Development of Motion Processing in Human Infants Karen Dobkins

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Development of Motion Processing in Human
InfantsKaren Dobkins
Psychology DepartmentUC San Diego
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MOTION PROCESSING in ADULTS
Direction Leftward or Rightward?
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Directional (Left vs. Right) Eye Movement Measure
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Eye Movement Direction Leftward or Rightward?
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What about higher-level motion processing?..
Motion Integration
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Plaid Patterns
Low-Level
Higher-Level
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Oops, there is a problem with this stimulus
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A Better Stimulus
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Integration Stimulus
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Directional (Left vs. Right) Eye Movement Measure
Percent Correct 50 - 100
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Subjects
Infants 2-month-olds (n 9) 3-month-olds (n
12) 4-month-olds (n 12) 5-month-olds (n
9)
Adults n 6
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Example Data (2 month old)
Eye Movement Reliability (EMR)
Percent Correct ()
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Performance vs. Age
Percent Correct ()
Integration Stimulus
Linear Regression, Effect of Age p lt 0.025
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Control Stimulus
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Control Stimulus
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Integration Effect
Integration - Control
1) Infants as young as 2 months integrate
component motion into coherent pattern
motion (suggests maturity of higher level motion
areas)
2) Motion integration across space decreases
with age, p lt 0.005
2) Motion integration across space decreases
with age, p lt 0.005
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Shrinking Motion Summation Fields with Age
Coherent Pattern Motion
Shrinking Receptive Fields Sizes with Age
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Barber Pole Experiments
.. Integration of 1D and 2D motion
2D motion (terminators)
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Barber Pole Stimuli
Control Stimulus (integration study)
Barber Pole (Vertical Aps)
Barber Pole (Horizontal Aps)
Perceived Direction Mostly Vertical
Perceived Direction Mostly Horizontal
Barber Pole Effect Horizontal Aps - Vertical
Aps (for Leftward vs. Rightward Eye Movement
Discrimination)
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Yes, infant motion processing is influenced by 2D
line terminator motion!
With clever exp design and a lot of math, we can
estimate the effective shift. 15 - 20 degrees
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Barber Diamond Effects of Context
Duncan, Albright Stoner, 2000
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Projects in Developmental Origins of Autism
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Social/Emotional/Communicative Deficits in Autism
Lack of interest in social interactions
Difficulty understanding the intentions of others
Deficits in Communication (Language Gestures)
Repetitive behaviors/ Obsessive interests
Reduced orienting to faces and voices
Visual Perceptual Differences
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EMBEDDED FIGURE TASK
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Visual Perceptual Differences
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In what part(s) of the brain do the problems in
Autism originate?
And WHEN?
MOTION
FACES
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• SOCIAL/EMOTIONAL/COMMUNICATIVE
• deficits are apparent by 12 months!
• (Retrospective studies of videotapes)

• VISUAL PERCEPTUAL abnormalities
• might be apparent at an even earlier
• time point in development!

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OUR RESEARCH QUESTION
Can we find evidence for visual (and
other) abnormalities in the FIRST YEAR of life?
OUR APPROACH Infant Siblings of Children with
Autism (At-Risk Infants) 10 risk for
Autism
. vs. 0.5 in general population
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Method At-Risk and Typical Infants
tested longitudinally from ages 6 - 36 months
1) Magno/Parvo Vision Test (6 months)
1) Magno/Parvo Vision Test (6 months)
2) Face Processing Test (10 months)
3) Emotional/Social Behaviors (18 months)
4) Language and Cognitive Processing (6 - 36
months)
Autism Testing (24 and 36 months)
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Red/Green (PARVO)
Light/Dark (MAGNO)
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Measuring Red/Geen (PARVO) and Light/Dark (MAGNO)
Sensitivity in Pre-Verbal Infants
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Forced-Choice Preferential Looking
6-month old infants
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Sensitivity
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Thank you
Ione Fine Linday Lewis Joe McCleery
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Performance vs. Age
Percent Correct ()
Integration Stimulus
Linear Regression, Effect of Age p lt 0.025
Linear Regression, Effect of Age p 0.27 (NS)
Control Stimulus
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Quadratic Regression Effect of Age, p lt 0.005
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Effect of Aperture Size in Adults
1? by 2?, 80 contrast
Stimulus Condition 2? by 4?, 80 (infants)
-10.1 (p 0.27, NS)
Integration Effect -9.3 (p 0.15, NS)
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Stimulus-dependent changes in size of motion
summation fields
e.g., Adults at HIGH contrasts, motion
integration across space is WEAKER (e.g.,
Lorenceau Shiffrar, 1992) i.e., smaller
motion summation fields
Effective contrast increases with age
No Integration Effect in Adults (from 5 to 80
contrast)
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This is for Jeff Mulligan
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Motion integration across space decreases
with age.. a million possibilities
1) Decreasing size of motion summation fields
2) Changes in stimulus conditions yielding
optimal motion integration, or optimal motion
integration across space
3) Changes in relative contribution of cortical
vs. subcortical mechanisms involved in eye
movements
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Measuring Perceived Angular Shift (between
Horizontal and Vertical Apertures)
Equivalent Direction (EqDIR)
The angle of gratings moving within horizontal
apertures required to yield the same
horizontalness as produced by gratings moving
within vertical apertures at an angle of X
degrees.
Effective Angular Shift EqDIR - X
Horizontalness Leftward vs. Rightward Eye
Movement Direction Discrimination Performance
X 45 degrees