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Chapter 7

Chapter 7 - Textbook Notes


Department
Psychology
Course Code
PSYB51H3
Professor
Matthias Niemeier
Chapter
7

Page:
of 7
Chapter 7: Motion Perception
-shape, location in space, color her fundamental perceptual dimensions
-motion as a low-level perceptual phenomenon–cells in primary visual cortex selectively respond
to
motion in one particular direction
-motion aftereffect
the illusion of motion of a stationary object that occurs after prolonged exposure to
moving objects
-just as color after effects are caused by opponent processes for color vision, the motion after
effect is
caused by opponent processes for motion detection
Computation of Visual Motionpage 171 look over
-promotion detector is velocity sensitive in their direction sensitive
Apparent Motion
-one possible objection to this neuronal circuit is that it does not, in fact, require continuous
motion in
order to fire
-the Reeichardt model provides an excellent explanations were visual illusions that modern
humans
experience on a daily basis
-apparent motion
that illusory impression of smooth motion resulting from the rapid alternation of objects
that appear in different locations and rapid succession
-first demonstrated by Sigmund Exner in 1875
The Correspondence and Aperture Problems
Aperture- an opening that allows only a partial view of the object
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correspondence problem - the problems faced by the motion detection system of knowing which
feature
in frame two corresponds to a particular feature in frame one example on page 173 figure 7.5
aperture problem- the fact that when a moving object is viewed t through an aperturer, the
direction of
motion of a local feature or part of the objects may be ambiguous
-every V1 cell sees the world through a small aperture therefore none of them can tell with
certainty
which visual elements correspond to one another when an object moves
-the solution to this problem is to have another set of neurons listen to the V1 neurons integrate
the
potentially conflicting signals
Detection of Global Motion and Area MT
-lesions in the magnocellular layers of the LGN impaired perception of large, rapidly moving
objects
-the vast majority of neurons in MT our selective promotion in one particular direction, but they
show little
selectivity for form or color
-Newsome and Pare trained monkeys to respond to correlated dot motion displays
-no single dot in these displays is sufficient to determine the overall direction of correlated
motion; so to
detect the correlated direction, neurons must integrate information
-monkeys could recognize a correlated motion direction on only 2 to 3% of the dots are moving in
the
direction; once there brings release and they needed about 10 times as many correlated dots in
order to
correctly identify the direction of motion
-the ability to discriminate orientation of stationary patterns was unimpaired
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-lesions may be incomplete or may influence other structures this may have led to a third
variable
affecting the outcome
-another experiment in which the researchers searched for groups of neurons that responded to
one
particular direction showed to monkey a new set of stimuli and electrically stimulated the
identified MT
neurons
-the monkeys showed a strong tendency to report motion in the stimulated neurons preferred
direction, even when the dogs they were seeing were actually moving in the opposite direction
-these show a strong case that the MT business site of global motion direction
Motion Aftereffects Revisited
-neurons sensitive to upward motion fire at the same rate as neurons sensitive to downward
motion, so
the signals cancel out and no motion is perceived
-the detectors are sensitive to downward motion become fatigued and when we switch our gaze to
a
stationary object in nonsense to the upward motion fire faster
-interocular transfer
the transfer of an effect from one night to the other
-the fact that a strong motion after effect is obtained with one eye is adaptive and the other tested
means
that the effect must be reflecting activities in their arms in a part of the visual system or
information
collected from the two eyes is combined–the V1 area
-the emerging evidence suggests that the motion after affecting humans is caused by the same
brain
region shown to be responsible for global motion detection and monkeys–the cortical area MT
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