Transcript Movement Perception

MOTION PERCEPTION
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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
comparator
• 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
movement
• 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
objects
• 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
object
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
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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
movements
• 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)