PSYC 212 Lecture Notes - Lecture 10: Binocular Summation, Binocular Disparity, Monocular Vision
6 Nov 2018
School
Department
Course
Professor
Binocular vision and stereopsis
Binocular summation: the combination (or
"summation") of signals from each eye in ways that
make performance on many tasks better with both
eyes than with either eye alone
□
Binocular disparity: the difference between the two
retinal images of the same scene
Disparity is the basis for stereopsis, a vivid
perception of the three-dimensionality of the
world that is not available with monocular
vision
®
□
Corresponding retinal points: a geometric concept
stating that points on the retina of each eye where
the monocular retinal images of a single object are
formed at the same distance from the fovea in each
eye
□
Vieth-Müller circle (Horopter): the location of
objects whose images lie on the corresponding
points. The surface of zero disparity
The Vieth-Müller circle and the horopter are
technically different, but for our purposes we
will consider them the same
®
Objects on the horopter are seen as single
images when viewed with both eyes
®
□
Objects significantly closer to or farther away from
the horopter fall on non corresponding points in the
two eyes and are seen as two images
□
Diplopia: double vision. If visible in both eyes,
stimuli falling outside of Panum's fusional area will
appear diplopic
□
Panum's fusional area: the region of space, in front
of and behind the horopter, within binocular single
vision is possible
□
Crossed disparity: the sign of disparity created by
objects in front of the plane of the horopter
Images in front of the horopter are displaced
to the left in the right eye and to the right in
the left eye
®
□
Uncrossed disparity: the sign of disparity created by
objects behind the plane of the horopter
Images behind the horopter are displaced to
the right in the right eye and to the left in the
left eye
®
□
Different binocular neurons in V1 encode all
categories of retinal disparity (zero, crossed (near),
and uncrossed (far))
These neurons are organized in columns
®
These neurons allow perceiving depth within
Panum's fusional area
®
□
Stereoscope: a device for presenting one image to
one eye and another image to the other eye
Stereoscopes were a popular item in the
1900s
®
Many children in modern days had a
ViewMaster, which is also a stereoscope
®
For movies to appear 3D, each eye must
receive a slightly different view of the scene
(just like in real life)
®
Early methods for seeing movies in 3D
involved "anaglyphic" glasses with a red lends
on one eye and a blue lens on the other
®
Current methods use polarized light and
polarizing glasses to ensure that each eye
sees a slightly different image
®
□
Correspondence problem: in binocular vision, the
problem of figuring out which bit of the image in
the left eye should be matched with which bit in the
right eye
Do we need to recognize objects to have
stereopsis?
®
□
Random dot stereogram (RDS): a stereogram made
of a large number of randomly placed dots
RDSs contain no monocular cues to depth
®
Stimuli visible stereoscopically in RDSs are
cyclopean stimuli
®
Cyclopean: referring to stimuli that are
defined by binocular disparity alone
®
If the "object" on the right eye is positioned
to the left of the object on the left eye (if
there is crossing), the object will be perceived
in front of the background (and vice-versa)
®
□
Free fusion: the technique of converging (crossing)
or diverging (uncrossing) the eyes in order to view a
stereogram without a stereoscope
□
Binocular rivalry: the competition between the two
eyes for control of visual perception, which is
evident when completely different stimuli are
presented to the two eyes
The retinal input is constant, but the percept
changes!
®
What tracks the percept? Patterns in V1-V3!
®
□
2.
Perceiving movement
Apparent motion
Logically speaking, motion perception shouldn't require
anything else, other than the ability to perceive successive still
frames
○
Akinetopsia: a rare neurophysiological disorder in which the
affected individual has no perception of motion
Can be caused by lesions of areas MT/MST
§
Movement was like a stream of static copies
§
○
Apparent motion: the illusory impression of smooth motion
resulting from the rapid alternation of objects that appear in
different locations in rapid succession
Cartoons
§
If the dot is far away and the flickering is very fast:
apparent motion won't be perceived
The dots are too far away, there's no way it's
moving that fast
□
§
If the dot is close and the flickering is slow: apparent
motion will not be perceived
§
The dot must be close and fast in order for apparent
motion to be perceived
§
○
Motion detection circuit
M neuron registers a change in position between A and B,
but…
Would also respond to 2 still ladybugs□
Would also respond to a ladybug moving backwards□
1.
