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Visual Development in Human Infants

Visual Development in Human Infants. Karen Dobkins Psychology Department UC San Diego. Today’s lecture: http://psy.ucsd.edu/~kdobkins/HDPnotes.ppt. OUTLINE. - Brief overview of neural development. - Methodology of “Psychophysics”. - 3 Stories in Infant Vision (Ages 1 - 6 months).

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Visual Development in Human Infants

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  1. Visual Development in Human Infants Karen DobkinsPsychology DepartmentUC San Diego Today’s lecture: http://psy.ucsd.edu/~kdobkins/HDPnotes.ppt

  2. OUTLINE - Brief overview of neural development - Methodology of “Psychophysics” - 3 Stories in Infant Vision (Ages 1 - 6 months) 1) PATTERN VISION Grating Resolution, Snellen acuity 2) COLOR VISION Red/Green vs. Black/White Sensitivity 3) MOTION PERCEPTION (if there’s time)

  3. Why Study Development? #1: Clinical Applications e.g., Children with Dyslexia Autism William’s Syndrome have trouble with Motion, but not Pattern or Color, Vision

  4. Neural connections (synapses): ADULT Myelination: matures very slowly Why Study Development? #2: What are the Perceptual consequences of Neural changes during postnatal development? Exuberant connections, then pruned away

  5. Another Example (specific to the visual system) But first…. a little background in VISION

  6. GRATING STIMULUS Sensitivity 2 properties 1) Contrast = (max-min)/(max+min) * 100 High Contrast

  7. GRATING STIMULUS Resolution (or “Acuity”) (like Snellen eye charts, but using GRATINGS, not letters!) 2) Spatial Frequency (cycles/deg)

  8. How are these stimuli seen by the Eye? THE EYE

  9. Adult 22 weeks gestation Newborn Hendrickson & Yuodelis, 1984 BACK TO DEVELOPMENT Infant Photoreceptors in the Eye A) Immature Morphology Do not capture light well, have low sensitivity to light

  10. GRATING Adult Infant Infant Photoreceptors in the Eye B) Immature Density Do not “resolve” stimuli well

  11. THE EYE

  12. GRATING Adult Infant Infant Photoreceptors in the Eye B) Immature Density Do not “resolve” stimuli well

  13. So…. How can we actually measure contrast sensitivity and grating resolution in pre-verbal INFANTS?

  14. In adults: a simple detection task Is the stimulus on the LEFT or RIGHT? (called a “2-AFC”)

  15. In Infants: Forced-Choice Preferential Looking

  16. Contrast Sensitivity

  17. STORY #1: PATTERN VISION IN INFANTS Spatial Contrast Sensitivity Function Tells us about Contrast Sensitivity at different Spatial Frequencies 2) tells us about Resolution

  18. Low Sensitivity in Infants -> Photoreceptor Morphology Contrast Sensitivity Low Resolution in Infants -> Photoreceptor Density resolution

  19. STORY #2: COLOR VISION IN INFANTS Testing this proposal: INFANTS DON’T SEE COLORS VERY WELL!

  20. Development of Sensitivity for: Chromatic (Red/Green) vs. Luminance (White/Black)

  21. Observer’s % Correct

  22. Infants possess equally low sensitivity for BOTH Luminance (Black/White) and Chromatic (Red/Green) stimuli INFANT COLOR VISION IS RELATIVELY FINE!!

  23. SLOW FAST STORY #3: MOTION VISION IN INFANTS Speed Contrast Sensitivity Function = Obtain Contrast Sensitivity at different Moving Speeds (keep SF constant)

  24. Contrast Sensitivity Speed tuning develops fast!

  25. Thank you!

  26. Contrast Sensitivity Speed tuning develops fast!

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