Summary
Sensation and perception part 2
UU
Contents
Chapter 8 Visual motor perception..................................................................2
Chapter 9 hearing..........................................................................................5
Chapter 10 hearing in the environment.........................................................10
Chapter 12 Vestibular sensation...................................................................13
Chapter 13 Touch.........................................................................................15
Chapter 14 Taste..........................................................................................17
Chapter 15 Olfaction....................................................................................20
,Chapter 8 Visual motor perception
Motion is a low-level perceptual phenomenon
Motion aftereffect (MAE) = the illusion of motion of a stationary object that occurs after
prolonged exposure to a moving object. After viewing motion in one direction, other objects
start moving in the other direction. An opponent process system
Interocular transfer shows that the middle temporal area: MT or V5 is responsible for
global-motion detection.
Motion involves a change in position over time. First order motion = the change in position
of luminance defined objects over time.
Reichardt model
Apparent motion (Sigmund Exner) = the illusory impression of smooth motion resulting
from the rapid alternation of objects that appear in different locations in rapid succession.
fast change of still frames
Aperture = a window like opening that allows only partial view of an object
Aperture problem
Every V1 cells as a limited receptive field and thus sees the world through a small aperture.
The solution is to have another set of neurons which integrate and compare the signals from
V1 neurons. = a global-motion detector
The MT and medial superior temporal area (MST) are considered the hub for motion
processing. The vast majority of MT cells are selective for motion in one particular direction
but have little selectivity for form or colour.
To detect correlated direction, a neuron must integrate information from many local motion
detectors.
Study monkeys by Newsome and Pare
Trained monkeys to respond to correlated-dot-motion displays. After training they could
detect correlated motion direction when only 2-3% of the dots were moving in this direction.
Then, the MT areas of the monkeys were lesioned, which resulted in the monkeys needing
about ten times as many correlated dots to correctly identify the direction of motion. Their
performance improved, presumably because they learned to use other brain areas.
Other study Newsome and colleagues looked for groups of neurons that responded to one
particular direction. Once they found a group, they electrically stimulated the group while
showing the monkeys a new set of stimuli. The monkeys then showed a strong tendency to
report motion in the stimulated neurons’ preferred direction, even when the dots were actually
moving in the opposite direction.
These results make a very strong case that the MT is critically involved in the processing of
global motion.
, Second order motion = the motion of an object that is defined by changes in contrast or
texture, but not by luminance.
Nothing actually moves in second-order motion, just like with apparent motion displays in
first order motion. There is even nothing to move. Evidence suggests that the visual system
includes special mechanisms for second order motion
Lucia Vaina and colleagues described a neurological patient who displayed brain damage that
impaired the perception of first order motion, but not second order motion. A second patient
showed the opposite pattern double disassociation of function.
Using motion information
Safe navigation is one of the primary functions of the visual system
Optic array = the collection of rays that interact with objects in the world in front of a
viewer. Some of these rays strike our retina, enabling us to see.
When we move through our environment, we experience patterns of optic flow = the
changing angular positions of points in a perspective image. Our visual systems use this to
determine where we are going.
Optic flow indicated locomotion; a lack of flow is a signal that you are stationary.
Time to collision (TTC) = the time required for a moving object to hit a stationary object.
Distance / rate
Tau = information in optic flow that could signal TTC without the necessity of estimating
distances or rates. The ratio of the retinal image size at any moment to the rate at which the
image is expanding. When something comes closer, the image on your retina grows larger.
The advantage of using tau to estimate TTC is that it relies solely on information available
directly from the retinal image
Motion can also provide information about the nature of objects. Biological motion = the
pattern of movement of living beings.
Biological motion activates the MT and other visual cortical areas. It also evokes signals in
action observation networks in the frontal regions of the brain (premotor cortex).
Biological motion plays an important role in how we interpret human actions.
Motion induced blindness
Motion can make you temporarily blind: if you fixate a central target, stationary targets in the
periphery will disappear when a global moving pattern is superimposed.
Eye movements
A critical aspect of knowing when to move and where to move to involves controlling where
we are looking. We must constantly move our eyes to fixate the object of interest with our
fovea and follow that object as it moves through space.
Saccades = rapid eye movements, made both voluntarily and involuntarily to change fixation
form one place to another.
Smooth pursuit = a type of voluntary eye movement in which the eyes move smoothly to
follow a moving object.
