4. Basics Of Visual Processing Flashcards
Objectivist view of vision
Perception reflects reality. An appealing idea, but incorrect.
Subjectivist view of vision
We perceive via inference.
Why is inference necessary?
Vision is your brain’s best guess / a story your brain tells you, based on assumptions and use of noisy, incomplete evidence.
What is phenomenology?
Applying physics to make subjective predictions about perception.
What is psychophysics?
Objective and quantifiable measure of the relationship between visual stimuli and behaviour.
Psychophysics is agnostic about _____________
__________________ about the processes that happen between stimuli and related behaviour.
Two perception based ways of studying vision
Phenomenology and psychophysics
Four hardware based ways of studying vision
Neuropsychology / brain imaging Stimulation / implants Physiology Anatomy
Studying hardware helps us to find out what happens between ____________ and ____________
Studying ___________ helps us to find out what happens between stimulus and behaviour
What can we find out from neuropsychology studies, like brain imaging or lesion cases?
Where is the system? (What kind of study would test this?)
What can we find out from stimulation / implant studies, like cortical implants for people with complete blindness?
Where is the system, and what does it do? (What kind of study would test this?)
What can we find out from physiology studies, like measuring the voltage of a cell with electrodes?
What do its components do? (What kind of study would test this?)
What can we find out from anatomy studies, like looking at the dendrites of a neutron?
How are its components organised? (What kind of study would test this?)
How does Marr describe: a) the goal of visual processing b) how we achieve it?
a) discovering from images what is present and where it is, to produce a description useful to the viewer, so that they can behave effectively b) through a hierarchy of increasingly symbolic representations
Retinal ganglion cells are the ____________
The first neurons in the visual pathway
Three types of retinal ganglion cells (RGCs)
Midget Parasol Small bistratified (Are all types of….)
Receptive field
A region of space where if visual info lands on it, it will affect the activity of the cell.
Three properties of retinal ganglion cells receptive fields:
- circular - antagonistic centre-surround organisation (on-centre or off-centre) - confers selectivity for size and polarity (onset/offset) of features
Spontaneous activity
Random baseline firing of cells at rest
How will an on-centre RGC respond to: a) a light spot in the centre b) a light surround
a) a light spot in the centre will stimulate the on response b) a light surround will stimulate the off response What type of cell am I?
How will an off-centre RGC respond to: a) a light spot in the centre b) a light surround
a) a light spot in the centre will stimulate the off response b) a light surround will stimulate the on response What type of cell am I?
How will an on-centre RGC respond to: a) a dark spot in the centre b) a dark surround
a) a dark spot in the centre will stimulate the off response b) a dark surround will stimulate the on response What type of cell am I?
How will an off-centre RGC respond to: a) a dark spot in the centre b) a dark surround
a) a dark spot in the centre will stimulate the on response b) a dark surround will stimulate the off response What type of cell am I?
How will a retinal ganglion cell respond to a uniform field of light?
A ____________ will not respond to a ______________. It responds to change (in space or time) and specificity (size and polarity)
Midget ganglion cells:
a) three features
b) associated pathway
I am:
a) sensitive to colour and fine detail (I have small RFs!) but I have poor temporal sensitivity (poor for motion)
b) associated with the parvocellular pathway What am I?
Parasol ganglion cells:
a) three features
b) associated pathway
I…
a) have no colour sensitivity, see coarse detail (I have large RFS!) and height temporal sensitivity (I’m good with motion!)
b) am associated with the magnocellular pathway What am I?
What are the specialised parallel pathways that start at the RGC level, and what streams do they mostly feed into in the visual cortex?
Parvocellular pathway —> ventral stream (what) Magnocellular pathway —> dorsal stream
The _________ pathway is the most primitive.
The dorsal pathway is the most __________
Properties of receptive fields in V1 (4 points)
- larger than previous receptive fields in visual pathway, but still small.
- detect more complexity
- selective for orientation of edges (still keep size specificity too)
- elongated
V1 provides _________ information. This can be ambiguous, so we need to pool/integrate ___________ into __________
V1 provides local information. This can be __________ , so we need to __________ local information into global cues.
What are receptive fields in V2 selective for?
Selective for contours
What are the receptive fields in V4 selective for?
Selective for 2D shape and colour
What are the receptive fields in the interotemporal (IT) cortex selective for?
Complex objects, like faces.
What is a theory for how receptive fields select for increasingly complex stimuli across the visual pathway?
The areas might sample the neurons of the areas that came before. This combined info would allow the receptive fields ________________.
Reverse card!
Perception reflects reality. An appealing idea, but incorrect.
Objectivist view of vision
Reverse card!
We perceive via inference.
Subjectivist view of vision
Reverse card!