Add neuron D which incorporates delay2.
Repeat this across many X comparator neurons3.
○
•
What and where pathways
What pathway
P ganglion cells receive inputs from midget bipolar cells (1
cone per midget cell). P cells project to the parvocellular
layers of the LGN
§
P ganglion cells have small receptive fields. The high-
resolution information coming from these P cells is at the
origins of the ventral 'what' pathway
§
○
Where pathway
M ganglion cells receive inputs from diffuse bipolar cells
(>1 cone per diffuse cell). M cells project to the
magnocellular layers of the LGN
§
M ganglion cells have large receptive fields and are
sensitive to movement
§
○
•
Correspondence problem - aperture
Correspondence problem: the problem faced by the motion
detection system of knowing which feature in frame 2
corresponds to which feature in frame 1
○
Aperture problem: the fact that when a moving object is viewed
through an aperture (or a receptive field), the direction of
motion of a local feature or part of an object may be ambiguous
○
Motion information from several local apertures (or receptive
fields) can be combined to determine the global motion of the
object
There are several directions of motion within each
aperture that are compatible with the stimulation the
receptor is receiving
§
Whichever possible motion direction is the same in all
apertures is the true global motion direction of the object
§
○
•
Anatomy
Lesions in magnocellular layers of LGN impair perception of
large, rapidly moving objects
○
Monkeys needed about ten times as many dots to correctly
identify
○
Middle temporal area (MT) also plays an important role in
motion perception
○
•
Thursday, February 8, 2018
1:05 PM
Lecture 10
Binocular vision and stereopsis
Binocular summation: the combination (or
"summation") of signals from each eye in ways that
make performance on many tasks better with both
eyes than with either eye alone
□
Binocular disparity: the difference between the two
retinal images of the same scene
Disparity is the basis for stereopsis, a vivid
perception of the three-dimensionality of the
world that is not available with monocular
vision
®
□
Corresponding retinal points: a geometric concept
stating that points on the retina of each eye where
the monocular retinal images of a single object are
formed at the same distance from the fovea in each
eye
□
Vieth-Müller circle (Horopter): the location of
objects whose images lie on the corresponding
points. The surface of zero disparity
The Vieth-Müller circle and the horopter are
technically different, but for our purposes we
will consider them the same
®
Objects on the horopter are seen as single
images when viewed with both eyes
®
□
Objects significantly closer to or farther away from
the horopter fall on non corresponding points in the
two eyes and are seen as two images
□
Diplopia: double vision. If visible in both eyes,
stimuli falling outside of Panum's fusional area will
appear diplopic
□
Panum's fusional area: the region of space, in front
of and behind the horopter, within binocular single
vision is possible
□
Crossed disparity: the sign of disparity created by
objects in front of the plane of the horopter
Images in front of the horopter are displaced
to the left in the right eye and to the right in
the left eye
®
□
Uncrossed disparity: the sign of disparity created by
objects behind the plane of the horopter
Images behind the horopter are displaced to
the right in the right eye and to the left in the
left eye
®
□
Different binocular neurons in V1 encode all
categories of retinal disparity (zero, crossed (near),
and uncrossed (far))
These neurons are organized in columns
®
These neurons allow perceiving depth within
Panum's fusional area
®
□
Stereoscope: a device for presenting one image to
one eye and another image to the other eye
Stereoscopes were a popular item in the
1900s
®
Many children in modern days had a
ViewMaster, which is also a stereoscope
®
For movies to appear 3D, each eye must
receive a slightly different view of the scene
(just like in real life)
®
Early methods for seeing movies in 3D
involved "anaglyphic" glasses with a red lends
on one eye and a blue lens on the other
®
Current methods use polarized light and
polarizing glasses to ensure that each eye
sees a slightly different image
®
□
Correspondence problem: in binocular vision, the
problem of figuring out which bit of the image in
the left eye should be matched with which bit in the
right eye
Do we need to recognize objects to have
stereopsis?
