Development of Motion Processing in Human Infants Karen Dobkins

1. Development of Motion Processing in Human InfantsKaren Dobkins Psychology DepartmentUC San Diego

2. MOTION PROCESSING in ADULTS Direction: Leftward or Rightward?

3. Directional (Left vs. Right) Eye Movement Measure

4. Eye Movement Direction: Leftward or Rightward?

5. What about higher-level motion processing?….. Motion Integration

6. Plaid Patterns Low-Level Higher-Level

7. Oops, there is a problem with this stimulus

8. A Better Stimulus

9. Integration Stimulus

10. Directional (Left vs. Right) Eye Movement Measure Percent Correct: 50% - 100%

11. 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

12. 30 trials 30 trials EMR Integration Example Data (2 month old) Eye Movement Reliability (EMR) Percent Correct (%)

13. 20 /sec ** p < 0.005 *p < 0.05 ** ** 2 /sec ** ** * Adults Performance vs. Age Percent Correct (%) Integration Stimulus: Linear Regression, Effect of Age:p < 0.025

14. 2 /sec Control Stimulus

15. Control Stimulus

16. “Integration Effect” ** ** ** Integration Effect (%) ** p < 0.005 Adults Adults (P) = 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 < 0.005 2) Motion integration across space decreases with age, p < 0.005

17. Shrinking Motion Summation Fields with Age Coherent Pattern Motion Shrinking Receptive Fields Sizes with Age

18. Barber Pole Experiments 1D motion (interior) Perceived Direction Perceived Direction ….. Integration of 1D and 2D motion 2D motion (terminators)

19. 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)

20. 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

21. Intrinsic (Real) Terminators Extrinsic (Accidental) Terminators Barber Diamond: Effects of Context Duncan, Albright & Stoner, 2000

22. Projects in Developmental Origins of Autism

23. 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”

24. EMBEDDED FIGURE TASK

25. FACES MOTION Visual Perceptual “Differences”

26. BRAIN AREAS MAGNO HIGHER-LEVEL COGNITIVE FUNCTIONS PARVO Visual cortex In what part(s) of the brain do the problems in Autism originate? And WHEN? MOTION FACES

27. 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!

28. 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

29. 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)

30. Red/Green (PARVO) Light/Dark (MAGNO)

31. Measuring Red/Geen (PARVO) and Light/Dark (MAGNO) Sensitivity in Pre-Verbal Infants

32. Forced-Choice Preferential Looking 6-month old infants

35. Sensitivity

36. Thank you Ione Fine Linday Lewis Joe McCleery

37. ** p < 0.005 *p < 0.05 ** * ** ** ** ** ** * * * Adults Performance vs. Age Percent Correct (%) Integration Stimulus: Linear Regression, Effect of Age: p < 0.025 Linear Regression, Effect of Age: p = 0.27 (NS) Control Stimulus:

38. Quadratic Regression: Effect of Age, p < 0.005

39. 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)

40. 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)

42. Integration Stimulus + Blur (from Refractive Error) Integration Stimulus This is for Jeff Mulligan

43. 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

44. 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