Vision is your brain’s best guess / a story your brain tells you, based on assumptions and use of noisy, incomplete evidence.
Why is inference necessary?
Reverse card!
Applying physics to make subjective predictions about perception.
What is phenomenology?
Reverse card!
Objective and quantifiable measure of the relationship between visual stimuli and behaviour.
What is psychophysics?
Reverse card!
Phenomenology and psychophysics
Two perception based ways of studying vision
Reverse card!
Neuropsychology / brain imaging Stimulation / implants Physiology Anatomy
Four hardware based ways of studying vision
Reverse card!
Studying ___________ helps us to find out what happens between stimulus and behaviour
Studying hardware helps us to find out what happens between ____________ and ____________
Reverse card!
Where is the system? (What kind of study would test this?)
What can we find out from neuropsychology studies, like brain imaging or lesion cases?
Reverse card!
Where is the system, and what does it do? (What kind of study would test this?)
What can we find out from stimulation / implant studies, like cortical implants for people with complete blindness?
Reverse card!
What do its components do? (What kind of study would test this?)
What can we find out from physiology studies, like measuring the voltage of a cell with electrodes?
Reverse card!
How are its components organised? (What kind of study would test this?)
What can we find out from anatomy studies, like looking at the dendrites of a neutron?
Reverse card!
a) discovering from images what is present and where it is, to produce a description useful to the viewer, so that they can behave effectively b) through a hierarchy of increasingly symbolic representations
How does Marr describe: a) the goal of visual processing b) how we achieve it?
Reverse card!
The first neurons in the visual pathway
Retinal ganglion cells are the ____________
Reverse card!
Midget Parasol Small bistratified (Are all types of….)
Three types of retinal ganglion cells (RGCs)
Reverse card!
A region of space where if visual info lands on it, it will affect the activity of the cell.
Receptive field
Reverse card!
- circular - antagonistic centre-surround organisation (on-centre or off-centre) - confers selectivity for size and polarity (onset/offset) of features
Three properties of retinal ganglion cells receptive fields:
Reverse card!
Random baseline firing of cells at rest
Spontaneous activity
Reverse card!
a) a light spot in the centre will stimulate the on response b) a light surround will stimulate the off response What type of cell am I?
How will an on-centre RGC respond to: a) a light spot in the centre b) a light surround
Reverse card!
a) a light spot in the centre will stimulate the off response b) a light surround will stimulate the on response What type of cell am I?
How will an off-centre RGC respond to: a) a light spot in the centre b) a light surround
Reverse card!
a) a dark spot in the centre will stimulate the off response b) a dark surround will stimulate the on response What type of cell am I?
How will an on-centre RGC respond to: a) a dark spot in the centre b) a dark surround
Reverse card!
a) a dark spot in the centre will stimulate the on response b) a dark surround will stimulate the off response What type of cell am I?
How will an off-centre RGC respond to: a) a dark spot in the centre b) a dark surround
Reverse card!
A ____________ will not respond to a ______________. It responds to change (in space or time) and specificity (size and polarity)
How will a retinal ganglion cell respond to a uniform field of light?
Reverse card!
I am:
a) sensitive to colour and fine detail (I have small RFs!) but I have poor temporal sensitivity (poor for motion)
b) associated with the parvocellular pathway
What am I?
Midget ganglion cells:
a) three features
b) associated pathway
Reverse card!
I…
a) have no colour sensitivity, see coarse detail (I have large RFS!) and height temporal sensitivity (I’m good with motion!)
b) am associated with the magnocellular pathway What am I?
Parasol ganglion cells:
a) three features
b) associated pathway
Reverse card!
Parvocellular pathway —> ventral stream (what) Magnocellular pathway —> dorsal stream
What are the specialised parallel pathways that start at the RGC level, and what streams do they mostly feed into in the visual cortex?
Reverse card!
The dorsal pathway is the most __________
The _________ pathway is the most primitive.
Reverse card!
- larger
- detect more complexity
- selective for orientation of edges (still keep size specificity too)
- elongated
Properties of receptive fields in V1 (4 points)
Reverse card!
V1 provides local information. This can be __________ , so we need to __________ local information into global cues.
V1 provides _________ information. This can be ambiguous, so we need to pool/integrate ___________ into __________
Reverse card!
Selective for contours
What are receptive fields in V2 selective for?
Reverse card!
Selective for 2D shape and colour
What are the receptive fields in V4 selective for?
Reverse card!
Complex objects, like faces.
What are the receptive fields in the interotemporal (IT) cortex selective for?
Reverse card!
The areas might sample the neurons of the areas that came before. This combined info would allow the receptive fields ________________.
What is a theory for how receptive fields select for increasingly complex stimuli across the visual pathway?
