Exam 3 shuffle Flashcards
How common are vertical disparities?
A daily occurrence, but vergence movements can overcome them
What acuity is a depth discrimination threshold?
Stereoacuity
As you bring a cube closer, the relative disparity increases. How do you say this mathematically?
Relative disparity between two points in real space is INVERSELY proportional to the square of the distance from the observer
____ disparity stimulates vergence in order to foveally fixate an object. ____ disparities encode the relative depth between the fixated object and other objects in the binocular field of view.
ABSOLUTE disparity stimulates vergence in order to foveally fixate an object. RELATIVE disparities encode the relative depth between the fixated object and other objects in the binocular field of view.
What is the geometric limit for disparity?
The farthest distance where disparity can help depth perception
Corresponding images arise from _____. And example is ___
The Same object. An example is looking at two dogs. Each eye has an image that’s slightly different
___ arcmin is the best stereoacuity to detect. Not so wide, not too close together
15-50
Thick cytochrome oxidase stripes (have magnocellular input) help with….
- Coarse stereopsis
- Low spatial frequency; high temporal frequency
- Selective for disparity and motion
in area V2
What is retinotopically mapped?
The LGN
What kind of cells help with this?
Fine stereopsis
High spatial frequency ; low temporal frequency
Pale (interstripes) cytochrome oxidase stripes (have parvocellular input via interblobs)
in area V2
Stereotheory in which eyes detect ____ over time is serial processing
Disparity change
How can foveal and parafoveal neurons differ from each other?
Half show preference with respect to binocular disparity, half don’t have a disparity preference
How are the stereoacuity and dynamic stereoacuity compare in normal vs strabismic?
Static is better than dynamic in normal. For strabs, they suck at both but have better dynamic compared to static
Good binocularity has what relationship between AC/A and CA/C ratios?
They are inversely related. A high AC/A balances out a low CA/C ratio
Stereotheory in which eyes detect retinal image velocity over time is ____ processing
Parallel. This likely isn’t true because stereomotion is serial processing, meaning more distractors make it harder to detect
Slant is with respect to the ___ meridian
90th meridian
How is the path for asymmetric disparity vergence?
Small vergence, then saccade to make disparity more symmetric, then symmetric vergence movement
Low spatial freq grating = (higher/lower) tolerance for vertical disparity?
High
Relative disparity increases ____ times when you move something 10 times closer.
Relative disparity increases 100 times when you move something 10 times closer. 10^2 = 100
Splitting the ____ results in a bitemporal hemianopia and complete loss of stereopsis for (CROSSED/UNCROSSED) disparities along the midline (in the primary direction of gaze).
They will have steropsis (behind/in front of) fixation point
Optic chiasm.
Uncrossed disparities.
They will have steropsis in front of fixation point
Lesions of the __ impaired stereopsis, spatial memory, spatial attention, and the ability to determine spatial
relationships among objects.
PPC (Posterior parietal cortex)
Left visual field represented in ___ hemisphere.
Left visual field represented in right hemisphere.
98% of population can achieve stereoacuity better than ___
40 arcsec
_____ is a change in the rate of disparity
Disparity curvature (like a tire swing)
A far neuron responds to what kind of disparity? Why does it exist?
Positive, uncrossed disparity. It helps vergence initiation
What clues can vertical disparities give about depth?
There are more vertical disparity for closer objects (especially when not at midline). Far objects have very little vertical disparity
What is SILO?
(small in large out) Target appears to shrink and move closer with BO prism
How is VECP useful for binocularity testing?
You can compare VECP between pt’s fused and unfused binocular stimuli
Measure bino “beat” response.
Stereotheory in which eyes detect disparity change over time is ____ processing
Serial
___% of V1 foveal and parafoveal neurons are binocular.
97
Non-corresponding images arise from ______
Distinct objects (that may be identical)
___% of V3 neurons respond to disparity. They respond ….
50%
Respond only to STATIC disparity. (I.E., seem NOT to respond to motion-in-depth)
_____ is the only direct means of seeing depth
Stereopsis
(serial/parallel) search is unaffected by number of distractors. Give an example.
Parallel search is unaffected by number of distractors.
an example is a blue circle among red squares
How does a small amount of x motion added to z motion affect performance for detecting motion and depth?
A small amount of X motion added to the Z motion greatly improves detecting motion and depth.
Static stereo and stereomotion are (serial/parallel) mechanisms.
Serial mechanisms, meaning more distractors make it harder to detect
Vergence is driven by ______
Binocular retinal disparity
What is the correspondence problem?
The elements do not differ in size, shape, luminance or color, so information from the elements themselves does not restrict the number of possible pairings between the left and right eyes’ images
Disparity in stereograms scales _____ with the target distance
Scales linearly with target distance
Coarse stereopsis is mediated by _____ system
magnocellular system
______ disparity is the the stimulus for stereopsis
Relative disparity
Strabs can make vergence movements with (large/small) stimuli and have a vergence amplitude that is (deficient/adequate/excessive) for the angle. This indicates ___
Strabs can make vergence movements with LARGE stimuli and have a vergence amplitude that is DEFICIENT for the angle. This indicates REDUCED GAIN.
Splitting the _____ leads to a loss of coarse stereopsis along the vertical midline of vision
Corpus callosum
___% of V2 neurons respond to disparity.
70% of V2 neurons respond to disparity.
Stereomotion threshold is ___
Stereomotion threshold = 36 arcsec
Absolute disparity = Negative AD is (crossed/uncrossed).
Alpha L - alpha R. Negative disparity is uncrossed
What happens when you put prism in front of strab fixating eye?
Fast vergence response is not seen, but adaptive response is present.
97% of V1 ____ and ____ neurons are binocular.
foveal and parafoveal neurons
What is SOLI?