®
□
Random dot stereogram (RDS): a stereogram made
of a large number of randomly placed dots
RDSs contain no monocular cues to depth
®
Stimuli visible stereoscopically in RDSs are
cyclopean stimuli
®
Cyclopean: referring to stimuli that are
defined by binocular disparity alone
®
If the "object" on the right eye is positioned
to the left of the object on the left eye (if
there is crossing), the object will be perceived
in front of the background (and vice-versa)
®
□
Free fusion: the technique of converging (crossing)
or diverging (uncrossing) the eyes in order to view a
stereogram without a stereoscope
□
Binocular rivalry: the competition between the two
eyes for control of visual perception, which is
evident when completely different stimuli are
presented to the two eyes
The retinal input is constant, but the percept
changes!
®
What tracks the percept? Patterns in V1-V3!
®
□
2.
Perceiving movement
Apparent motion
Logically speaking, motion perception shouldn't require
anything else, other than the ability to perceive successive still
frames
○
Akinetopsia: a rare neurophysiological disorder in which the
affected individual has no perception of motion
Can be caused by lesions of areas MT/MST
§
Movement was like a stream of static copies
§
○
Apparent motion: the illusory impression of smooth motion
resulting from the rapid alternation of objects that appear in
different locations in rapid succession
Cartoons
§
If the dot is far away and the flickering is very fast:
apparent motion won't be perceived
The dots are too far away, there's no way it's
moving that fast
□
§
If the dot is close and the flickering is slow: apparent
motion will not be perceived
§
The dot must be close and fast in order for apparent
motion to be perceived
§
○
Motion detection circuit
M neuron registers a change in position between A and B,
but…
Would also respond to 2 still ladybugs□
Would also respond to a ladybug moving backwards□
1.
Add neuron D which incorporates delay2.
Repeat this across many X comparator neurons3.
○
•
What and where pathways
What pathway
P ganglion cells receive inputs from midget bipolar cells (1
cone per midget cell). P cells project to the parvocellular
layers of the LGN
§
P ganglion cells have small receptive fields. The high-
resolution information coming from these P cells is at the
origins of the ventral 'what' pathway
§
○
Where pathway
M ganglion cells receive inputs from diffuse bipolar cells
(>1 cone per diffuse cell). M cells project to the
magnocellular layers of the LGN
§
M ganglion cells have large receptive fields and are
sensitive to movement
§
○
•
Correspondence problem - aperture
Correspondence problem: the problem faced by the motion
detection system of knowing which feature in frame 2
corresponds to which feature in frame 1
○
Aperture problem: the fact that when a moving object is viewed
through an aperture (or a receptive field), the direction of
motion of a local feature or part of an object may be ambiguous
○
Motion information from several local apertures (or receptive
fields) can be combined to determine the global motion of the
object
There are several directions of motion within each
aperture that are compatible with the stimulation the
receptor is receiving
§
Whichever possible motion direction is the same in all
apertures is the true global motion direction of the object
§
○
•
Anatomy
Lesions in magnocellular layers of LGN impair perception of
large, rapidly moving objects
○
Monkeys needed about ten times as many dots to correctly
identify
○
Middle temporal area (MT) also plays an important role in
motion perception
○
•
Thursday, February 8, 2018 1:05 PM
Lecture 10
Document Summary
summation) of signals from each eye in ways that make performance on many tasks better with both eyes than with either eye alone. Binocular disparity: the difference between the two retinal images of the same scene. Disparity is the basis for stereopsis, a vivid perception of the three-dimensionality of the world that is not available with monocular vision. Corresponding retinal points: a geometric concept stating that points on the retina of each eye where the monocular retinal images of a single object are formed at the same distance from the fovea in each eye. Vieth-m ller circle (horopter): the location of objects whose images lie on the corresponding points. The vieth-m ller circle and the horopter are technically different, but for our purposes we will consider them the same. Objects on the horopter are seen as single images when viewed with both eyes.
