Transcript Development of Motion Processing in Human Infants Karen

Development of Motion
Processing in Human Infants
Karen Dobkins
Psychology Department
UC San Diego
MOTION PROCESSING in ADULTS
+
Direction:
Leftward or Rightward?
Directional (Left vs. Right) Eye Movement Measure
Eye Movement Direction:
Leftward or Rightward?
What about higher-level motion processing?…..
Motion Integration
Plaid Patterns
90
135
45
+
"COMPONENT"
MOTIONS
Low-Level
=
COHERENT
"PATTERN"
MOTION
Higher-Level
Oops, there is a problem with this stimulus
A Better Stimulus
Cohe re nt Patte rn Motion
108 & 252
0
Integration Stimulus
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
Directional (Left vs. Right) Eye Movement Measure
Percent Correct: 50% - 100%
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
Percent Correct (%)
Example Data (2 month old)
Eye Movement Reliability
(EMR)
100
90
80
70
60
50
Integration
EMR
180
Percent Correct (%)
Performance vs. Age
100
** p < 0.005
* p < 0.05
20 /sec
90 **
80
70
**
**
**
2 /sec
*
60
50
2 3 4 5
Infants (months)
Integration Stimulus: Linear Regression, Effect of Age: p < 0.025
Control Stimulus
2 /sec
108 , 288 or 252
Control Stimulus
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
Integration Effect (%)
“Integration Effect”
= Integration - Control
20
**
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 < 0.005
10
0
-10
-20
2 3 4 5
Infants (months)
Shrinking Motion Summation Fields with Age
Coherent
Pattern Motion
Shrinking Receptive Fields Sizes with Age
Barber Pole Experiments
….. Integration of 1D and 2D motion
1D motion
(interior)
2D motion
(terminators)
Perceived Direction
Perceived Direction
Barber Pole Stimuli
Control
Barber
Stimulus
Pole (Vertical
(integration
Aps)study)
Barber Pole (Horizontal Aps)
72
72
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
72
Perceived Direction
Mostly Vertical
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
Perceived Direction
Mostly Horizontal
Barber Pole Effect = Horizontal Aps - Vertical Aps
(for Leftward vs. Rightward Eye Movement Discrimination)
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
Barber Diamond: Effects of Context
Intrinsic (Real)
Terminators
Duncan, Albright & Stoner, 2000
Extrinsic (Accidental)
Terminators
Projects in Developmental
Origins of Autism
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”
EMBEDDED FIGURE TASK
Visual Perceptual “Differences”
FACES
MOTION
In what part(s) of the brain do the
problems in Autism originate?
And WHEN?
BRAIN AREAS
MOTION
MAGNO
HIGHER-LEVEL
COGNITIVE
PARVO
FUNCTIONS
Visual
cortex
FACES
- 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!
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
Method: At-Risk and Typical Infants tested
longitudinally from ages 6 - 36 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)
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
Threshold =
6.5%
Sensitivity = 1/thr * 100
= 15.4
Typical (n = 26)
At-Risk (n = 13)
1.8
Sensitivity
1.7
1.6
1.5
1.4
Light/Dark
(Magno)
Red/Green
(Parvo)
Thank you
Ione Fine
Linday Lewis
Joe McCleery
** p < 0.005
* p < 0.05
100
90 **
80
70
60
*
**
**
** **
**
*
*
*
Percent Correct (%)
Performance vs. Age
50
2 3 4 5
Infants (months)
Integration Stimulus: Linear Regression, Effect of Age: p < 0.025
Control Stimulus: Linear Regression, Effect of Age: p = 0.27 (NS)
Percent Correct
(Leftward vs. Rightward
Discrimination)
100
Vertical Apertures (2 by 4 degrees)
Horizontal Apertures (4 by 2 degrees)
90
80
70
72
60
1 2 3 4 5
Infants (months)
Adults
50
Quadratic Regression: Effect of Age, p < 0.005
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 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)
Integration Stimulus
Integration 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 integration
across space
3) 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