Development of Motion Processing in Human

Infants

Karen DobkinsKaren Dobkins

Psychology DepartmentPsychology DepartmentUC San DiegoUC San Diego

Direction:Leftward or Rightward?

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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

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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)

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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