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Questions and Answers
What is the definition of real motion?
What is the definition of real motion?
What is apparent motion commonly demonstrated by?
What is apparent motion commonly demonstrated by?
What does the motion after-effect indicate?
What does the motion after-effect indicate?
Which type of motion is characterized by the movement of part of an image affecting the perception of another part?
Which type of motion is characterized by the movement of part of an image affecting the perception of another part?
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How do Reichardt motion detectors function?
How do Reichardt motion detectors function?
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What does the term 'aperture problem' refer to?
What does the term 'aperture problem' refer to?
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Which type of motion detectors are sensitive to global motion?
Which type of motion detectors are sensitive to global motion?
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What characterizes biological motion perception?
What characterizes biological motion perception?
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What is necessary for motion detection using Reichardt motion detectors?
What is necessary for motion detection using Reichardt motion detectors?
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What do detection tuning properties of motion detectors indicate?
What do detection tuning properties of motion detectors indicate?
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What phenomenon occurs when you view a stationary scene after observing a moving stimulus?
What phenomenon occurs when you view a stationary scene after observing a moving stimulus?
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Apparent motion can be perceived through static images presented in rapid succession.
Apparent motion can be perceived through static images presented in rapid succession.
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What type of motion involves the movement of part of an image causing the perception of motion in another part?
What type of motion involves the movement of part of an image causing the perception of motion in another part?
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The __________ illusion refers to the motion after-effect, where a stationary object appears to move after viewing a moving stimulus.
The __________ illusion refers to the motion after-effect, where a stationary object appears to move after viewing a moving stimulus.
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Match the types of motion with their definitions:
Match the types of motion with their definitions:
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Which of the following best describes the role of Reichardt motion detectors?
Which of the following best describes the role of Reichardt motion detectors?
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Detection tuning indicates that motion detectors are perfect for specific directions.
Detection tuning indicates that motion detectors are perfect for specific directions.
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What is the aperture problem in motion perception?
What is the aperture problem in motion perception?
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What is the primary function of the focus of expansion (FOE) in self-motion?
What is the primary function of the focus of expansion (FOE) in self-motion?
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Saccadic suppression allows us to perceive the visual information during a saccade.
Saccadic suppression allows us to perceive the visual information during a saccade.
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What type of eye movement is characterized by voluntary tracking?
What type of eye movement is characterized by voluntary tracking?
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The __________ is responsible for the upward and downward motion of the eye.
The __________ is responsible for the upward and downward motion of the eye.
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Match the following types of motion with their definitions:
Match the following types of motion with their definitions:
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At what age do children typically reach adult-like sensitivity to visual motion?
At what age do children typically reach adult-like sensitivity to visual motion?
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Akinetopsia is a common condition where individuals experience normal perception of motion.
Akinetopsia is a common condition where individuals experience normal perception of motion.
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What is the function of the corollary discharge in eye movement?
What is the function of the corollary discharge in eye movement?
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The __________ is responsible for tracking an object smoothly across a visual field.
The __________ is responsible for tracking an object smoothly across a visual field.
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Match the types of eye movements with their definitions:
Match the types of eye movements with their definitions:
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When do infants show some reflexive eye movements?
When do infants show some reflexive eye movements?
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Akinetopsia is primarily caused by impairment in which area of the brain?
Akinetopsia is primarily caused by impairment in which area of the brain?
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Which type of eye movement involves voluntary tracking of a moving object?
Which type of eye movement involves voluntary tracking of a moving object?
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What is the role of corollary discharge in the process of eye movement?
What is the role of corollary discharge in the process of eye movement?
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Which type of eye movement is characterized by nearly immobile eyes focused on a single point?
Which type of eye movement is characterized by nearly immobile eyes focused on a single point?
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Study Notes
Types of Motion
- Real motion: Objects physically moving through our visual field.
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Apparent motion: Static images presented in quick succession, creating the illusion of movement.
- Examples: Animations, flip books, and movies.
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Induced motion: The movement of one part of an image causing the perception of movement in another part.
- Example: Clouds moving across the moon, making the moon seem to move.
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Motion after-effect: After viewing a moving stimulus for a long time, a stationary scene appears to move in the opposite direction.
