Movement Perception

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Transcript Movement Perception

Types of Motion Perception
Corollary Discharge Theory
Movement Detectors
Motion Perception and Object Perception
Ecological Perception
Vestibular System
Types of Motion Perception
• Real Movement occurs when an object
actually moves
• Apparent Movement is a perception of motion
caused by the appearance of two stationary
stimuli at different times
Types of Motion Perception
• Induced Movement occurs when movement
of one object causes a perception of motion in
another object
• Movement After-Effects occur when a
perception of motion is caused by viewing real
movement in the opposite direction
Corollary Discharge Theory
• When the brain sends a message to move the
eyes, it sends a copy (corollary discharge) to a
• Information about image movement is also
sent to the comparator
Corollary Discharge Theory
• If the comparator receives information that
the image is moving but the eyes are not
moving, motion is perceived
• If the comparator receives information that
the image is not moving but the eyes are
moving, motion is perceived
Corollary Discharge Theory
• If the comparator receives information that
the image is moving and the eyes are also
moving, motion is not perceived
Movement Detectors
• Real Movement Detectors in V3 respond only
when the stimulus actually moves, whether
the eyes are moving or not
• Neurons in the Medial Temporal (MT) cortex
respond to movement in a particular direction
Motion and Object Perception
• Recognition of patterns affects perception of
• shortest path constraint - movement appears
to occur on the shortest possible path
• When the shortest path violates knowledge
about objects, a longer path is perceived
Motion and Object Perception
• Recognition of motion affects perception of
• Kinetic Depth Effect
• Biological Motion
Motion and Object Perception
• The “What” and “How” streams communicate
with each other
Ecological Perception
• How do we use perception to guide our
actions in the environment?
• Invariant information - information that
remains constant during observer movement
Ecological Approach (Gibson)
• We can perceive motion by using information
from the environment
• Optic array - surfaces, textures, and contours
in the environment
• Local disturbance - one object moves relative
to the environment, deleting and accreting
Optic Flow
• Optic flow - movement of elements relative to
the observer
• Focus of Expansion(FOE) - point in the
distance at which there is no flow
Navigation Neurons
• Collision-sensitive neurons - respond only
when an object is on a collision course; found
in pigeon brain
• Neurons in the human Medial Superior
Temporal (MST) area respond to flow
patterns; have large receptive fields
Mirror Neurons
• Located in Premotor Area (PM) in frontal lobes
• Respond when the monkey grasps an object
OR when the monkey sees someone grasp an
Vestibular System
• This system provides information to the brain
on orientation and movement of body
• The sensory organs are the semicircular
canals and vestibular sacs in the inner ear
Semicircular Canals
three tubes at right angles
fluid filled
hair cells at the base of each canal
detect rotation in three dimensions
Vestibular Sacs
• two sacs at the base of semicircular canals
• detect linear motion
• motion causes movement of statolith which
bends hair cells
Vestibular Pathway
• 8th Cranial nerve carries information from
hair cells
• brain stem
• cerebellum (movement and balance)
• thalamus
• cortex
Interaction with Vision
• Vestibulo-ocular Reflex - stabilizes visual field
by coordinating eye movements with head
• Motion sickness - mismatch between visual
and vestibular information
Interaction with Vision
• Visual cues can affect balance, overcoming
influence of vestibular information
• Swinging room experiment (Lee & Aronson)