karen dobkins development of motion processing in human infants karen dobkins psychology department...
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Development of Motion Processing in Human
Infants
Karen DobkinsKaren Dobkins
Psychology DepartmentPsychology DepartmentUC San DiegoUC San Diego
Direction:Leftward or Rightward?
++
MOTION PROCESSING in ADULTS
Directional (Left vs. Right) Eye Movement Measure
Eye Movement Direction:Leftward or Rightward?
What about higher-level motion processing?…..
Motion Integration
Plaid Patterns
+
"COMPONENT"MOTIONS
45135
COHERENT"PATTERN"MOTION
90
=
Low-Level Higher-Level
Oops, there is a problem with this stimulus
A Better Stimulus
Coherent Pattern Motion0
108 & 252
Integration Stimulus
QuickTime™ and aPhoto - JPEG decompressor
are needed to see this picture.
Directional (Left vs. Right) Eye Movement Measure
Percent Correct: 50% - 100%
Infants: 2-month-olds (n = 9)
3-month-olds (n = 12)
4-month-olds (n = 12)5-month-olds (n = 9)
Subjects
Adults: n = 6
Example Data (2 month old)
50
60
70
80
90
100
Percent Correct (%) Eye Movement Reliability
(EMR)
180EMR
30 trials
Integrati
on
30 trials
Performance vs. Age
Percent Correct (%)
Infants (months)2 3 4 5 A
dults
50
60
70
80
90
100
**
**
***
**
Integration Stimulus:Linear Regression, Effect of Age: p < 0.025
** p < 0.005* p < 0.05 20 /sec
2 /sec
Control Stimulus
108 , 288 or 252
2 /sec
Control Stimulus
QuickTime™ and aPhoto - JPEG decompressor
are needed to see this picture.
“Integration Effect”= Integration -
Control
** p < 0.005
Integration Effect (%)
Infants (months)2 3 4 5 A
dults
-20
0
10
20
-10
** **
**
2) Motion integration across space decreases with age, p < 0.0052) Motion integration across space decreases with age, p < 0.005
1) Infants as young as 2 months integrate component motion into coherent pattern motion(suggests maturity of higher level motion areas)
Shrinking Motion Summation Fields with Age
Coherent Pattern Motion
Shrinking Receptive Fields Sizes with Age
Barber Pole Experiments
Perceived DirectionPerceived Direction
1D motion(interior)
2D motion (terminators)
….. Integration of 1D and 2D motion
Barber Pole Stimuli
72
72
Control Stimulus (integration study)Barber Pole (Vertical Aps) Barber Pole (Horizontal Aps)
72
Barber Pole Effect = Horizontal Aps - Vertical Aps(for Leftward vs. Rightward Eye Movement Discrimination)
QuickTime™ and aPhoto - JPEG decompressor
are needed to see this picture.
QuickTime™ and aPhoto - JPEG decompressor
are needed to see this picture.
Perceived DirectionMostly Vertical
Perceived DirectionMostly Horizontal
Yes, infant motion processingis influenced by 2D line terminatormotion!
With clever exp design and a lot of math, we can estimatethe “effective shift”…. =15 - 20 degrees
Barber Diamond: Effects of Context
Duncan, Albright & Stoner, 2000
Intrinsic (Real) Terminators
Extrinsic (Accidental) Terminators
Projects in Developmental
Origins of Autism
Social/Emotional/Communicative Deficits in AutismLack of interest in social interactions
Deficits in Communication (Language & Gestures)Repetitive behaviors/ Obsessive interests
Reduced orienting to faces and voices
Difficulty understanding the intentions of others
Visual Perceptual “Differences”
EMBEDDED FIGURE TASK
FACESMOTION
Visual Perceptual “Differences”
And WHEN?
In what part(s) of the brain do theproblems in Autism originate?
BRAIN AREAS
Visualcortex
HIGHER-LEVELCOGNITIVEFUNCTIONS
MAGNO
PARVO
MOTION
FACES
- SOCIAL/EMOTIONAL/COMMUNICATIVEdeficits are apparent by 12
months!(Retrospective studies of
videotapes)
-VISUAL PERCEPTUAL abnormalities might be apparent at an even earlier time point in development!
Can we find evidence for visual (and other)abnormalities in the FIRST YEAR of life?
OUR RESEARCH QUESTION:
OUR APPROACH:Infant Siblings of Children with Autism(“At-Risk” Infants):
~10% risk for Autism
…. vs. 0.5% in general population
Method: At-Risk and Typical Infants testedlongitudinally from ages 6 - 36 months
1) Magno/Parvo Vision Test (6 months)
2) Face Processing Test (10 months)
3) Emotional/Social Behaviors (18 months)
Autism Testing (24 and 36 months)
4) Language and Cognitive Processing(6 - 36 months)
1) Magno/Parvo Vision Test (6 months)
Red/Green(PARVO)
Light/Dark(MAGNO)
Measuring Red/Geen (PARVO) and Light/Dark (MAGNO)
Sensitivity in Pre-Verbal Infants
Forced-Choice Preferential Looking
6-month old infants
T h r e s h o l d =
6 . 5 %
S e n s i t i v i t y = 1 /t h r * 1 0 0
= 1 5 .4
Light/Dark(Magno)
Typical (n = 26)
1.7
1.6
1.5
1.4
1.8
Red/Green(Parvo)
Sensitivity
At-Risk (n = 13)
Thank you
Ione FineLinday LewisJoe McCleery
Performance vs. Age
** p < 0.005* p < 0.05
Percent Correct (%)
Infants (months)2 3 4 5 A
dults
50
60
70
80
90
100
**
**
***
**
** **
*
**
Integration Stimulus:Linear Regression, Effect of Age: p < 0.025
Control Stimulus:Control Stimulus:Linear Regression, Effect of Age: p = 0.27 (NS)Linear Regression, Effect of Age: p = 0.27 (NS)
50
60
70
80
90
100
32 41 5Infants (months)
Adults
Percent Correct
(Leftward vs. Rightward
Discrimination)
Vertical Apertures (2 by 4 degrees)
72
Quadratic Regression: Effect of Age, p < 0.005
Horizontal Apertures (4 by 2 degrees)
Effect of Aperture Size in Adults
Stimulus Condition: 2 by 4, 80% (infants)
Integration Effect: -9.3% (p = 0.15, NS)
1 by 2, 80% contrast
-10.1% (p = 0.27, NS)
Stimulus-dependent changes in sizeof 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)
Integration StimulusIntegration Stimulus + Blur
(from Refractive Error)
This is for Jeff Mulligan
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 integrationacross space3) Changes in relative contribution of cortical vs. subcortical mechanisms involved in eye movements
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
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