- Also known as the waterfall illusion.
- Occurs due to adaptation to a specific motion.
Biological Motion
- We are very sensitive to the familiar motion of people or animals, even when only represented by points of light.
- This is evident in "point-light walkers" where simple light dots create the perception of human movement.
Reichardt Motion Detectors
- Motion: Defined as the change in position over time.
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Motion detection: Occurs when a moving object activates one receptive field (RF) followed by an adjacent RF.
- Larger objects activate two RFs simultaneously.
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Reichardt motion detector: A model for motion detection that captures the output from the second RF and a delayed output from the first RF.
- Requires mirrored circuits to detect motion in both directions.
- Multiple detectors are joined together to detect motion over larger areas.
- Adaptation: This model can explain the motion after-effect.
Detection Tuning
- Motion detectors are not perfectly selective for a specific direction.
- They have a preferred direction and respond less strongly to other directions depending on their distance to the preferred direction.
Aperture Problem
- Aperture problem: The ambiguity in determining the direction of motion of an object when viewed through a restricted window (aperture).
- Neural motion detectors: Function as apertures.
Global Motion Detectors
- Combine multiple local detectors with different preferred directions and spatial locations.
- Each local detector can respond to various directions of motion with a preferred one.
- Some neurons in the MT (middle temporal lobe) receive input from multiple motion-sensitive neurons in different RFs in V1 (primary visual cortex) and are sensitive to the global motion of a stimulus.
Types of Motion
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Real motion: An object physically moving through our visual field.
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Apparent motion: Static images presented in rapid succession, creating the illusion of movement. Examples include flip books, animations, and movies.
-
Induced motion: The perception of motion in a stationary object due to the movement of another nearby object. Example: the moon appearing to move through the clouds.
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Motion after-effect: Stationary objects appear to move in the opposite direction after prolonged exposure to a moving stimulus. Also known as the waterfall illusion. Occurs due to adaptation of our visual system to the motion.
Biological Motion
- Humans are highly sensitive to the familiar motion of people and animals.
- This sensitivity extends to recognizing motion represented by just a few points of light, as demonstrated by "point-light walkers."
Reichardt Motion Detectors
- Motion: Defined as a change in position over time.
- Detectors have receptive fields (RFs) that respond to stimuli.
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Motion Detection:
- A moving object activates one RF followed by an adjacent one.
- Larger objects activate two RFs simultaneously.
- To detect motion, detectors require input from both RFs, with a delayed signal from the first RF.
- Requires mirrored circuits for detecting motion in different directions.
- Requires several simple detectors connected to detect motion over a larger area.
- Motion After-effect: Adaptation of the motion detectors can explain the motion after-effect.
Detection Tuning
- Motion detectors are not perfectly selective for a specific direction of motion.
- They respond most strongly to their preferred direction, and less strongly to other directions depending on their closeness to the preferred direction.
Aperture Problem
- Aperture problem: Occurs when a moving object is viewed through a limited window, making it difficult to determine the true direction of motion.
- The RF of neural motion detectors act as apertures.
Global Motion Detectors
- Integration of multiple local detectors with various preferred directions and locations.
- Each local detector can respond to many possible directions of motion with a preferred direction.
- Neurons in the middle temporal (MT) area receive input from multiple V1 neurons responsible for motion sensitivity and respond to global motion.
Sources of Motion
- Motion of our environment.
- Motion of our eyes.
Self-Motion
- Our movement in the environment causes optic flow, which is the perceived motion of objects in the visual field.
- The focus of expansion (FOE) of optic flow tells us the direction we are moving in.
Eye Movements
- Fixation involves small, involuntary movements of the eye: micro-saccades, drift, and tremor.
- Smooth pursuit is voluntary, tracking eye movement.
- Nystagmus is an involuntary eye movement, often associated with inner ear problems.
- Saccades are voluntary, rapid eye movements used to shift gaze.
- Vergence involves turning the eyes inward or outward to focus on objects at different distances.
Anatomy
- Six muscles control eye movement, organized as three pairs:
- Inferior/Superior Rectus: control up and down movements.