Brain circuits control the muscles of the eye
Superior colliculus = a structure in the midbrain that is important in initiating and guiding
eye movements. It also gets some input directly from retinal ganglion cells, which presumably
Sensation and perception part 2
UU
Contents
Chapter 8 Visual motor perception..................................................................2
Chapter 9 hearing..........................................................................................5
Chapter 10 hearing in the environment.........................................................10
Chapter 12 Vestibular sensation...................................................................13
Chapter 13 Touch.........................................................................................15
Chapter 14 Taste..........................................................................................17
Chapter 15 Olfaction....................................................................................20
,Chapter 8 Visual motor perception
Motion is a low-level perceptual phenomenon
Motion aftereffect (MAE) = the illusion of motion of a stationary object that occurs after
prolonged exposure to a moving object. After viewing motion in one direction, other objects
start moving in the other direction. An opponent process system
Interocular transfer shows that the middle temporal area: MT or V5 is responsible for
global-motion detection.
Motion involves a change in position over time. First order motion = the change in position
of luminance defined objects over time.
Reichardt model
Apparent motion (Sigmund Exner) = the illusory impression of smooth motion resulting
from the rapid alternation of objects that appear in different locations in rapid succession.
fast change of still frames
Aperture = a window like opening that allows only partial view of an object
Aperture problem
Every V1 cells as a limited receptive field and thus sees the world through a small aperture.
The solution is to have another set of neurons which integrate and compare the signals from
V1 neurons. = a global-motion detector
The MT and medial superior temporal area (MST) are considered the hub for motion
processing. The vast majority of MT cells are selective for motion in one particular direction
but have little selectivity for form or colour.
To detect correlated direction, a neuron must integrate information from many local motion
detectors.
Study monkeys by Newsome and Pare
Trained monkeys to respond to correlated-dot-motion displays. After training they could
detect correlated motion direction when only 2-3% of the dots were moving in this direction.
Then, the MT areas of the monkeys were lesioned, which resulted in the monkeys needing
about ten times as many correlated dots to correctly identify the direction of motion. Their
performance improved, presumably because they learned to use other brain areas.
Other study Newsome and colleagues looked for groups of neurons that responded to one
particular direction. Once they found a group, they electrically stimulated the group while
showing the monkeys a new set of stimuli. The monkeys then showed a strong tendency to
report motion in the stimulated neurons’ preferred direction, even when the dots were actually
moving in the opposite direction.
These results make a very strong case that the MT is critically involved in the processing of
global motion.
, Second order motion = the motion of an object that is defined by changes in contrast or
texture, but not by luminance.
Nothing actually moves in second-order motion, just like with apparent motion displays in
first order motion. There is even nothing to move. Evidence suggests that the visual system
includes special mechanisms for second order motion
Lucia Vaina and colleagues described a neurological patient who displayed brain damage that
impaired the perception of first order motion, but not second order motion. A second patient
showed the opposite pattern double disassociation of function.
Using motion information
Safe navigation is one of the primary functions of the visual system
Optic array = the collection of rays that interact with objects in the world in front of a
viewer. Some of these rays strike our retina, enabling us to see.
When we move through our environment, we experience patterns of optic flow = the
changing angular positions of points in a perspective image. Our visual systems use this to
determine where we are going.
Optic flow indicated locomotion; a lack of flow is a signal that you are stationary.
Time to collision (TTC) = the time required for a moving object to hit a stationary object.
Distance / rate
Tau = information in optic flow that could signal TTC without the necessity of estimating
distances or rates. The ratio of the retinal image size at any moment to the rate at which the
image is expanding. When something comes closer, the image on your retina grows larger.
The advantage of using tau to estimate TTC is that it relies solely on information available
directly from the retinal image
Motion can also provide information about the nature of objects. Biological motion = the
pattern of movement of living beings.
Biological motion activates the MT and other visual cortical areas. It also evokes signals in
action observation networks in the frontal regions of the brain (premotor cortex).
Biological motion plays an important role in how we interpret human actions.
Motion induced blindness
Motion can make you temporarily blind: if you fixate a central target, stationary targets in the
periphery will disappear when a global moving pattern is superimposed.
Eye movements
A critical aspect of knowing when to move and where to move to involves controlling where
we are looking. We must constantly move our eyes to fixate the object of interest with our
fovea and follow that object as it moves through space.
Saccades = rapid eye movements, made both voluntarily and involuntarily to change fixation
form one place to another.
Smooth pursuit = a type of voluntary eye movement in which the eyes move smoothly to
follow a moving object.
Brain circuits control the muscles of the eye
Superior colliculus = a structure in the midbrain that is important in initiating and guiding
eye movements. It also gets some input directly from retinal ganglion cells, which presumably
