object is in the world but also how far away it is
True or False?
Any line on the retina could have been produced by infinite different lines in
the world
simply = Different widths of lines at different differences could’ve produced this exact image on the retina
True
Size of your thumb get bigger in the retinal image as you move it closer to you, with lower spatial frequency in the retinal image but we don’t perceive it that way
How do we perceive it instead?
We perceive it in terms of its size in the world and we know it is just getting closer to us
Define size constancy
We perceive an object’s real size in the world regardless of distance
We perceive an object’s real size in the world regardless of distance
This is known as…?
Size constancy
Define orientation constancy
We perceive an object’s
orientation in the world regardless of the orientation
on the retina
We perceive an object’s
orientation in the world regardless of the orientation
on the retina
This is known as…?
Orientation constancy
We translate retinal properties into …?
World properties (and experience them how they are in the world)
What are images composed of?
Lines and edges of differing
orientation, size and contrast
What is the visual image processed by?
Neurons tuned to
orientation and spatial
frequency
The visual image is processed by neurons
What are these neurons tuned to? List 2 points
- Orientation
- Spatial frequency
Demonstrations in humans
rely on ____ techniques such as the tilt after-effect
Psychophysical
Name 2 common psychophysical techniques to demonstrate how neurons in humans are tuned to orientation and spatial frequency
- Tilt after-effect
- Size after-effect