- Medial/Lateral Rectus: control left and right movements.
- Inferior/Superior Oblique: control rotation of the eyeball.
Visual Motion and Eye Movements
- A copy of the motor command for eye movement (corollary discharge) is used to predict the sensory consequences of that movement.
- This prediction helps our brain interpret the retinal image.
- If our eyes are moving and the retinal image doesn't move, we know the object must be stationary.
Saccadic Suppression
- During a saccade, our visual system suppresses information from the retinal image to avoid blurring.
- The corollary discharge signal remaps the receptive field of frontal eye field (FEF) neurons to their future target before the movement starts.
Visual Motion Types
- First-order motion is defined by changes in luminance.
- Second-order motion is defined by changes in contrast.
Visual Motion Sensitivity
- Sensitivity to visual motion develops over time in infants.
- Infants have reflexive eye movements at birth.
- Adult-like sensitivity to motion does not mature until 3-4 years.
Akinetopsia
- Akinetopsia is a rare neurological disorder characterized by the inability to perceive motion.
- Caused by impairment in the medial temporal (MT) area of the brain.
Motor Command & Eye Movement
- When we make an eye movement, a copy of the motor command (called a corollary discharge) is used to predict the sensory consequences of the movement.
- This prediction is used to interpret the retinal image.
- If our eyes are moving, a stationary retinal image indicates that the object is moving.
Eye Muscles
- Six muscles control eye movement in three pairs:
- Inferior/Superior rectus (Up & Down)
- Medial/lateral rectus (Left & Right)
- Inferior/Superior oblique (rotation of eyeball)
Types of Eye Movements
- Fixation: Eyes are almost still; consists of micro-saccades, drift, and tremor.
- Smooth pursuit: Voluntary tracking of a moving object.
- Nystagmus: Reflexive eye movements.
- Saccades: Voluntary, rapid eye movements.
- Vergence: Turning eyes inwards or outwards.
Global Motion Detectors
- Global motion detectors are formed by a combination of multiple local motion detectors.
- The local detectors have different preferred directions and spatial locations.
- Each local detector responds to many possible directions of motion, but has a preferred direction.
- Neurons in the MT area receive input from multiple motion-sensitive neurons in different receptive fields (RFs) in V1 (visual cortex).
- The MT neurons are sensitive to the global motion of a stimulus.
Visual Motion Development
- Sensitivity to visual motion emerges gradually during infancy.
- Basic reflexive eye movements are present at birth.
- Adults reach full motion sensitivity around the ages of 3-4 years.
Akinetopsia
- A rare neurological disorder marked by the inability to perceive motion.
- Occurs due to damage to the medial temporal (MT) area of the brain.
Motor Command & Perception
- When we move our eyes (or any body part), a copy of the motor command (called corollary discharge) is used to anticipate the sensory outcome of the movement.
- This prediction helps interpret retinal images and determine if an object is static or moving.
- Stationary retinal images during eye movement indicate object movement.
Eye Muscles
- Six muscles control eye movement, organized in three pairs:
- Inferior/Superior rectus (up & down)
- Medial/Lateral rectus (left & right)
- Inferior/Superior oblique (rotational movement)
Eye Movements
- Different eye movements serve distinct functions:
- Fixation: Maintaining a relatively still gaze, with micro-saccades, drift, and tremor.
- Smooth Pursuit: Voluntary, continuous tracking of a moving object.
- Nystagmus: Involuntary, rapid eye movements, often reflexive.
- Saccades: Voluntary, rapid eye shifts between points of interest.
- Vergence: Converging or diverging the eyes to adjust focus at different distances.
Global Motion Detection
- Global motion perception emerges from integrating information from local motion detectors.
- Multiple local detectors with varying preferred directions and spatial positions contribute.
- Each local detector can respond to several motion directions but has a favoured one.
- Neurons in the MT area receive input from various motion-sensitive neurons in V1, enabling them to identify the global motion of a stimulus.
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Description
Explore various types of motion, including real, apparent, and induced motion. Understand the motion after-effect and its implications, as well as the concept of biological motion and Reichardt motion detectors. This quiz will deepen your understanding of how we perceive motion in our environment.