(Small out large in) Target appears to look bigger because of prior expectation as BO prism increases
Which neurons prefer stimuli on the horopter? Off the horopter?
T0 and TI prefer on the horopter
TN and TF prefer off the horopter
Which neuron type?
• Specificity for motion and binocular disparity
• May also be related in detecting monocular motion-related distance cues (ex. motion parallax and structure-from motion).
V5 (MT) neurons
Orientation disparity (of two tilted lines) is really ______
A gradient of horizontal disparity
Vergence burst vs vergence tonic neurons.
- Burst fires before and during vergence, encoding maximum velocity
- Tonic fires before vergence with rate proportional to vergence angle.
____ is a stimulus for vergence
Absolute disparity
A near neuron responds to what kind of disparity? Why does it exist?
Negative, crossed disparity. It helps vergence initiation
How does V5 (MT) contribute to disparity processing?
- Specificity for motion and binocular disparity
- May also be related in detecting monocular motion-related distance cues (ex. motion parallax and structure-from motion).
Fast or slow vergence movement can only occur with correlated images? What’s the difference
Slow vergence. Fast explodes on the scene but then fades away, slow disparity vergence grows at times goes on
What neurons help initiate vergence?
T0, TI
TN, TF
What neurons are specific for optic flow patterns and analyze information about self-motion? (the motion-in-depth you perceive as you move your body through space).
MST (Middle superior temporal area)
Vergence sensitivity to absolute disparity is _____ ___ of arc
6 minutes of arc. This is way bigger than the fine sensitivity of stereopsis (which can be 20 sec of arc)
Correlation of 100% means what? 0% means what?
100% means both half views are identical. 0% means nothing matches up and there is no flat plane percept
Which part of the visual field projects to BOTH hemispheres?
Approximately +/-2° from vertical midline
Splitting the Corpus callosum leads to a loss of coarse stereopsis along the ____ of vision
vertical midline
What neuron controls the slow, adapting component of accommodation or vergence?
Tonic controller
____ happens when there is no binocular correspondence
Binocular rivalry.
How convert angle and prism diopters?
Theta = arctan(prism/100)
What is binocular parallax?
Depth perceived from angle of object going to both foveas
What are reciprocal neurons?
Binocular Neurons Found in Macaque areas V1-V3 that prefer far or near bino disparity
How does Duane’s retraction syndrome affect binocular beat?
Both normal and Duane’s show response to 18 and 20 hz, but Duane’s has a much lower response to 2 Hz.
Inclination/declination is with respect to the ___ meridian
180th meridian
What minimum duration is needed for best stereo threshold detection?
100 msec
Absolute vertical disparity is difference in…
Elevation of a point for the two eyes
What are flat neurons?
Binocular Neurons Found in Macaque areas V1-V3 that don’t have disparity preference
If you have difficulty grasping things in the environment with your hand, what could be the problem?
PPC (Posterior parietal cortex)
Thin cytochrome oxidase stripes receive what kind of input?
parvocellular input via blobs
Which vergence motion develops sooner?
Convergence develops sooner than divergence
What neuron serves as the cross-link mechanism between accommodation and vergence?
Phasic controller
Stereo Threshold are worse for ____ color targets. Why?
Blue color targets because blue cones have larger receptive fields.
What is magnocellular input responsible for in V2?
- Coarse stereopsis
- Low spatial frequency; high temporal frequency
- Selective for disparity and motion
How does V3 contribute to disparity processing?
- 50% of neurons respond to disparity
- Respond only to STATIC disparity. (I.E., seem NOT to respond to motion-in-depth)
What kind of cells help with this?
• Coarse stereopsis
• Low spatial frequency; high temporal frequency
• Selective for disparity and motion
Thick cytochrome oxidase stripes (have magnocellular input)
in area V2
Pale (interstripes) cytochrome oxidase stripes (have parvocellular input via interblobs) help with….
Fine stereopsis
High spatial frequency ; low temporal frequency
in area V2
Which neuron type?
- 50% of neurons respond to disparity
- Respond only to STATIC disparity. (I.E., seem NOT to respond to motion-in-depth)
V3 neurons
What neuron controls slows increments of accommodation or vergence?
Funnel limiter
What are the characteristics of binocularly linked images?
The images can be corresponding or noncorresponding, can be fused or slightly diplopic, images engage the disparity detection system
What is absolute disparity?
The difference between convergence angle of the eyes and the binocular parallax of an object
Fine stereopsis is mediated by the ____ system
parvocellular system
First “binocular” neurons of the primary visual pathway are found in____. ___% here they are binoclar
50% of Area V1 neurons are binocular
Peak vergence velocity relates to vergence demand how?
Peak velocity increases as amplitude increases, with a ratio of about 4:1.
What neuron limits the max vergence or accommodation response?
Range limiter
What is parvocellular input responsible for in V2?
Fine stereopsis
High spatial frequency ; low temporal frequency
As you bring a cube closer, the relative disparity increases to the square. What is the impact of this?
Relative depth is more vibrant the closer you are.
What neuron controls the fast accommodation or vergence response?
Phasic controller
What is the purpose of small errors of accommodation and fixation?
They provide continuous signals to sustain focus and eye position
Micro eye movements (Help/Hinder) us to detect motion in depth
They help!
The average latency of vergence signal is ______
160 ms
What does ocular albinism do?
It causes compete decussation of optic fibers. This results in loss of stereopsis and they can have strabismus
Smooth pursuits and OK develop in infants from ___ visual field to _____ visual field. When does this even out?
Temporal visual field to nasal visual field. 3-6 months both directions becomes smooth
Stereotheory in which eyes detect _____ over time is parallel processing
retinal image velocity
How many prism diopters is in 1 meter-angle?
1 meter-angle = 6 pD. Their ipd in cm
