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PSYB51H3 Study Guide - Midterm Guide: Binocular Disparity, Frontal Eye Fields, Superior Rectus Muscle

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Matthias Niemeier
Study Guide

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Chapter 6: Space Perception and Binocular Vision
6 Muscles controlled by cranial nerves
Superior Rectus
Lateral Rectus
Medial Rectus
Inferior Rectus
Superior Obliquegoes thru the hook-like structure (trochlea)
Inferior Oblique
3 Cranial Nerves
#3-Occulomotor nerve: does most of the job; in the midbrain (works ipsilaterally)
#4-Trochlear nerve: innovates the superior oblique (works contralaterally)
#6-Abducens nerve: innovates the lateral rectus (works ipsilaterally)
Frontal Eye fields & Parietal Cortex
Frontal eye fields and parietal cortex projects onto the Superior Colliculus
Eye movements are controlled by cerebral cortex
Superior Colliculus: structure in midbrain; initiates and guides eye movements
Types of Eye Movements
Smooth Pursuit: movement of eyes of a moving object
Saccades: rapid movements of eyes to fixating points
Vergence: eye movement where two eyes move in opposite directions;
Functions of Eye Movements
Smooth Pursuit
To keep things stable in our fovea

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To move fovea to object of interest; move as quickly as possible to reduce travel
time during which vision is blurred
Yarbus: scanpaths
False motion and retinal smear: the object looks like it’s moving, but really it’s
our eyes that’s moving
We don’t notice this b/c of spatial constancy
Spatial constancy: tricky problem of discriminating in the retina if the
object is moving or if the eyes are moving
Saccadic suppression: reduction of visual sensitivity that occurs
when a saccadic eye movement is made; eliminates smear from
retinal image motion during an eye movement
Compensation Theory--comparator: inhibits other parts of the
visual system from interpreting the object as moving; solves
problem of motion illusions
Euclidian Geometry
Parallel lines remain parallel as they are extended in spaceonly in the real world; not in
the retinal image
Objects become smaller as we move away because the image takes less space in our
Parallax: the 2 retinal images are not the same b/c the retinas are at slightly different
Binocular Disparity: the differences b/w the images seen on both retinal images; the basis
for stereoscopic vision
Binocular depth cues provide:
Convergencegives us an additional sense of depth
Ability to see more of an object with both eyes than one eye
Monocular cues
Occlusion: when one object in front blocks another but it’s a nonmetrical depth cue b/c it
doesn’t tell us magnitude(distance)

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Size and position cues
Relative size: the same object seems to be smaller when it’s further away
Texture gradient: items of the same size form smaller images when further away
Relative height: images further away seem to be higher
Familiar size: using previous knowledge to estimate size of an object
Relative: doesn’t tell exact distance
Absolute: tells us the exact distance
Aerial Perspective: when fainter objects seem to be further away
Linear Perspective: when parallel lines are not parallel in 2D worldthey converge; only
provides relative metrical depth info
Vanishing point: the point where the lines meet
Foreshortening: when an object appears to be shorter than it actually is
Anamorphosis: when special devices need to be used to actually view the image
Motion cues
Motion parallax: objects that are closer move faster and more than objects that are
further away (need to move head); eyes are in different positions in the head at the
same time; provides relative metrical info about how far away objects are
Accommodation and Convergence: depth; can tell us the exact distance to
an object
Binocular Vision and Stereopsis
Corresponding retinal points: when images points are corresponding to the retinal image
in both eyes; same distance from the foveaZero binocular disparity
Horopter: place where zero binocular disparity is; depends on amount of convergence
Panum’s fusion area: area in front and behind the horopter
Diplopia: objects closer to or farther away from the horopter form images on non-
corresponding points in the 2 eyesdouble vision
Crossed disparity: when image is projected to the right side of the left eye and to the left
side of the right eye
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